MCA631_Advanced Internet Programming

192 Advanced Internet Programming Hibernate detects that the @Id annotation is on a field and assumes that it should access properties of an object directly through fields at runtime. If you placed the @Id annotation on the getId() method, you would enable access to properties through getter and setter methods by default. Hence, all other annotations are also placed on either fields or getter methods, following the selected strategy. Following section will explain the annotations used in the above class. @Entity Annotation The EJB 3 standard annotations are contained in the javax.persistence package, so we import this package as the first step. Second, we used the @Entity annotation to the Employee class, which marks this class as an entity bean, so it must have a no-argument constructor that is visible with at least protected scope. @Table Annotation The @Table annotation allows you to specify the details of the table that will be used to persist the entity in the database. The @Table annotation provides four attributes, allowing you to override the name of the table, its catalogue, and its schema, and enforce unique constraints on columns in the table. For now, we are using just table name, which is EMPLOYEE. @Id and @GeneratedValue Annotations Each entity bean will have a primary key, which you annotate on the class with the @Id annotation. The primary key can be a single field or a combination of multiple fields depending on your table structure. By default, the @Id annotation will automatically determine the most appropriate primary key generation strategy to be used but you can override this by applying the @GeneratedValue annotation, which takes two parameters strategy and generator that I’m not going to discuss here, so let us use only the default key generation strategy. Letting Hibernate determine which generator type to use makes your code portable between different databases. @Column Annotation The @Column annotation is used to specify the details of the column to which a field or property will be mapped. You can use column annotation with the following most commonly used attributes −  name attribute permits the name of the column to be explicitly specified. CU IDOL SELF LEARNING MATERIAL (SLM)

Java Hibernate 193  length attribute permits the size of the column used to map a value particularly for a String value.  nullable attribute permits the column to be marked NOT NULL when the schema is generated.  unique attribute permits the column to be marked as containing only unique values. Create Application Class Finally, we will create our application class with the main() method to run the application. We will use this application to save few Employee’s records and then we will apply CRUD operations on those records. Import java.util.List; return employeeID; } /* Method to READ all the employees */ import java.util.Date;import java.util.Iterator; public void listEmployees( ){ import org.hibernate.HibernateException; Session session = factory.openSession(); import org.hibernate.Session; import Transaction tx = null; org.hibernate.Transaction;import try { org.hibernate.cfg.AnnotationConfiguration;impo tx = session.beginTransaction(); rt List employees = session.createQuery(\"FROM Employee\").list(); org.hibernate.SessionFactory;import org.hibernate.cfg.Configuration; for (Iterator iterator = employees.iterator(); iterator.hasNext();){ public class ManageEmployee { Employee employee = (Employee) iterator.next(); private static SessionFactory factory; System.out.print(\"First Name: \" + employee.getFirstName()); public static void main(String[] args) { System.out.print(\" Last Name: \" + try { employee.getLastName()); System.out.println(\" Salary: \" + factory = new AnnotationConfiguration(). employee.getSalary()); } configure(). tx.commit(); //addPackage(\"com.xyz\") //add package if } catch (HibernateException e) { used. if (tx!=null) tx.rollback(); addAnnotatedClass(Employee.class). e.printStackTrace(); } finally { buildSessionFactory(); session.close(); } catch (Throwable ex) { System.err.println(\"Failed to create sessionFactory object.\" + ex); throw new ExceptionInInitializerError(ex); } ManageEmployee ME = new ManageEmployee(); CU IDOL SELF LEARNING MATERIAL (SLM)

194 Advanced Internet Programming /* Add few employee records in database */ }} Integer empID1 = ME.addEmployee(\"Zara\", /* Method to UPDATE salary for an employee \"Ali\", 1000); */ Integer empID2 = ME.addEmployee(\"Daisy\", public void updateEmployee(Integer \"Das\", 5000); EmployeeID, int salary ){ Integer empID3 = ME.addEmployee(\"John\", Session session = factory.openSession(); \"Paul\", 10000); Transaction tx = null; try { /* List down all the employees */ tx = session.beginTransaction(); ME.listEmployees(); Employee employee = (Employee)session.get(Employee.class, /* Update employee's records */ EmployeeID); ME.updateEmployee(empID1, 5000); employee.setSalary( salary ); session.update(employee); /* Delete an employee from the database */ tx.commit(); ME.deleteEmployee(empID2); } catch (HibernateException e) { if (tx!=null) tx.rollback(); /* List down new list of the employees */ e.printStackTrace(); ME.listEmployees(); } finally { } session.close(); /* Method to CREATE an employee in the }} database */ /* Method to DELETE an employee from the public Integer addEmployee(String fname, records */ String lname, int salary){ public void deleteEmployee(Integer Session session = factory.openSession(); EmployeeID){ Transaction tx = null; Session session = factory.openSession(); Integer employeeID = null; Transaction tx = null; try { try { tx = session.beginTransaction(); tx = session.beginTransaction(); Employee employee = new Employee(); Employee employee = employee.setFirstName(fname); (Employee)session.get(Employee.class, employee.setLastName(lname); EmployeeID); employee.setSalary(salary); session.delete(employee); employeeID = (Integer) tx.commit(); session.save(employee); } catch (HibernateException e) { tx.commit(); if (tx!=null) tx.rollback(); e.printStackTrace(); CU IDOL SELF LEARNING MATERIAL (SLM)

Java Hibernate 195 } catch (HibernateException e) { } finally { if (tx!=null) tx.rollback(); session.close(); e.printStackTrace(); } } finally { }} session.close(); } Database Configuration Now let us create hibernate.cfg.xml configuration file to define database related parameters. <?xml version = \"1.0\" encoding = \"utf- <!-- Assume students is the database name --> 8\"?><!DOCTYPE hibernate-configuration <property name = \"hibernate.connection.url\"> SYSTEM jdbc:mysql://localhost/test </property> \"http://www.hibernate.org/dtd/hibernate- <property name = configuration-3.0.dtd\"> \"hibernate.connection.username\"> root <hibernate-configuration> </property> <property name = <session-factory> \"hibernate.connection.password\"> cohondob <property name = \"hibernate.dialect\"> </property> </session-factory></hibernate-configuration> org.hibernate.dialect.MySQLDialect </property> <property name = \"hibernate.connection.driver_class\"> com.mysql.jdbc.Driver </property> Compilation and Execution Here are the steps to compile and run the above mentioned application. Make sure, you have set PATH and CLASSPATH appropriately before proceeding for the compilation and execution.  Delete Employee.hbm.xml mapping file from the path.  Create Employee.java source file as shown above and compile it.  Create ManageEmployee.java source file as shown above and compile it.  Execute ManageEmployee binary to run the program. You would get the following result, and records would be created in EMPLOYEE table. $java ManageEmployee.......VARIOUS LOG MESSAGES WILL DISPLAY HERE........ CU IDOL SELF LEARNING MATERIAL (SLM)

196 Advanced Internet Programming First Name: Zara Last Name: Ali Salary: 1000First Name: Daisy Last Name: Das Salary: 5000First Name: John Last Name: Paul Salary: 10000First Name: Zara Last Name: Ali Salary: 5000First Name: John Last Name: Paul Salary: 10000 If you check your EMPLOYEE table, it should have the following records − mysql> select * from EMPLOYEE;+----+------------+-----------+--------+| id | first_name | last_name | salary |+----+------------+-----------+--------+| 29 | Zara | Ali | 5000 || 31 | John | Paul | 10000 |+----+------------+-------- ---+--------+2 rows in set (0.00 sec mysql> 9.9 Hibernate Query languages  Hibernate Query Language  Advantage of HQL  Query Interface Hibernate Query Language (HQL) is same as SQL (Structured Query Language) but it doesn’t depends on the table of the database. Instead of table name, we use class name in HQL. So it is database independent query language. Advantage of HQL There are many advantages of HQL. They are as follows:  database independent  supports polymorphic queries  easy to learn for Java Programmer Query Interface It is an object oriented representation of Hibernate Query. The object of Query can be obtained by calling the createQuery() method Session interface. The query interface provides many methods. There is given commonly used methods: 1. public int executeUpdate() is used to execute the update or delete query. 2. public List list() returns the result of the relation as a list. 3. public Query setFirstResult(int rowno) specifies the row number from where record will be retrieved. CU IDOL SELF LEARNING MATERIAL (SLM)

Java Hibernate 197 4. public Query setMaxResult(int rowno) specifies the no. of records to be retrieved from the relation (table). 5. public Query setParameter(int position, Object value) it sets the value to the JDBC style query parameter. 6. public Query setParameter(String name, Object value) it sets the value to a named query parameter. Example of HQL to get all the records 1. Query query=session.createQuery(\"from Emp\");//here persistent class name is Emp 2. List list=query.list(); Example of HQL to get records with pagination 1. Query query=session.createQuery(\"from Emp\"); 2. query.setFirstResult(5); 3. query.setMaxResult(10); 4. List list=query.list();//will return the records from 5 to 10th number FROM Clause You will use FROM clause if you want to load a complete persistent objects into memory. Following is the simple syntax of using FROM clause − String hql = \"FROM Employee\";Query query = session.createQuery(hql);List results = query.list(); If you need to fully qualify a class name in HQL, just specify the package and class name as follows String hql = \"FROM com.hibernatebook.criteria.Employee\";Query query = session.createQuery(hql);List results = query.list(); AS Clause The AS clause can be used to assign aliases to the classes in your HQL queries, especially when you have the long queries. For instance, our previous simple example would be the following − String hql = \"FROM Employee AS E\";Query query = session.createQuery(hql);List results = query.list(); The AS keyword is optional and you can also specify the alias directly after the class name, as follows − CU IDOL SELF LEARNING MATERIAL (SLM)

198 Advanced Internet Programming String hql = \"FROM Employee E\";Query query = session.createQuery(hql);List results = query.list(); SELECT Clause The SELECT clause provides more control over the result set then the from clause. If you want to obtain few properties of objects instead of the complete object, use the SELECT clause. Following is the simple syntax of using SELECT clause to get just first_name field of the Employee object − String hql = \"SELECT E.firstName FROM Employee E\";Query query = session.createQuery(hql);List results = query.list(); It is notable here that Employee.firstName is a property of Employee object rather than a field of the EMPLOYEE table. WHERE Clause If you want to narrow the specific objects that are returned from storage, you use the WHERE clause. Following is the simple syntax of using WHERE clause − String hql = \"FROM Employee E WHERE E.id = 10\";Query query = session.createQuery(hql);List results = query.list(); ORDER BY Clause To sort your HQL query’s results, you will need to use the ORDER BY clause. You can order the results by any property on the objects in the result set either ascending (ASC) or descending (DESC). Following is the simple syntax of using ORDER BY clause − String hql = \"FROM Employee E WHERE E.id > 10 ORDER BY E.salary DESC\";Query query = session.createQuery(hql);List results = query.list(); If you wanted to sort by more than one property, you would just add the additional properties to the end of the order by clause, separated by commas as follows − String hql = \"FROM Employee E WHERE E.id > 10 \" + \"ORDER BY E.firstName DESC, E.salary DESC \";Query query = session.createQuery(hql);List results = query.list(); GROUP BY Clause This clause lets Hibernate pull information from the database and group it based on a value of an attribute and, typically, use the result to include an aggregate value. Following is the simple syntax of using GROUP BY clause − CU IDOL SELF LEARNING MATERIAL (SLM)

Java Hibernate 199 String hql = \"SELECT SUM(E.salary), E.firtName FROM Employee E \" + \"GROUP BY E.firstName\";Query query = session.createQuery(hql);List results = query.list(); Using Named Parameters Hibernate supports named parameters in its HQL queries. This makes writing HQL queries that accept input from the user easy and you do not have to defend against SQL injection attacks. Following is the simple syntax of using named parameters − String hql = \"FROM Employee E WHERE E.id = :employee_id\";Query query = session.createQuery(hql); query.setParameter(\"employee_id\",10);List results = query.list(); UPDATE Clause Bulk updates are new to HQL with Hibernate 3, and delete work differently in Hibernate 3 than they did in Hibernate 2. The Query interface now contains a method called executeUpdate() for executing HQL UPDATE or DELETE statements. The UPDATE clause can be used to update one or more properties of an one or more objects. Following is the simple syntax of using UPDATE clause − String hql = \"UPDATE Employee set salary = :salary \" + \"WHERE id = :employee_id\";Query query = session.createQuery(hql); query.setParameter(\"salary\", 1000); query.setParameter(\"employee_id\", 10);int result = query.executeUpdate();System.out.println(\"Rows affected: \" + result); DELETE Clause The DELETE clause can be used to delete one or more objects. Following is the simple syntax of using DELETE clause − String hql = \"DELETE FROM Employee \" + \"WHERE id = :employee_id\";Query query = session.createQuery(hql); query.setParameter(\"employee_id\", 10);int result = query.executeUpdate();System.out.println(\"Rows affected: \" + result); INSERT Clause HQL supports INSERT INTO clause only where records can be inserted from one object to another object. Following is the simple syntax of using INSERT INTO clause − CU IDOL SELF LEARNING MATERIAL (SLM)

200 Advanced Internet Programming String hql = \"INSERT INTO Employee(firstName, lastName, salary)\" + \"SELECT firstName, lastName, salary FROM old_employee\";Query query = session.createQuery(hql);int result = query.executeUpdate();System.out.println(\"Rows affected: \" + result); Aggregate Methods HQL supports a range of aggregate methods, similar to SQL. They work the same way in HQL as in SQL and following is the list of the available functions − You may call avg(), min(), max() etc. aggregate functions by HQL. Let’s see some common examples: The distinct keyword only counts the unique values in the row set. The following query will return only unique count − String hql = \"SELECT count(distinct E.firstName) FROM Employee E\";Query query = session.createQuery(hql);List results = query.list(); 9.10 Hibernate Criteria Query Language The Hibernate Criteria Query Language (HCQL) is used to fetch the records based on the specific criteria. The Criteria interface provides methods to apply criteria such as retrieving all the records of table whose salary is greater than 50000 etc. Advantage of HCQL The HCQL provides methods to add criteria, so it is easy for the java programmer to add criteria. The java programmer is able to add many criteria on a query. Criteria Interface The Criteria interface provides many methods to specify criteria. The object of Criteria can be obtained by calling the createCriteria() method of Session interface. Syntax of createCriteria() method of Session interface public Criteria createCriteria(Class c) The commonly used methods of Criteria interface are as follows: 1. public Criteria add(Criterion c) is used to add restrictions. 2. public Criteria addOrder(Order o) specifies ordering. CU IDOL SELF LEARNING MATERIAL (SLM)

Java Hibernate 201 3. public Criteria setFirstResult(int firstResult) specifies the first number of record to be retreived. 4. public Criteria setMaxResult(int totalResult) specifies the total number of records to be retrieved. 5. public List list() returns list containing object. 6. public Criteria setProjection(Projection projection) specifies the projection. Restrictions class Restrictions class provides methods that can be used as Criterion. The commonly used methods of Restrictions class are as follows: 1. public static SimpleExpression lt(String propertyName,Object value) sets the less than constraint to the given property. 2. public static SimpleExpression le(String propertyName,Object value) sets the less than or equal constraint to the given property. 3. public static SimpleExpression gt(String propertyName,Object value) sets the greater than constraint to the given property. 4. public static SimpleExpression ge(String propertyName,Object value) sets the greater than or equal than constraint to the given property. 5. public static SimpleExpression ne(String propertyName,Object value) sets the not equal constraint to the given property. 6. public static SimpleExpression eq(String propertyName,Object value) sets the equal constraint to the given property. 7. public static Criterion between(String propertyName, Object low, Object high) sets the between constraint. 8. public static SimpleExpression like(String propertyName, Object value) sets the like constraint to the given property. Order class The Order class represents an order. The commonly used methods of Restrictions class are as follows: 1. public static Order asc(String propertyName) applies the ascending order on the basis of given property. CU IDOL SELF LEARNING MATERIAL (SLM)

202 Advanced Internet Programming 2. public static Order desc(String propertyName) applies the descending order on the basis of given property. Examples of Hibernate Criteria Query Language There are given a lot of examples of HCQL. Example of HCQL to get all the records 1. Crietria c=session.createCriteria(Emp.class);//passing Class class argument 2. List list=c.list(); Example of HCQL to get the 10th to 20th record 1. Crietria c=session.createCriteria(Emp.class); 2. c.setFirstResult(10); 3. c.setMaxResult(20); 4 List list=c.list(); Example of HCQL to get the records whose salary is greater than 10000 1. Crietria c=session.createCriteria(Emp.class); 2. c.add(Restrictions.gt(\"salary\",10000));//salary is the propertyname 3. List list=c.list(); Example of HCQL to get the records in ascending order on the basis of salary 1. Crietria c=session.createCriteria(Emp.class); 2. c.addOrder(Order.asc(\"salary\")); 3. List list=c.list(); HCQL with Projection We can fetch data of a particular column by projection such as name etc. Let’s see the simple example of projection that prints data of NAME column of the table only. 1.Criteria c=session.createCriteria(Emp.class); 2. c.setProjection(Projections.property(\"name\")); 3. List list=c.list(); CU IDOL SELF LEARNING MATERIAL (SLM)

Java Hibernate 203 9.11 Native SQL Native SQL is another technique of performing bulk operations on the data using hibernate  By using Native SQL, we can perform both select, non-select operations on the data  In face Native SQL means using the direct SQL command specific to the particular (current using) database and executing it with using hibernate Advantages and Disadvantages of Native SQL  We can use the database specific keywords (commands), to get the data from the database  While migrating a JDBC program into hibernate, the task becomes very simple because JDBC uses direct SQL commands and hibernate also supports the same commands by using this Native SQL  The main draw back of Native SQL is, some times it makes the hibernate application as database dependent one If we want to execute Native SQL Queries on the database then, we need to construct an object of SQLQuery, actually this SQLQuery is an interface extended from Query and it is given in ” org.hibernate package ” In order to get an object of SQLQuery, we need to use a method createSQLQuery() given by session interface. While executing native sql queries on the database, we use directly tables, column names directly in our command. Remember, while executing Native SQL Queries, even though we are selecting complete objects from teh database we need to type cast into object array only, not into our pojo class type, because we are giving direct table, column names in the Native SQL Querie so it does’nt know our class name If we execute the command, always first it will put’s data in ResultSet and from there List Usage: SQLQuery qry = session.createSQLQuery(\"select * from PRODUCTS\"); // Here PRODUCTS is the table in the database... List l = qry.list(); Iterator it = l.iterator(); CU IDOL SELF LEARNING MATERIAL (SLM)

204 Advanced Internet Programming while(it.hasNext()) { Object row[] = (Object[])it.next(); --- -------}  while selecting data from the table, even though you are selecting the complete object from the table, in while loop still we type cast into object array only right  See the above code, we typecast into the object[] arrays right.., in case if we want to type cast into our POJO class (i mean to get POJO class obj), then we need to go with entityQuery concept  In order to inform the hibernate that convert each row of ResultSet into an object of the POJO class back, we need to make the query as an entityQuery  to make the query as an entityQuery, we need to call addEntity() method //We are letting hibernate to know our pojo class too SQLQuery qry = session.createSQLQuery(\"select * from PRODUCTs\").addEntity(Product.class); List l = qry.list(); Iterator it = l.iterator(); while(it.hasNext()) { Product p = (Product)it.next(); --- -------} 9.12 Hibernate Caching and Interceptor Caching Caching is a mechanism to enhance the performance of a system. It is a buffer memory that lies between the application and the database. Cache memory stores recently used data items in order to reduce the number of database hits as much as possible. Caching is important to Hibernate as well. It utilizes a multilevel caching scheme as explained below First-level Cache The first-level cache is the Session cache and is a mandatory cache through which all requests must pass. The Session object keeps an object under its own power before committing it to the database. CU IDOL SELF LEARNING MATERIAL (SLM)

Java Hibernate 205 If you issue multiple updates to an object, Hibernate tries to delay doing the update as long as possible to reduce the number of update SQL statements issued. If you close the session, all the objects being cached are lost and either persisted or updated in the database. Database Hibernate First-level Cache Client Session Object Second-level Cache Optional Fig. 9.8: Hibernate Cache Second-level Cache Second level cache is an optional cache and first-level cache will always be consulted before any attempt is made to locate an object in the second-level cache. The second level cache can be configured on a per-class and per-collection basis and mainly responsible for caching objects across sessions. Any third-party cache can be used with Hibernate. An org.hibernate.cache.CacheProvider interface is provided, which must be implemented to provide Hibernate with a handle to the cache implementation. Query-level Cache Hibernate also implements a cache for query resultsets that integrates closely with the second-level cache. This is an optional feature and requires two additional physical cache regions that hold the cached query results and the timestamps when a table was last updated. This is only useful for queries that are run frequently with the same parameters. The Second Level Cache Hibernate uses first-level cache by default and you have nothing to do to use first-level cache. Let's go straight to the optional second-level cache. Not all classes benefit from caching, so it's important to be able to disable the second-level cache. CU IDOL SELF LEARNING MATERIAL (SLM)

206 Advanced Internet Programming The Hibernate second-level cache is set up in two steps. First, you have to decide which concurrency strategy to use. After that, you configure cache expiration and physical cache attributes using the cache provider. Concurrency Strategies A concurrency strategy is a mediator, which is responsible for storing items of data in the cache and retrieving them from the cache. If you are going to enable a second-level cache, you will have to decide, for each persistent class and collection, which cache concurrency strategy to use.  Transactional: Use this strategy for read-mostly data where it is critical to prevent stale data in concurrent transactions, in the rare case of an update.  Read-write: Again use this strategy for read-mostly data where it is critical to prevent stale data in concurrent transactions, in the rare case of an update.  Nonstrict-read-write: This strategy makes no guarantee of consistency between the cache and the database. Use this strategy if data hardly ever changes and a small likelihood of stale data is not of critical concern.  Read-only: A concurrency strategy suitable for data, which never changes. Use it for reference data only. Interceptor In Hibernate, an object will be created and persisted. Once the object has been changed, it must be saved back to the database. This process continues until the next time the object is needed, and it will be loaded from the persistent store. Thus an object passes through different stages in its life cycle and Interceptor Interface provides methods, which can be called at different stages to perform some required tasks. These methods are callbacks from the session to the application, allowing the application to inspect and/or manipulate properties of a persistent object before it is saved, updated, deleted or loaded. Following is the list of all the methods available within the Interceptor interface − Sr.No. Method & Description 1 findDirty() This method is be called when the flush() method is called on a Session object. 2 instantiate() This method is called when a persisted class is instantiated. CU IDOL SELF LEARNING MATERIAL (SLM)

Java Hibernate 207 3 isUnsaved() This method is called when an object is passed to the saveOrUpdate() method/ 4 onDelete() This method is called before an object is deleted. 5 onFlushDirty() This method is called when Hibernate detects that an object is dirty (i.e. have been changed) during a flush i.e. update operation. 6 onLoad() This method is called before an object is initialized. 7 onSave() This method is called before an object is saved. 8 postFlush() This method is called after a flush has occurred and an object has been updated in memory. 9 preFlush() This method is called before a flush. Hibernate Interceptor gives us total control over how an object will look to both the application and the database. 9.13 Practical Assignment 1. Design Hibernate application to store employee object to the database. 2. Create a maven based hibernate application using annotation in eclipse IDE. 9.14 Summary Hibernate is a high-performance Object/Relational persistence and query service, which is licensed under the open source GNU Lesser General Public License (LGPL) and is free to download. Hibernate not only takes care of the mapping from Java classes to database tables (and from Java data types to SQL data types), but also provides data query and retrieval facilities. This tutorial will teach you how to use Hibernate to develop your database based web applications in simple and easy steps. CU IDOL SELF LEARNING MATERIAL (SLM)

208 Advanced Internet Programming 9.15 Key Words/Abbreviations  Object-Relational Persistence: Hibernate is an Object-Relational Mapping (ORM) solution for JAVA. It is an open source persistent framework created by Gavin King in 2001. It is a powerful, high performance Object-Relational Persistence and Query service for any Java Application.  EJB: Enterprise Java Bean  HQL: Hibernate Query Language 9.16 Learning Activity 1. What is HCQL? ----------------------------------------------------------------------------------------------------------- ----------------------------------------------------------------------------------------------------------- 2. Explain different Interceptor? ----------------------------------------------------------------------------------------------------------- ----------------------------------------------------------------------------------------------------------- 9.17 Unit End Questions (MCQs and Descriptive) A. Descriptive Types Questions 1. Explain what is Hibernate. 2. Explain Hibernate Architecture with neat diagram. 3. Explain Hibernate Configuration in detail. 4. Explain Session class in Hibernate. 5. Explain Persistent class in Hibernate 6. Explain Hibernate Mapping. 7. Explain O/R mapping in Hibernate 8. Explain Annotation mapping 9. Explain Hibernate Query language. 10. Explain Hibernate Criteria Queries. CU IDOL SELF LEARNING MATERIAL (SLM)

Java Hibernate 209 11. Explain Hibernate Native SQL. 12. Explain Hibernate Caching and Interceptor. B. Multiple Choice/Objective Type Questions 1. Which of the following is true about ORM? (a) ORM stands for Object-Relational Mapping. (b) ORM is a programming technique for converting data between relational databases. (c) Both of the above. (d) None of the above. 2. Which of the following is true about configuration component of Hibernate? (a) The Configuration object is the first Hibernate object you create in any Hibernate application. (b) The Configuration object is usually created only once during application initialization. (c) The Configuration object represents a configuration or properties file required by the Hibernate. (d) All of the above. 3. Which method is used to get a persistent instance from the datastore? (a) Session.read() (b) Session.get() (c) Session.retrieve() (d) Session.fetch() 4. Which of the following element is used to represent one-to-one relationship in hibernate? (a) <many-to-one> (b) <many-one> (c) <ManyToOne> (d) None of the above. 5. What HQL stands for? (a) Hibernate Query Language (b) High Query Language (c) Hybrid Query Language (d) None of the above. Answers 1. (c), 2. (d), 3. (b), 4. (a), 5. (a) CU IDOL SELF LEARNING MATERIAL (SLM)

210 Advanced Internet Programming 9.18 References 1. https://java2blog.com/introduction-to-hibernate-framework/ 2. https://www.geeksforgeeks.org/introduction-to-hibernate-framework/ 3. Java Persistence with Hibernate by Christian Bauer, Gavin King CU IDOL SELF LEARNING MATERIAL (SLM)

UNIT 10 JAVA STRUTS - I Structure: 10.0 Learning Objectives 10.1 Introduction 10.2 Basic MVC Architecture 10.3 Model 1 and Model 2(MCV) Architecture 10.4 Struts 2 Framework Features 10.5 Environment Setup 10.6 Configuration 10.7 Actions 10.8 Interceptors 10.9 Value Stack 10.10 Result Types 10.11 File Uploads 10.12 Practical Assignment 10.13 Database Access 10.14 Summary 10.15 Key Words/Abbreviations 10.16 Learning Activity CU IDOL SELF LEARNING MATERIAL (SLM)

212 Advanced Internet Programming 10.17 Unit End Questions (MCQs and Descriptive) 10.18 References 10.0 Learning Objectives After studying this unit, you will be able to:  Describe environment setupconfiguration  Discuss actions, interceptors, resulttypes  Elaborate File uploads, databaseaccess 10.1 Introduction Struts is a popular and mature web application framework based on the MVC design pattern. Struts2 is not just a new version of Struts 1, but it is a complete rewrite of the Struts architecture. The Webwork framework initially started with Struts framework as the basis and its goal was to offer an enhanced and improved framework built on Struts to make web development easier for the developers. After a while, the Webwork framework and the Struts community joined hands to create the famous Struts2 framework. 10.2 MVC Architecture Model–view–controller (MVC) is a software architectural patternfor implementing user interfaces on computers. It divides a given application into three interconnected parts. This is done to separate internal representations of information from the ways information is presented to, and accepted from, the user. Let me put it this way: Entire web development goes in distinct way where we have entire process categorized to different developers working on it such as Database, Back-end programming and front-end programming. “Model” consist of database operations(CRUD operations; Create, Read, Update, Delete queries), “View” consist of Front end development (HTML, CSS, JavaScript etc) and “Controller” consist of the main business logic (Backend programming through server side CU IDOL SELF LEARNING MATERIAL (SLM)

Java Struts - I 213 languages such as PHP, JAVA etc). ‘Controller” controls the interaction/transactions between the “Model” and “Viewer”. MODEL VIEWER CONTROLLER Fig. 10.1: MVC Architecture Struts 2 MVC is released by three core framework components: actions, results, and the ServletFilter. The diagram below shows how these three components interact with each other. request Invoke action Model Web Browser Client Action Controller Interceptor Servlet Filter Select result View Result Render result Fig. 10.2: Struts 2 MVC Servlet Filter The servlet filter acts as a controller in Struts 2. It inspects each incoming request to determine which Struts 2 action should handle the request. The framework handles all of the controller work for the application. All request URLs need to be mapped to actions with XML- based configuration files or Java annotations. Interceptors Interceptors execute before and after the request processing. They provide cross-cutting tasks so that they can be easily reused as well as separated from other architectural concerns. For example, validation parameters before invoking login action. CU IDOL SELF LEARNING MATERIAL (SLM)

214 Advanced Internet Programming Action Action handles the client requests in two different ways. First, the action plays an important role in the transfer of data from the request through to the view, whether its a JSP or other type of result. Second, the action must assist the framework in determining which result should render the view that will be returned in the response to the request. Result Result is a JSP or HTML page to create a view for client response. Struts 2 provides their own tags that we can use in JSP pages to create a response. Struts tags are great example of JSP Custom Tags. 10.4 Features of Struts 2 Java struts is an open source framework that extends Java Servlet API (Application Program Interface) and employs a Model, Viewer and controller (MVC) architecture. It enables you to create maintainable, extensible, and flexible web applications based on standard technologies, such as JSP pages, JavaBeans, resource bundles, and XML. The struts framework was initially created byCraig McClanahanand donated to Apache Foundation in May, 2000 and Struts 1.0 was released in June 2001. The current stable release of Struts is Struts 2.3.16.1 in March 2, 2014. Struts 2 will also supports POJO ( plain old java objects) based actions, AJAX support, validation support and several other frameworks integrations such as Hibernate, Spring etc. We have also shown the demo of the same. Here are formal Struts2 Framework Features: 1. Configurable MVC components 2. POJO based actions 3. AJAX support 4. Integration support 5. Various Result Types 6. Various Tag support 7. Theme and Template support 1. Configurable MVC components: Struts2 framework, provides all the components (view components and action) information in struts.xml file. We simply need to change strut.xml file for changing any information. CU IDOL SELF LEARNING MATERIAL (SLM)

Java Struts - I 215 2. POJO based actions: Struts2, action class is POJO (Plain Old Java Object) i.e. a simple java class. 3. AJAX support: Struts2 provides support to AJAX technology. Using AJAX one can make webpage load only the desired content on request, hence reduces page load. One glitch we must know that; AJAX is not suitable for slow internet options. 4. Integration Support: Integration struts2 application with hibernate, spring, tiles etc. Frameworks is possible. 5. Various Result Types: Use of JSP, velocity etc. Technologies in the result type in Struts2 is possible. 6. Various Tag support: Struts 2 provides various types of tags such as UI tags, Data tags, control tags etc to ease the development of struts2 application. 7. Theme and Template support: Struts2 provides 3 types of theme support: Simple, XHTML and CSS_XHTML. The XHTML is default theme of struts2. Themes and templates can be used for common look and feel especially when look and feel doesn’t matter much. Also it saves time for design. 10.5 Environment Setup Step 1 - Setup Java Development Kit (JDK) You can download the latest version of SDK from Oracle's Java site −Java SE Downloads. You will find instructions for installing JDK in downloaded files, follow the given instructions to install and configure the setup. Finally, set PATH and JAVA_HOME environment variables to refer to the directory that contains java and javac, typically java_install_dir/bin and java_install_dir respectively. If you are running Windows and installed the SDK in C:\\jdk1.5.0_20, you should be inputting the following line in your C:\\autoexec.bat file. set PATH = C:\\jdk1.5.0_20\\bin;%PATH%set JAVA_HOME = C:\\jdk1.5.0_20 Alternatively, on Windows NT/2000/XP −  You can right-click on My Computer, Select Properties, then Advanced, then Environment Variables. Then, you would update the PATH value and press the OK button. CU IDOL SELF LEARNING MATERIAL (SLM)

216 Advanced Internet Programming  On Unix (Solaris, Linux, etc.), if the SDK is installed in /usr/local/jdk1.5.0_20 and you use the C shell, you would put the following into your .cshrc file.  On Unix (Solaris, Linux, etc.), if the SDK is installed in /usr/local/jdk1.5.0_20 and you use the C shell, you would put the following into your .cshrc file. setenv PATH /usr/local/jdk1.5.0_20/bin:$PATH setenv JAVA_HOME /usr/local/jdk1.5.0_20 Alternatively, if you use an Integrated Development Environment (IDE) like Borland JBuilder, Eclipse, IntelliJ IDEA, or Sun ONE Studio, compile and run a simple program to confirm that the IDE knows where you installed Java, otherwise do proper setup as per the given document of IDE. Step 2 - Setup Apache Tomcat You can download the latest version of Tomcat fromhttps://tomcat.apache.org/. Once you downloaded the installation, unpack the binary distribution into a convenient location. For example in C:\\apache-tomcat-6.0.33 on windows, or /usr/local/apachetomcat-6.0.33 on Linux/Unix and create CATALINA_HOME environment variable pointing to these locations. You can start Tomcat by executing the following commands on windows machine, or you can simply double click on startup.bat %CATALINA_HOME%\\bin\\startup.bat Or C:\\apache-tomcat-6.0.33\\bin\\startup.bat Tomcat can be started by executing the following commands on Unix (Solaris, Linux, etc.) machine − $CATALINA_HOME/bin/startup.sh Or /usr/local/apache-tomcat-6.0.33/bin/startup.sh After a successful startup, the default web applications included with Tomcat will be available by visitinghttp://localhost:8080/. If everything is fine, then it should display the following result − CU IDOL SELF LEARNING MATERIAL (SLM)

Java Struts - I 217 Fig. 10.3: Apache Tomcat Further information about configuring and running Tomcat can be found in the documentation included here, as well as on the Tomcat website:https://tomcat.apache.org/ Tomcat can be stopped by executing the following commands on windows machine − %CATALINA_HOME%\\bin\\shutdown Or C:\\apache-tomcat-5.5.29\\bin\\shutdown Tomcat can be stopped by executing the following commands on Unix (Solaris, Linux, etc.) machine − $CATALINA_HOME/bin/shutdown.sh Or /usr/local/apache-tomcat-5.5.29/bin/shutdown.sh Step 3 - Setup Eclipse (IDE) All the examples in this tutorial are written using Eclipse IDE. I suggest that, you have the latest version of Eclipse installed in your machine. To install Eclipse Download the latest Eclipse binaries from https://www.eclipse.org/downloads/. Once you download the installation, unpack the binary distribution into a convenient location. CU IDOL SELF LEARNING MATERIAL (SLM)

218 Advanced Internet Programming For example in C:\\eclipse on windows, or /usr/local/eclipse on Linux/Unix and finally set PATH variable appropriately. Eclipse can be started by executing the following commands on windows machine, or you can simply double click on eclipse.exe %C:\\eclipse\\eclipse.exe Eclipse can be started by executing the following commands on Unix (Solaris, Linux, etc.) machine − $/usr/local/eclipse/eclipse After a successful startup, if everything is fine, it should display the following result − Fig. 10.4: Eclipse (IDE) Step 4 - Setup Struts2 Libraries Now if everything is fine, then you can proceed to setup your Struts2 framemwork. Following are the simple steps to download and install Struts2 on your machine.  Make a choice whether you want to install Struts2 on Windows, or Unix and then proceed to the next step to download .zip file for windows and .tz file for Unix.  Download the latest version of Struts2 binaries from https://struts.apache.org/download.cgi. CU IDOL SELF LEARNING MATERIAL (SLM)

Java Struts - I 219  I downloaded struts-2.3.4.1-all.zip. Unzip this zip file to any location. for example E:/struts-2.3.4.1.  E:/struts-2.3.4.1/lib folder contains all required jar files for struts 2 framework.  AndE:/struts-2.3.4.1/appsfolder contains some sample webapplication war files includingstruts2-blank.war file.  struts2-blank.war file contains all configuration required for running sample Struts 2 web application. you can run this sample using Eclipse like this:  import war file: File ->import->choosestruts2-blank.war file (in Eclipse).It should look like this: Fig. 10.5: Struts2 Blank War File After importing struts2-blank.war file,struts2-blank application directory structure look like this: CU IDOL SELF LEARNING MATERIAL (SLM)

220 Advanced Internet Programming Fig. 10.6: Struts2 Application Structure Now run this struts2-blank application, result on browser should be look like this: Fig. 10.7: Struts 2 Blank Application 10.6 Configuration The Model-View-Controller Framework in Struts2 has five core components for configuration: CU IDOL SELF LEARNING MATERIAL (SLM)

Java Struts - I 221  Actions  Interceptors  Value Stack / OGNL  Results / Result types  View technologies Struts 2 is slightly different from a traditional MVC framework in that the action takes the role of the model rather than the controller, although there is some overlap. Browser Results/Result Types Controller View Dispatcher Filter JSP Interceptors Free marker Execute() setXxx() Model Value Action Stack/OGN getXxx() Fig. 10.8: Image Courtesy : tutorialspoint.com The above diagram depicts theModel,View andController to the Struts2 high level architecture. The controller is implemented with a Struts2 dispatch servlet filter as well as interceptors, the model is implemented with actions, and the view as a combination of result types and results. The value stack and OGNL provide common thread, linking and enabling integration between the other components. Object-Graph Navigation Language(OGNL) is an open-source Expression Language (EL) for Java, which, while using simpler expressions than thefullrange of those supported by the Java language, allows getting and setting properties (through defined setProperty and getProperty methods, found in JavaBeans), and execution of methods of Java classes. It also allows for simpler array manipulation. CU IDOL SELF LEARNING MATERIAL (SLM)

222 Advanced Internet Programming Apart from the above components, there will be a lot of information that relates to configuration. Configuration for the web application, as well as configuration for actions, interceptors, results, etc. This is the architectural overview of the Struts 2 MVC pattern. We will go through each component in more detail in the subsequent chapters. 10.7 Struts 2 Action In struts 2, action class isPOJO(Plain Old Java Object). POJO means you are not forced to implement any interface or extend any class. Generally,executemethod should be specified that represents the business logic. The simple action class may look like: Welcome.java package com.javatpoint; public class Welcome { publicStringexecute() { return\"success\"; }} Action Interface A convenient approach is to implement thecom.opensymphony.xwork2.Actioninterface that defines 5 constants and one execute method. Constants of Action Interface Action interface provides 5 constants that can be returned from the action class. They are: 1. SUCCESS indicates that action execution is successful and a success result should be shown to the user. 2. ERROR indicates that action execution is failed and a error result should be shown to the user. 3. LOGIN indicates that user is not logged-in and a login result should be shown to the user. 4. INPUT indicates that validation is failed and a input result should be shown to the user again. CU IDOL SELF LEARNING MATERIAL (SLM)

Java Struts - I 223 5. NONE indicates that action execution is successful but no result should be shown to the user. Let's see what values are assigned to these constants: 1. publicstaticfinalStringSUCCESS=\"success\"; 2. publicstaticfinalStringERROR=\"error\"; 3. publicstaticfinalStringLOGIN=\"login\"; 4. publicstaticfinalStringINPUT=\"input\"; 5. publicstaticfinalStringNONE=\"none\"; Method of Action Interface Action interface contains only one method execute that should be implemented overridden by the action class even if you are not forced. 1. publicStringexecute(); Example of Struts Action that implements Action interface If we implement the Action interface, we can directly use the constants instead of values. Welcome.java Package com.javatpoint; import com.opensymphony.xwork2.Action; public class Welcome implements Action{ public Stringexecute() { returnSUCCESS; }} ActionSupport Class It is a convenient class that implements many interfaces such as Action, Validateable, ValidationAware, TextProvider, LocaleProvider and Serializable. So it is mostly used instead of Action. Example of Struts Action that extends ActionSupport class Let's see the example of Action class that extends the ActionSupport class. Welcome.java package com.javatpoint; CU IDOL SELF LEARNING MATERIAL (SLM)

224 Advanced Internet Programming import com.opensymphony.xwork2.ActionSupport; public class Welcome extends ActionSupport { public Stringexecute() { return SUCCESS; }} Role of Action 1. Performs as a model: Action performs as a Model by encapsulating the actual work to be done for a given request based on the input parameters. Encapsulation is done using the execute() method. The code spec inside this method should only hold the business logic to serve a Request. Example: public String execute() { setWelcomeMessage(msg+getUserName()); return “SUCCESS”; } In above code, a welcome message is shown to the user along with the name using String Concatenation 2. Serves as a data Carrier: Action server as a data carrier from the Request to the View. Action being the Model component of the framework carries the data around. The data it requires is held locally which makes it is easy to access using JavaBeans properties during the actual execution of the business logic. The execute() method simply references the data using JavaBeans properties. Example: private String uname; public String getUName() { return uname; } public void setUName(String uname) { this.uname=uname; } private String msg; public String getWelcomeMsg() { this.msg=msg; } CU IDOL SELF LEARNING MATERIAL (SLM)

Java Struts - I 225 In above code, Action implements JavaBeans properties for all the data being carried. The framework automatically maps the FORM Request parameters to the JavaBeans properties that have matching names. 3. Helps Determine Results: Action determines the Result that will render the View that will be returned in the request’s response. This is achieved by returning a control string that selects the result that should be rendered. The value of return string must be identical to the result name as configured. Example: public String execute() { setWelcomeMsg(MSG+getUName()); return “SUCCESS”; } In above code, Action returns the SUCCESS. We have to modify struts.xml configuration file as follows: <action name=”WelcomeStruts” class=”test. WelcomeStruts”> <result name=”SUCCESS”>/ welcome.jsp</result> </action> Here SUCCESS is the name of the one of the result components that is identical to the return String. 4. Single or Multiple Results: For returning single action result we have to code like follows: class MyAction { { public void String execute()throws Exception public void String execute () throws Exception { { If(LogicIsSOK()) setWelcomeMsg(MSG+getUName()); { return “SUCCESS”; setWelcomeMsg(MSG+getUName()); }} return “SUCCESS”; An action can also return multiple results } depending on the complexity of the business else logic, { In such cases, we have code like follows: return “ERROR”; Class MyMultipleAction }}} CU IDOL SELF LEARNING MATERIAL (SLM)

226 Advanced Internet Programming In above code, there are two different results that can be returned depending upon the business logic flow. Since Action returns more than one kind of results, we need make appropriate configuration in the struts.xml configuration file as follows. <action name=”WelcomeStruts” class=”test.WelcomeStruts”> <result name=”SUCCESS”>/ Welcome.jsp</result> <result name=”ERROR”>/ Error.jsp</result> </action> 10.8 Interceptors Interceptors allow developing code that can be run before and / or after the execution of an action. A request is usually processed as follows:  A user requests a resource that maps to an action.  The Struts 3 framework invokes the appropriate action to serve the request. If interceptors are written, available and configured, then:  Before the action is executed the invocation could be intercepted by another object.  After the action executes, the invocation could be intercepted again by another object. Such objects who intercept the invocation are called Interceptors. Conceptually, interceptors are very similar to Servlet Filters or the JDKs Proxy class. Interceptors Configuration: Interceptors configured in the struts.xml file appear as: <interceptors> <interceptor name=”test1” class=”…”/> <interceptor name=”test2” class=”…”/> </interceptors> <action name=”Welcome Struts”> <interceptor-ref name=”test1”/> <interceptor-ref name=”test2”/> <result name=”SUCCESS”>/ Welcome.jsp</result> <result name=”ERROR”>/ Error.jsp</result> </action> In above code two interceptors named test 1 and test 2 are defined. Both of these are them mapped to the action named WelcomeStruts. CU IDOL SELF LEARNING MATERIAL (SLM)

Java Struts - I 227 Interceptor Stack: We can bind Interceptor together using an Interceptor Stack which can be referenced together. We can use the same set of interceptors multiple times. So, instead of configuring a number of interceptors every time, an interceptor stack can be configured with all the required interceptors held within. To use Intercept Stack we need to modify the strutd.xml file as follows: <interceptors> <interceptor name=”test1” class=”…”/> <interceptor name=”test2” class=”…”/> <interceptor-stack name=”MyStack”> <interceptor-ref name=”test 1”/> <interceptor-ref name=”test 2”/> </interceptor-stack> </interceptors> <action name=”WelcomeStruts” class=”test. WelcomeStruts”> <result name=”SUCCESS”>/Welcome.jsp</result> <result name=”ERROR”>/Error.jsp</result> </action> In above code two interceptors named test 1 and test 2 are defined and a stack named MyStack group them both. The stack holding both these interceptors is then mapped to the Action named WelcomeStruts. Execution Flow of Interceptors Interceptors are executed as follows: 1. The framework receives a request and decides on the action the URL maps to 2. The framework consults the application’s configuration file, to discover which interceptors should fire and in what sequence 3. The framework starts the invocation process by executing the first Interceptor in the Stack 4. After all the interceptors are invoked; the framework causes the action itself to be executed CU IDOL SELF LEARNING MATERIAL (SLM)

228 Advanced Internet Programming 10.9 Value Stack Value Stack is nothing but stack of objects. The Value Stack is a storage area that holds all of the data associated with the processing of a Request. Execution Flow of Value Stack 1. The framework receives a request and decides on the action the URL maps to 2. The framework moves the data to the Value Stack whilst preparing for request processing. 3. The framework manipulates the data as required during the action execution 4. The framework reads the data from there and renders the results i.e. Response page struts 2 maintains a stack of the following objects in the Value Stack: 5. Temporary Objects: these are generated and placed in the Value Stack during execution. These objects provide temporary storage and are normally generated while processing a request. For example, the current iteration value for collection being looped over in JSP tag. 6. The Model Object: If the application user Model objects, the current model object is placed in the Value Stack before the Action executes. 7. The Action Object: It is the Action that is currently being executed. 8. Named objects: Any object assigned to an identifier called as a Named Object. These object can either be created by the developer of pre.-defined such as #application Accessing value Stack: The Value Stack can be accessed by simply using the tags provided for JSP. When the Value Stack Is queried for an attribute value, each stack element, in the provided order, is asked whether it holds the queried property. If it holds the queried property, then the value is returned. If it does not hold the queried property, then the next element down is queried. This continues until the last element in the stack is scanned. 10.10 Result Types After executing the Action class , the target view page will be executed based on configuration in struts.xml. The Srruts2 framework provides set of Result types like; chaining, dispatcher, redirect action, velocity and free market etc, that has to be configure in struts.xml for different kind of result. The result type is used to change the behaviour of view page to render the contents of action class. CU IDOL SELF LEARNING MATERIAL (SLM)

Java Struts - I 229 Thecom.opensymphony.xwork2.Resultinterface implemented by all the result classes. The Result interface has a single method public void execute (Action Invocation ) throws Exception. Thecom.opensymphony.xwork2.config.entities.ResultConfigclass stores the configuration information from struts.xml for each result configured with Action class. Thecom.opensymphony.xwork2.config.entities.ResultTypeConfigclass stores information about result type in struts.xml for each action class. Default Parameter: To minimize configuration, Results can be configured with default value in the struts.xml configuration file. For example, here is a result defined in XML that uses a default parameter: <result>/Success.jsp</result> That is the equivalent to this: <result name=\"success\"type=\"dispatcher\"> <param name=\"location\">/Success.jsp</param> </result> Result Configuration: When method of action class completes, it returns a String value. This value of the String(\"success\", \"input\", \"error\" etc ) is used to select a result element in struts.xml configuration file. The String value matched with an action mapping will often have a set of results representing different possible outcomes. A standard set of result tokens are defined by theActionSupportbase class. Predefined result names in Action interface : String SUCCESS = \"success\"; String NONE = \"none\"; String ERROR = \"error\"; String INPUT = \"input\"; String LOGIN = \"login\"; Configure multiple results : Please interpret below code as follows. (a) If method return \"success\" it forward to /hello/Result.jsp (b) If method return \"error\" it forward to /hello/Error.jsp CU IDOL SELF LEARNING MATERIAL (SLM)

230 Advanced Internet Programming (c) If method return \"input\" it forward to /hello/Input.jsp (d) if method return other than success, error and input then forward to /hello/Other.jsp page <action name=\"Hello\"> of the <result>/hello/Result.jsp</result> <result name=\"error\">/hello/Error.jsp</result> <result name=\"input\">/hello/Input.jsp</result> <result name=\"*\">/hello/Other.jsp</result> </action> The Struts2 framework provides several implementations com.opensymphony.xwork2.Result interface, ready to use in your own applications. There are eleven types of results in Struts2 : 1. Dispatcher Result : Used for dispatch the request to other JSP page to include contents or forward contents. It is default result type. 2. Chain Result : Used for Action Chaining 3. Free Marker Result : Used for Free Marker integration 4. Redirect Result : Used to redirect to another URL 5. Redirect Action Result: Used to redirect to another action mapping 6. Stream Result: Used to stream an InputStream back to the browser 7. Velocity Result: Used for Velocity integration 8. XSL Result : Used for XML/XSLT integration 9. PlainText Result: Used to display the raw content of a particular page The user defined result types can be categorized as follows: Result Types Dispatcher Result Redirect Result Velocity Result Chain Result Redirect Action XSL Result FreeMarker Result Stream Result PlainText Result Fig. 10.9: Result Types CU IDOL SELF LEARNING MATERIAL (SLM)

Java Struts - I 231 1. Dispatcher Result:  The dispatcher result is used to include or forward to a target view page (JSP). It is default result type in Struts2 framework.  It uses RequestDispatcher interface to achieve it, where the target Server or JSP receive the same request and response either using forward() or include() method. 2. Chain Action Result:  It is used to achieve action chaining. In the action chaining the multiple actions can be executed in defined sequence. And the target view page will be displayed after last action. In the chain result type, the target resource will be any action which is already configured in struts.xml file 3. FreeMarker Result:  It is used to integrate the Freemarker templates in the view page. The Freemarker engine renders the freemarker view page and extension will be .ftl of view page. 4. Redirect Result:  The redirect result is used to redirect the browser request to the new resource. It works based on HttpServletResponse.sendRedirect() method. It is redirected by browser and the target resource can be part of the same application or cannot be part of the same application. That is, the resource should be apart from the application resources. 5. Redirect Action  Redirect action is same as redirect result type. But here, the target result must be an action either in same application or in the other application. It can be used for both the purposes. 6. Stream Result  Streaming refers to input stream and output stream classes in java.  It is used to Streaming the InputStream back to the client and client can download the content in the specified format. This is very useful for allowing users to download content from our web application in any format, for example, pdf, doc, xls etc. 10.11 File Uuploads ThefileUploadinterceptor automatically works for all the requests that includes files. CU IDOL SELF LEARNING MATERIAL (SLM)

232 Advanced Internet Programming We can use this interceptor to control the working of file upload in struts2 such as defining allowed types, maximum file size etc. Parameters of fileupload interceptor There are 2 parameters defined for fileupload interceptor. Parameter Table 10.1: Parameters of fileupload Interceptor MaximumSize Description allowedTypes specifies maximum size of the file to be uploaded. specifies allowed types. It may be image/png, image/jpg etc. Automatically added parameters It automatically adds 2 parameters in the request: 1. String fileNamerepresents the filename of the file. 2. String contentTypespecifies the content type of the file. Image upload example using struts 2 Let's see the directory structure of file upload application. Fig. 10.10: Struts2 Upload Application CU IDOL SELF LEARNING MATERIAL (SLM)

Java Struts - I 233 1. Create UserImage.jsp This jsp page creates a form using struts UI tags. It receives file from the user. index.jsp <%@pagecontentType=\"text/html;charset=UTF- <s:actionerror/> 8\"%> <s:formaction=\"userImage\"method=\"post\"enc <%@taglibprefix=\"s\"uri=\"/struts-tags\"%> type=\"multipart/form-data\"> <html> <s:filename=\"userImage\"label=\"Image\"/> <head> <title>UploadUserImage</title> </head> <s:submitvalue=\"Upload\"align=\"center\"/> <body> </s:form> <h2> </body> Struts2FileUpload&SaveExamplewithoutDatabas </html> e </h2> 2. Create SuccessUserImage.jsp This jsp page creates a form using struts UI tags. It receives name, password and email id from the user. SuccessUserImage.jsp <%@pagecontentType=\"text/html;charset=UTF UserImage:<s:propertyvalue=\"userImage\"/><br/ -8\"%><%@taglibprefix=\"s\" > uri=\"/struts-tags\"%> ContentType:<s:propertyvalue=\"userImageCont <html> entType\"/><br/> <head> <title>Success:UploadUserImage</title> FileName:<s:propertyvalue=\"userImageFileNa me\"/><br/> </head> <body> UploadedImage:<imgsrc=\"userimages/<s:prope <h2> Struts2FileUploadExample </h2> rtyvalue=\"userImageFileName\"/>\" width=\"100\"height=\"100\"/> </body> </html> 3. Create the action class This action class inherits the ActionSupport class and overrides the execute method. RegisterAction.java package com.javatpoint; File import java.io.File; Utils.copyFile(userImage,fileToCreate);//copyi CU IDOL SELF LEARNING MATERIAL (SLM)

234 Advanced Internet Programming impor tjavax.servlet.http.HttpServletRequest; ngsourcefiletonewfile return SUCCESS; import org.apache.commons.io.FileUtils; } public void setUserImage(FileuserImage) { import this.userImage=userImage; } com.opensymphony.xwork2.ActionSupport; publicStringgetUserImageContentType() { returnuserImageContentType; } public class publicvoidsetUserImageContentType(Stringus FileUploadActionextendsActionSupport { erImageContentType) { this.userImageContentType=userImageConte private FileuserImage; ntType; } private StringuserImageContentType; publicStringgetUserImageFileName() { returnuserImageFileName; } private StringuserImageFileName; publicvoidsetUserImageFileName(StringuserI mageFileName) { public Stringexecute() { this.userImageFileName=userImageFileName ; try { }} StringfilePath=ServletActionContext.getServletC ontext().getRealPath(\"/\").concat(\"userimages\"); System.out.println(\"ImageLocation:\"+filePath);//s eetheserverconsoleforactuallocation File fileToCreate=newFile(filePath,userImageFileNa me); public FilegetUserImage() { return userImage; } 4. Create struts.xml This xml file defines an extra result by the name input, and an interceptor jsonValidatorWorkflowStack. struts.xml <paramname=\"allowedTypes\"> <!DOCTYPEstrutsPUBLIC image/png,image/gif,image/jpeg,image/pj \"- peg //ApacheSoftwareFoundation//DTDStrutsConfiguratio n2.0//EN\" </param> \"http://struts.apache.org/dtds/struts-2.0.dtd\"> <struts> </interceptor-ref> <packagename=\"fileUploadPackage\"extends=\"struts -default\"> <interceptor- <actionname=\"userImage\"class=\"com.javatpoint.File refname=\"defaultStack\"></interceptor- UploadAction\"> ref> <interceptor-refname=\"fileUpload\"> <paramname=\"maximumSize\">2097152</param> <resultname=\"success\">SuccessUserIma ge.jsp</result> <resultname=\"input\">UserImage.jsp</res ult> </action> </package> </struts> CU IDOL SELF LEARNING MATERIAL (SLM)

Java Struts - I 235 Output 10.12 Database Access Login Application in Struts2 with Database Access.  It is a complete web application in Struts 2. The program creates login application without validations.  The program uses static user name and password. The same program can be modified to have dynamic authentication by using the data stored from database. This will require creation of DOJO classes and JSON objects.  The program prints username on successful login attempt and error page on failure or error event. // first.jsp <%-- Document : first Created on : Nov 14, 2014, 12:49:46 PM Author : Infinity --%> <%@page contentType = \"text/html\" pageEncoding = \"UTF-8\"%> <%@taglib uri = \"/struts-tags\" prefix = \"s\" %> <!DOCTYPE html> CU IDOL SELF LEARNING MATERIAL (SLM)

236 Advanced Internet Programming <html> <body> <h1> Login Application </h1> <hr/> <s:form action = \"verify\"> <s:textfield name = \"uname\" label = \"Enter Username\" /> <br> <s:password name = \"password\" label = \"Enter Password\" /> <br> <s:submit value = \"Login\" align = \"center\" /> </s:form> </body> </html> ? // Redirect.java /* * To change this license header, choose License Headers in Project Properties. * To change this template file, choose Tools | Templates * and open the template in the editor. */ package jsp_action; import com.opensymphony.xwork2.ActionSupport; public class Redirect extends ActionSupport{ private static final long serialVersionUID = 1L; private String uname,password; public String getUname() { return uname; } public void setUname(String uname) { this.uname = uname; } public String getPassword() { return password; } public void setPassword(String password) { this.password = password; } public String execute() { if(uname.equals(\"abc\") && password.equals(\"xyz\")) CU IDOL SELF LEARNING MATERIAL (SLM)

Java Struts - I 237 { return SUCCESS; }else return ERROR; }} // successpage.jsp <%-- Document : next Created on : Nov 14, 2014, 1:19:42 PM Author : Infinity --%> <%@page contentType = \"text/html\" pageEncoding = \"UTF-8\"%> <%@taglib prefix = \"s\" uri = \"/struts-tags\" %> <!DOCTYPE html> <h1> Welcome <s:property value = \"uname\" />, you have been successfully logged in.. </h1> <hr/> //errorpage.jsp <%@ taglib prefix = \"s\" uri = \"/struts-tags\" %> <%-- <!DOCTYPE html> <html> Document : errorpage Created on : Feb 6, 2015, 6:43:24 PM <body> Author : Infinity Login failed...! --% <%@page contentType = \"text/html\" </body> </html> pageEncoding = \"UTF-8\"%> <package name = \"default\" extends = \"struts- // struts.xml default\"> <!DOCTYPE struts PUBLIC \"-//Apache Software Foundation//DTD <action name = \"verify\" class = Struts Configuration 2.0//EN\" \"jsp_action.Redirect\"> \"http://struts.apache.org/dtds/struts- 2.0.dtd\"> <result name = \"success\"> successpage.jsp <struts> </result> <result name = \"error\"> errorpage.jsp </result> </action> </package> </struts> CU IDOL SELF LEARNING MATERIAL (SLM)

238 Advanced Internet Programming // web.xml <?xml version = \"1.0\" encoding = \"UTF-8\"?> <web-app version = \"3.1\" xmlns = \"http://xmlns.jcp.org/xml/ns/javaee\" xmlns:xsi = = \"http://www.w3.org/2001/XMLSchema-instance\" xsi:schemaLocation \"http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd\"> <filter> <filter-name>struts2</filter-name> <filter-class>org.apache.struts2.dispatcher.FilterDispatcher</filter-class> </filter> <filter-mapping> <filter-name>struts2</filter-name> <url-pattern>/*</url-pattern> </filter-mapping> <session-config> <session-timeout> 30 </session-timeout> </session-config> <welcome-file-list> <welcome-file>jsp/first.jsp</welcome-file> </welcome-file-list> </web-app> The application will run as follows: CU IDOL SELF LEARNING MATERIAL (SLM)

Java Struts - I 239 First screenshot unsuccessful login attempt second run of application 10.13 Practical Assignment 1. Create Struts application to give demo of Date Range Field Validator. 2. Create Form Handling with Struts. CU IDOL SELF LEARNING MATERIAL (SLM)

240 Advanced Internet Programming 10.14 Summary .A framework that allowed them to focus on building their application without spending a lot of time writing the code that organized and coordinated processing. After reviewing a number of other competing frameworks, they settled on Struts for a number of reasons—some technical and some not. The Struts technical features that were important to them were:  Struts performs well.  Struts has a sound architectural model with a modest learning curve.  Struts is very solid and stable.  Struts has a strong set of custom tag libraries that simplify JSP development. 10.15 Key Words/Abbreviations  Interceptors: Interceptors are used in conjunction with Java EE managed classes to allow developers to invoke interceptor methods on an associated target class, in conjunction with method invocations or lifecycle events. Common uses of interceptors are logging, auditing, and profiling.  Velocity: Velocity is a Java-based template engine. It permits web page designers to reference methods defined in Java code. 10.16 Learning Activity 1. Explain the five core components of configuration. ----------------------------------------------------------------------------------------------------------- ----------------------------------------------------------------------------------------------------------- 2. Explain ActionSupport Class. ----------------------------------------------------------------------------------------------------------- ----------------------------------------------------------------------------------------------------------- CU IDOL SELF LEARNING MATERIAL (SLM)

Java Struts - I 241 10.17 Unit End Questions (MCQs and Descriptive) A. Descriptive Types Questions 1. Explain MVC architecture with the help of suitable diagram. 2. Explain steps for Environment setup of Struts. 3. Explain Configuration of struts 2. 4. What are Actions in Struts? Explain Execution flow of Actions. 5. Write short notes on interceptors in Struts. 6. What is value stack in Struts? state and explain Execution flow. 7. Explain Result types in Struts. 8. Explain steps to upload File through Struts. 9. Explain with any suitable example of database Access by using Struts. B. Multiple Choice/Objective Type Questions 1. Which technology can be used at View Layer in Struts? (a) J2EE (b) DHTML (c) XML/XSLT (d) JavaScript 2. ActionServlet, RequestProcessor and Action classes are the components of __________. (a) View (b) Model (c) Controller (d) Deployment 3. Which of the following acts as a bridge between user-invoked URL and a business method? (a) RequestProcessor (b) ActionServlet (c) Action Class (d) HttpRequest 4. The Dispatch from the controller to the action class is based on a configuration that is provided by a __________. (a) struts-config.xml (b) strts-processor-conifg.xml (c) struts-configs.xml (d) struts-action-config.xml CU IDOL SELF LEARNING MATERIAL (SLM)