Java EE Application Development using Tomcat, OpenEJB and Hibernate
Before I start writing this blog entry, I’d better point out a few things.
- This blog entry is not about how to make a good Java EE application yet is about how to use OpenEJB on Apache Tomcat server with Hibernate as an implementation of the JPA. If you are looking for better Java EE development or similar, this one is not for you. Image may be NSFW.
Clik here to view. - I don’t have enough time to explain all the details of how to install JDK, Eclipse, Tomcat and so on. So this post doesn’t have that level of details. I simply assume that you’ve already known how to install JDK, Eclipse and Tomcat. Well, anyway, installing Eclipse and Tomcat are as easy as extracting a zip or gzip file and JDK installation is also not difficult at all.
- This post does not cover how to use those tools and frameworks in the production environment. In other words, it is only for the development. Setting up the environment for development and for the production use have some differences. It is, however not that hard to figure out once you know how to use those in your development environment.
1. Development Environment
First of all, I’m going to list the development environment and tools I have for this introductory tutorial post.
(Click each name and it will take you to the download page).
OS: Ubuntu Linux Jaunty Jackalope 9.04 Desktop 64bit
Java: Sun JDK 1.6.0_16 (64 bit) (it’s from the Ubuntu repository).
Database: MySQL Community Server 5.0 (it’s from the Ubuntu repository).
JDBC Driver: MySQL Connector/J 5.1.10
Eclipse: Eclipse IDE for Java EE Developer Ganymede SR2 (Eclipse 3.4.2)
Tomcat: Tomcat 6.0.20
OpenEJB: OpenEJB 3.1.1 (openejb.war)
Hibernate: Hibernate 3.2.1GA (including hibernate-3.2.1.ga, hibernate-annotations-3.2.1.ga, hibernate-entitymanager-3.2.1.ga) (OR just >>download this<<)
2. Installing OpenEJB
Java EE server normally means a Java application server which consists of a Servlet container and an EJB container. Apache Tomcat is a servlet container but not an EJB container so you need to have an EJB container like OpenEJB or use a Java EE server instead of Tomcat in order to use EJB unless you’re using the frameworks supporting EJB such as Spring framework. “So if I use Tomcat server and Spring framework, do I not need OpenEJB or other Java EE servers to use EJB?” No, you don’t.
Since this post is, as already mentioned, about using using EJB on Tomcat with OpenEJB and Hibernate, I will first show you how to install OpenEJB.
Before installing OpenEJB, don’t forget to copy JDBC driver that is, in this post, MySQL Connector/J to the $TOMCAT/lib directory.
-Copy the Connector/J jar file to the Tomcat’s library directory ($TOMCAT_HOME/lib)
Clik here to view.

Select Connector/J and Extract to the $TOMCAT/lib directory.
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Make sure the Connector/J jar file is in the $TOMCAT/lib directory.
-Run Eclipse and add Tomcat server: Menu – Window -> Preferences -> Server -> Runtime Environments -> Add
-Download the openejb.war, OpenEJB for Tomcat, and import the file from Eclipse.
-Right click on the project explorer -> Import -> WAR file
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Right Click on the project explorer -> Import -> WAR File
-Click the ‘Browse’ button and select the openejb.war file -> Select your Tomcat 6.0 as the target runtime. -> Click the ‘Finish’ button.
Clik here to view.

Click the 'Browse' button and select the openejb.war file -> Select your Tomcat 6.0 as the target runtime. -> Click the 'Finish' button.
3. Add OpenEJB project to the Server to deploy
-Right click on the server name in the ‘Server’ view -> Select the ‘Add and Remove Projects…’
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Right click on the server name in the 'Server' view -> Select the 'Add and Remove Projects...'
-Select openejb -> Click the ‘Add’ button -> Click the ‘Finish’ button
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Select openejb -> Click the 'Add' button -> Click the 'Finish' button
-openejb is ready to be deployed.
Clik here to view.

openejb is deployed.
-Now run the server to deploy openejb.
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Run the server to deploy openejb
-openejb is successfully deployed.
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the openejb is successfully deployed.
4. Set up DataSource
-openejb.xml has to be copied to the Tomcat configuration folder of the Eclipse workspace.
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openejb.xml has to be copied to the Tomcat configuration folder of the Eclipse workspace.
If you are using Tomcat without OpenEJB and want to create a DataSource, you might do by putting the DataSource info to Tomcat’s server.xml file or your application’s context configuration file (your_app/META-INF/context.xml). Yet to create the DataSource for JPA, you need to do through openejb.xml
file. It is created in the Tomcat folder in the .metadata
folder of your Eclipse workspace when the openejb project is deployed. However, it is not copied automatically to the configuration folder of your Eclipse workspace, you should copy the openejb.xml file to the Server configuration folder manually. If the location of the workspace is ‘/home/username/workspace’, the Tomcat is in ‘/home/username/test-workspace/.metadata/.plugins/org.eclipse.wst.server.core’ and the openejb.xml file can be found in the ‘/home/username/workspace/.metadata/.plugins/org.eclipse.wst.server.core/tmp0/conf’ directory.
-Find the openejb.xml file and copy to the Tomcat configuration folder of the Eclipse workspace.
Clik here to view.

Find the openejb.xml file and copy to the Tomcat configuration folder of the Eclipse workspace.
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Paste the file to the Tomcat configuration folder of the Eclipse workspace.
-Open the ‘openejb.xml’ file then you can find the default DataSources.
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Open the 'openejb.xml' file then you can find the default DataSources
One is JTA managed while the other is not. Both use HSQLDB which is a Java database. If you don’t have any database installed on you computer or if you want, you can use it. As mentioned early, I am going to use MySQL so a new data source set up for MySQL is required.
-Add the following lines and modify for your own database.
<Resource id="mysqlDataSource" type="javax.sql.DataSource"> JdbcDriver com.mysql.jdbc.Driver JdbcUrl jdbc:mysql://localhost:3306/test_db UserName test_user Password 1234 JtaManaged true DefaultAutoCommit true InitialSize 3 MaxActive 20 MinIdle 20 MaxIdle 0 MaxWait 50000 ValidationQuery SELECT 1 TestOnBorrow true TestOnReturn false TestWhileIdle false </Resource>
Clik here to view.

DataSource to access the MySQL database.
If you want to use OpenJPA as an implmentation of the JPA, you can do now. However, to use Hibernate there is one more step to do.
5. Install Hibernate
If you just have the Hibernate jar files in your application directory (e.g. your_app/WEB-INF/lib), the EJB container that is OpenEJB cannot find the hibernate classes as it is the container, it tries to find the hibernate class from the server’s lib directory. Thus just like you need to copy the JDBC driver, in this post it’s ‘Connector/J’, to the tomcat’s lib directory, the hibernate jar files should be placed in the Tomcat’s lib directory.
Otherwise, you will get an error like this.
ERROR - Unable to deploy collapsed ear in war /test-web-hibernate: Exception: Creating application failed: /home/username/workspace/.metadata/.plugins/org.eclipse.wst.server.core/tmp0/wtpwebapps/test-web-hibernate: java.lang.ClassNotFoundException: org.hibernate.ejb.HibernatePersistence: org.hibernate.ejb.HibernatePersistence org.apache.openejb.OpenEJBException: Creating application failed: /home/username/workspace/.metadata/.plugins/org.eclipse.wst.server.core/tmp0/wtpwebapps/test-web-hibernate: java.lang.ClassNotFoundException: org.hibernate.ejb.HibernatePersistence: org.hibernate.ejb.HibernatePersistence at org.apache.openejb.assembler.classic.Assembler.createApplication(Assembler.java:658) at org.apache.openejb.assembler.classic.Assembler.createApplication(Assembler.java:442) at org.apache.openejb.tomcat.catalina.TomcatWebAppBuilder.start(TomcatWebAppBuilder.java:249) at org.apache.openejb.tomcat.catalina.GlobalListenerSupport.lifecycleEvent(GlobalListenerSupport.java:58) at org.apache.catalina.util.LifecycleSupport.fireLifecycleEvent(LifecycleSupport.java:119) at org.apache.catalina.core.StandardContext.start(StandardContext.java:4339) at org.apache.catalina.core.StandardContext.reload(StandardContext.java:3190) at org.apache.catalina.loader.WebappLoader.backgroundProcess(WebappLoader.java:404) at org.apache.catalina.core.ContainerBase.backgroundProcess(ContainerBase.java:1309) at org.apache.catalina.core.ContainerBase$ContainerBackgroundProcessor.processChildren(ContainerBase.java:1601) at org.apache.catalina.core.ContainerBase$ContainerBackgroundProcessor.processChildren(ContainerBase.java:1610) at org.apache.catalina.core.ContainerBase$ContainerBackgroundProcessor.processChildren(ContainerBase.java:1610) at org.apache.catalina.core.ContainerBase$ContainerBackgroundProcessor.run(ContainerBase.java:1590) at java.lang.Thread.run(Thread.java:619) Caused by: org.apache.openejb.OpenEJBException: java.lang.ClassNotFoundException: org.hibernate.ejb.HibernatePersistence: org.hibernate.ejb.HibernatePersistence at org.apache.openejb.assembler.classic.Assembler.createApplication(Assembler.java:487) ... 13 more Caused by: java.lang.ClassNotFoundException: org.hibernate.ejb.HibernatePersistence at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1387) at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1233) at org.apache.openejb.assembler.classic.PersistenceBuilder.createEntityManagerFactory(PersistenceBuilder.java:177) at org.apache.openejb.assembler.classic.Assembler.createApplication(Assembler.java:482) ... 13 more
Click Here to Download the File!
After downloading, extract all the files inside to the Tomcat’s lib directory ($TOMCAT/lib
) just like what you did to install JDBC driver, Connector/J.
6. Adding logger configuration (Optional)
By default, OpenEJB creates a log file in the Eclipse’s $TOMCAT/logs directory. It is very inconvenient as you have to open the file when you want to get information from the log. However, it is very easy to change this to make it displayed on the Console view of Eclipse.
-Right click on the Tomcat configuration folder -> Select ‘New’ -> Select ‘File’ -> crated a file with the name ‘logging.properties’.
Clik here to view.

Right click on the Tomcat configuration folder -> Select 'New' -> Select 'File' -> crated a file with the name 'logging.properties'.
-Open the file and put the following lines
log4j.rootLogger = fatal,C log4j.category.OpenEJB = warn log4j.category.OpenEJB.options = info log4j.category.OpenEJB.server = info log4j.category.OpenEJB.startup = info log4j.category.OpenEJB.startup.service = warn log4j.category.OpenEJB.startup.config = info log4j.category.OpenEJB.hsql = info log4j.category.CORBA-Adapter = info log4j.category.Transaction = warn log4j.category.org.apache.activemq = error log4j.category.org.apache.geronimo = error log4j.category.openjpa = error log4j.appender.C = org.apache.log4j.ConsoleAppender log4j.appender.C.layout = org.apache.log4j.SimpleLayout
Clik here to view.

Put the logger config details
7. Create Web Application Project
Now, you can develop a web application using EJB3 and Hibernate as the implementation of the JPA.
-Right click on the project explorer -> Select ‘New’ -> Select ‘Dynamic Web Project’
Clik here to view.

Right click on the project explorer -> Select 'New' -> Select 'Dynamic Web Project'
-Put the name you like -> Select the ‘Apache Tomcat v6.0′ as the target runtime -> Select ’2.5′ as the version of ‘Dynamic Web Module’ -> Select the default Tomcat configuration or your own one -> Click the ‘Next’ button.
Clik here to view.

Put the name you like -> Select the 'Apache Tomcat v6.0' as the target runtime -> Select '2.5' as the version of 'Dynamic Web Module' -> Select the default Tomcat configuration or your own one -> Click the 'Next' button.
-Change the project context root and directory names if you like -> Click the ‘Finish’ button.
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Change the project context root and directory names if you like -> Click the 'Finish' button.
-Right click on the Server to add the project -> Select the ‘Add and Remove Projects…’.
Clik here to view.

Right click on the Server to add the project -> Select the 'Add and Remove Projects...'.
-Select the project you created -> Click the ‘Add’ button -> Click the ‘Finish’ button.
Clik here to view.

Select the project you created -> Click the 'Add' button -> Click the 'Finish' button.
-Both openejb and your project are added.
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Both openejb and your project are added.
8. Make JPA Project
To use the JPA support feature of Eclipse, you need to change the project facet configuration.
-Right click on your project -> Select the ‘Properties’.
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Right click on your project -> Select the 'Properties'.
-Select the ‘Project Facets’ -> Check ‘Java Persistence 1.0′ -> Click the ‘Further configuration available…’ link.
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Select the 'Project Facets' -> Check 'Java Persistence 1.0' -> Click the 'Further configuration available...' link.
-Select ‘Generic’ -> Select ‘None’ or your own connection or add a new connection if you wish -> Select ‘Use implementation provided by server runtime’ -> Select ‘Discover annotated classes automatically’ -> Uncheck ‘Create orm.xml’ option -> Click the ‘OK’ button.
Clik here to view.

Select 'Generic' -> Select 'None' or your own connection or add a new connection if you wish -> Select 'Use implementation provided by server runtime' -> Select 'Discover annotated classes automatically' -> Uncheck 'Create orm.xml' option -> Click the 'OK' button.
(I do usually not set up the connection yet if you want to generate entity classes from the existing tables, you’d better set it up).
9. Add Java EE 5 API library file
You also need to add the Java EE 5 API library file so you can use all the necessary annotations required for EJB3 and JPA.
-Select ‘Java Build Path on the left-hand side menu -> Select the ‘Libraries’ tab -> Click the ‘Add JARs…’ button.
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Select 'Java Build Path on the left-hand side menu -> Select the 'Libraries' tab -> Click the 'Add JARs...' button.
-Select ‘javaee-api-5.0-2.jar in the openejb/WebContent/lib directory -> Click the ‘OK’ button.
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Select 'javaee-api-5.0-2.jar in the openejb/WebContent/lib directory -> Click the 'OK' button.
-Click the ‘OK’ button.
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Click the 'OK' button.
-JPA configuration file (persistence.xml) is added.
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JPA configuration file (persistence.xml) is added
10. Configure persistence.xml file
It’s the last step before starting to programme the actual application.
-Open the persistence.xml file -> Type ‘org.hibernate.ejb.HibernatePersistence’ to the ‘Persistence Provider’.
org.hibernate.ejb.HibernatePersistence
Clik here to view.

Open the persistence.xml file -> put 'org.hibernate.ejb.HibernatePersistence' to the 'Persistence Provider'.
-Click the ‘Connection’ tab -> Select the ‘JTA’ as the ‘Transaction Type’ -> Type ‘mysqlDataSource’ or your datasource name added in the previous steps. -> Press ‘Ctrl + S’ keys to save the file.
Clik here to view.

Click the 'Connection' tab -> Select the 'JTA' as the 'Transaction Type' -> Type 'mysqlDataSource' or your datasource name added in the previous steps. -> Press 'Ctrl + S' keys to save the file.
-If you select the ‘Source’ tab, you should see the XML like this.
Clik here to view.

If you select the 'Source' tab, you should see the XML like above.
<?xml version="1.0" encoding="UTF-8"?> <persistence version="1.0" xmlns="http://java.sun.com/xml/ns/persistence" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/persistence http://java.sun.com/xml/ns/persistence/persistence_1_0.xsd"> <persistence-unit name="test-web-hibernate" transaction-type="JTA"> <provider>org.hibernate.ejb.HibernatePersistence</provider> <jta-data-source>mysqlDataSource</jta-data-source> </persistence-unit> </persistence>
-If you want Hibernate to automatically create the database tables based on your entity classes every time the server is restarted (in other words, the application is re-deployed), You can add Hibernate specific properties.
<?xml version="1.0" encoding="UTF-8"?> <persistence version="1.0" xmlns="http://java.sun.com/xml/ns/persistence" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/persistence http://java.sun.com/xml/ns/persistence/persistence_1_0.xsd"> <persistence-unit name="test-web-hibernate" transaction-type="JTA"> <provider>org.hibernate.ejb.HibernatePersistence</provider> <jta-data-source>mysqlDataSource</jta-data-source> <properties> <property name="hibernate.hbm2ddl.auto" value="create" /> </properties> </persistence-unit> </persistence>
11. Test
Finally, we have the development environment ready. To test, if I can use EJB3 and JPA with Hibernate on Tomcat, I made a very simple application. The way I design it is not my usual way yet I used Generic DAO pattern which I usually use.
11.1. Entity classes
Here is my only entity class in this test.
package com.lckymn.kevin.test.openejb.domain; import java.io.Serializable; import javax.persistence.Column; import javax.persistence.Entity; import javax.persistence.GeneratedValue; import javax.persistence.GenerationType; import javax.persistence.Id; import javax.persistence.Table; @Entity @Table(name = "users") public class User implements Serializable { private static final long serialVersionUID = 1L; @Id @GeneratedValue(strategy = GenerationType.AUTO) @Column(name = "user_id") private Long id; @Column(name = "username", nullable = false, length = 30) private String username; @Column(name = "surname", nullable = false, length = 50) private String surname; @Column(name = "given_name", nullable = false, length = 50) private String givenName; @Column(name = "email", nullable = true, length = 255) private String email; public Long getId() { return id; } public String getUsername() { return username; } public void setUsername(String username) { this.username = username; } public String getSurname() { return surname; } public void setSurname(String surname) { this.surname = surname; } public String getGivenName() { return givenName; } public void setGivenName(String givenName) { this.givenName = givenName; } public String getEmail() { return email; } public void setEmail(String email) { this.email = email; } @Override public boolean equals(Object obj) { if (this == obj) { return true; } if (!(obj instanceof User)) { return false; } User that = (User) obj; return (username == that.getUsername() || (null != username && username.equals(that.getUsername()))); } @Override public int hashCode() { return (null == username ? 0 : username.hashCode()); } }
11.2. Generic DAOs
package com.lckymn.kevin.test.openejb.dao; public interface GenericDao<E, K> { E find(K id); void persist(E e); void remove(E e); }
package com.lckymn.kevin.test.openejb.dao; import java.lang.reflect.ParameterizedType; import javax.persistence.EntityManager; import javax.persistence.PersistenceContext; public abstract class AbstractGenericDao<E, K> implements GenericDao<E, K> { private Class<E> classType; @PersistenceContext(unitName = "test-web-hibernate") private EntityManager entityManager; @SuppressWarnings("unchecked") public AbstractGenericDao() { ParameterizedType parameterizedType = (ParameterizedType) getClass().getGenericSuperclass(); classType = (Class<E>) parameterizedType.getActualTypeArguments()[0]; } protected final EntityManager getEntityManager() { if (null == entityManager) { throw new IllegalStateException("EntityManager is not injected."); } return entityManager; } @Override public E find(K id) { return getEntityManager().find(classType, id); } @Override public void persist(E e) { getEntityManager().persist(e); } @Override public void remove(E e) { getEntityManager().remove(e); } }
package com.lckymn.kevin.test.openejb.dao; import java.util.List; import javax.ejb.Local; import com.lckymn.kevin.test.openejb.domain.User; @Local public interface UserDao extends GenericDao<User, Long> { List<User> getUsersByGivenName(String givenName); }
package com.lckymn.kevin.test.openejb.dao; import java.util.List; import javax.ejb.Stateless; import com.lckymn.kevin.test.openejb.domain.User; @Stateless public class UserDaoImpl extends AbstractGenericDao<User, Long> implements UserDao { @SuppressWarnings("unchecked") @Override public List<User> getUsersByGivenName(String givenName) { return getEntityManager().createQuery("from User where givenName = ?") .setParameter(1, givenName) .getResultList(); } }
11.3. Services
package com.lckymn.kevin.test.openejb.service; import java.util.List; import javax.ejb.Local; import com.lckymn.kevin.test.openejb.domain.User; @Local public interface UserService { User getUser(long id); void AddUser(User user); List<User> getUserByGivenName(String givenName); }
package com.lckymn.kevin.test.openejb.service; import java.util.List; import javax.ejb.EJB; import javax.ejb.Stateless; import com.lckymn.kevin.test.openejb.dao.UserDao; import com.lckymn.kevin.test.openejb.domain.User; @Stateless public class UserServiceBean implements UserService { @EJB private UserDao userDao; @Override public User getUser(long id) { return userDao.find(id); } @Override public void AddUser(User user) { userDao.persist(user); } @Override public List<User> getUserByGivenName(String givenName) { return userDao.getUsersByGivenName(givenName); } }
11. 4. Servlets
package com.lckymn.kevin.test.openejb.web; import java.io.IOException; import javax.ejb.EJB; import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import javax.servlet.http.HttpSession; import com.lckymn.kevin.test.openejb.domain.User; import com.lckymn.kevin.test.openejb.service.UserService; public class TestServlet extends HttpServlet { private static final long serialVersionUID = 1L; @EJB private UserService userService; protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { doPost(request, response); } protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { User user = new User(); user.setUsername("kevinlee"); user.setSurname("Lee"); user.setGivenName("Kevin"); user.setEmail("test@test.test"); userService.AddUser(user); HttpSession session = request.getSession(); session.setAttribute("user", user); getServletContext().getRequestDispatcher("/index.jsp") .forward(request, response); } }
11.5. Deployment Descriptor (web.xml)
<?xml version="1.0" encoding="UTF-8"?> <web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xmlns:web="http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" id="WebApp_ID" version="2.5"> <display-name>test-web-hibernate</display-name> <servlet> <description></description> <display-name>TestServlet</display-name> <servlet-name>TestServlet</servlet-name> <servlet-class>com.lckymn.kevin.test.openejb.web.TestServlet</servlet-class> </servlet> <servlet-mapping> <servlet-name>TestServlet</servlet-name> <url-pattern>/Test</url-pattern> </servlet-mapping> <welcome-file-list> <welcome-file>index.jsp</welcome-file> </welcome-file-list> </web-app>
11. 6. index.jsp
<?xml version="1.0" encoding="UTF-8" ?> <%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8"%> <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml"> <head> <meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /> <title>Insert title here</title> </head> <body> <div> <table> <tr> <td>User ID: </td><td>${user.id }</td> </tr> <tr> <td>Username: </td><td>${user.username }</td> </tr> <tr> <td>Surname: </td><td>${user.surname }</td> </tr> <tr> <td>Given name: </td><td>${user.givenName }</td> </tr> <tr> <td>Email: </td><td>${user.email }</td> </tr> </table> </div> </body> </html>
12. Run the test application
Access the application URI
http://localhost:8080/test-web-hibernate/Test
It gives me this result.
User ID: 1 Username: kevinlee Surname: Lee Given name: Kevin Email: test@test.test
Note: Whenever you make changes in your application, Tomcat restarts the application context so that you don’t need to restart the server to apply the changes you made. However, as mentioned several times, you are now using the EJB container so restarting application context is not enough to get your changes applied. Therefore, the EJB container has to be restarted which means you need to restart the Tomcat server to get the changes applied.