10년후의 미래는 현재가 말해준다

In this exercise, you are going to build a Web application step by step in which a servlet invokes a method of an EJB.  You will see both servlet and EJB beans are included in a single war file.

(1.1) Create a new project

0. Start NetBeans IDE. 
1. Create a new Web project.

Figure-1.11

Figure-1.12

Figure-1.13

(1.2) Create a Session bean

Figure-1.21

Figure-1.21a

Figure-1.22

2. Modify IDE generated MySessionBean.java as shown below.  The modification is to add a simple business method called sayHello(..) to the bean.

Figure-1.23

(1.3) Create a Servlet

Figure-1.31

Figure-1.32

2. Inject MySessionBean into the servlet.

• Type @EJB My and observe code completion feature kicks in. (If the code completion does not appear, press CTRL+Space or CTRL+CMD+Backslash on Mac OS X.)
  
• Select MySessionBean  (server).
  
• Type client;  
  

Figure-1.33

• Observe that you have added the line in bold and red-colored font below.
  

... @WebServlet(name="HelloServlet", urlPatterns={"/HelloServlet"}) public class HelloServlet extends HttpServlet {     @EJB MySessionBean client;        /**      * Processes requests for both HTTP <code>GET</code> and <code>POST</code> methods.      * @param request servlet request      * @param response servlet response      * @throws ServletException if a servlet-specific error occurs      * @throws IOException if an I/O error occurs      */     protected void processRequest(HttpServletRequest request, HttpServletResponse response)     throws ServletException, IOException { ...

3. Fix imports.

Figure-1.34

4. Call the EJB.

Figure-1.35

NetBeans Tip: You can leverage code-completion feature of the IDE as shown below.  When you type client. and press CTRL+SPACE ( CTRL+Space or CTRL+CMD+Backslash on Mac OS X.), observe that sayHello(String name) is one of the selections.

Figure-1.36

(1.4) Build and run the application

Figure-1.41

Figure-1.42

2. Build and run the application.

Figure-1.43

Figure-1.44

                                                                                                                    (1.5) Check the war file

Figure-1.51

Solution: The solution of this exercise is provided as "ready to build and run" NetBeans project as EJB-in-a-war under <LAB_UNZIPPED_DIRECTORY>/javaee6_ejb3.1/solutions directory. 

Summary

In this exercise,  you built a Web application in which EJB is used.  You observed that you don't need to create EJB module jar file and you don't have to create EAR file.  Instead, the war file contains the EJB.

Singletons are POJOs just like our Session beans, and the container is guaranteed to maintain a single shared instance of this Singleton. These Singletons are thread safe and also transactional. Like all other EJB’s, singletons have all the services such as security, remoting, dependency injection, web services, interceptors and so on.

In this exercise, you are going to use a singleton-based counter, which is used as an application-wide counter.  You are also going to use @Startup annotation, which provides life-cycle methods.

1. Singleton based counter: "counter" sample application.
2. Study the code
3. Application Startup/Shutdown callbacks through @Startup

(2.1) Singleton-based counter: "counter" sample application

1. Open counter NetBeans project (from "Java EE 6 tutorial"). 

2. Build and run counter project.

• Right-click counter project and select Run.
• Browser gets displayed.
• Observe that "This page has been accessed 1 time(s)." message gets displayed.
  

Figure-2.11

• Click Refresh button to access the page again.
• Observe that the counter has been changed to 2 (from 1).
  

Figure-2.12

3. Access the application from a different user - the 2nd user.  Since the counter is application-wide scope, accessing the page from the second user should increase the counter's value to 3.

• Using another instance of the browser, or different type of browser (here Safari is being used), go to http://localhost:8080/counter/
  

Figure-2.13

• Observe that the value of the counter is increased to 3 as expected.
  

Figure-2.14

4. Access the application from the first user.  Now accessing the counter from the first user should increase the counter to 4.


Figure-2.15

• Observe that the counter is increased to 4 as expected.
  

Figure-2.16

                                                                                                                   

(2.2) Study code

(2.3) Application Startup/Shutdown callbacks

The introduction of singletons also provides a convenient way for EJB applications to receive callbacks during application initialization or shutdown. By default, the container decides when to instantiate the singleton instance. However, you can force the container to instantiate the singleton instance during application initialization by using the @Startup annotation. This allows the bean to define a @PostConstruct method that is guaranteed to be called at startup time. In addition, any @PreDestroy method for a singleton is guaranteed to be called when the application is shutting down, regardless of whether the singleton was instantiated using lazy instantiation or eager instantiation. In lazy instantiation, the singleton isn't instantiated until it's method's are first needed. In eager instantiation, the singleton is instantiated at startup time whether or not it gets used.

1. Add MyStartupBean.java to the project.

package counter.ejb; import javax.annotation.PostConstruct; import javax.annotation.PreDestroy; import javax.ejb.Singleton; import javax.ejb.Startup; @Singleton @Startup public class MyStartupBean {     @PostConstruct     private void startup() {         System.out.println("----startup() method of MyStartupBean is called");     }     @PreDestroy     private void shutdown() {         System.out.println("----shutdown() method of MyStartupBean is called");     } }

MyStartupBean.java


Figure-2.31

2. Build and run the application.

• Right-click counter project and select Run.
• Browser gets displayed.
  
• Observe that "This page has been accessed 1 time(s)." message gets displayed.

Figure-2.32

3. Observe the message "----startup() method of MyStartupBean is called" in the GlassFish v3 Domain system.log.


Figure-2.33

  Note: if you do the exercise 2 in sequence, you will see several instances of "----startup() method of MyStartupBean is called"
and "----shutdown() method of MyStartupBean is called" because the project is redeployed before it is run or because you close the browser window inbetween.

4. Undeploy the application.


Figure-2.34

5. Observe the message "----shutdown() method of MyStartupBean is called" in the GlassFish v3 Domain system.log.


Figure-2.35

Summary

In this exercise, you learned how to use @Singleton annotation.  You have also used @Startup annotation, which provides life-cycle methods.

In previous version of EJB, the only way to accomplish asynchronous processing was by using Message Driven Beans.  Even though writing MDBs was very trivial, configuring all the necessary server resources like connection factories, topics and queues made it a little bit of a chore, especially since all I needed was an asynchronous method invocation.

With EJB 3.1 these issues are easily solved by a simple annotation placed on the Session Bean: @Asynchronous. Under normal circumstances, a Session bean method call blocks the client for the duration of that call. With this annotation in place, the container returns control to the client and executes the method on a separate thread.

The Session bean method call which is annotated with the @ Asynchronous annotation can return a java.util.Future object that allows the client to retrieve a result value, check for exceptions, or attempt to cancel an in-progress invocation.

1. Asynchronous method
   
2. Study the code.
3. Asynchronous method with Future
4. Study the code
   

(4.1) Asynchronous method

In this exercise, a method, which performs a potentially long-ruuning database operration,  in ItemEJB is called with @Asynchronous.  The method returns void.

1. Open ejb3.1_asynch NetBeans project (from "Lab samples"). 

2. Build and run ejb3.1_asynch project.

• Right-click ejb3.1_asynch project and select Run.
• Browser gets displayed.
  

• For the Title field, enter Life is good! (or whatever book title of your choice).
• Click Submit Query button.
  

Figure-4.11

• Observe that the name of the Book title gets displayed.
  

Figure-4.12

                                                                                                                   

(4.2) Study code

(4.3) Open, build, and run "ejb3.1_asynch_using_Future" sample application (from "Hands-on lab samples")

In this exercise, a method, which performs a potentially long-ruuning database operration,  in ItemEJB is called with @Asynchronous.  The method returns Future object.

1. Open ejb3.1_asynch_using_Future NetBeans project. 

2. Build and run ejb3.1_asynch_using_Future project.

• Right-click ejb3.1_asynch_using_Future project and select Run.
• Browser gets displayed.

• For the Title field, enter Life is good! (or whatever book title of your choice).
• Click Submit Query button.
  

Figure-4.31


Figure-4.32

                                                                                                                   

(4.4) Study code

Summary

In this exercise, you have learned how to use @Asynchronous annotation to invoke a EJB method in asynchronous manner. 

Testing EJBs was a herculean task all these years. It isn’t anymore with the timely and useful innovation of the embeddable container. The embeddable container allows you to use JPA and EJB 3.1 outside a container including testing. 

In this exercise, you are going to build a standalone Java SE application in which you are going to test EJB-based application logic step by step.

1. Create a new "Java Application" (Java SE) project
   
2. Create EJB beans
   
3. Add libraries
   
4. Create persistence unit
5. Add testing code
   
6. Build a jar file (that contains EJB beans)
   
7. Run the testing
8. Use APP_NAME JNDI name
   

(5.1) Create a new "Java Application" (Java SE) project

Figure-5.11

Figure-5.12

2. Give a name to the project.

Figure-5.13

(5.2) Add EJB beans

In this step, you are going to add a simple Book entity class and ItemBook Stateless bean class.

1. Add Book entity class.

• Right click project and select New->Entity Class.  (If you don't see Entity class from the pop-up menu, select Other, select Persistence on the left.)

Figure-5.21

Figure-5.22

2. Modify the IDE generated Book.java as shown below.

Figure-5.23

3. Create ItemEJB Stateless bean.

Figure-5.24

Figure-5.25

4. Modify IDE generated ItemEJB.java as shown below.

package mypackage; import javax.ejb.Stateless; import javax.persistence.EntityManager; import javax.persistence.PersistenceContext; import java.util.List; @Stateless public class ItemEJB {     @PersistenceContext     private EntityManager em;     public Book createBook(Book book) {         em.persist(book);         return book;     }     public List<Book> findAllBooks() {         return em.createNamedQuery("findAllBooks").getResultList();     } }

Figure-5.26

                                                                                                                    return to top of exercise

(5.3) Add libraries

Figure-5.31

Figure-5.32

Figure-5.33

2. Add library files from <GlassFish-v3-Installation-Directory>/glassfish/modules/endorsed directory

Figure-5.34

3. Add library files from <GlassFish-v3-Installation-Directory>/glassfish/lib/embedded directory.

Figure-5.35

4. Verify that the library files are added.

Figure-5.36

                                                                                                                    return to top of exercise

(5.4) Create persistence unit

Figure-5.41

2. Set the values of the persistence unit.

Figure-5.42

3. Add entity class to the persistence unit.

Figure-5.43

Figure-5.44

4. Change Transaction Type to JTA.

Figure-5.45

(5.5) Add testing code

In this step, you are going to add testing code in which EJBContainer gets created, EJB are deployed and tested.

1. Create ItemEJBTest.java.

• Right click Test Packages and select New->Java Class.

Figure-5.51

Figure-5.52

2. Modify IDE generated code with the one below.

package testpackage; import mypackage.Book; import javax.ejb.embeddable.EJBContainer; import javax.naming.Context; import mypackage.ItemEJB; import org.junit.AfterClass; import org.junit.BeforeClass; import org.junit.Test; import static org.junit.Assert.*; public class ItemEJBTest {     private static EJBContainer ec;     private static Context ctx;     @BeforeClass     public static void initContainer() throws Exception {         System.out.println("----Creating EJBContainer...");         ec = EJBContainer.createEJBContainer();         ctx = ec.getContext();     }     @AfterClass     public static void closeContainer() throws Exception {         if (ec != null) {             System.out.println("----Closing EJBContainer...");             ec.close();         }     }     @Test     public void createBook() throws Exception {         System.out.println("----Looking up EJB...");         ItemEJB itemEJB = (ItemEJB) ctx.lookup("java:global/classes/ItemEJB");         // ItemEJB itemEJB = new ItemEJB();         // Counts all the books in the database         int nbBooks = itemEJB.findAllBooks().size();         // Creates a new book         Book book = new Book();         book.setTitle("Passion");         // Persists the book to the database         System.out.println("----Creating a book...");         book = itemEJB.createBook(book);         assertNotNull("ID should not be null", book.getId());         // Checks that there is an extra book in the database         assertEquals("Should have an extra book", itemEJB.findAllBooks().size(), nbBooks + 1);     } }

Figure-5.53

                                                                                                                   

(5.6) Build a jar file that contains EJB

Figure-5.61

2. Verify that the build was successful.

Figure-5.62

(5.7) Run the testing

1. Right click ItemEJBTest.java under Test Packages->testpackages and select either Run File or Test File.

Figure-5.71

2. Observe the debugging messages from the testing.

Figure-5.72

3. Observe the testing result.

Figure-5.73

Figure-5.74

Figure-5.75

Solution: The solution is available as "ready to open and build" NetBeans project as ejb3.1_embedded under <LAB_UNZIPPED_DIRECTORY>/javaee6_ejb3.1/solution directory.

(5.8) Use APP_NAME JNDI name

1. Modify the ItemEJBTest.java as shown below.

package testpackage; import java.util.HashMap; import java.util.Map; import mypackage.Book; import javax.ejb.embeddable.EJBContainer; import javax.naming.Context; import mypackage.ItemEJB; import org.junit.AfterClass; import org.junit.BeforeClass; import org.junit.Test; import static org.junit.Assert.*; public class ItemEJBTest {     private static EJBContainer ec;     private static Context ctx;     @BeforeClass     public static void initContainer() throws Exception {         System.out.println("----Creating EJBContainer...");         Map<String, Object> map = new HashMap<String, Object>();         map.put(EJBContainer.APP_NAME, "myapp");         ec = EJBContainer.createEJBContainer(map);         ctx = ec.getContext();     }     @AfterClass     public static void closeContainer() throws Exception {         if (ec != null) {             System.out.println("----Closing EJBContainer...");             ec.close();         }     }     @Test     public void createBook() throws Exception {         System.out.println("----Looking up EJB...");         ItemEJB itemEJB = (ItemEJB) ctx.lookup("java:global/myapp/ItemEJB");         // ItemEJB itemEJB = new ItemEJB();         // Counts all the books in the database         int nbBooks = itemEJB.findAllBooks().size();         // Creates a new book         Book book = new Book();         book.setTitle("Passion");         // Persists the book to the database         System.out.println("----Creating a book...");         book = itemEJB.createBook(book);         assertNotNull("ID should not be null", book.getId());         // Checks that there is an extra book in the database         assertEquals("Should have an extra book", itemEJB.findAllBooks().size(), nbBooks + 1);     } }

2. Do the clean build.


Figure-5.81

3. Run the testing.

Solution: The solution is available as "ready to open and build" NetBeans project as ejb3.1_embedded_jndi_APP_NAME under <LAB_UNZIPPED_DIRECTORY>/javaee6_ejb3.1/solutions directory.

Summary

In this exercise,  you have learned how to test EJB through "Embeddable EJB container" feature of EJB 3.1, in which EJB container can be created programmatically and EJB are deployed and tested.

In JAX-RS 1.1, EJB can be exposed as RESTful web service.

1. Verify a simple EJB application is working
   
2. Expose EJB as restful web service
   
3. Use "Curl" to test response format
4. Use @ApplicationPath annotation
   

(6.1) Verify a simple EJB application is working

In this step, you are going to verify a simple EJB application is working as expected.  We are going to expose Session bean as RESTful services.

1. Open ejb3.1_rest_base NetBeans project (from "Lab samples"). 

2. Build and run ejb3.1_rest_base project.

• Right-click ejb3.1_rest_base project and select Run.
• Browser gets displayed.

Figure-6.11

• Observe that the newly created book title is displayed.  This verifies the sample app is a working EJB application.
  

Figure-6.12

                                                                                                                   

(6.2) Make the Session bean as RESTful service

1. Modify ItemEJB.java as shown below. The code fragments that need to be added are highlighted in bold and red-colored font.

package mypackage; import javax.ejb.Stateless; import javax.persistence.EntityManager; import javax.persistence.PersistenceContext; import java.util.List; import javax.ws.rs.GET; import javax.ws.rs.Path; import javax.ws.rs.PathParam; import javax.ws.rs.Produces; @Stateless @Path("/items") public class ItemEJB {     @PersistenceContext     private EntityManager em;     public Book createBook(Book book) {         em.persist(book);         return book;     }     @GET     @Path("{bookKey}")     @Produces({"application/xml", "application/json"})     public Book getBook(@PathParam("bookKey") String key) {         Book theBook = em.find(Book.class, new Long(key));         return theBook;     }     @GET     public List<Book> findAllBooks() {         return em.createNamedQuery("findAllBooks").getResultList();     } }

Figure-6.21

2. Modify Book.java as shown below.

package mypackage; import java.io.Serializable; import javax.persistence.*; import javax.xml.bind.annotation.XmlRootElement; @Entity @NamedQueries({     @NamedQuery(name = "findAllBooks", query = "SELECT b FROM Book b") }) @XmlRootElement public class Book implements Serializable {     @Id     @GeneratedValue     private Long id;     private String title;     public Long getId() {         return id;     }     public String getTitle() {         return title;     }     public void setTitle(String title) {         this.title = title;     } }

Figure-6.22

3. Build and run the application and add two Book items into Book table.


Figure-6.23


Figure-6.24


Figure-6.25


Figure-6.26

4. Verify that the BOOK table has two entries. 



5. Test the ItemEJB RESTful web service.

• Observe that the browser gets displayed.
  

6. Access ItemEJB as RESTful web services using browser.

• From your browser, go to http://localhost:8080/ejb3.1_rest_base/resources/items
• Observe that the two books you added are displayed in XML format.
  

Figure-6.27

Trouble-shooting: If you are using Safari over MacOS, the response might not be prorperly formated in XML.  Please use Firefox instead..

• From your browser, go to http://localhost:8080/ejb3.1_rest_base/resources/items/1
• Observe that the book item whose ID is 1 is displayed in XML format.
  

Figure-6.28

                                                                                                                   

(6.3) Use "Curl" utility

0. Install "Curl" utility only if you are running Windows or OpenSolaris.  For MacOS or other Linux OS'es, "Curl" utility comes with the OS.  Reinstallation of "Curl" might cause some mal-functioning behavior on Mac OS X or other Linux OS'es.

• From your browser, go to http://curl.haxx.se/
• Download and install it.
  

1. Retrieve the response in JSON format.
The command to type in the terminal is highlighted in red color, the answer in blue color.

curl -H "Accept:application/json" http://localhost:8080/ejb3.1_rest_base/resources/items {"book":[{"title":"Life is passion!"},{"title":"2nd book title"}]}

Figure-6.31

2. Retrieve the response in XML format
The command to type in the terminal is highlighted in red color, the answer in blue color.

curl -H "Accept:application/xml" http://localhost:8080/ejb3.1_rest_base/resources/items <?xml version="1.0" encoding="UTF-8" standalone="yes"?><books><book><title>Life is passion!</title></book><book><title>2nd book title</title></book></books>

Figure-6.32

Solution: The solution is available as "ready to open and build" NetBeans project as ejb3.1_rest under <LAB_UNZIPPED_DIRECTORY>/javaee6_ejb3.1/solutions directory. (You will have to use ejb3.1_rest rather than ejb3.1_rest_base as application context.)

                

(6.4) Use @ApplicationPath annotation

1. Add ApplicationConfig.java.  Note that the value of the Application path is et to resources1.

package mypackage; @javax.ws.rs.ApplicationPath("resources1") public class ApplicationConfig  extends javax.ws.rs.core.Application { }

Figure-6.41

2. Build and run the application and add two Book items into Book table.

3. Now observe that you can use resources1 application path.


Figure-6.42


Figure-6.43

Summary

In this exercise, you have learned how to use JAX-RS annotations to expose EJB as RESTful web service.