TOTD #95: EJB 3.1 + Java Server Faces 2.0 + JPA 2.0 web application - Getting Started with Java EE 6 using NetBeans 6.8 M1 & GlassFish v3

href="http://blogs.sun.com/arungupta/entry/totd_93_getting_started_with">TOTD
#93
showed how to get started with href="http://jcp.org/en/jsr/detail?id=316">Java EE 6
using href="http://www.netbeans.org/servlets/NewsItemView?newsItemID=1413">NetBeans
6.8 M1 and
GlassFish v3 by
building a simple Servlet 3.0 + JPA 2.0 web
application. href="http://blogs.sun.com/arungupta/entry/totd_94_a_simple_java">TOTD
#94 built upon it by using Java Server Faces 2 instead of
Servlet 3.0 for displaying the results. However we are still using a
POJO
for all the database interactions. This works fine if we are only
reading values from the database but that's not how a typical web
application behaves. The web application would typically perform all
CRUD operations. More typically they like to perform one or more CRUD
operations within the context of a transaction. And how do you do
transactions in the context of a web application ? Java EE 6 comes to
your rescue.



The EJB 3.1
specification (another new specification in Java EE 6) allow
POJO classes to be annotated with @EJB and bundled within
WEB-INF/classes of a WAR file. And so you get all transactional
capabilities in your web application very easily.



This Tip
Of style="font-weight: bold;">The style="font-weight: bold;">Day (TOTD) shows how
to enhance the application created in TOTD #94 and use EJB 3.1 instead
of the JSF managed bean
for
performing the business logic. There are two ways to achieve this
pattern as described below.



Lets call this TOTD #95.1

1. The easiest way to back a JSF page with an EJB is to
   convert the managed bean into an EJB by adding @javax.ejb.Stateless
   annotation. So change the  "StateList" class from TOTD #94 as
   shown below:
   
   
   
   style="text-align: left; background-color: rgb(204, 204, 255); width: 100%;"
   cellpadding="2" cellspacing="2">
   @javax.ejb.Stateless
   
   @ManagedBean
   
   public class StateList {
   
       @PersistenceUnit
   
       EntityManagerFactory emf;
   
   
   
       public List<States>
   getStates() {
   
          
   return
   emf.createEntityManager().createNamedQuery("States.findAll").getResultList();
   
       }
   
   }

   
   
   The change is highlighted in bold, and that's it!

Because of "Deploy-on-save" feature in NetBeans and GlassFish v3, the
application is autodeployed. Otherwise right-click on the project and
select Run (default shortcut "F6"). As earlier, the results can be seen
at "http://localhost:8080/HelloEclipseLink/forwardToJSF.jsp" or
"http://localhost:8080/HelloEclipseLink/faces/template-client.xhtml"
and looks like:



alt=""
src="http://blogs.sun.com/arungupta/resource/images/nb68m1-jee6-ejb-1st-output.png">



The big difference this time is that the business logic is executed by
an EJB in a fully transactional manner. Even though the logic in this
case is a single read-only operation to the database, but you get the
idea :)



Alternatively, you can use the delegate pattern in the style="font-style: italic;">managed bean as
described below. Lets call this #95.2.

1. Right-click on the project, select "New", "Session Bean
   ..." and create a stateless session bean by selecting the options as
   shown below:
   
   
   
   style="border: 1px solid ; width: 371px; height: 378px;" alt=""
   src="http://blogs.sun.com/arungupta/resource/images/nb68m1-jee6-ejb-create.png">
   
   
   
   This creates a stateless session with the name "StateBeanBean" ( href="http://www.netbeans.org/issues/show_bug.cgi?id=170392">bug
   #170392 for redundant "Bean" in the name).
2. Simplify your managed bean by refactoring all the business
   logic to the EJB as shown below:
   
   
   
   style="text-align: left; background-color: rgb(204, 204, 255); width: 100%;"
   cellpadding="2" cellspacing="2">
   @Stateless
   
   public class StateBeanBean {
   
       @PersistenceUnit
   
       EntityManagerFactory emf;
   
       
   
       public List<States>
   getStates() {
   
          
   return
   emf.createEntityManager().createNamedQuery("States.findAll").getResultList();
   
       }
   
   }

   
   
   and
   
   
   

   style="text-align: left; background-color: rgb(204, 204, 255); width: 100%;"
   cellpadding="2" cellspacing="2">
   @ManagedBean
   
   public class StateList {
   
       @EJB StateBeanBean bean;
   
   
   
       public List<States>
   getStates() {
   
          
   return bean.getStates();
   
       }
   
   }
   
   

   
   
   In fact the EJB code can be further simplified to:
   
   
   

   style="text-align: left; background-color: rgb(204, 204, 255); width: 100%;"
   cellpadding="2" cellspacing="2">
   @Stateless
   
   public class StateBeanBean {
   
       @PersistenceContext style="font-weight: bold;">
      
   EntityManager em;
   
      
   
       public List<States>
   getStates() {
   
          
   return em.createNamedQuery("States.findAll").getResultList();
   
       }
   
   }
   
   

   
   
   The changes are highlighted in bold.
   

If the application is already running then style="font-style: italic;">Deploy-on-Save
would have automatically deployed the entire application. Otherwise
right-click on the project and select Run (default shortcut "F6").
Again, the
results can be seen at
"http://localhost:8080/HelloEclipseLink/forwardToJSF.jsp" or
"http://localhost:8080/HelloEclipseLink/faces/template-client.xhtml"
and are displayed as shown in the screenshot above.



The updated directory structure looks like:



alt=""
src="http://blogs.sun.com/arungupta/resource/images/nb68m1-jee6-ejb-dir-structure.png">



The important point to note is that our EJB is bundled in the WAR file
and no additional deployment descriptors were added or existing ones
modified to achieve that. Now, that's really clean :)



The next blog in this series will show how managed beans can be
replaced with WebBeans, err JCDI.



Also refer to other href="http://blogs.sun.com/arungupta/tags/javaee6">Java EE 6
blog entries.



Please leave suggestions on other TOTD that
you'd like to see.
A complete archive of all the tips is available href="http://blogs.sun.com/arungupta/tags/totd">here.




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