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| Ejb Injection Example |
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| <H1><A name="EjbInjectionExample-Overview"></A>Overview</H1> |
| |
| <P>This example shows how to use the @EJB annotation on a bean class to refer to other beans.</P> |
| |
| <P>This functionality is often referred as dependency injection (see |
| http://www.martinfowler.com/articles/injection.html), and has been recently introduced in |
| Java EE 5.</P> |
| |
| <P>In this particular example, we will create two session stateless beans</P> |
| |
| <UL> |
| <LI>a DataStore session bean</LI> |
| <LI>a DataReader session bean</LI> |
| </UL> |
| |
| |
| <P>The DataReader bean uses the DataStore to retrieve some informations, and |
| we will see how we can, inside the DataReader bean, get a reference to the |
| DataStore bean using the @EJB annotation, thus avoiding the use of the |
| JNDI API.</P> |
| |
| |
| <H1><A name="EjbInjectionExample-TheCode"></A>The Code</H1> |
| |
| <P>In this example we develop two simple session stateless beans (DataReader and DataStore), and show how we can use the @EJB annotation in one of these beans to get the reference to the other session bean</P> |
| |
| <H4><A name="EjbInjectionExample-DataStoresessionbean"></A>DataStore session bean</H4> |
| |
| <H5><A name="EjbInjectionExample-Localbusinessinterface"></A>Local business interface</H5> |
| |
| <DIV class="code"><DIV class="codeContent"> |
| <PRE class="code-java">@Local |
| <SPAN class="code-keyword">public</SPAN> <SPAN class="code-keyword">interface</SPAN> DataStoreLocal { |
| |
| <SPAN class="code-keyword">public</SPAN> <SPAN class="code-object">String</SPAN> getData(); |
| |
| }</PRE> |
| </DIV></DIV> |
| |
| <H5><A name="EjbInjectionExample-Remotebusinessinterface"></A>Remote business interface</H5> |
| |
| <DIV class="code"><DIV class="codeContent"> |
| <PRE class="code-java">@Remote |
| <SPAN class="code-keyword">public</SPAN> <SPAN class="code-keyword">interface</SPAN> DataStoreRemote { |
| |
| <SPAN class="code-keyword">public</SPAN> <SPAN class="code-object">String</SPAN> getData(); |
| |
| }</PRE> |
| </DIV></DIV> |
| |
| <H5><A name="EjbInjectionExample-Bean"></A>Bean</H5> |
| |
| <DIV class="code"><DIV class="codeContent"> |
| <PRE class="code-java">@Stateless |
| <SPAN class="code-keyword">public</SPAN> class DataStoreImpl <SPAN class="code-keyword">implements</SPAN> DataStoreLocal, DataStoreRemote{ |
| |
| <SPAN class="code-keyword">public</SPAN> <SPAN class="code-object">String</SPAN> getData() { |
| <SPAN class="code-keyword">return</SPAN> <SPAN class="code-quote">"42"</SPAN>; |
| } |
| |
| }</PRE> |
| </DIV></DIV> |
| |
| <H4><A name="EjbInjectionExample-DataReadersessionbean"></A>DataReader session bean</H4> |
| |
| <H5><A name="EjbInjectionExample-Localbusinessinterface"></A>Local business interface</H5> |
| |
| <DIV class="code"><DIV class="codeContent"> |
| <PRE class="code-java">@Local |
| <SPAN class="code-keyword">public</SPAN> <SPAN class="code-keyword">interface</SPAN> DataReaderLocal { |
| |
| <SPAN class="code-keyword">public</SPAN> <SPAN class="code-object">String</SPAN> readDataFromLocalStore(); |
| <SPAN class="code-keyword">public</SPAN> <SPAN class="code-object">String</SPAN> readDataFromRemoteStore(); |
| }</PRE> |
| </DIV></DIV> |
| |
| <H5><A name="EjbInjectionExample-Bean"></A>Bean</H5> |
| |
| <DIV class="code"><DIV class="codeContent"> |
| <PRE class="code-java">@Stateless |
| <SPAN class="code-keyword">public</SPAN> class DataReaderImpl <SPAN class="code-keyword">implements</SPAN> DataReaderLocal, DataReaderRemote { |
| |
| @EJB <SPAN class="code-keyword">private</SPAN> DataStoreRemote dataStoreRemote; |
| @EJB <SPAN class="code-keyword">private</SPAN> DataStoreLocal dataStoreLocal; |
| |
| <SPAN class="code-keyword">public</SPAN> <SPAN class="code-object">String</SPAN> readDataFromLocalStore() { |
| <SPAN class="code-keyword">return</SPAN> <SPAN class="code-quote">"LOCAL:"</SPAN>+dataStoreLocal.getData(); |
| } |
| |
| <SPAN class="code-keyword">public</SPAN> <SPAN class="code-object">String</SPAN> readDataFromRemoteStore() { |
| <SPAN class="code-keyword">return</SPAN> <SPAN class="code-quote">"REMOTE:"</SPAN>+dataStoreRemote.getData(); |
| } |
| }</PRE> |
| </DIV></DIV> |
| |
| <P>(The remote business interface is not shown for the sake of brevity).</P> |
| |
| <TABLE cellpadding="5" width="85%" cellspacing="8px" class="tipMacro" border="0" align="center"><COLGROUP><COL width="24"><COL></COLGROUP><TR><TD valign="top"><IMG src="http://cwiki.apache.org/confluence/images/icons/emoticons/check.gif" width="16" height="16" align="absmiddle" alt="" border="0"></TD><TD><B class="strong">@EJB annotation</B><BR> |
| <P>You can use the @EJB annotation to refer a session bean in other components specified by the Java EE platform, for instance:</P> |
| <UL> |
| <LI>Servlets</LI> |
| <LI>ServletContextListeners</LI> |
| <LI>Servlet Filters</LI> |
| <LI>JSF managed beans</LI> |
| <LI>EJB interceptors</LI> |
| <LI>JAX-WS service endpoints</LI> |
| </UL> |
| </TD></TR></TABLE> |
| |
| <H1><A name="EjbInjectionExample-Writingaunittestfortheexample"></A>Writing a unit test for the example</H1> |
| |
| <P>Writing an unit test for this example is quite simple. We need just to write a setup method to create and initialize the InitialContext, and then write our test methods</P> |
| |
| <H4><A name="EjbInjectionExample-setUp"></A>setUp</H4> |
| |
| <DIV class="code"><DIV class="codeContent"> |
| <PRE class="code-java"><SPAN class="code-keyword">private</SPAN> InitialContext initialContext; |
| |
| <SPAN class="code-keyword">protected</SPAN> void setUp() <SPAN class="code-keyword">throws</SPAN> Exception { |
| Properties properties = <SPAN class="code-keyword">new</SPAN> Properties(); |
| properties.setProperty(Context.INITIAL_CONTEXT_FACTORY, <SPAN class="code-quote">"org.apache.openejb.client.LocalInitialContextFactory"</SPAN>); |
| |
| initialContext = <SPAN class="code-keyword">new</SPAN> InitialContext(properties); |
| }</PRE> |
| </DIV></DIV> |
| |
| <H4><A name="EjbInjectionExample-Test"></A>Test</H4> |
| |
| <DIV class="code"><DIV class="codeContent"> |
| <PRE class="code-java"><SPAN class="code-keyword">public</SPAN> void testViaLocalInterface() <SPAN class="code-keyword">throws</SPAN> Exception { |
| <SPAN class="code-object">Object</SPAN> object = initialContext.lookup(<SPAN class="code-quote">"DataReaderImplLocal"</SPAN>); |
| |
| assertNotNull(object); |
| assertEquals(LOCAL_STORE_RESULT, ((DataReaderLocal)object).readDataFromLocalStore()); |
| assertEquals(REMOTE_STORE_RESULT, ((DataReaderLocal)object).readDataFromRemoteStore()); |
| }</PRE> |
| </DIV></DIV> |
| |
| <H1><A name="EjbInjectionExample-Running"></A>Running</H1> |
| |
| <P>Running the example is fairly simple, just run:</P> |
| |
| <P>$ cd injection-of-ejb<BR> |
| $ mvn clean install</P> |
| |
| <P>Which should create output like the following.</P> |
| |
| <DIV class="preformatted"><DIV class="preformattedContent"> |
| <PRE>------------------------------------------------------- |
| T E S T S |
| ------------------------------------------------------- |
| [OPENEJB:surefire] Running org.apache.openejb.examples.injection.EjbDependencyTest |
| log4j:WARN No appenders could be found for logger (OpenEJB). |
| log4j:WARN Please initialize the log4j system properly. |
| Apache OpenEJB 3.0-incubating-SNAPSHOT build: 20070105-12:45 |
| http://incubator.apache.org/openejb |
| OpenEJB ready. |
| [OPENEJB:surefire] Tests run: 2, Failures: 0, Errors: 0, Time elapsed: 2.006 sec |
| [OPENEJB:INFO] [jar:jar] |
| [OPENEJB:INFO] Building jar: openejb3/examples/injection-of-ejbs/target/ejb-injection-sample-1.0-SNAPSHOT.jar |
| [OPENEJB:INFO] [install:install] |
| [OPENEJB:INFO] Installing openejb3/examples/injection-of-ejbs/target/ejb-injection-sample-1.0-SNAPSHOT.jar to ... |
| [OPENEJB:INFO] ------------------------------------------------------------------------ |
| [OPENEJB:INFO] BUILD SUCCESSFUL |
| [OPENEJB:INFO] ------------------------------------------------------------------------ |
| |
| </PRE> |
| </DIV></DIV> |
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