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Connecting to EJBs from Spring

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Connecting to EJBs from Spring

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While preparing my next exercise I had to first find a way how to connect to a remote SLSB from Spring.

It turned out to be childishly simple. See how I did it.

Writing SLSB component

First I needed a remote SLSB.

Using M2Eclipse create a Maven 2 project. From the archetypes selection window I typed mojo in filter field (mojo archetypes are codehaus archetypes, I wrote about them in: Don't use org.apache.maven.archetypes!) and selected ejb3 archetype.

I wrote a simple SLSB component:
package org.xh.studies.openejb;
import javax.ejb.Remote;
@Remote
public interface Greeter {
 String sayHello(String to);
}

package org.xh.studies.openejb;
import javax.ejb.Stateless;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
@Stateless
public class GreeterImpl implements Greeter { 
 private static final Log log = LogFactory.getLog(GreeterImpl.class);
 public String sayHello(String to) {
  log.info("Saying hi to: " + to);
  return "Hello " + to + "! How are you?";
 }
}
I built it with:
mvn package
Deploying to OpenEJB

I downloaded OpenEJB archive from here: http://openejb.apache.org/download.html and unzipped it. I was done with installation :)

I copied built in previous step jar to apps directory, then went to bin directory and ran openejb(.bat).

Writing JUnit integration test

First I wrote a simple integration test (using failsafe plugin, there are many post on my blog about it, the key one is: Maven2 integration testing with failsafe and jetty plugins) to verify if the SLSB is actually working:
public class GreeterIT {
 private static Context ctx;
 @BeforeClass
 public static void setUp() throws NamingException {
  Properties env = new Properties();
  env.put(Context.INITIAL_CONTEXT_FACTORY, "org.apache.openejb.client.RemoteInitialContextFactory");
  env.put(Context.PROVIDER_URL, "ejbd://localhost:4201");
  ctx = new InitialContext(env);
 }
 @AfterClass
 public static void tearDown() throws NamingException {
  ctx.close();
 }
 @Test
 public void sayHelloRemoteEJBTest() throws NamingException {
  Greeter greeter = (Greeter) ctx.lookup("GreeterImplRemote");
  String result = greeter.sayHello("Łukasz");
  String expected = "Hello Łukasz! How are you?";
  Assert.assertEquals(expected, result);
 }
}
I ran the test and it passed.

Connecting to EJB from Spring

I found out a Spring component called org.springframework.ejb.access.SimpleRemoteStatelessSessionProxyFactoryBean. It uses AOP behinde the scenes to create a proxy for a remote SLSB. All you need is just an interface.

First I had to add Spring dependencies to my pom.xml. These were:
spring-beans
spring-context
spring-aop
Then I created a file called META-INF/spring/beans.xml and wrote:
<beans xmlns="http://www.springframework.org/schema/beans"
 xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
 xsi:schemaLocation="
  http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd">
 <bean id="jndiTemplate" class="org.springframework.jndi.JndiTemplate">
  <property name="environment">
   <props>
    <prop key="java.naming.factory.initial">org.apache.openejb.client.RemoteInitialContextFactory</prop>
    <prop key="java.naming.provider.url">ejbd://localhost:4201</prop>
   </props>
  </property>
 </bean>
 <bean id="greeterBean"
  class="org.springframework.ejb.access.SimpleRemoteStatelessSessionProxyFactoryBean">
  <property name="jndiName" value="GreeterImplRemote" />
  <property name="jndiTemplate" ref="jndiTemplate" />
  <property name="businessInterface" value="org.xh.studies.openejb.Greeter" />
 </bean>
</beans>
In the above file I created a greeterBean which was a dynamic proxy and, thanks to AOP, would behave like a Greeter object.

Writing Spring test

I added one more field to my test:
private static ApplicationContext springCtx;
Then in @BeforeClass class I added ApplicationContext initialisation code:
springCtx = new ClassPathXmlApplicationContext("META-INF/spring/beans.xml");
Finally I wrote a new method to test what I intended to do first, connecting to a remote SLSB from Spring:
@Test
public void sayHelloSpringProxyTest() throws NamingException {
 Greeter greeter = (Greeter) springCtx.getBean("greeterBean");
 String result = greeter.sayHello("Łukasz");
 String expected = "Hello Łukasz! How are you?";
 Assert.assertEquals(expected, result);
}
It worked!

Source code download

A complete source code download can be found here: Connecting-to-EJB-from-Spring.zip.

Summary

Isn't it beautiful? You get an instance of a remote SLSB as a Spring bean. I definitely like it!

thanks,
Łukasz



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