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Łukasz works as a Technical Architect for an international IT company and is responsible for delivering applications written in Java EE, Spring, and .NET. He has been involved in many various projects ranging from online insurance systems, voice and video solutions, mobile systems (both native and HTML5-based), medical systems, and large system integration projects. Łukasz is an expert in distributed systems, SOA, and cloud. Łukasz holds PhD in Computer Science. Łukasz is a DZone MVB and is not an employee of DZone and has posted 20 posts at DZone. You can read more from them at their website. View Full User Profile

Connecting to EJBs from Spring

06.23.2012
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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



Published at DZone with permission of Łukasz Budnik, author and DZone MVB. (source)

(Note: Opinions expressed in this article and its replies are the opinions of their respective authors and not those of DZone, Inc.)

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Comments

Thomas Eichberger replied on Sun, 2012/06/24 - 5:34am

The Sprig proxy has some nice features like re-connect etc.

Michał Minicki replied on Sun, 2012/07/01 - 12:56pm

Isn't it easier to use a namespace with <jee:remote-slsb>?

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