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Chapter 25. EJB

EJB Component
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Available as of Apache Camel 2.4
The ejb: component binds EJBs to message exchanges.

URI format
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ejb:ejbName[?options]
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Where ejbName can be any string which is used to look up the EJB in the Application Server JNDI Registry

Options
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Expand
Name Type Default Description
method String null The method name that bean will be invoked. If not provided, Apache Camel will try to pick the method itself. In case of ambiguity an exception is thrown. See Bean Binding for more details.
multiParameterArray boolean false How to treat the parameters which are passed from the message body; if it is true, the In message body should be an array of parameters.
You can append query options to the URI in the following format, ?option=value&option=value&...
The EJB component extends the Bean component in which most of the details from the Bean component applies to this component as well.

Bean Binding
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How bean methods to be invoked are chosen (if they are not specified explicitly through the method parameter) and how parameter values are constructed from the MessageMessage are all defined by the Bean Binding mechanism which is used throughout all of the various Bean Integration mechanisms in Apache Camel.

Examples
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In the following examples we use the Greater EJB which is defined as follows: 
public interface GreaterLocal {

    String hello(String name);

    String bye(String name);

}
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And the implementation 
@Stateless
public class GreaterImpl implements GreaterLocal {

    public String hello(String name) {
        return "Hello " + name;
    }

    public String bye(String name) {
        return "Bye " + name;
    }

}
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Using Java DSL
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In this example we want to invoke the hello method on the EJB. Since this example is based on an unit test using Apache OpenEJB we have to set a JndiContext on the EJB component with the OpenEJB settings. 
@Override
protected CamelContext createCamelContext() throws Exception {
    CamelContext answer = new DefaultCamelContext();

    // enlist EJB component using the JndiContext
    EjbComponent ejb = answer.getComponent("ejb", EjbComponent.class);
    ejb.setContext(createEjbContext());

    return answer;
}

private static Context createEjbContext() throws NamingException {
    // here we need to define our context factory to use OpenEJB for our testing
    Properties properties = new Properties();
    properties.setProperty(Context.INITIAL_CONTEXT_FACTORY, "org.apache.openejb.client.LocalInitialContextFactory");

    return new InitialContext(properties);
}
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Then we are ready to use the EJB in the Apache Camel route: 
from("direct:start")
    // invoke the greeter EJB using the local interface and invoke the hello method
    .to("ejb:GreaterImplLocal?method=hello")
    .to("mock:result");
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Note
In a real application server you most likely do not have to setup a JndiContext on the EJB component as it will create a default JndiContext on the same JVM as the application server, which usually allows it to access the JNDI registry and lookup the EJBs. However if you need to access a application server on a remote JVM or the likes, you have to prepare the properties beforehand.

Using Spring XML
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And this is the same example using Spring XML instead:
Again since this is based on an unit test we need to setup the EJB component: 
<!-- setup Camel EJB component -->
<bean id="ejb" class="org.apache.camel.component.ejb.EjbComponent">
    <property name="properties" ref="jndiProperties"/>
</bean>

<!-- use OpenEJB context factory -->
<p:properties id="jndiProperties">
    <prop key="java.naming.factory.initial">org.apache.openejb.client.LocalInitialContextFactory</prop>
</p:properties>
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Before we are ready to use EJB in the Apache Camel routes: 
<camelContext xmlns="http://camel.apache.org/schema/spring">
    <route>
        <from uri="direct:start"/>
        <to uri="ejb:GreaterImplLocal?method=hello"/>
        <to uri="mock:result"/>
    </route>
</camelContext>
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