Axis2 Integration With The Spring Framework

Axis2 Integration With The Spring Framework

This document is a guide on how to use Axis2 with the Spring Framework

Content

• Introduction
• Configuring Axis2 to be Spring aware
  • Programming Model
  • Simple Spring config example
  • With a ServletContext
  • Without a ServletContext
  • Putting it all together
  • Spring inside an AAR
    • The Spring inside an AAR layout
    • The Spring inside an AAR init class
    • Known issues running Spring inside the AAR

Introduction

The idea behind Axis2 and Spring integration is that Axis2 simply needs to have Spring supply one of its pre-loaded beans to the Axis2 Message Receiver defined in the AAR services.xml . While Axis2 typically uses reflection to instantiate the ServiceClass defined in the services.xml that the Message Receiver will use, alternatively one can define a ServiceObjectSupplier that will supply the Object.

This guide will show how to use two separate ServiceObjectSupplier classes that are part of the Axis2 standard distribution: One for use with a ServletContext, and one without. Once configured, the web service itself acts like any other Spring wired bean. These Spring beans can be loaded any way desired, as Axis2 has no configuration file dependencies from Spring. Spring versions 1.2.6, 1.2.8 and 2.0 have been tested, but probably any version would work as only core functionality is required.

This guide assumes some basic knowledge of Axis2. See the User's Guide for more information.

Configuring Axis2 to be Spring Aware

Programming Model

From an Axis2 standpoint, two hooks are needed to be placed into the AAR services.xml: The ServiceObjectSupplier that hooks Axis2 and Spring together, and the name of Spring bean that Axis2 will use as the service. All Message Receivers are currently supported, as would be any Message Receiver that extends org.apache.axis2.receivers.AbstractMessageReceiver .

Simple Spring Config Example

For the purpose of this example, and for no other reason besides simplicity, we'll configure Spring via a WAR file's web.xml. Lets add a context-param and a listener:

<listener>
        <listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
</listener>
<context-param>
      <param-name>contextConfigLocation</param-name>
      <param-value>/WEB-INF/applicationContext.xml</param-value>
    </context-param>

Next we will show two examples of Spring's /WEB-INF/applicationContext.xml referenced in the web.xml listener - one using a ServletContext, and one without.

With a ServletContext

This 'with a ServletContext' example applicationContext.xml should be familiar to any Spring user:

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE beans PUBLIC "-//SPRING//DTD BEAN//EN" "http://www.springframework.org/dtd/spring-beans.dtd">

<beans>
  <!-- Axis2 Web Service, but to Spring, its just another bean that has dependencies -->
  <bean id="springAwareService" class="spring.SpringAwareService">
    <property name="myBean" ref="myBean"/>
  </bean>

  <!-- just another bean / interface with a wired implementation, that's injected by Spring
          into the Web Service -->
   <bean id="myBean" class="spring.MyBeanImpl">
     <property name="val" value="Spring, emerge thyself" />
  </bean>
</beans>

If the service is running in a Servlet Container, i.e., Axis2 will be able to get a hold of ServletContext, the services.xml for the example would be using SpringServletContextObjectSupplier such as:

<service name="SpringAwareService">
    <description>
        simple spring example
    </description>
    <parameter name="ServiceObjectSupplier" locked="false">org.apache.axis2.extensions.spring.receivers.SpringServletContextObjectSupplier</parameter>
    <parameter name="SpringBeanName" locked="false">springAwareService</parameter>
    <operation name="getValue">
        <messageReceiver class="org.apache.axis2.receivers.RawXMLINOutMessageReceiver"/>
    </operation>
</service>

While the above example uses RawXMLINOutMessageReceiver as its messageReceiver class, all Message Receivers are currently supported, as would be any Message Receiver that extends org.apache.axis2.receivers.AbstractMessageReceiver .

Without a ServletContext

In the case Axis2 can't get a ServletContext, ie another transport or running inside the AAR etc, you have the option of defining a bean that takes advantage of Spring's internal abilities (ApplicationContextAware interface, specifically) to provide an Application Context to Axis2, with a bean ref 'applicationContext' :

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE beans PUBLIC "-//SPRING//DTD BEAN//EN" "http://www.springframework.org/dtd/spring-beans.dtd">

<beans>
  <!-- Configure spring to give a hook to axis2 without a ServletContext -->
  <bean id="applicationContext" 
    class="org.apache.axis2.extensions.spring.receivers.ApplicationContextHolder" />

  <!-- Axis2 Web Service, but to Spring, its just another bean that has dependencies -->
  <bean id="springAwareService"
        class="spring.SpringAwareService">
    <property name="myBean" ref="myBean" />
  </bean>

  <!-- just another bean with a wired implementation, that's injected by Spring 
          into the Web Service -->
   <bean id="myBean"
        class="spring.MyBeanImpl">
     <property name="val" value="Spring, emerge thyself" />
  </bean>
</beans>

If the service is _NOT_ running in a Servlet Container, i.e., Axis2 will _NOT_ be able to get a hold of ServletContext or you prefer not to, the services.xml for the example would be using SpringAppContextAwareObjectSupplier such as:

<service name="SpringAwareService">
    <description>
        simple spring example
    </description>
    <parameter name="ServiceObjectSupplier" locked="false">org.apache.axis2.extensions.spring.receivers.SpringAppContextAwareObjectSupplier</parameter>
    <parameter name="SpringBeanName" locked="false">springAwareService</parameter>
    <operation name="getValue">
        <messageReceiver class="org.apache.axis2.receivers.RawXMLINOutMessageReceiver"/>
    </operation>
</service>

While the above example uses RawXMLINOutMessageReceiver as its messageReceiver class, all Message Receivers are currently supported, as would be any Message Receiver that extends org.apache.axis2.receivers.AbstractMessageReceiver .

In a 'without a ServletContext' environment, one way you could load the applicationContext.xml file is in a place that will be run once, upon start-up, execute:

import org.springframework.context.support.ClassPathXmlApplicationContext;

 public void createSpringAppCtx(ClassLoader cl)
            throws Exception {

    ClassPathXmlApplicationContext ctx = new
      ClassPathXmlApplicationContext(new String[] {Constants.MY_PATH +
      "spring/applicationContext.xml"}, false);
           ctx.setClassLoader(cl);
           ctx.refresh();

}

Putting It All Together

From here, its just standard Axis2 coding, only now the service has Spring wiring capabilities. The implementation is the same whether using either SpringServletContextObjectSupplier or SpringAppContextAwareObjectSupplier. The service is below:

package spring;

import org.apache.axiom.om.OMAbstractFactory;
import org.apache.axiom.om.OMElement;
import org.apache.axiom.om.OMFactory;
import org.apache.axiom.om.OMNamespace;
import org.apache.axiom.om.OMText;

public class SpringAwareService {

    private MyBean myBean = null;

    //spring 'injects' this implementation
    public void setMyBean(MyBean myBean) {
            this.myBean = myBean;
    }

    // The web service
    public OMElement getValue(OMElement ignore) {
            OMFactory factory=
                OMAbstractFactory.getOMFactory();
            OMNamespace payloadNs= factory.createOMNamespace(
                "http://springExample.org/example1", "example1");
            OMElement payload =
                factory.createOMElement("string", payloadNs);
            OMText response = factory.createOMText(this.myBean.emerge());
            payload.addChild(response);
            return payload;
    }
}

For those new to Spring, one of the ideas is that you program to an Interface, and the implementation is pluggable. This idea is referenced in the Spring config file above. Below is the interface:

package spring;

/** Interface for Spring aware Bean */
public interface MyBean {
         String emerge();
}

Here's the implementation:

/** Spring wired implementation */
public class MyBeanImpl implements MyBean {

    String str = null;
    // spring 'injects' this value
    public void setVal(String s) {
        str = s;
    }
    // web service gets this value
    public String emerge() {
        return str;
    }
}

Lastly here's the client - not really necessary for the example, other than for completeness:

package client;

import java.io.StringWriter;

import javax.xml.stream.XMLOutputFactory;

import org.apache.axiom.om.OMAbstractFactory;
import org.apache.axiom.om.OMElement;
import org.apache.axiom.om.OMFactory;
import org.apache.axiom.om.OMNamespace;
import org.apache.axis2.addressing.EndpointReference;
import org.apache.axis2.client.Options;
import org.apache.axis2.client.ServiceClient;

public class TestClient {
    private static EndpointReference targetEPR =
        new EndpointReference(
               "http://localhost:8080/axis2/services/SpringAwareService");

    /**
     * Simple axis2 client.
     *
     * @param args Main
     */
    public static void main(String[] args) {
        try {
            OMFactory factory = OMAbstractFactory.getOMFactory();
            OMNamespace omNs = factory.createOMNamespace(
                        "http://springExample.org/example1", "example1");

            OMElement method = factory.createOMElement("getValue", omNs);
            OMElement value = factory.createOMElement("Text", omNs);
            value.addChild(factory.createOMText(value, "Some String "));
            method.addChild(value);

            ServiceClient serviceClient = new ServiceClient();

            Options options = new Options();
            serviceClient.setOptions(options);
            options.setTo(targetEPR);

            //Blocking invocation
            OMElement result = serviceClient.sendReceive(method);

            StringWriter writer = new StringWriter();
            result.serialize(XMLOutputFactory.newInstance()
                    .createXMLStreamWriter(writer));
            writer.flush();

            System.out.println("Response: " + writer.toString());
        } catch (Exception ex) {
            ex.printStackTrace();
        }
    }
}

The examples above assumes that both the spring framework jar and the axis2-spring-*.jar are under WEB-INF/lib. In such a case, the classes shown in this tutorial need to be placed in a JAR under WEB-INF/lib. In this example the JAR layout is:

./mySpring.jar
./META-INF
./META-INF/MANIFEST.MF
./spring
./spring/MyBean.class
./spring/MyBeanImpl.class
./spring/SpringAwareService.class

Since all the user classes are in mySpring.jar in this example, the AAR merely contains the services.xml file:

./springExample.aar
./META-INF
./META-INF/MANIFEST.MF
./META-INF/services.xml

To run this example, make sure you have the axis2-spring*.jar that comes from the axis2-std-*-bin distro in the server side WEB-INF/lib, as well as the appropriate Spring jar - most will use the full spring.jar, but the minimum requirements are spring-core, spring-beans, spring-context and spring-web. Running the client, you should see this output:

Response: <example1:string xmlns:example1="http://springExample.org/example1" 
  xmlns:tns="http://ws.apache.org/axis2">Spring, emerge thyself</example1:string>

Spring Inside an AAR

Frequently Axis2 users wish to run Spring inside the AAR. Here we show you how. There are four points to be aware of:

(A) You need to configure Spring to use the Axis2 Service Classloader. See the Known issues running Spring inside the AAR area.

(B) Its up to you to load Spring, though we give an example below.

(C) For reasons such as classloader isolation the SpringAppContextAwareObjectSupplier is the best choice.

(D) The springframework jar and axis2-spring-*.jar will be placed inside the AAR under the lib directory. Please MOVE the axis2-spring-*.jar from WEB-INF/lib to inside the AAR, as shown below - it will NOT work otherwise.

• The Spring inside an AAR layout

./springExample.aar
./META-INF
./META-INF/MANIFEST.MF
./META-INF/services.xml
./applicationContext.xml
./lib
./lib/axis2-spring-SNAPSHOT.jar
./lib/spring.jar
./spring
./spring/MyBean.class
./spring/MyBeanImpl.class
./spring/SpringAwareService.class
./spring/SpringInit.class

As explained in the Without a ServletContext section, likewise the 'Spring inside an AAR' config needs to hook Axis2 and Spring together via a Spring bean. Place the following in your Spring config file:

<!-- Configure spring to give a hook to axis2 without a ServletContext -->
  <bean id="applicationContext" 
    class="org.apache.axis2.extensions.spring.receivers.ApplicationContextHolder" />

• The Spring inside an AAR init class

One way to initialize Spring inside the AAR is to use the org.apache.axis2.engine.ServiceLifeCycle interface. Here we give an example:

package spring;

import org.apache.axis2.engine.ServiceLifeCycle;
import org.apache.axis2.context.ConfigurationContext;
import org.apache.axis2.description.AxisService;
import org.springframework.context.support.ClassPathXmlApplicationContext;

public class SpringInit implements ServiceLifeCycle {

    /**
     * This will be called during the deployement time of the service. 
     * irrespective
     * of the service scope this method will be called
     */
    public void startUp(ConfigurationContext ignore, AxisService service) {

        try {
            System.out.println("Starting spring init");
            ClassLoader classLoader = service.getClassLoader();
            ClassPathXmlApplicationContext appCtx = new
            ClassPathXmlApplicationContext(new String[] {"applicationContext.xml"}, false);
                appCtx.setClassLoader(classLoader);
                appCtx.refresh();
            System.out.println("spring loaded");
        } catch (Exception ex) {
            ex.printStackTrace();
        }
    }

    /**
     * This will be called during the system shut down time. 
     * irrespective
     * of the service scope this method will be called
     */
    public void shutDown(ConfigurationContext ctxIgnore, AxisService ignore) {
    }
}

Here's the services.xml that now includes SpringInit and the SpringAwareService shown above. There is also the composite parameter which is needed when loading Spring in the AAR - see the Known issues running Spring inside the AAR area.

<serviceGroup>
  <!-- Invoke SpringInit on server startup and shutdown -->
  <service name="SpringAwareService" class="spring.SpringInit">
    <description>
         simple spring example - inside the AAR
    </description>
    <!-- need the TCCL param when using spring inside the AAR -->
    <parameter name="ServiceTCCL" locked="false">composite</parameter>
    <parameter name="ServiceObjectSupplier" locked="false">org.apache.axis2.extensions.spring.rec ...