Tutorial-Example-ReportIncident-Part5

Part 5

We continue from part 4 where we have the routing in place. However as you might have noticed we aren't quiet there yet with a nice solution, we are still coding to much. In this part we will look into to address these two concerns:

• Starting Camel automatically
• Using CXF in routing

Starting Camel automatically

Our current deployment model is as a war and we have the web.xml to help start things. Well in fact we will leverage Spring to start the world . We use it's ContextListener

	<!-- the listener that kick-starts Spring -->
	<listener>
		<listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
	</listener>

Then we need a standard Spring XML file so we create a new file in src/main/resources and name it camel-config.xml. Before we start editing this XML file we need to link to it from the web.xml file. So we add this snippet to the web.xml:

	<!-- location of spring xml files -->
	<context-param>
	    <param-name>contextConfigLocation</param-name>
            <param-value>classpath:camel-config.xml</param-value>
	</context-param>

Now we are ready to edit the camel-config.xml file that is a standard Spring XML bean file. So you can add standard spring beans and whatnot you like to do and can do with Spring.

<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-2.5.xsd">

</beans>

Now we are nearly there, we just need to add Camel to the Spring XML file, so Spring knows Camel exists and can start it. First we need to add Camel to the schema location in the top of the XML file.

       ...
       xsi:schemaLocation="
            http://activemq.apache.org/camel/schema/spring http://activemq.apache.org/camel/schema/spring/camel-spring.xsd
            http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-2.5.xsd">

Now we are ready to let Spring and Camel work together. What we need to do is adding a CamelContext to the Spring XML file. Camel ships with a CamelContextFactoryBean that is a Spring factory bean we should use for creating and initializing the SpringCamelContext. SpringCamelContext is extending CamelContext to be Spring aware so Camel and Spring can work nicely together. For instance the Registry will now use Spring bean lookup. So any spring bean can now easily be lookup and used from Camel. Well back to today's lesson. So we can create a SpringCamelContext using the factory bean as illustrated below:

   <bean id="camel" class="org.apache.camel.spring.CamelContextFactoryBean"/>

However this is not used very often as Spring has support for custom namespace, so Camel has a CamelNamespaceHandler so we can create Camel using nice XML syntax as:

    <camelContext id="camel" xmlns="http://activemq.apache.org/camel/schema/spring">
       ...
    </camelContext>

Adding route builder

Now we have Camel integrated but we still need to add our route bulder that we did manually from the javacode as:

    // append the routes to the context
    context.addRoutes(new ReportIncidentRoutes());

There are two solutions to this

• using spring bean
• package scanning

Using a spring bean we just declare the route builder using a regular spring bean:

   <bean id="myrouter" class="org.apache.camel.example.reportincident.ReportIncidentRoutes"/>

And then we can refer to it from our CamelContext:

    <camelContext id="camel" xmlns="http://activemq.apache.org/camel/schema/spring">
       <routeBuilderRef ref="myrouter"/>
    </camelContext>

So now when Spring start's it will read the camel-context.xml file and thus also start Camel as well. As SpringCamelContext is spring lifecycle event aware, Camel will also shutdown when Spring is shutting down. So when you stop the web application Spring will notify this and Camel is also shutdown nice and properly. So as an end user no need to worry.

The package scanning solution is for convenience to refer to a java package and Camel will scan all classes within this package for RouteBuilder classes. If using this then you dont need to declare your route builder as a Spring bean. So the XML can be reduced to.

    <camelContext id="camel" xmlns="http://activemq.apache.org/camel/schema/spring">
       <package>org.apache.camel.example.reportincident</package>
    </camelContext>

Using CXF directly

Now we have seen how you can leverage Spring to start Camel, in fact it handles the lifecycle of Camel, so you can say Camel is embedded with Spring in your application.

From the very start of this tutorial we have used CXF as the webservice framework and we haven't integrated it directly with Camel as it can do out-of-the-box. Camel ships with a camel-cxf component for integrating CXF directly within Camel routing. In our tutorial we are exposing a webservice so we want continue to do this. Before we continue let's recap at what the webservice implementation we have from part 4

/**
 * The webservice we have implemented.
 */
public class ReportIncidentEndpointImpl implements ReportIncidentEndpoint {

    private CamelContext context;

    public ReportIncidentEndpointImpl() throws Exception {
        // create the context
        context = new DefaultCamelContext();

        // append the routes to the context
        context.addRoutes(new ReportIncidentRoutes());

        // at the end start the camel context
        context.start();
    }

    public OutputReportIncident reportIncident(InputReportIncident parameters) {
        // create the producer template to use for sending messages
        ProducerTemplate producer = context.createProducerTemplate();
        // send the body and the filename defined with the special header key
        Object mailBody = producer.sendBody("direct:start", parameters);
        System.out.println("Body:" + mailBody);

        // return an OK reply
        OutputReportIncident out = new OutputReportIncident();
        out.setCode("OK");
        return out;
    }

}

We have already seen how we can get Spring starting Camel so the constructor method can be removed. What next is that the CamelContext needed in this code should be the one from our camel-context.xml file. So we change the code to use a plain setter injection (we can use Spring annotations and whatelse but we keep it simple with a setter):

/**
 * The webservice we have implemented.
 */
public class ReportIncidentEndpointImpl implements ReportIncidentEndpoint {

    private CamelContext context;

    public void setCamelContext(CamelContext context) {
        this.context = context;
    }

    public OutputReportIncident reportIncident(InputReportIncident parameters) {
        // create the producer template to use for sending messages
        ProducerTemplate producer = context.createProducerTemplate();
        // send the body and the filename defined with the special header key
        Object mailBody = producer.sendBody("direct:start", parameters);
        System.out.println("Body:" + mailBody);

        // return an OK reply
        OutputReportIncident out = new OutputReportIncident();
        out.setCode("OK");
        return out;
    }

}

And then we need to instruct Spring to set this property. Turning back to cxf-config.xml from part 4 we can add a reference to our camel context

<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xmlns:jaxws="http://cxf.apache.org/jaxws"
       xsi:schemaLocation="
            http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-2.0.xsd
            http://cxf.apache.org/jaxws http://cxf.apache.org/schemas/jaxws.xsd">

    <import resource="classpath:META-INF/cxf/cxf.xml"/>
    <import resource="classpath:META-INF/cxf/cxf-extension-soap.xml"/>
    <import resource="classpath:META-INF/cxf/cxf-servlet.xml"/>

    <!-- implementation of the webservice, and we refer to our camel context with the id = camel from camel-context.xml -->
    <bean id="reportIncidentEndpoint" class="org.apache.camel.example.reportincident.ReportIncidentEndpointImpl">
       <property name="context" ref="camel"/>
    </bean>

    <!-- export the webservice using jaxws -->
    <jaxws:endpoint id="reportIncident"
                    implementor="#reportIncidentEndpoint"
                    address="/incident"
                    wsdlLocation="/WEB-INF/wsdl/report_incident.xml"
                    endpointName="s:ReportIncidentPort"
                    serviceName="s:ReportIncidentService"
                    xmlns:s="http://reportincident.example.camel.apache.org"/>
</beans>

So now we have two spring XML files

• cxf-config.xml
• camel-config.xml

And since cxf-config.xml is dependent on camel-config.xml we need to have correct ordering in our web.xml where we have defined the XML files to load by Spring. So we set the camel-config.xml before the cxf-config.xml so Spring have created the SpringCamelContext and registered it in its registry with the id = camel.

    <!-- location of spring xml files -->
    <context-param>
        <param-name>contextConfigLocation</param-name>
        <param-value>classpath:camel-config.xml</param-value>
        <param-value>classpath:cxf-config.xml</param-value>
    </context-param>

But hey this isn't using CXF directly in the routing? Yes it's not but I wanted to show the halfway solution as well. What we have now is having Spring creating and handling lifecycle of Camel and showing how you can inject CamelContext using standard Spring into whatever code you have. This is very powerful as you can use the solution that you (or your team) already master and is familiar with. If they have Spring experience then the IoC principle of injecting resources is of course also possible with Camel as well. In fact it's a best practice principle. Later you will learn that you can inject other Camel types such as Endpoint, ProducerTemplate as well.

Using the camel-cxf component

Okay let's continue and try to integrate CXF directly into our routing in Camel. This can be a bit more tricky than at first sight. Our goal is to avoid implementing the ReportIncidentEndpoint as we did with our code in ReportIncidentEndpointImpl (see above). Camel should be able to handle this automatically and integrate directly within our route.

Before we started our routing using the Direct endpoint with "direct:start". We should replace this with the CXF endpoint.

But before going to far we have to make a few adjustments to the .wsdl file and it's location in our project folder. We move report_incident.wsdl from src/main/webapp/WEB-INF/wsdl* to src/main/resources as we want to be able to refer to it from within our route builder from Java code and thus it should be on the classpath for easy access. Secondly we have upgrade the CXF to a newer version and it identified a minor issue with the .wsdl file itself. We have to give the complexType a name otherwise we get some JAXB error.

So the .wsdl should be changed from:

    <xs:element name="inputReportIncident">
        <xs:complexType>

To include a name attribute of the complex types:

    <xs:element name="inputReportIncident">
        <xs:complexType name="inputReportIncident">

Using CXF endpoint

Okay now we are ready to turn our attention to using CXF directly in Camel routing. So we zap ReportIncidentEndpointImpl as we no longer need this code. So what's left is:

• FilenameGenerator.java
• ReportIncidentRoutes.java
  And that is all what's needed, well for now...

The idea now is to replace the endpoint the starts the ball going from "direct:start" to the CXF endpoint.

CXF endpoint can be configured in either or both CXF spring configuration file or/and in the route directly. It accepts one parameter and others are optional. The parameter it must have is the service class. The service class is the interface for the WSDL operation's. As we have the wsdl2java goal to generate this class for us, we have it already as org.apache.camel.example.reportincident.ReportIncidentEndpoint.

The other parameter we will provide is the url to the .wsdl file. And finally we must provide the http address we expose the webservice at. The URI is therefore:

        // endpoint to our CXF webservice
        String cxfEndpoint = "cxf://http://localhost:8080/part-five/webservices/incident"
                + "?serviceClass=org.apache.camel.example.reportincident.ReportIncidentEndpoint"
                + "&wsdlURL=report_incident.wsdl";

Then we can replace "direct:start" with our cxf endpoint instead, so it's:

        from(cxfEndpoint)...

The next issue you might now have guessed is that before (in part 4) we did a traditional codeing style to start a task and return a response to the caller in the method:

  public OutputReportIncident reportIncident(InputReportIncident parameters) {
        // create the producer template to use for sending messages
        ProducerTemplate producer = context.createProducerTemplate();
        // send the body and the filename defined with the special header key
        Object mailBody = producer.sendBody("direct:start", parameters);
        System.out.println("Body:" + mailBody);

        // return an OK reply
        OutputReportIncident out = new OutputReportIncident();
        out.setCode("OK");
        return out;
    }

As you can see the method reportIncident is invoked with the webservice input parameters and we return the response to to the webservice from the method. But our situation now is that we don't have this method anymore. So how do we return a response to the webservice?

Houston we have a problem! Well of course not but the mindset have to be changed slightly to understand the routing concept, and how it works. So let's step back a bit. What we have here is a webservice that we expose. And our webservice is synchronous request/response based so the caller waits for a response. This is a InOut Message Exchange Pattern. Camel will default use InOut for webservices so we don't need to specify this explicitly. When we have a InOut pattern then Camel will return the response to the original caller when the routes ends. Looking at our route we have:

        from(cxfEndpoint)
            .to("velocity:MailBody.vm")
            // then set the file name using the FilenameGenerator bean
            .setHeader(FileComponent.HEADER_FILE_NAME, BeanLanguage.bean(FilenameGenerator.class, "generateFilename"))
            // and store the file    
            .to("file://target/subfolder")

When the route ends after the file endpoint has been processed Camel will return the OUT message to the original caller (the caller of the webservice). However our route currently as it stands have not set any OUT message, so this is what we need to do, transforming (Message Translator EIP) the message into the response. We will therefore use a processor where we have 100% control in the Java code to set the response.

        public void process(Exchange exchange) throws Exception {
            // the response we want to send
            OutputReportIncident OK = new OutputReportIncident();
            OK.setCode("0");

            // set the response on the OUT message as we use InOut
            exchange.getOut().setBody(OK);
       }

And with the route:

        // first part from the webservice -> file backup
        from(cxfEndpoint)
            .to("velocity:MailBody.vm")
            // then set the file name using the FilenameGenerator bean
            .setHeader(FileComponent.HEADER_FILE_NAME, BeanLanguage.bean(FilenameGenerator.class, "generateFilename"))
            // and store the file    
            .to("file://target/subfolder")
            // return OK as response
            .process(new Processor() {
                public void process(Exchange exchange) throws Exception {
                    // the response we want to send
                    OutputReportIncident OK = new OutputReportIncident();
                    OK.setCode("0");

                    // set the response on the OUT message as we use InOut
                    exchange.getOut().setBody(OK);
                }
            });