Nsryjdtyk

I am attempting a tutorial from the book 'MULE_ESB_COOKBOOK' by packt publishing and I have posted this question in another forum too. In the first chapter, there is a 'Deploying your first Hello World application on the Mule server' exercise which I am trying out. The expected output is Hello/(The value I enter as part of the url)

However when I run the application, I am getting the following error in the browser when I enter this: http://localhost:9081. The error message is as follow: "Component that caused exception is: DefaultJavaComponent{helloworldFlow.component.1468192631}. Message payload is of type: NullPayload"

The XML file is as follow:

 <?xml version="1.0" encoding="UTF-8"?>



 <mule xmlns:http="http://www.mulesoft.org/schema/mule/http" xmlns="http://www.mulesoft.org/schema/mule/core" xmlns:doc="http://www.mulesoft.org/schema/mule/documentation"

     xmlns:spring="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-current.xsd

 http://www.mulesoft.org/schema/mule/core http://www.mulesoft.org/schema/mule/core/current/mule.xsd

 http://www.mulesoft.org/schema/mule/http http://www.mulesoft.org/schema/mule/http/current/mule-http.xsd">

     <http:listener-config name="HTTP_Listener_Configuration" host="localhost" port="9081" doc:name="HTTP Listener Configuration"/>

     <flow name="helloworldFlow">

         <http:listener config-ref="HTTP_Listener_Configuration" path="/" doc:name="HTTP"/>

         <component class="com.org.Greeting" doc:name="Java"/>

     </flow>

 </mule>

The Greeting.java file is as follows:

package com.org;



public class Greeting {



     public String sayHi(String str)

     {

         return "Hello " +str;

     }



 }

I am not sure why I am getting this error. Hope someone can help, thanks.

This is expected because you are not passing any input to your Java class.

Try setting some input using set-payload component before java class component:

 <http:listener-config name="HTTP_Listener_Configuration" host="localhost" port="9081" doc:name="HTTP Listener Configuration"/>

     <flow name="helloworldFlow">

         <http:listener config-ref="HTTP_Listener_Configuration" path="/" doc:name="HTTP"/>

         <set-payload value="Anirban" doc:name="Set Payload"/>

         <component class="com.org.Greeting" doc:name="Java"/>

     </flow>

You Java class is wrong. To invoke a Java class in Mule 3.x it has to implement the Mule org.mule.api.lifecycle.Callable interface. See the example at https://docs.mulesoft.com/mule-runtime/3.9/java-component-reference#basic-hello-world-java-component-class

I'm guessing the complete error in the log points to the correct issue.