How to use XStream in Mule?

Question

I have written three classes implementing XStream. It marshalls/unmarshalls the following XML.

<Message calledProgram="XXX" programName="YYY">
  <Fields>
    <Field name="SupplierName" value="ABC"/>
    <Field name="SupplierNo" value="123456"/>
    <Field name="SupplierCountry" value="AA"/>
    <Field name="TermsOfDelivery" value="5"/>
    <Field name="PaymentTerms" value="90"/>
    <Field name="Currency" value="GBP"/>
  </Fields>
</Message>

How do I use these classes in Mule? It is one Class that uses the other two so it is just one class to use.

I will be receiving an XML like above. I want to transform it to an Object.

It works in plain Java, but how do I use it in a flow. Getting all possible Exceptions from Mule.

Exception in thread "main" org.mule.module.launcher.DeploymentInitException: InstantiationException: xxx.com.GenericClass
at org.mule.module.launcher.application.DefaultMuleApplication.init(DefaultMuleApplication.java:220)
at org.mule.module.launcher.application.ApplicationWrapper.init(ApplicationWrapper.java:64)
at org.mule.module.launcher.DefaultMuleDeployer.deploy(DefaultMuleDeployer.java:46)
at org.mule.tooling.server.application.ApplicationDeployer.run(ApplicationDeployer.java:56)
at org.mule.tooling.server.application.ApplicationDeployer.main(ApplicationDeployer.java:88)
Caused by: org.mule.api.config.ConfigurationException: Error creating bean with name 'MyB24Flow1': Invocation of init method failed; nested exception is org.mule.api.lifecycle.InitialisationException: Unable to initialize XStream (org.mule.api.lifecycle.InitialisationException) (org.mule.api.config.ConfigurationException)
at org.mule.config.builders.AbstractConfigurationBuilder.configure(AbstractConfigurationBuilder.java:52)
at org.mule.config.builders.AbstractResourceConfigurationBuilder.configure(AbstractResourceConfigurationBuilder.java:78)
at org.mule.context.DefaultMuleContextFactory.createMuleContext(DefaultMuleContextFactory.java:80)
at org.mule.module.launcher.application.DefaultMuleApplication.init(DefaultMuleApplication.java:208)
... 4 more


Caused by: org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'MyB24Flow1': Invocation of init method failed; nested exception is org.mule.api.lifecycle.InitialisationException: Unable to initialize XStream
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1455)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:519)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:456)
at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:294)
at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:225)
at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:291)
at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:193)
at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:585)
at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:913)
at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:464)
at org.mule.config.spring.SpringRegistry.doInitialise(SpringRegistry.java:89)
at org.mule.registry.AbstractRegistry.initialise(AbstractRegistry.java:109)
... 14 more
Caused by: org.mule.api.lifecycle.InitialisationException: Unable to initialize XStream
at org.mule.module.xml.transformer.AbstractXStreamTransformer.initialise(AbstractXStreamTransformer.java:52)
at org.mule.processor.chain.AbstractMessageProcessorChain.initialise(AbstractMessageProcessorChain.java:79)
at org.mule.construct.AbstractFlowConstruct.initialiseIfInitialisable(AbstractFlowConstruct.java:309)
at org.mule.construct.AbstractPipeline.doInitialise(AbstractPipeline.java:161)
at org.mule.construct.AbstractFlowConstruct$1.onTransition(AbstractFlowConstruct.java:111)
at org.mule.construct.AbstractFlowConstruct$1.onTransition(AbstractFlowConstruct.java:105)
at org.mule.lifecycle.AbstractLifecycleManager.invokePhase(AbstractLifecycleManager.java:141)
at org.mule.construct.FlowConstructLifecycleManager.fireInitialisePhase(FlowConstructLifecycleManager.java:81)
at org.mule.construct.AbstractFlowConstruct.initialise(AbstractFlowConstruct.java:104)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.invokeCustomInitMethod(AbstractAutowireCapableBeanFactory.java:1581)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.invokeInitMethods(AbstractAutowireCapableBeanFactory.java:1522)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1452)
... 25 more

Update:

Though this is not my real code. But how do you mean OOTB? This doesn't work either. Have tried without the File-2-String as well.

<?xml version="1.0" encoding="UTF-8"?>
<mule xmlns:file="http://www.mulesoft.org/schema/mule/file" xmlns:mulexml="http://www.mulesoft.org/schema/mule/xml" 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" version="CE-3.3.1" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="
http://www.mulesoft.org/schema/mule/xml         http://www.mulesoft.org/schema/mule/xml/current/mule-xml.xsd 
http://www.mulesoft.org/schema/mule/file     http://www.mulesoft.org/schema/mule/file/current/mule-file.xsd 
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 ">
    <flow name="MyXStreamFlow1" doc:name="MyXStreamFlow1">
    <file:inbound-endpoint path="E:\JavaDev\Test" responseTimeout="10000" doc:name="File"/>
    <logger level="INFO" doc:name="Logger"/>
    <file:file-to-string-transformer doc:name="File to String"/>
    <logger message="WTF" level="INFO" doc:name="Logger"/>
    <mulexml:xml-to-object-transformer doc:name="XML to Object"/>
    <logger level="INFO" doc:name="Logger"/>
    <mulexml:object-to-xml-transformer doc:name="Object to XML"/>
    <logger level="INFO" doc:name="Logger"/>
</flow>

Here's my main Java Class.

package test;
import java.io.FileInputStream;
import java.io.FileNotFoundException;

import com.thoughtworks.xstream.XStream;
import com.thoughtworks.xstream.annotations.XStreamAlias;
import com.thoughtworks.xstream.annotations.XStreamAsAttribute;
import com.thoughtworks.xstream.io.xml.DomDriver;

@XStreamAlias("Message")
public class GenericClass {

@XStreamAlias("calledProgram")
@XStreamAsAttribute
private String calledProgram;

@XStreamAlias("programName")
@XStreamAsAttribute
private String programName;

@XStreamAlias("Fields")
private Fields flds = new Fields(
    new Field("nameValue1", "valueValue1"),
    new Field("nameValue2", "valueValue2"),
    new Field("nameValue3", "valueValue2"));

private static XStream xstream;

public GenericClass() {
    new GenericClass("calledProgram", "programName");
}

public GenericClass(String calledProgram, String programName) {
    xstream = new XStream(new DomDriver());
    xstream.processAnnotations(GenericClass.class);
    this.calledProgram = calledProgram;
    this.programName = programName;
}

public static void main(String[] args) {

    GenericClass msg = new GenericClass();

    // Unmarshall
    FileInputStream file = null;
    try {
        file = new FileInputStream(
                "E:\\JavaDev\\JRecordFiles\\Samples\\LevisTest.xml");
    } catch (FileNotFoundException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
     msg = (GenericClass) xstream.fromXML(file);
     System.out.println("<?xml version=\"1.0\" encoding=\"utf-8\"?>\n" + xstream.toXML(msg));
}
}

-

package test;

import com.thoughtworks.xstream.annotations.XStreamAsAttribute;


public class Field {

private String field;

@XStreamAsAttribute
private String name;

@XStreamAsAttribute
private String value;

/**
 * @param field
 */
public Field(String name, String value) {
    this.name = name;
    this.value = value;
}

/**
 * @return the field
 */
public String getField() {
    return field;
}

/**
 * @param field
 *            the field to set
 */
public void setField(String field) {
    this.field = field;
}

/**
 * @return the name
 */
public String getName() {
    return name;
}

/**
 * @param name
 *            the name to set
 */
public void setName(String name) {
    this.name = name;
}

/**
 * @return the value
 */
public String getValue() {
    return value;
}

/**
 * @param value
 *            the value to set
 */
public void setValue(String value) {
    this.value = value;
}

}

-

package test;

import java.util.Arrays;
import java.util.List;

import com.thoughtworks.xstream.annotations.XStreamImplicit;



public class Fields {

@XStreamImplicit(itemFieldName = "Field")
private List<Field> fields;

public Fields(Field... field) {
    this.fields = Arrays.asList(field);
}

/**
 * @return the fields
 */
public List<Field> getFields() {
    return fields;
}

/**
 * @param fields
 *            the fields to set
 */
public void setFields(List<Field> fields) {
    this.fields = fields;
}

}

How do I use XStream in Mule?

Answer 1

The problem

The default Object to XML transformer only supports the alias annotation for classes:

<mulexml:object-to-xml-transformer doc:name="Object to XML">
    <mulexml:alias name="myAlias" class="com.my.package.MyClass"/>
</mulexml:object-to-xml-transformer>

and ignores every other annotation. There is a already an issue since July 2012 on the official bug tracker, but it's unresolved until now.

Solution: Custom XML to Object transformer

1. Create the transformer

Create a custom transformer in Java which extends AbstractMessageTransformer:

public class ObjectToXml extends AbstractMessageTransformer {

  public Object transformMessage(MuleMessage message, String outputEncoding) throws TransformerException {

    XStream xstream = new XStream();

    // The payload should be the object to transform into XML
    Object object = message.getPayload();

    // Register all annotations in the XStream instance 
    xstream.processAnnotations(object.getClass());

    // Convert the object to XML and set it as payload
    message.setPayload(xstream.toXML(object));

    return message;
  }
}

2. Use the custom transformer in your Mule flow

Add a Java Transfromer (not Java Component) to your flow:

<custom-transformer class="com.my.package.ObjectToXml" doc:name="Object to XML"/>

That's it!