MULE: JAVA TRANSFORMERENABLES THE DEVELOPER TO PACKAGE CUSTOM JAVA CODE

BASIC CONSIDERATIONS• Anypoint Studio provides a set of transformers to

handle the most common data transformation scenarios•Developer can chain transformers if a transformer

did not exist for specific needs• The DataWeave Transform Message component can

be used in place of most other transformers

SPECIAL CASES• Transforming complex data structures• Applying complex business rules• The available transformers cannot meet the requirement• Simply throw the old lines of code into a component

instead of having to reengineer the code’s behavior through a series of different Mule components

POSSIBLE SOLUTIONS•Building custom components and/or transformers• Turning to the most favorite Programming

Languages:o Javao .NETo Scripting languages: Groovy, Javascript, Python or Ruby

JAVA• Java is the native language in which Mule is coded• The Java component enables the developer to package

custom Java code that executes when the component receives a message• The Java component can be used to enhance the

functionality and capability of your web-based applications written in Java

JAVA TRANSFORMER (1/2)• Transforms a message from its original

format to a new, modified format.• If rather than just changing the

message/payload, trigger a more complex set of processes coded in Java, use a Java Component.

JAVA TRANSFORMER (2/2)To configure the Java Transformer, selecting a class is the only required entry:•Browse for an existing

Java class• Add a new Java class

BASIC JAVA CLASS• A class must extends:

o org.mule.transformer.AbstractMessageTransformerModifies the message and returns it as the output message of the transformer.

o org.mule.transformer.AbstractTransformerModifies the payload and returns it as the output payload.

• A class must be referenced in a fully-qualified name

JAVA CLASS: MESSAGE (1/3)package com.mulesoft.learning;

import java.util.Map;import org.mule.api.MuleMessage;import org.mule.api.transformer.TransformerException;import org.mule.transformer.AbstractMessageTransformer;

public class MessageTransformer extends AbstractMessageTransformer { @Override public Object transformMessage(MuleMessage message, String outputEncoding) throws TransformerException { Map<String, String> params = message.getInboundProperty("http.query.params"); message.setInvocationProperty("myProperty", "Hello, " + params.get("name")); return message; }}

JAVA CLASS: MESSAGE (2/3)The class has access to Mule Message:• Inbound Properties•Outbound Properties• Payload• Attachments

JAVA CLASS: MESSAGE (3/3)Run/debug a simple flow• http://localhost:8081/?name=Max• It will produce a variable

myProperty, and its value is: Hello, Max• It will keep the payload as is

JAVA CLASS: PAYLOAD (1/3)package com.mulesoft.learning;

import org.mule.api.transformer.TransformerException;import org.mule.transformer.AbstractTransformer;

public class PayloadTransformer extends AbstractTransformer {

@Override protected Object doTransform(Object src, String enc) throws TransformerException { return "Hello, " + src; }}

JAVA CLASS: PAYLOAD (2/3)The class has only access to Payload, therefore:• Add new Byte Array to String Transformer•Update the custom-transformer class to refer to the new

class

JAVA CLASS: PAYLOAD (3/3)Run/debug the new flow• Post a raw message: Max• Send it to http://localhost:8081• It will produce a new payload: Hello, Max

SUMMARYMule allows developers to:•Build their own component and/or transformer• Simply write their favorite programming language•Choose the transformation scope

RESOURCES:• https://

docs.mulesoft.com/mule-user-guide/v/3.8/java-transformer-reference