Transformers convert message payloads between formats. There are several types of built-in transformers in Mule Studio for tasks like XML to JSON conversion. Custom transformers can be created by annotating methods or by extending the AbstractTransformer class and implementing the transform logic.

1. Transformers
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2. • Transformers convert message payloads to formats expected by their destinations
• A Transformer prepares a message to be processed through a Mule flow by enhancing or altering the
message header or message payload
• For example, if the message source that triggers your flow receives data in XML format, but a
downstream message processor requires JSON-formatted data
• one or more transformers positioned between the message source and the message processor can achieve
the necessary translation

3. Transformers Available in Studio
Script Transformers
Java Object Transformers

4. Content Transformers
SAP Transformers
Message and Variable Transformers

5. Creating Custom Transformers
1. Use a Transformer Annotation on a method.
2. The traditional Mule way of creating custom transformers by extending AbstractTransformer
custom transformer is a user-defined transformer class that implements org.mule.api.transformer.Transformer.
Your class can extend AbstractTransformer or AbstractMessageTransform
There are two ways to create a transformer.
The transformer is then configured as follows:
(OR)

6. @ContainsTransformerMethods // since Mule 3.0.1
public class MyTransformers {
@Transformer
public URL stringToURL(String string) throws MalformedURLException {
return new java.net.URL(string);
}
@Transformer
public List<URL> stringsToURLs(String string) throws MalformedURLException {
List<URL urls = new ArrayList<URL>();
for (StringTokenizer tokenizer = new StringTokenizer(string); tokenizer.hasMoreTokens();)
{
urls.add(new URL(tokenizer.nextToken())); }
return urls;
}
}
@Transformer Annotation

7. public class HelloWorldTransformer extends AbstractMessageTransformer{
public Object transformMessage(MuleMessage message, String outputEncoding) throws TransformerException {
@SuppressWarnings("unchecked")
List<employee> employee= (List<employee>) message.getPayload();
message.setOutboundProperty("a", "Hello sai");
for ( employee employee1 : employee) {
System.out.println(employee1.getEid());
System.out.println(employee1.getEmployeename());
System.out.println("******");
if (employee1.getEid()==1) {
System.out.println("i am first variable......");
message.setOutboundProperty("a", employee1.getEid());
}
}
message.setOutboundProperty("b", message.getPayload());
message.setPayload(employee);
return employee;
}
}
-- For example, to make the helloWorldTransformer
discoverable, you would define it as follows:

8. references
• https://docs.mulesoft.com/mule-user-guide/v/3.8/transformers
• https://docs.mulesoft.com/mule-user-guide/v/3.8/creating-custom-
transformers