This document describes how to use a custom transformer in Mule to convert a JSON payload to XML. The Mule flow uses a file inbound endpoint to pick up a JSON file, passes it through a custom transformer Java class that converts it to XML using JSON.toString(), and writes the XML output to a file using a file outbound endpoint. The JSON and generated XML contents are displayed. The custom transformer provides a simple way to transform between JSON and XML formats in Mule without writing additional code.

1. By Anirban Sen Chowdhary

4. .

5. Here I will show you how ……

6. Let us consider we have a following Mule flow :-
Now you can see in the above flow the inbound endpoint will pic
a file that contains JSON content from a location and put it into
another location and the outbound file will contain it’s
corresponding XML content.
You can also see a custom transformer in the middle which is
responsible for this JSON payload conversion to XML directly.

7. Now, let’s check the code for this flow :-
<flow name="CustomJSONtoXMLTransformer"
doc:name="CustomJSONtoXMLTransformer">
<file:inbound-endpoint path="E:backuptestnewfolder"
responseTimeout="10000" doc:name="File">
<file:filename-regex-filter pattern="jsonFile.txt" caseSensitive="false"/>
</file:inbound-endpoint>
<file:file-to-string-transformer doc:name="File to String"/>
<custom-transformer class="CustomJSONtoXMLTransformer"
doc:name="JsonToXml"/>
<logger message="#[message.payload]" level="INFO" doc:name="Logger" />
<file:outbound-endpoint path="E:backuptest" outputPattern="xmlFile.txt"
responseTimeout="10000" doc:name="File" />
</flow>
As you can see the file jsonFile.txt contains JSON content that will be
converted directly into XML by the custom-transformer into a file
xmlFile.txt

8. Now let’s check the JSON content of file jsonFile.txt :-
So, the above is the JSON content we need to convert using our
custom transformer into a corresponding XML

9. So our custom transformer java class is the following :-
public class CustomJSONtoXMLTransformer extends AbstractMessageTransformer implements
DiscoverableTransformer {
@Override
public Object transformMessage(MuleMessage message, String outputEncoding)
throws TransformerException {
String jsonStr = (String) message.getPayload();
JSONObject jsonObj;
try {
jsonObj = new JSONObject(jsonStr);
System.out.println(XML.toString(jsonObj));
//To append <?xml version="1.0"?>
/* StringBuilder builder = new StringBuilder();
builder
.append("<?xml version="1.0"?>")
.append(XML.toString(jsonObj));
String xml_version= XML.toString(jsonObj);
xml_version= builder.toString();
return xml_version;*/
//Append ends
return XML.toString(jsonObj);
}
catch (JSONException e) {
System.out.println("Error: " + e);
e.printStackTrace();
}
return null;
}
@Override
public int getPriorityWeighting() {
return 0;
}
@Override
public void setPriorityWeighting(int weighting) {
}
}

10. Now let’s test our application . We will see the following in our Mule console
:-
You can see the payload is transformed into XML and has been
dispatched to location E:backuptest with file name xmlFile.txt

11. Now if we open the file xmlFile.txt from location
E:backuptest we will get our XML content as following
You can see you have generated the XML for the JSON directly just
using a simple custom transformer component

12. Hope you enjoyed the simple yet an amazing trick in Mule