How to Convert JSON to XML in Java

Use json-lib, a library which adds JSON support to any Java program. json-lib provides an XMLSerializer which can be used to output XML from a JSON object.

1. Add these dependencies to your project:

    <dependency>
    	<groupId>net.sf.json-lib</groupId>
    	<artifactId>json-lib</artifactId>
    	<version>2.3</version>
    	<type>jar</type>
    	<classifier>jdk15</classifier>
    	<scope>compile</scope>
    </dependency>
    <dependency>
    	<groupId>org.apache.commons</groupId>
    	<artifactId>commons-io</artifactId>
    	<version>1.3.2</version>
    	<type>jar</type>
    	<scope>compile</scope>
    </dependency>
    <dependency>
    	<groupId>xom</groupId>
    	<artifactId>xom</artifactId>
    	<version>1.1</version>
    </dependency>

What does this mean? See How to Add a Dependency to a Java Project

2. Put the following JSON sample in your classpath:

{'foo':'bar',
 'coolness':2.0,
 'altitude':39000,
 'pilot':{'firstName':'Buzz',
      	  'lastName':'Aldrin'},
 'mission':'apollo 11'}

3. Load the resource from the classpath, parse this JSON, and convert it to XML with the following class:

package com.discursive.answers;

import java.io.InputStream;

import net.sf.json.JSON;
import net.sf.json.JSONSerializer;
import net.sf.json.xml.JSONTypes;
import net.sf.json.xml.XMLSerializer;

import org.apache.commons.io.IOUtils;

public class ConvertJSONtoXML {

	public static void main(String[] args) throws Exception {
		InputStream is = 
			ConvertJSONtoXML.class.getResourceAsStream("sample-json.txt");
		String jsonData = IOUtils.toString(is);
		
		XMLSerializer serializer = new XMLSerializer(); 
		JSON json = JSONSerializer.toJSON( jsonData ); 
		String xml = serializer.write( json );  
		System.out.println(xml);  		
		
	}
}

4. The previous class will produce the following XML output:

<?xml version="1.0" encoding="UTF-8"?>
<o>
  <altitude type="number">39000</altitude>
  <coolness type="number">2.0</coolness>
  <foo type="string">bar</foo>
  <mission type="string">apollo 11</mission>
  <pilot class="object">
    <firstName type="string">Buzz</firstName>
    <lastName type="string">Aldrin</lastName>
  </pilot>
</o>

5. To get rid of the type hints, use this code instead:

package com.discursive.answers;

import java.io.InputStream;

import net.sf.json.JSON;
import net.sf.json.JSONSerializer;
import net.sf.json.xml.JSONTypes;
import net.sf.json.xml.XMLSerializer;

import org.apache.commons.io.IOUtils;

public class ConvertJSONtoXMLNoHints {

	public static void main(String[] args) throws Exception {
		InputStream is = 
			ConvertJSONtoXMLNoHints.class.getResourceAsStream("sample-json.txt");
		String jsonData = IOUtils.toString(is);
		
		XMLSerializer serializer = new XMLSerializer(); 
		JSON json = JSONSerializer.toJSON( jsonData ); 
		serializer.setTypeHintsEnabled(false);
		String xml = serializer.write( json );  
		System.out.println(xml);  		
		
	}
}

6. The previous class will produce the following XML without type hints:

<?xml version="1.0" encoding="UTF-8"?>
<o>
  <altitude>39000</altitude>
  <coolness>2.0</coolness>
  <foo>bar</foo>
  <mission>apollo 11</mission>
  <pilot>
    <firstName>Buzz</firstName>
    <lastName>Aldrin</lastName>
  </pilot>
</o>

7. "o" isn't a very friendly root node name, is it? To change the root node name, use the following code:

package com.discursive.answers;

import java.io.InputStream;

import net.sf.json.JSON;
import net.sf.json.JSONSerializer;
import net.sf.json.xml.JSONTypes;
import net.sf.json.xml.XMLSerializer;

import org.apache.commons.io.IOUtils;

public class ConvertJSONtoXMLSetRoot {

	public static void main(String[] args) throws Exception {
		InputStream is = 
			ConvertJSONtoXMLNoHints.class.getResourceAsStream("sample-json.txt");
		String jsonData = IOUtils.toString(is);
		
		XMLSerializer serializer = new XMLSerializer(); 
		JSON json = JSONSerializer.toJSON( jsonData ); 
		serializer.setRootName("SampleJSON");
		serializer.setTypeHintsEnabled(false);
		String xml = serializer.write( json );  
		System.out.println(xml);  		
		
	}
}

8. This previous class will produce the following XML:

<?xml version="1.0" encoding="UTF-8"?>
<SampleJSON>
  <altitude>39000</altitude>
  <coolness>2.0</coolness>
  <foo>bar</foo>
  <mission>apollo 11</mission>
  <pilot>
    <firstName>Buzz</firstName>
    <lastName>Aldrin</lastName>
  </pilot>
</SampleJSON>

This sample project is available on GitHub here: http://github.com/to...le-json-parsing

For more information about the json-lib project, see JSON-LIB project page