Converting JSON to XML in Java

Underscore-java library has static method U.jsonToXml(jsonstring). Live example

import com.github.underscore.U;

public class MyClass {
    public static void main(String args[]) {
        String json = "{\"name\":\"JSON\",\"integer\":1,\"double\":2.0,\"boolean\":true,\"nested\":{\"id\":42},\"array\":[1,2,3]}";  
        System.out.println(json); 
        String xml = U.jsonToXml(json);  
        System.out.println(xml); 
    }
}

Output:

{"name":"JSON","integer":1,"double":2.0,"boolean":true,"nested":{"id":42},"array":[1,2,3]}
<?xml version="1.0" encoding="UTF-8"?>
<root>
  <name>JSON</name>
  <integer number="true">1</integer>
  <double number="true">2.0</double>
  <boolean boolean="true">true</boolean>
  <nested>
    <id number="true">42</id>
  </nested>
  <array number="true">1</array>
  <array number="true">2</array>
  <array number="true">3</array>
</root>

For json to xml use the following Jackson example:

final String str = "{\"name\":\"JSON\",\"integer\":1,\"double\":2.0,\"boolean\":true,\"nested\":{\"id\":42},\"array\":[1,2,3]}";
ObjectMapper jsonMapper = new ObjectMapper();
JsonNode node = jsonMapper.readValue(str, JsonNode.class);
XmlMapper xmlMapper = new XmlMapper();
                xmlMapper.configure(SerializationFeature.INDENT_OUTPUT, true);
                xmlMapper.configure(ToXmlGenerator.Feature.WRITE_XML_DECLARATION, true);
                xmlMapper.configure(ToXmlGenerator.Feature.WRITE_XML_1_1, true);
ObjectWriter ow = xmlMapper.writer().withRootName("root");
StringWriter w = new StringWriter();
ow.writeValue(w, node);
System.out.println(w.toString());

Prints:

<?xml version='1.1' encoding='UTF-8'?>
<root>
  <name>JSON</name>
  <integer>1</integer>
  <double>2.0</double>
  <boolean>true</boolean>
  <nested>
    <id>42</id>
  </nested>
  <array>1</array>
  <array>2</array>
  <array>3</array>
</root>

To convert it back (xml to json) take a look at this answer https://stackoverflow.com/a/62468955/1485527 .

Use the (excellent) JSON-Java library from json.org then

JSONObject json = new JSONObject(str);
String xml = XML.toString(json);

toString can take a second argument to provide the name of the XML root node.

This library is also able to convert XML to JSON using XML.toJSONObject(java.lang.String string)

Check the Javadoc

Link to the the github repository

POM

<dependency>
    <groupId>org.json</groupId>
    <artifactId>json</artifactId>
    <version>20160212</version>
</dependency>

original post updated with new links