From: http://answers.oreilly.com/topic/257-how-to-parse-json-in-java/

How to Parse JSON in Java

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  Submitted by tmo9d      
Posted Sep 23 2009 12:25 PM

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Use json-lib, a library which adds JSON support to any Java program. json-lib can take a String and turn it into a JSONObject which can then be used to retrieve specific attributes.

1. Add this dependency to your project:

<dependency>      <groupId>net.sf.json-lib</groupId>      <artifactId>json-lib</artifactId>      <version>2.3</version>      <scope>compile</scope>    </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 and parse this JSON as follows:

package com.discursive.answers;import java.io.InputStream;import net.sf.json.JSONObject;import net.sf.json.JSONSerializer;import org.apache.commons.io.IOUtils;public class JsonParsing {    public static void main(String[] args) throws Exception {        InputStream is =                 JsonParsing.class.getResourceAsStream( "sample-json.txt");        String jsonTxt = IOUtils.toString( is );                JSONObject json = (JSONObject) JSONSerializer.toJSON( jsonTxt );                double coolness = json.getDouble( "coolness" );        int altitude = json.getInt( "altitude" );        JSONObject pilot = json.getJSONObject("pilot");        String firstName = pilot.getString("firstName");        String lastName = pilot.getString("lastName");                System.out.println( "Coolness: " + coolness );        System.out.println( "Altitude: " + altitude );        System.out.println( "Pilot: " + lastName );    }}

Note that JSONSerializer returns a JSON object. This is a general object which could be a JSONObject or a JSONArray depending on the JSON you are trying to parse. In this example, since I know that the JSON is a JSONObject, I can cast the result directly to a JSONObject. If you are dealing with JSON that could return a JSONArray, you'll likely want to check the type of the object that is returned by toJSON.

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

Learn more about this topic from Java Web Services: Up and Running. 

This quick, practical, and thorough introduction to Java web services -- the JAX-WS and JAX-RS APIs -- offers a mix of architectural overview, complete working code examples, and short yet precise instructions for compiling, deploying, and executing a sample application. You'll not only learn how to write web services from scratch, but also how to integrate existing services into your Java applications.

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Tags: 

• java
•  json

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2 Replies

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  Alternative solution by Stuart12345 
Posted Sep 30 2011 10:13 AM

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Be sure to add the classifier:

<dependency>
<groupId>net.sf.json-lib</groupId>
<artifactId>json-lib</artifactId>
<version>2.4</version>
<classifier>jdk15</classifier>
</dependency>

see http://stackoverflow...net-sf-json-lib 

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  Alternative solution by Adam Musial-Bright  
Posted Oct 03 2011 09:39 AM

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Gson, the Google JSON library is also very nice.

You will need a simple POJOs for the JSON representation:

// JSON representationclass MyJson {  public MyJson() {}  private String foo;  private float coolness;  // other attributes  public void setFoo(String foo) {    this.foo = foo;  }  public String getFoo() {    return foo;  }  public void setCoolness(float coolness) {    this.coolness = coolness;  }  public float getCoolness() {    return coolness;  }}

Now you can convert a JSON representation into a JSON object:

  Gson gson = new Gson();  MyJson myJson = new gson.fromJson(jsonTxt, MyJson.class);  // now you have a real java object  System.out.println(myJson.getFoo());

done.