Java JSON Tutorial

JSON (JavaScript Object Notation), is a simple and easy to read and write data exchange format. It’s popular and implemented in countless projects worldwide, for those don’t like XML, JSON is a very good alternative solution.

In this series of Java JSON tutorials, we focus on three popular third party Java libraries to process JSON data, which are Jackson, Google Gson and JSON.simple

Jackson

A High-performance JSON processor.

Jackson data binding example – Object & JSON
Example to use ObjectMapper writeValue() and readValue() to convert Java object to / from JSON.
Jackson data binding example – Map & JSON
Example to convert Java Map to / from JSON
Jackson Tree Model example
Read JSON into Tree, like DOM for XML.
Jackson Streaming example
Example to use JsonGenerator() and JsonParser() to stream read and write JSON data.
Pretty print JSON output in Jackson
Pretty print JSON output via defaultPrettyPrintingWriter().

Google Gson

It was originally created for use inside Google, now it is used by many public projects.

Gson data model example – Object & JSON
Example to use toJson() and fromJson() to convert Java Object to / from JSON.
Gson Streaming example
Example to use JsonWriter() and JsonReader () to stream read and write JSON data.
Pretty print JSON output in Gson
Pretty print JSON output via GsonBuilder.

JSON.simple

Simple Java library for JSON, to read and write JSON data.

JSON.simple example – Read and write JSON
Example to show you how to read and write JSON data to / from file.

References

mkyong

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@GET @Produces("application/xml") public Response getList() { List<Person> personArray = new ArrayList<Person>(); Person p1 = new Person(); p1.setName("First Person"); p1.setId(1); p1.setGender("M"); Person p2 = new Person(); p2.setName("Second Person"); p2.setId(2); p2.setGender("M"); Person p3 = new Person(); p3.setName("Third Person"); p3.setId(3); p3.setGender("M"); personArray.add(p1); personArray.add(p2); personArray.add(p3); @SuppressWarnings("rawtypes") GenericEntity entity = new GenericEntity<List<Person>>(personArray){}; return Response.ok(entity).build(); }

com.google.gson.CircularReferenceException: circular reference error at com.google.gson.JsonSerializationVisitor.start(JsonSerializationVisitor.java:61) at com.google.gson.ObjectNavigator.accept(ObjectNavigator.java:109) at com.google.gson.JsonSerializationVisitor.getJsonElementForChild(JsonSerializationVisitor.java:147) at com.google.gson.JsonSerializationVisitor.addAsChildOfObject(JsonSerializationVisitor.java:127) at com.google.gson.JsonSerializationVisitor.visitObjectField(JsonSerializationVisitor.java:114) at com.google.gson.ReflectingFieldNavigator.visitFieldsReflectively(ReflectingFieldNavigator.java:69) at com.google.gson.ObjectNavigator.accept(ObjectNavigator.java:120)

Anuj April 8, 2013 at 7:40 pm

This code works fine for me

@GET
	@Produces(&quot;application/xml&quot;)
	public Response getList() {
		List&lt;Person&gt; personArray = new ArrayList&lt;Person&gt;();
		Person p1 = new Person();
		p1.setName(&quot;First Person&quot;);
		p1.setId(1);
		p1.setGender(&quot;M&quot;);
		Person p2 = new Person();
		p2.setName(&quot;Second Person&quot;);
		p2.setId(2);
		p2.setGender(&quot;M&quot;);
		Person p3 = new Person();
		p3.setName(&quot;Third Person&quot;);
		p3.setId(3);
		p3.setGender(&quot;M&quot;);
		personArray.add(p1);
		personArray.add(p2);
		personArray.add(p3);
		@SuppressWarnings(&quot;rawtypes&quot;)
		GenericEntity entity = new GenericEntity&lt;List&lt;Person&gt;&gt;(personArray){};
		return Response.ok(entity).build();
	}

Where as if I change Media Type to JSON, it throws error -500.

16558 [http-8080-2] ERROR org.apache.wink.server.internal.handlers.FlushResultHandler – The system could not find a javax.ws.rs.ext.MessageBodyWriter or a DataSourceProvider class for the java.util.ArrayList type and application/json mediaType. Ensure that a javax.ws.rs.ext.MessageBodyWriter exists in the JAX-RS application for the type and media type specified.

Bhagavan March 14, 2013 at 9:21 pm
Nice one
felix October 12, 2012 at 12:19 pm
if the value has a double quotation(“), which function should I use?
thanks :)

Laxman Chowdary September 28, 2012 at 9:23 pm

You are just posting, we followed you, become victims while developing the applications.
We got the following error.If we would have followed,JDK JSON we might not face this problem…

Laxman Chowdary September 29, 2012 at 4:11 pm
I realized that this is not your mistake, Googles product bug…
Inconvenience regretted..
- Sara Ali March 17, 2013 at 9:03 pm
  Laxman, he is only helping you and before posting any anything you should have been sure !

jyothsana September 4, 2012 at 2:44 pm
Thanks Mkyong… This site is really very useful for all the queries related to JSON..
- Shubhrajyoti satpathy November 1, 2012 at 2:58 am
  ITS RIGHT THIS WEBSITE GOOD FOR JSON
sagar srinivas August 9, 2012 at 5:41 pm
Hi,
My doubt on struts2 jquery grid. I want to get the column names of a grid from struts2 Action class.
Please help me
how to get property names of Action class or DAO class.
based on the property names i generate grid dynamically.
Thank u…..
Bhaskar Reddy July 31, 2012 at 2:15 pm
Really its a very good tutorial …… Thank you so much.
tttrung43 March 6, 2012 at 10:45 am
Thank you so much.
This tutorial is very useful with me.
rojer January 3, 2012 at 7:21 pm
very nice for understanding i never see like this before.
Sylar January 3, 2012 at 1:18 pm
Implementing an interface means overiding its methods. So @overide was used.
- chandan singh March 25, 2013 at 7:34 pm
  we can not override abstract methods we can implement abstract methods.
???? December 13, 2011 at 7:18 am
you are a very good engineer.
Muskandaza August 13, 2011 at 1:14 am
Excellent , mkyong @ BEST . Really Appreciable .Tons of Best Wishes.
Thanks
Muskandaza

Java JSON Tutorial

Jackson

Google Gson

JSON.simple

References

Popular Posts

What is your opinion?

Do you know the answer?

Jackson

Google Gson

JSON.simple

References

Related Posts

Popular Posts

What is your opinion?

Do you know the answer?