1. Overview
Working with JSON data in Java can be easy, but – like most anything in Java – there are a lot of options and libraries we can chose from.
This guide should make that choice easier and should give you a solid understanding of the ecosystem right now. We’ll discuss the most common JSON processing libraries in Java:
We’re following a simple structure for each library – first some useful resources to get started (both here on Baeldung as well as external). Then we’re going to go over a basic code example, just to see how working with the library actually looks like.
2. Popularity and Basic Stats
First, let’s start with some statistics as a proxy for the popularity of each library:
2.1. Jackson
2.2. Gson
2.3. json-io
2.4. Genson
2.5. JSON-P
- Github Stars: 119
- Github Forks: 54
3. Jackson
Next, let’s have a look at the most popular of these – Jackson. Jackson is a multi-purpose Java library for processing JSON data.
3.1. Useful Resources
Here are some official resources for the library:
On Baeldung:
Other Interesting Writeups:
3.2. Maven Dependency
To use the library – here’s the Maven dependency to add into your pom.xml:
<dependency>
<groupId>com.fasterxml.jackson.core</groupId>
<artifactId>jackson-databind</artifactId>
<version>2.17.2</version>
</dependency>
Make sure to get the latest version of Jackson.
3.3. Simple Example with Jackson
Now, let’s see how to use Jackson in a simple example:
@Test
public void whenSerializeAndDeserializeUsingJackson_thenCorrect()
throws IOException{
Foo foo = new Foo(1,"first");
ObjectMapper mapper = new ObjectMapper();
String jsonStr = mapper.writeValueAsString(foo);
Foo result = mapper.readValue(jsonStr, Foo.class);
assertEquals(foo.getId(),result.getId());
}
Note that:
- ObjectMapper.writeValueAsString() is used to serialize Object to JSON string.
- ObjectMapper.readValue() is used to deserialize JSON string to Java Object.
- Sample JSON output:
{
"id":1,
"name":"first"
}
4. Gson
Gson is the next Java JSON library that we’re going to be looking at.
4.1. Useful Resources
Here are some official resources for the library:
On Baeldung:
Other Interesting Writeups:
4.2. Maven Dependency
<dependency>
<groupId>com.google.code.gson</groupId>
<artifactId>gson</artifactId>
<version>${gson.version}</version>
</dependency>
Note that the latest version of Gson right now is 2.8.8.
4.3. Simple Example with Gson
Here is a simple example clarify how to use Gson to serialize/desrialize JSON:
@Test
public void whenSerializeAndDeserializeUsingGson_thenCorrect(){
Gson gson = new Gson();
Foo foo = new Foo(1,"first");
String jsonStr = gson.toJson(foo);
Foo result = gson.fromJson(jsonStr, Foo.class);
assertEquals(foo.getId(),result.getId());
}
Note that:
- Gson.toJson() is used to serialize Object to JSON
- Gson.fromJson() is used to desrialize JSON to Java Object
5. Json-io
Json-io is a simple Java library to serialize/deserialize JSON.
5.1. Useful Resources
Here are some official resources for the library:
5.2. Maven Dependency
<dependency>
<groupId>com.cedarsoftware</groupId>
<artifactId>json-io</artifactId>
<version>${json-io.version}</version>
</dependency>
Note that the latest version of json-io right now is 4.13.0.
5.3. Simple Example with json-io
Now, let’s take a look at a simple example of using json-io:
@Test
public void whenSerializeAndDeserializeUsingJsonio_thenCorrect(){
Foo foo = new Foo(1,"first");
String jsonStr = JsonWriter.objectToJson(foo);
Foo result = (Foo) JsonReader.jsonToJava(jsonStr);
assertEquals(foo.getId(),result.getId());
}
Note that:
- JsonWriter.objectToJson() is used to serialize Object to JSON.
- JsonReader.jsonToJava() is used to deserialize Json to Java Object.
- Sample JSON output:
{
"@type":"org.baeldung.Foo",
"id":1,
"name":"first"
}
6. Genson
Genson is a Java and Scala to JSON conversion library, providing full databinding and streaming.
6.1. Useful Resources
Here are some official resources for the library:
6.2. Maven Dependency
<dependency>
<groupId>com.owlike</groupId>
<artifactId>genson</artifactId>
<version>${genson.version}</version>
</dependency>
Note that the latest version of Genson right now is 1.6.
6.3. Simple Example with Genson
Here’s a simple example of working with the library:
@Test
public void whenSerializeAndDeserializeUsingGenson_thenCorrect(){
Genson genson = new Genson();
Foo foo = new Foo(1,"first");
String jsonStr = genson.serialize(foo);
Foo result = genson.deserialize(jsonStr, Foo.class);
assertEquals(foo.getId(),result.getId());
}
Note that:
- Genson.serialize() is used to serialize Object to JSON
- Genson.desrialize() is used to deserialize JSON to Java Object
7. JSON-P
JSON-P is a Java API for parsing, building, transforming, and querying JSON messages. Java Specification Request (JSR) 353 proposed the API. JSR 353 aims to develop a Java API to process JSON. Most of the popular libraries, like Jackson, Gson, etc., don’t implement the specification directly.
7.1. Useful Resources
Here are some official resources for the library:
7.2. Maven Dependencies
<dependency>
<groupId>jakarta.json</groupId>
<artifactId>jakarta.json-api</artifactId>
<version>${jsonp.version}</version>
</dependency>
<dependency>
<groupId>org.glassfish</groupId>
<artifactId>jakarta.json</artifactId>
<version>${provider.version}</version>
<classifier>module<classifier>
</dependency>
Note that we need the API module and the default provider dependencies. The latest version is 2.1.1 and 2.0.1, respectively.
7.3. Simple Example With JSON-P
Let’s take a look at the simple use case of JSON-P:
@Test
public void whenTransformingAndParsingUsingJsonp_thenCorrect() {
Foo foo = new Foo(1, "First");
JsonObject json = Json.createObjectBuilder()
.add("id", foo.getId())
.add("name", foo.getName())
.build();
String result = json.toString();
JsonParser parser = Json.createParser(new StringReader(result));
while (parser.hasNext()) {
Event event = parser.next();
switch (event) {
case VALUE_STRING:
String value = parser.getString();
assertEquals(foo.getName(), value);
break;
}
}
parser.close();
}
Note that:
- Json.createObjectBuilder() is used to transform an object to JSON.
- Json.createParser() is used to parse the JSON message.
- JSON-P API is low-level compared to other JSON processing libraries in Java.
8. Conclusion
In this quick overview article, we learned about the most common JSON processing libraries in Java.
