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FASTJSON v2

FASTJSON 2 is an extremely performant and easy-to-use Java JSON library.

FASTJSON 2 is an important upgrade of the FASTJSON project. Compared with FASTJSON 1, the performance has been greatly improved and the security issues of the autoType function due to compatibility and whitelisting have been solved.
Extreme performance, performance far exceeds other popular JSON libraries, including jackson/gson/org.json, performance data: https://github.com/alibaba/fastjson2/wiki/fastjson_benchmark
Support new JDK features, including JDK 11 / JDK 17 , optimized for compact string , support Record, support GraalVM Native-Image
Complete JSONPath support, supporting SQL:2016 JSONPath syntax
Support Android 8+ , a set of APIs for client and server
Support Kotlin https://alibaba.github.io/fastjson2/kotlin_cn
Support JSON Schema https://alibaba.github.io/fastjson2/json_schema_cn
Newly added support for binary format JSONB https://alibaba.github.io/fastjson2/jsonb_format_cn

fastjson logo

1. Preparation for use

1.1 Add dependencies

In fastjson v2 , groupId is different from 1.x , it is com.alibaba.fastjson2 :

Maven :

< dependency >
    < groupId >com.alibaba.fastjson2</ groupId >
    < artifactId >fastjson2</ artifactId >
    < version >2.0.53</ version >
</ dependency >

Gradle :

dependencies {
    implementation ' com.alibaba.fastjson2:fastjson2:2.0.53 '
}

You can view the latest available version at maven.org.

1.2 Other modules

`Fastjson v1` compatible module

If you originally used the fastjson 1.2.x version, you can use the compatibility package. The compatibility package cannot guarantee 100% compatibility. Please test and verify it carefully and provide timely feedback if you find any problems.

Maven :

< dependency >
    < groupId >com.alibaba</ groupId >
    < artifactId >fastjson</ artifactId >
    < version >2.0.53</ version >
</ dependency >

Gradle :

dependencies {
    implementation ' com.alibaba:fastjson:2.0.53 '
}

`Fastjson Kotlin` integration module

If the project uses Kotlin , you can use the fastjson-kotlin module and adopt the features of kotlin .

Maven :

< dependency >
    < groupId >com.alibaba.fastjson2</ groupId >
    < artifactId >fastjson2-kotlin</ artifactId >
    < version >2.0.53</ version >
</ dependency >

Add the standard library (kotlin-stdlib) and reflection library (kotlin-reflect) as appropriate. If you use a data class (data class) and pass parameters through the constructor, add the reflection library.

< dependency >
    < groupId >org.jetbrains.kotlin</ groupId >
    < artifactId >kotlin-stdlib</ artifactId >
    < version >${kotlin-version}</ version >
</ dependency >

< dependency >
    < groupId >org.jetbrains.kotlin</ groupId >
    < artifactId >kotlin-reflect</ artifactId >
    < version >${kotlin-version}</ version >
</ dependency >

Kotlin Gradle :

dependencies {
    implementation( " com.alibaba.fastjson2:fastjson2-kotlin:2.0.53 " )
}

dependencies {
    implementation( " org.jetbrains.kotlin:kotlin-stdlib: $kotlin_version " )
    implementation( " org.jetbrains.kotlin:kotlin-reflect: $kotlin_version " )
}

`Fastjson Extension` extension module

If the project uses a framework such as SpringFramework , you can use the fastjson-extension module. For usage, refer to SpringFramework Support.

Maven :

< dependency >
    < groupId >com.alibaba.fastjson2</ groupId >
    < artifactId >fastjson2-extension-spring5</ artifactId >
    < version >2.0.53</ version >
</ dependency >

< dependency >
    < groupId >com.alibaba.fastjson2</ groupId >
    < artifactId >fastjson2-extension-spring6</ artifactId >
    < version >2.0.53</ version >
</ dependency >

Gradle :

dependencies {
    implementation ' com.alibaba.fastjson2:fastjson2-extension-spring5:2.0.53 '
}

dependencies {
    implementation ' com.alibaba.fastjson2:fastjson2-extension-spring6:2.0.53 '
}

2. Easy to use

In fastjson v2 , package is different from 1.x , it is com.alibaba.fastjson2 . If you were using fastjson1 before, in most cases you can just change the package name.

2.1 Parse `JSON` into `JSONObject`

Java :

 String text = "..." ;
JSONObject data = JSON . parseObject ( text );

byte [] bytes = ...;
JSONObject data = JSON . parseObject ( bytes );

Kotlin :

 import com.alibaba.fastjson2.*

val text = .. . // String
val data = text.parseObject()

val bytes = .. . // ByteArray
val data = bytes.parseObject() // JSONObject

2.2 Parse `JSON` into `JSONArray`

Java :

 String text = "..." ;
JSONArray data = JSON . parseArray ( text );

Kotlin :

 import com.alibaba.fastjson2.*

val text = .. . // String
val data = text.parseArray() // JSONArray

2.3 Parse `JSON` into `Java` objects

Java :

 String text = "..." ;
User data = JSON . parseObject ( text , User . class );

Kotlin :

 import com.alibaba.fastjson2.*

val text = .. . // String
val data = text.to< User >() // User
val data = text.parseObject< User >() // User

2.4 Serialize `Java` objects to `JSON`

Java :

 Object data = "..." ;
String text = JSON . toJSONString ( data );
byte [] text = JSON . toJSONBytes ( data );

Kotlin :

 import com.alibaba.fastjson2.*

val data = .. . // Any
val text = text.toJSONString() // String
val bytes = text.toJSONByteArray() // ByteArray

2.5 Using `JSONObject` and `JSONArray`

2.5.1 Get simple attributes

 String text = "{ " id " : 2, " name " : " fastjson2 " }" ;
JSONObject obj = JSON . parseObject ( text );

int id = obj . getIntValue ( "id" );
String name = obj . getString ( "name" );

 String text = "[2, " fastjson2 " ]" ;
JSONArray array = JSON . parseArray ( text );

int id = array . getIntValue ( 0 );
String name = array . getString ( 1 );

2.5.2 Reading `JavaBean`

Java :

 JSONArray array = ...
JSONObject obj = ...

User user = array . getObject ( 0 , User . class );
User user = obj . getObject ( "key" , User . class );

Kotlin :

 val array = .. . // JSONArray
val obj = .. . // JSONObject

val user = array.to< User >( 0 )
val user = obj.to< User >( " key " )

2.5.3 Convert to `JavaBean`

Java :

 JSONArray array = ...
JSONObject obj = ...

User user = obj . toJavaObject ( User . class );
List < User > users = array . toJavaList ( User . class );

Kotlin :

 val array = .. . // JSONArray
val obj = .. . // JSONObject

val user = obj.to< User >() // User
val users = array.toList< User >() // List<User>

2.6 Serialize `JavaBean` objects to `JSON`

Java :

 class User {
    public int id ;
    public String name ;
}

User user = new User ();
user . id = 2 ;
user . name = "FastJson2" ;

String text = JSON . toJSONString ( user );
byte [] bytes = JSON . toJSONBytes ( user );

Kotlin :

 class User (
    var id : Int ,
    var name : String
)

val user = User ()
user.id = 2
user.name = " FastJson2 "

val text = user.toJSONString() // String
val bytes = user.toJSONByteArray() // ByteArray

Serialization result:

{
    "id"   : 2 ,
    "name" : " FastJson2 "
}

3. Advanced use

3.1 Using `JSONB`

3.1.1 Serialize `JavaBean` objects `JSONB`

 User user = ...;
byte [] bytes = JSONB . toBytes ( user );
byte [] bytes = JSONB . toBytes ( user , JSONWriter . Feature . BeanToArray );

3.1.2 Parse `JSONB` data into `JavaBean`

 byte [] bytes = ...
User user = JSONB . parseObject ( bytes , User . class );
User user = JSONB . parseObject ( bytes , User . class , JSONReader . Feature . SupportBeanArrayMapping );

3.2 Using `JSONPath`

3.2.1 Use `JSONPath` to read some data

 String text = ...;
JSONPath path = JSONPath . of ( "$.id" ); // 缓存起来重复使用能提升性能

JSONReader parser = JSONReader . of ( text );
Object result = path . extract ( parser );

3.2.2 Use `JSONPath` to read partial `byte[]` data

 byte [] bytes = ...;
JSONPath path = JSONPath . of ( "$.id" ); // 缓存起来重复使用能提升性能

JSONReader parser = JSONReader . of ( bytes );
Object result = path . extract ( parser );

3.2.3 Use `JSONPath` to read partial `byte[]` data

 byte [] bytes = ...;
JSONPath path = JSONPath . of ( "$.id" ); // 缓存起来重复使用能提升性能

JSONReader parser = JSONReader . ofJSONB ( bytes ); // 注意这里使用ofJSONB方法
Object result = path . extract ( parser );