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https://github.com/alibaba/fastjson2

🚄 FASTJSON2 is a Java JSON library with excellent performance.
https://github.com/alibaba/fastjson2

android big-data deserialization fastjson fastjson2 graal graalvm-native-image high-performance java java-json json json-deserialization json-parser json-path json-serialization json-serializer jsonb serialization

Last synced: 6 days ago
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🚄 FASTJSON2 is a Java JSON library with excellent performance.

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##### [📖 English Documentation](README_EN.md) | 📖 中文文档

##### 本项目的Issues会被同步沉淀至[阿里云开发者社区](https://developer.aliyun.com/ask/)



# FASTJSON v2



`FASTJSON 2`是一个性能极致并且简单易用的Java JSON库。



- `FASTJSON 2`是`FASTJSON`项目的重要升级，和FASTJSON 1相比，性能有非常大的提升，解决了autoType功能因为兼容和白名单的安全性问题。

- 性能极致，性能远超过其他流行JSON库，包括jackson/gson/org.json，性能数据: [https://github.com/alibaba/fastjson2/wiki/fastjson_benchmark](https://github.com/alibaba/fastjson2/wiki/fastjson_benchmark)

- 支持JDK新特性，包括`JDK 11`/`JDK 17`，针对`compact string`优化，支持Record，支持`GraalVM Native-Image`

- 完善的[`JSONPath`](https://alibaba.github.io/fastjson2/jsonpath_cn)支持，支持[SQL:2016](https://en.wikipedia.org/wiki/SQL:2016)的JSONPath语法

- 支持`Android 8+`，客户端和服务器一套API

- 支持`Kotlin` [https://alibaba.github.io/fastjson2/kotlin_cn](https://alibaba.github.io/fastjson2/kotlin_cn)

- 支持`JSON Schema` [https://alibaba.github.io/fastjson2/json_schema_cn](https://alibaba.github.io/fastjson2/json_schema_cn)

- 新增加支持二进制格式JSONB [https://alibaba.github.io/fastjson2/jsonb_format_cn](https://alibaba.github.io/fastjson2/jsonb_format_cn)



![fastjson logo](https://user-images.githubusercontent.com/1063891/233821110-0c912009-4de3-4664-a27e-25274f2fa9c1.jpg)



# 1. 使用准备



## 1.1 添加依赖



在`fastjson v2`中，`groupId`和`1.x`不一样，是`com.alibaba.fastjson2`：



`Maven`:



```xml



    com.alibaba.fastjson2

    fastjson2

    2.0.53



```



`Gradle`:



```groovy

dependencies {

    implementation 'com.alibaba.fastjson2:fastjson2:2.0.53'

}

```



可以在 [maven.org](https://search.maven.org/artifact/com.alibaba.fastjson2/fastjson2) 查看最新可用的版本。



## 1.2 其他模块



### `Fastjson v1`兼容模块



如果原来使用`fastjson 1.2.x`版本，可以使用兼容包，兼容包不能保证100%兼容，请仔细测试验证，发现问题请及时反馈。



`Maven`:



```xml



    com.alibaba

    fastjson

    2.0.53



```



`Gradle`:



```groovy

dependencies {

    implementation 'com.alibaba:fastjson:2.0.53'

}

```



### `Fastjson Kotlin`集成模块



如果项目使用`Kotlin`，可以使用`fastjson-kotlin`模块，使用方式上采用`kotlin`的特性。



* `Maven`:



```xml



    com.alibaba.fastjson2

    fastjson2-kotlin

    2.0.53



```



酌情添加标准库(kotlin-stdlib)、反射库(kotlin-reflect)，

其中若使用数据类(data class)、通过构造函数传入参数则添加反射库。



```xml



    org.jetbrains.kotlin

    kotlin-stdlib

    ${kotlin-version}



    org.jetbrains.kotlin

    kotlin-reflect

    ${kotlin-version}



```



* `Kotlin Gradle`:



```kotlin

dependencies {

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

}

```



```kotlin

dependencies {

    implementation("org.jetbrains.kotlin:kotlin-stdlib:$kotlin_version")

    implementation("org.jetbrains.kotlin:kotlin-reflect:$kotlin_version")

}

```



### `Fastjson Extension`扩展模块



如果项目使用`SpringFramework`等框架，可以使用`fastjson-extension`模块，使用方式参考 [SpringFramework Support](docs/spring_support_cn.md)。



`Maven`:



```xml



    com.alibaba.fastjson2

    fastjson2-extension-spring5

    2.0.53



```



```xml



    com.alibaba.fastjson2

    fastjson2-extension-spring6

    2.0.53



```



`Gradle`:



```groovy

dependencies {

    implementation 'com.alibaba.fastjson2:fastjson2-extension-spring5:2.0.53'

}

```



```groovy

dependencies {

    implementation 'com.alibaba.fastjson2:fastjson2-extension-spring6:2.0.53'

}

```



# 2. 简单使用



在`fastjson v2`中，`package`和`1.x`不一样，是`com.alibaba.fastjson2`。如果你之前用的是`fastjson1`，大多数情况直接更包名就即可。



### 2.1 将`JSON`解析为`JSONObject`



`Java`:



```java

String text = "...";

JSONObject data = JSON.parseObject(text);



byte[] bytes = ...;

JSONObject data = JSON.parseObject(bytes);

```



`Kotlin`:



```kotlin

import com.alibaba.fastjson2.*



val text = ... // String

val data = text.parseObject()



val bytes = ... // ByteArray

val data = bytes.parseObject() // JSONObject

```



### 2.2 将`JSON`解析为`JSONArray`



`Java`:



```java

String text = "...";

JSONArray data = JSON.parseArray(text);

```



`Kotlin`:



```kotlin

import com.alibaba.fastjson2.*



val text = ... // String

val data = text.parseArray() // JSONArray

```



### 2.3 将`JSON`解析为`Java`对象



`Java`:



```java

String text = "...";

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

```



`Kotlin`:



```kotlin

import com.alibaba.fastjson2.*



val text = ... // String

val data = text.to() // User

val data = text.parseObject() // User

```



### 2.4 将`Java`对象序列化为`JSON`



`Java`:



```java

Object data = "...";

String text = JSON.toJSONString(data);

byte[] text = JSON.toJSONBytes(data);

```



`Kotlin`:



```kotlin

import com.alibaba.fastjson2.*



val data = ... // Any

val text = data.toJSONString() // String

val bytes = data.toJSONByteArray() // ByteArray

```



### 2.5 使用`JSONObject`、`JSONArray`



#### 2.5.1 获取简单属性



```java

String text = "{\"id\": 2,\"name\": \"fastjson2\"}";

JSONObject obj = JSON.parseObject(text);



int id = obj.getIntValue("id");

String name = obj.getString("name");

```



```java

String text = "[2, \"fastjson2\"]";

JSONArray array = JSON.parseArray(text);



int id = array.getIntValue(0);

String name = array.getString(1);

```



#### 2.5.2 读取`JavaBean`



`Java`:



```java

JSONArray array = ...

JSONObject obj = ...



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

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

```



`Kotlin`:



```kotlin

val array = ... // JSONArray

val obj = ... // JSONObject



val user = array.to(0)

val user = obj.to("key")

```



#### 2.5.3 转为`JavaBean`



`Java`:



```java

JSONArray array = ...

JSONObject obj = ...



User user = obj.toJavaObject(User.class);

List users = array.toJavaList(User.class);

```



`Kotlin`:



```kotlin

val array = ... // JSONArray

val obj = ... // JSONObject



val user = obj.to() // User

val users = array.toList() // List

```



### 2.6 将`JavaBean`对象序列化为`JSON`



`Java`:



```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`:



```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

```



序列化结果:



```json

{

    "id"   : 2,

    "name" : "FastJson2"

}

```



# 3. 进阶使用



### 3.1 使用`JSONB`



#### 3.1.1 将`JavaBean`对象序列化`JSONB`



```java

User user = ...;

byte[] bytes = JSONB.toBytes(user);

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

```



#### 3.1.2 将`JSONB`数据解析为`JavaBean`



```java

byte[] bytes = ...

User user = JSONB.parseObject(bytes, User.class);

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

```



### 3.2 使用`JSONPath`



#### 3.2.1 使用`JSONPath`读取部分数据



```java

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 使用`JSONPath`读取部分`byte[]`的数据



```java

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 使用`JSONPath`读取部分`byte[]`的数据



```java

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);

```



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