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介绍

Fastjson是一个Java语言编写的高性能功能完善的JSON库。它采用一种“假定有序快速匹配”的算法，把JSON Parse的性能提升到极致，是目前Java语言中最快的JSON库。Fastjson接口简单易用，已经被广泛使用在缓存序列化、协议交互、Web输出、Android客户端等多种应用场景。

教程

maven依赖

<dependency>
    <groupId>com.alibaba</groupId>
    <artifactId>fastjson</artifactId>
    <version>1.2.47</version>
</dependency>

API使用

涉及到User和Address两个类，分别如下：

User 类

class User {
    private int id;
    private String name;
    private int age;
    private List<Address> addrList;

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }

    public List<Address> getAddrList() {
        return addrList;
    }

    public void setAddrList(List<Address> addrList) {
        this.addrList = addrList;
    }

}

Address 类

class Address {
    private String province;
    private String city;
    private String district;
    private String detail;

    public String getProvince() {
        return province;
    }

    public void setProvince(String province) {
        this.province = province;
    }

    public String getCity() {
        return city;
    }

    public void setCity(String city) {
        this.city = city;
    }

    public String getDistrict() {
        return district;
    }

    public void setDistrict(String district) {
        this.district = district;
    }

    public String getDetail() {
        return detail;
    }

    public void setDetail(String detail) {
        this.detail = detail;
    }

}

1、序列化

主要通过 JSON.toJSONString方法将Bean转换为json。

String com.alibaba.fastjson.JSON.toJSONString(Object object) 

User user = new User();
user.setId(1);
user.setName("ricky");
user.setAge(27);

List<Address> addrList = new ArrayList<>();
Address addr1 = new Address();
addr1.setProvince("北京");
addr1.setCity("北京市");
addr1.setDistrict("朝阳区");
addr1.setDetail("大望路金地中心");
addrList.add(addr1);

Address addr2 = new Address();
addr2.setProvince("湖北省");
addr2.setCity("武汉市");
addr2.setDistrict("武昌区");
addr2.setDetail("江汉路步行街");
addrList.add(addr2);

user.setAddrList(addrList);

System.out.println(user);

String jsonStr = JSON.toJSONString(user);

System.out.println(jsonStr);

结果如下：

{“addrList”:[{“city”:”北京市”,”detail”:”大望路金地中心”,”district”:”朝阳区”,”province”:”北京”},{“city”:”武汉市”,”detail”:”江汉路步行街”,”district”:”武昌区”,”province”:”湖北省”}],”age”:27,”id”:1,”name”:”ricky”}

2、反序列化

主要通过JSON.parseObject方法将json转换为Bean对象，如下：

<T> T com.alibaba.fastjson.JSON.parseObject(String text, Class<T> clazz) 

String jsonStr = "...";
User user = JSON.parseObject(jsonStr, User.class);
System.out.println(user);

3、JSONField 介绍

package com.alibaba.fastjson.annotation;

public @interface JSONField {
    // 配置序列化和反序列化的顺序，1.1.42版本之后才支持
    int ordinal() default 0;

     // 指定字段的名称
    String name() default "";

    // 指定字段的格式，对日期格式有用
    String format() default "";

    // 是否序列化
    boolean serialize() default true;

    // 是否反序列化
    boolean deserialize() default true;
}

3.1 指定序列化名称

指定User的addrList属性在序列化时变成addr_list，如下：

class User {
    private int id;
    private String name;
    private int age;

    @JSONField(name = "addr_list")
    private List<Address> addrList;

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }

    public List<Address> getAddrList() {
        return addrList;
    }

    public void setAddrList(List<Address> addrList) {
        this.addrList = addrList;
    }

}

结果：

{“addr_list”:[{“city”:”北京市”,”detail”:”大望路金地中心”,”district”:”朝阳区”,”province”:”北京”},{“city”:”武汉市”,”detail”:”江汉路步行街”,”district”:”武昌区”,”province”:”湖北省”}],”age”:27,”id”:1,”name”:”ricky”} 

3.2 使用serialize/deserialize指定字段不序列化

控制age属性不序列化，如下：

class User {
    private int id;
    private String name;
    @JSONField(serialize = false)
    private int age;

    @JSONField(name = "addr_list")
    private List<Address> addrList;

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }

    public List<Address> getAddrList() {
        return addrList;
    }

    public void setAddrList(List<Address> addrList) {
        this.addrList = addrList;
    }

}

结果：

{“addr_list”:[{“city”:”北京市”,”detail”:”大望路金地中心”,”district”:”朝阳区”,”province”:”北京”},{“city”:”武汉市”,”detail”:”江汉路步行街”,”district”:”武昌区”,”province”:”湖北省”}],”id”:1,”name”:”ricky”}

3.3 使用ordinal指定字段的顺序

class User {
    @JSONField(ordinal = 1)
    private int id;
    @JSONField(ordinal = 2)
    private String name;
    @JSONField(ordinal = 3)
    private int age;

    @JSONField(name = "addr_list", ordinal = 4)
    private List<Address> addrList;

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }

    public List<Address> getAddrList() {
        return addrList;
    }

    public void setAddrList(List<Address> addrList) {
        this.addrList = addrList;
    }

}

结果：

{“id”:1,”name”:”ricky”,”age”:27,”addr_list”:[{“city”:”北京市”,”detail”:”大望路金地中心”,”district”:”朝阳区”,”province”:”北京”},{“city”:”武汉市”,”detail”:”江汉路步行街”,”district”:”武昌区”,”province”:”湖北省”}]}

参考：https://github.com/alibaba/fastjson/wiki/JSONField