fastjson工具类

1.什么是fastjson

fastjson是阿里巴巴的开源JSON解析库，它可以解析JSON格式的字符串，支持将Java Bean序列化为JSON字符串，也可以从JSON字符串反序列化到JavaBean。

2.fastjson的优点

• 速度快
• 使用广泛
• 测试完备
• 使用简单

3.下载和使用

3.1官方github

https://github.com/alibaba/fastjson

3.2 Maven

    com.alibaba
    fastjson
    x.x.x

3.3常用API介绍与使用

3.3.1常用API列表

public static final JSONObject parseObject(String text); // 把JSON文本转换成对象  
public static final  T parseObject(String text, Class clazz); // 把JSON文本转换为指定对象 
public static final JSONArray parseArray(String text); // 把JSON文本转换成集合 
public static final  List parseArray(String text, Class clazz); //把JSON文本转换成指定对象集合 
public static final String toJSONString(Object object); // 将对象序列化为JSON文本 
public static final String toJSONString(Object object, boolean prettyFormat); // 将对象序列化为带格式的JSON文本

3.3.2 具体例子：

简单User类

class User{
    private String name;
    private Integer age;

    public User() {
    }

    public User(String name, Integer age) {
        this.name = name;
        this.age = age;
    }

    public String getName() {
        return name;
    }

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

    public Integer getAge() {
        return age;
    }

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

    @Override
    public String toString() {
        return "User{" +
                "name='" + name + '\'' +
                ", age=" + age +
                '}';
    }
}

public static final JSONObject parseObject(String text); // 把JSON文本转换成对象

    //{"age":16,"name":"zhangsan"}
    @Test
    public void fastjsonTest01(){
        JSONObject jsonObject = JSON.parseObject("{\"age\":16,\"name\":\"zhangsan\"}");
        String name = jsonObject.getObject("name", String.class); //使用getObject获取指定属性
        Integer age = jsonObject.getObject("age", Integer.class);
        System.out.println(name + "=" + age);
    }  

结果：
zhangsan=16

public static final T parseObject(String text, Class clazz); // 把JSON文本转换为指定对象

    //{"age":16,"name":"zhangsan"}
    @Test
    public void fastjsonTest01(){
        User jsonObject = JSON.parseObject("{\"age\":16,\"name\":\"zhangsan\"}",User.class);
        System.out.println(jsonObject);

    }

结果：
User{name=‘zhangsan’, age=16}

public static final JSONArray parseArray(String text); // 把JSON文本转换成集合

    //[{"age":16,"name":"zhangsan"},{"age":17,"name":"wangwu"},{"age":18,"name":"lisi"}]
    @Test
    public void fastjsonTest01(){
        JSONArray jsonArray = JSON.parseArray("[{\"age\":16,\"name\":\"zhangsan\"},{\"age\":17,\"name\":\"wangwu\"},{\"age\":18,\"name\":\"lisi\"}]");
        List users = jsonArray.toJavaList(User.class); //使用toJavaList转换成User集合
        for (User user : users) {
            System.out.println(user);
        }
    }

结果：
User{name=‘zhangsan’, age=16}
User{name=‘wangwu’, age=17}
User{name=‘lisi’, age=18}

public static final List parseArray(String text, Class clazz); //把JSON文本转换成指定对象集合

    //[{"age":16,"name":"zhangsan"},{"age":17,"name":"wangwu"},{"age":18,"name":"lisi"}]
    @Test
    public void fastjsonTest01(){
        List users = JSON.parseArray("[{\"age\":16,\"name\":\"zhangsan\"},{\"age\":17,\"name\":\"wangwu\"},{\"age\":18,\"name\":\"lisi\"}]",User.class);
        for (User user : users) {
            System.out.println(user);
        }
    }

结果：
User{name=‘zhangsan’, age=16}
User{name=‘wangwu’, age=17}
User{name=‘lisi’, age=18}

public static final String toJSONString(Object object); // 将对象序列化为JSON文本

    @Test
    public void fastjsonTest01(){
        User user0 = new User("zhangsan",16);
        User user1 = new User("lisi",17);
        User user2 = new User("wangwu",18);
        List users = new ArrayList<>();
        users.add(user0);
        users.add(user1);
        users.add(user2);

        String user0Json = JSON.toJSONString(user0);
        String usersJson = JSON.toJSONString(users);

        System.out.println(user0Json);
        System.out.println(usersJson);
    }

结果：
{“age”:16,“name”:“zhangsan”}
[{“age”:16,“name”:“zhangsan”},{“age”:17,“name”:“lisi”},{“age”:18,“name”:“wangwu”}]

public static final String toJSONString(Object object, boolean prettyFormat); // 将对象序列化为带格式的JSON文本

    //{"age":16,"name":"zhangsan"}
    //[{"age":16,"name":"zhangsan"},{"age":17,"name":"lisi"},{"age":18,"name":"wangwu"}]
    @Test
    public void fastjsonTest01(){
        User user0 = new User("zhangsan",16);
        User user1 = new User("lisi",17);
        User user2 = new User("wangwu",18);
        List users = new ArrayList<>();
        users.add(user0);
        users.add(user1);
        users.add(user2);

        String user0Json = JSON.toJSONString(user0,true);
        String usersJson = JSON.toJSONString(users,true);

        System.out.println(user0Json);
        System.out.println(usersJson);
    }

结果：
{
“age”:16,
“name”:“zhangsan”
}
[
{
“age”:16,
“name”:“zhangsan”
},
{
“age”:17,
“name”:“lisi”
},
{
“age”:18,
“name”:“wangwu”
}
]