1、写好一个实体类，这里以Student.java为例

public class Student {
    private int id;
    private String name;
    private int age;
    private String sex;

    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 String getSex() {
        return sex;
    }

    public void setSex(String sex) {
        this.sex = sex;
    }
}

2、重写bean类的toString方法（第一次使用json需要配置json的模板）

3、自己新建一个自定义的模板，然后在右侧输入生成json模板的代码

public java.lang.String toString() {
final java.lang.StringBuilder sb = new java.lang.StringBuilder("{");
#set ($i = 0)
#foreach ($member in $members)#if ($i == 0)
sb.append("#####
#else
sb.append(",####
#end#if ($member.string || $member.date)
\"$member.name\":\"")
#else
\"$member.name\":")
#end#if ($member.primitiveArray || $member.objectArray)
.append(java.util.Arrays.toString($member.name));
#elseif ($member.string || $member.date)
.append($member.accessor).append('\"');
#else
.append($member.accessor);
#end#set ($i = $i + 1)
#end
sb.append('}');
return sb.toString();
}

 4、后续重写bean.toString()方法的时候就直接生成json类型的了

    @Override
    public String toString() {
        final StringBuilder sb = new StringBuilder("{");
        sb.append("\"id\":")
                .append(id);
        sb.append(",\"name\":\"")
                .append(name).append('\"');
        sb.append(",\"age\":")
                .append(age);
        sb.append(",\"sex\":\"")
                .append(sex).append('\"');
        sb.append('}');
        return sb.toString();
    }

 此时bean就转换成json字符串了

 bean转换成json

        Student stu = new Student();
        stu.setAge(11);
        stu.setId(1000);
        stu.setName("小明");
        stu.setSex("男");
        String json = stu.toString();
        System.out.println("json="+json);

输出结果： json={"id":1000,"name":"小明","age":11,"sex":"男"}

 json字符串转成bean

        Student bean = JSONObject.parseObject(json,Student.class);
        System.out.println("bean="+bean);

输出结果：bean={"id":1000,"name":"小明","age":11,"sex":"男"}

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