java中常见的JSON格式转换方法

来源：https://blog.csdn.net/qq_42688149/article/details/122275540

1 JsonLib示例

package com.jsonDemo;


import net.sf.json.JSONObject;

import java.util.HashMap;
import java.util.Map;

/**
 * @author LanceQ
 * @date 2022年01月01日 15:40
 */
public class JsonLibDemo {
    public static void main(String[] args) {
        jsonTest();
    }

    private static void jsonTest() {
        //java序列化为json
        Student student = Student.getStudent();
        JSONObject jsonObject = JSONObject.fromObject(student);
        System.out.println("json string");
        System.out.println(jsonObject.toString());
        //Json反序列化为java
        //如果对象中含有复杂对象，如List、Map或自定义javaBean,
        // 需要使用一下的classMap,否则转换过程中会报错

        Map<String,Class> classMap=new HashMap<>();
        classMap.put("stuObject",Student.class);
        student=(Student)JSONObject.toBean(jsonObject,Student.class,classMap);
        System.out.println("java Object");
        System.out.println(student);
        System.out.println(student.getId());
        System.out.println(student.getName());
        System.out.println(student.getSex());
    }
}

运行结果

json string
{"teacher":{"name":"老赵","id":888},"sex":"男","name":"小明","id":1}
java Object
Student{id=1, name='小明', sex='男', teacher=Teacher{id=888, name='老赵'}}
1
小明
男

2 Jackson示例

package com.jsonDemo;

import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.JsonNode;
import com.fasterxml.jackson.databind.ObjectMapper;

import java.io.IOException;
import java.util.HashMap;
import java.util.Map;

/**
 * @author LanceQ
 * @date 2022年01月01日 21:09
 */
public class JacksonDemo {
    public static void main(String[] args) {
        String jsonString=null;

        try {
            Map jsonMap=new HashMap();
            ObjectMapper mapper = new ObjectMapper();
            Student student = Student.getStudent();
            jsonMap.put("param1","value1");
            jsonMap.put("param2","value2");
            jsonMap.put("student",student);

            jsonString= mapper.writeValueAsString(jsonMap);

            System.out.println("Json String");
            System.out.println(jsonString);
        } catch (JsonProcessingException e) {
            e.printStackTrace();
        }
        //反序列化
        try {
            ObjectMapper objectMapper = new ObjectMapper();
            JsonNode root = objectMapper.readTree(jsonString);
            Map jsonMap = objectMapper.readValue(jsonString, Map.class);
            System.out.println("json Object");
            System.out.println(jsonMap);
            Object student = jsonMap.get("student");
            System.out.println(student);
            System.out.println(jsonMap.get("param1"));
            System.out.println(jsonMap.get("param2"));
            System.out.println("----------------");
            System.out.println(root.get("student"));
            System.out.println(root.get("student").get("id"));
            System.out.println(root.get("student").get("teacher"));

        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

运行结果

Json String
{"student":{"id":1,"name":"小明","sex":"男","teacher":{"id":888,"name":"老赵"}},"param1":"value1","param2":"value2"}
json Object
{student={id=1, name=小明, sex=男, teacher={id=888, name=老赵}}, param1=value1, param2=value2}
{id=1, name=小明, sex=男, teacher={id=888, name=老赵}}
value1
value2
----------------
{"id":1,"name":"小明","sex":"男","teacher":{"id":888,"name":"老赵"}}
1
{"id":888,"name":"老赵"}

3 Gson示例

package com.jsonDemo;

import com.google.gson.Gson;

/**
 * @author LanceQ
 * @date 2022年01月01日 18:16
 */
public class GsonDemo {
    public static void main(String[] args) {
        String jsonString=null;
        //java序列化为json
        Student student = Student.getStudent();

        Gson gson = new Gson();
        jsonString=gson.toJson(student);
        System.out.println("json String");
        System.out.println(jsonString);

        //json反序列化为java
        student=gson.fromJson(jsonString,student.getClass());
        System.out.println("java Object");
        System.out.println(student);
        System.out.println(student.getId());
        System.out.println(student.getName());
        System.out.println(student.getSex());
        System.out.println(student.getTeacher().getId());
        System.out.println(student.getTeacher().getName());

    }
}

运行结果

json String
{"id":1,"name":"小明","sex":"男","teacher":{"id":888,"name":"老赵"}}
java Object
Student{id=1, name='小明', sex='男', teacher=Teacher{id=888, name='老赵'}}
1
小明
男
888
老赵

4 Fast示例

package com.jsonDemo;

import com.alibaba.fastjson.JSON;
import com.alibaba.fastjson.JSONObject;

/**
 * @author LanceQ
 * @date 2022年01月01日 21:53
 * 以上几款开源的 JSON 工具库的性能也并不是完全一样的，其速度关系是：
 * Fastjson > Gson > Jackson> Json-lib
 * https://www.json.org/json-en.html
 */
public class FastDemo {
    public static void main(String[] args) {
        String jsonString=null;
        //java序列化为java
        Student student = Student.getStudent();
        jsonString=JSON.toJSONString(student);
        System.out.println("json String");
        System.out.println(jsonString);
        //json反序列化为java
        Student student1 = JSON.parseObject(jsonString, Student.class);
        System.out.println("java Object");
        System.out.println(student1);
        System.out.println(student1.getId());
        System.out.println(student1.getName());
        System.out.println(student1.getTeacher());
        System.out.println("-----------------------------------");
        JSONObject jsonObject = JSON.parseObject(jsonString);
        System.out.println(jsonObject.getInteger("id"));
        System.out.println(jsonObject.getString("name"));
        System.out.println(jsonObject.getJSONObject("teacher").get("id"));
    }
}

运行结果

json String
{"id":1,"name":"小明","sex":"男","teacher":{"id":888,"name":"老赵"}}
java Object
Student{id=1, name='小明', sex='男', teacher=Teacher{id=888, name='老赵'}}
1
小明
Teacher{id=888, name='老赵'}
-----------------------------------
1
小明
888

5 实体类

package com.jsonDemo;

/**
 * @author LanceQ
 * @date 2022年01月01日 15:58
 */
public class Student {
    private int id;
    private String name;
    private String sex;
    private Teacher teacher;

    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 String getSex() {
        return sex;
    }

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

    public Teacher getTeacher() {
        return teacher;
    }

    public void setTeacher(Teacher teacher) {
        this.teacher = teacher;
    }

    @Override
    public String toString() {
        return "Student{" +
                "id=" + id +
                ", name='" + name + '\'' +
                ", sex='" + sex + '\'' +
                ", teacher=" + teacher +
                '}';
    }

    public static Student getStudent(){
        Student student = new Student();
        student.setId(001);
        student.setName("小明");
        student.setSex("男");
        Teacher teacher = new Teacher();
        teacher.setId(888);
        teacher.setName("老赵");
        student.setTeacher(teacher);
        return student;
    }
}

package com.jsonDemo;

/**
 * @author LanceQ
 * @date 2022年01月01日 18:19
 */
public class Teacher {
    private int id;
    private String name;

    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;
    }

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

6 依赖

        <!-- json转实体类  fastjson-->
        <dependency>
            <groupId>com.alibaba</groupId>
            <artifactId>fastjson</artifactId>
            <version>1.2.4</version>
        </dependency>

        <!-- json转实体类  jsonlib-->
        <dependency>
            <groupId>commons-beanutils</groupId>
            <artifactId>commons-beanutils</artifactId>
            <version>1.9.3</version>
        </dependency>
        <dependency>
            <groupId>commons-lang</groupId>
            <artifactId>commons-lang</artifactId>
            <version>2.6</version>
        </dependency>
        <dependency>
            <groupId>net.sf.ezmorph</groupId>
            <artifactId>ezmorph</artifactId>
            <version>1.0.6</version>
        </dependency>
        <!-- https://mvnrepository.com/artifact/net.sf.json-lib/json-lib -->
        <dependency>
            <groupId>net.sf.json-lib</groupId>
            <artifactId>json-lib</artifactId>
            <version>2.4</version>
            <classifier>jdk15</classifier>
        </dependency>
        <!-- json转实体类gson -->
        <dependency>
            <groupId>com.google.code.gson</groupId>
            <artifactId>gson</artifactId>
            <version>2.8.5</version>
        </dependency>

        <!--Jackson包-->
        <dependency>
            <groupId>com.fasterxml.jackson.core</groupId>
            <artifactId>jackson-core</artifactId>
            <version>2.9.0</version>
        </dependency>
        <dependency>
            <groupId>com.fasterxml.jackson.core</groupId>
            <artifactId>jackson-databind</artifactId>
            <version>2.9.0</version>
        </dependency>
        <dependency>
            <groupId>com.fasterxml.jackson.core</groupId>
            <artifactId>jackson-annotations</artifactId>
            <version>2.9.0</version>
        </dependency>

java中常见的JSON格式转换方法:

import net.sf.json.JSONArray;  //用于集合或数组
import net.sf.json.JSONObject; //用于对象
JSONObject object = new JSONObject();

1.把java 对象列表转换为json对象数组，并转为字符串

JSONArray array = JSONArray.fromObject(userlist);
String jsonstr = array.toString();

2.把java对象转换成json对象，并转化为字符串(好像是map)

JSONObject object = JSONObject.fromObject(invite);
String str=object.toString();

3.把JSON字符串转换为JAVA 对象数组

String personstr = getRequest().getParameter("persons");
JSONArray json = JSONArray.fromObject(personstr);
List<InvoidPerison> persons = (List<InvoidPerson>)JSONArray.toCollection(json, nvoidPerson.class);

4.把JSON字符串转换为JAVA 对象

JSONObject jsonobject = JSONObject.fromObject(str);
PassportLendsEntity passportlends = null;
try {
　　//获取一个json数组
　　JSONArray array = jsonobject.getJSONArray("passports");
　　//将json数组 转换成 List<PassPortForLendsEntity>泛型
　　List<PassPortForLendsEntity> list = new ArrayList<PassPortForLendsEntity>();
　　for (int i = 0; i < array.size(); i++) {   
　　　　JSONObject object = (JSONObject)array.get(i);  
　　　　PassPortForLendsEntity passport = (PassPortForLendsEntity)JSONObject.toBean(object,
　　　　PassPortForLendsEntity.class);

　　if(passport != null){
　　list.add(passport);
　　}
}