JAVA中的四种JSON解析方式详解

我们在日常开发中少不了和JSON数据打交道，那么我们来看看JAVA中常用的JSON解析方式。

1、JSON官方 脱离框架使用

2、GSON

3、FastJSON 有问题

4、jackson 常用

JSON操作涉及到的类：

public class Student {

private int id;

private String name;

private int age;

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 Student(int id, String name, int age) {

super();

this.id = id;

this.name = name;

this.age = age;

}

public Student() {

super();

}

@Override

public String toString() {

return "Student [id=" + id + ", name=" + name + ", age=" + age + "]";

}

}

public class Grade {

private int id;

private String name;

private ArrayList stus;

public Grade(int id, String name, ArrayList stus) {

super();

this.id = id;

this.name = name;

this.stus = stus;

}

public Grade() {

super();

}

@Override

public String toString() {

return "Grade [id=" + id + ", name=" + name + ", stus=" + stus + "]";

}

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 ArrayList getStus() {

return stus;

}

public void setStus(ArrayList stus) {

this.stus = stus;

}

}

JSON官方的解析最具有通用性，但是有点小麻烦。

package cn.itcast.test;

import net.sf.json.JSONArray;

import net.sf.json.JSONObject;

import org.junit.Test;

import java.util.ArrayList;

public class JsonTest {

@Test

public void test1() {

String json1 = "{'id':1,'name':'JAVAEE-1703','stus':[{'id':101,'name':'刘一','age':16},{'id':102,'name':'刘二','age':23}]}";

//数组

String json2 = "['北京','天津','杭州']";

// JSONObject jObject = new JSONObject(json1);

JSONObject jsonObject = JSONObject.fromObject(json1);

// System.out.println(jsonObject);

// Map map = jsonObject;

// for (Map.Entry entry : map.entrySet()) {

// System.out.println(entry.getKey());

// System.out.println(entry.getValue());

// System.out.println("=========");

// }

Grade grade = new Grade();

grade.setId(jsonObject.getInt("id"));

grade.setName(jsonObject.getString("name"));

ArrayList students = new ArrayList<>();

grade.setStus(students);

JSONArray stus = jsonObject.getJSONArray("stus");

for (Object o : stus) {

// System.out.println(o);

JSONObject jsonObject1 = JSONObject.fromObject(o);

Student student = new Student(jsonObject1.getInt("id"), jsonObject1.getString("name"), jsonObject1.getInt("age"));

grade.getStus().add(student);

}

System.out.println(grade);

}

@Test

public void test2(){

JSONObject jsonObject = new JSONObject();

jsonObject.put("id", 100);

jsonObject.put("name", "二弟");

jsonObject.put("age", 30);

JSONObject jsonObject1 = new JSONObject();

jsonObject1.put("id", 102);

jsonObject1.put("name", "狗蛋");

jsonObject1.put("age", 10);

JSONArray jsonArray = new JSONArray();

jsonArray.add(jsonObject);

jsonArray.add(jsonObject1);

System.out.println(jsonArray);

}

}

GSON解析是谷歌的，也比较好用

public class GSONTest {

//解析

@Test

public void test1() {

// 对象嵌套数组嵌套对象

String json1 = "{'id':1,'name':'JAVAEE-1703','stus':[{'id':101,'name':'刘一','age':16}]}";

// 数组

String json2 = "['北京','天津','杭州']";

Gson gson=new Gson();

//1、

//解析对象：第一个参数：待解析的字符串 第二个参数结果数据类型的Class对象

Grade grade=gson.fromJson(json1, Grade.class);

System.out.println(grade);

//2、

//解析数组要求使用Type

ArrayList list=gson.fromJson(json2,

new TypeToken>(){}.getType());

System.out.println(list);

}

//生成

@Test

public void test2(){

ArrayList list=new ArrayList<>();

for(int i=1;i<3;i++){

list.add(new Student(101+i, "码子", 20+i));

}

Grade grade=new Grade(100001,"张三", list);

Gson gson=new Gson();

//将对象转换为诶JSON格式字符串

String json=gson.toJson(grade);

System.out.println(json);

}

}

FastJSON是阿里巴巴的产品，效率最高

public class FASTJson {

//解析

@Test

public void test1() {

// 对象嵌套数组嵌套对象

String json1 = "{'id':1,'name':'JAVAEE-1703','stus':[{'id':101,'name':'刘铭','age':16}]}";

// 数组

String json2 = "['北京','天津','杭州']";

//1、

//静态方法

Grade grade=JSON.parseObject(json1, Grade.class);

System.out.println(grade);

//2、

List list=JSON.parseArray(json2, String.class);

System.out.println(list);

}

//生成

@Test

public void test2(){

ArrayList list=new ArrayList<>();

for(int i=1;i<3;i++){

list.add(new Student(101+i, "码子", 20+i));

}

Grade grade=new Grade(100001,"张三", list);

String json=JSON.toJSONString(grade);

System.out.println(json);

}

}

jackSon解析JSON，SpringMVC内置的解析器就是这个

package cn.itcast.test;

import com.fasterxml.jackson.core.JsonProcessingException;

import com.fasterxml.jackson.core.type.TypeReference;

import com.fasterxml.jackson.databind.ObjectMapper;

import org.junit.Test;

import java.io.IOException;

import java.util.ArrayList;

import java.util.List;

public class jackSonTest {

@Test

public void test1() throws IOException {

// 对象嵌套数组嵌套对象

String json1 = "{\"id\":1,\"name\":\"JAVAEE-1703\",\"stus\":[{\"id\":101,\"name\":\"刘一\",\"age\":16}]}";

// 数组

String json2 = "[\"北京\",\"天津\",\"杭州\"]";

ObjectMapper mapper = new ObjectMapper();

Grade grade = mapper.readValue(json1, Grade.class);

System.out.println(grade);

List list = mapper.readValue(json2, new TypeReference>() {

});

System.out.println(list);

}

@Test

public void test2() throws JsonProcessingException {

ArrayList students = new ArrayList<>();

for (int i = 0; i < 3; i++) {

students.add(new Student(100 + i, "二稿" + i, 1000 + i));

}

Grade grade = new Grade(22, "语文", students);

// System.out.println(grade);

ObjectMapper objectMapper = new ObjectMapper();

String s = objectMapper.writeValueAsString(grade);

System.out.println(s);

}

}

除了JSON官方的对类没有要求，剩下的都要求是标准的类，否则无法解析，因为都用到了反射。