JSON解析
JAVA中的四种JSON解析方式详解
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<Student> stus;
public Grade(int id, String name, ArrayList<Student> 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<Student> getStus() {
return stus;
}
public void setStus(ArrayList<Student> 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<String,Object> map = jsonObject;
// for (Map.Entry<String, Object> 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<Student> 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<String> list=gson.fromJson(json2,
new TypeToken<ArrayList<String>>(){}.getType());
System.out.println(list);
}
//生成
@Test
public void test2(){
ArrayList<Student> 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<String> list=JSON.parseArray(json2, String.class);
System.out.println(list);
}
//生成
@Test
public void test2(){
ArrayList<Student> 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<String> list = mapper.readValue(json2, new TypeReference<List<String>>() {
});
System.out.println(list);
}
@Test
public void test2() throws JsonProcessingException {
ArrayList<Student> 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。
