Gson 的快速使用

<!-- https://mvnrepository.com/artifact/com.google.code.gson/gson --><dependency>    <groupId>com.google.code.gson</groupId>    <artifactId>gson</artifactId>    <version>2.8.6</version></dependency>

package com.jsonTest.test;

import com.google.gson.reflect.TypeToken;import com.google.gson.Gson;import com.jsonTest.entity.Student;import com.jsonTest.entity.StudentListType;import com.jsonTest.entity.StudentMapType;import org.junit.Test;

import java.util.ArrayList;import java.util.HashMap;import java.util.List;import java.util.Map;
public class GsonTest {
  /**   * javabean与json中的关系   */  @Test  public void  test1(){
    Student student=new Student("1","web");
    Gson gson=new Gson();    String toJson = gson.toJson(student);    System.out.println(student);    System.out.println("普通对象变成json"+toJson);    /**     * Student(id=1, name=web)     * 普通对象变成json{"id":"1","name":"web"}     */
    /**     * 将当前的json转化成Javabean     */    Student student1 = gson.fromJson(toJson, Student.class);    System.out.println(student1);
  }

  @Test  public  void TestList(){
    List<Student> studentList=new ArrayList<>();    studentList.add(new Student("2","小路卡"));    studentList.add(new Student("3","小卢卡"));    Gson gson=new Gson();
     //list转成json    String jsonList = gson.toJson(studentList);    System.out.println("lIST"+studentList);    System.out.println("list-->JSON"+jsonList);    /**     * lIST[Student(id=2, name=小路卡), Student(id=3, name=小卢卡)]     * list-->JSON[{"id":"2","name":"小路卡"},{"id":"3","name":"小卢卡"}]     */

//    jsonList转成对象或者List    List list = gson.fromJson(jsonList, List.class);    System.out.println(list);//这个会发生类型转化异常

    /**     * lIST转成对象需要一个type做标准     */    List list1 = gson.fromJson(jsonList, new StudentListType().getType());    System.out.println(list1);  }

  @Test  public  void TestMap(){
   Map<String,Student> studentMap=new HashMap();    studentMap.put("1",new Student("4","lucas"));    studentMap.put("2",new Student("5","xiaoLucas"));

    Gson gson=new Gson();    //将map转成json
    String toJsonMap = gson.toJson(studentMap);    System.out.println("jsonMap"+toJsonMap);    /**     * jsonMap{"1":{"id":"4","name":"lucas"},"2":{"id":"5","name":"xiaoLucas"}}     */

    /**     * 将map转成一个个对象     */    Map<String,Student> student = gson.fromJson(toJsonMap, new StudentMapType().getType());    System.out.println(student);    Student student1 = student.get(1);    System.out.println(student1);

    /**     * 在每次转换的时候都会出现新增的Type类，所以我们可以使用匿名内部类的方式     */  }
  @Test  public  void TestMap2(){
    Map<String,Student> studentMap=new HashMap();    studentMap.put("1",new Student("4","lucas"));    studentMap.put("2",new Student("5","xiaoLucas"));

    Gson gson=new Gson();    //将map转成json
    String toJsonMap = gson.toJson(studentMap);    System.out.println("jsonMap"+toJsonMap);    /**     * jsonMap{"1":{"id":"4","name":"lucas"},"2":{"id":"5","name":"xiaoLucas"}}     */

    /**     * 将map转成一个个对象     */    Map<String,Student> student = gson.fromJson(toJsonMap,new TypeToken<Map<String,Student>>(){}.getType());    System.out.println(student);
      Student student1 = student.get("1");      System.out.println(student1);
/** * jsonMap{"1":{"id":"4","name":"lucas"},"2":{"id":"5","name":"xiaoLucas"}} * {1=Student(id=4, name=lucas), 2=Student(id=5, name=xiaoLucas)} * Student(id=4, name=lucas) */
      /**     * 在每次转换的时候都会出现新增的Type类，所以我们可以使用匿名内部类的方式     */  }}

package com.jsonTest.entity;

import lombok.Data;import lombok.EqualsAndHashCode;
import java.io.Serializable;
@EqualsAndHashCode@Datapublic class Student implements Serializable {
    private  String id ;
    private  String name;
    public Student(String s, String web) {        this.id=s;        this.name=web;    }}

package com.jsonTest.entity;
import com.google.gson.reflect.TypeToken;
import java.util.List;
/** * List转换的时候， json转换成一个type 继承这个typeToken类 */public class StudentListType extends TypeToken<List<Student>> {
}

package com.jsonTest.entity;
import com.google.gson.reflect.TypeToken;
import java.util.HashMap;
public class StudentMapType extends TypeToken<HashMap<String,Student>> {}