安卓中使用Gson解析json方法详解与使用例子

        //转换器
         GsonBuilder builder = new GsonBuilder();
         // 不转换没有 @Expose 注解的字段   @Expose的作用是支持序列化，没有@Expose不会被序列化
         builder.excludeFieldsWithoutExposeAnnotation();
         Gson gson = builder.create();
    @Expose注解的作用：区分实体中不想被序列化的属性，其自身包含两个属性deserialize(反序列化)和serialize（序列化），默认都为true。  使用 new GsonBuilder().excludeFieldsWithoutExposeAnnotation().create();创建Gson对象，没有@Expose注释的属性将不会被序列化.。              private class User{
      private int id;
      @Expose
      private String name;
      .......

}这样create() gson对象序列化user，只会有name这一个属性

         //1、对象转string
         Student stu = new Student();
         stu.setStudentId(333);
         stu.setStudentName("qqq");
         String stuStr = gson.toJson(stu);
         System.out.println(stuStr); //{"studentName":"qqq","studentId":333}


         //2、string转对象
         Student user2 = gson.fromJson(stuStr, Student.class);
         System.out.println(user2);
         String stuTemp = "{\"studentName\":\"qqq2\",\"studentId\":3335}";
         Student user4 = gson.fromJson(stuTemp, Student.class);
         System.out.println(user4);

         //3、对象List转string
         List<Student> testBeanList = new ArrayList<Student>();
         Student testBean = new Student();
         testBean.setStudentId(555);
         testBean.setStudentName("552");
         testBeanList.add(testBean);

         //Gson gsonList = new Gson();
         Type type = new TypeToken<List<Student>>(){}.getType();  //指定集合对象属性
         String beanListToJson = gson.toJson(testBeanList, type);
         System.out.println(beanListToJson); //[{"studentName":"552","studentId":555}]

         //集合string转对象list
         List<Student> testBeanListFromJson = gson.fromJson(beanListToJson, type);
         System.out.println(testBeanListFromJson); //[555:552]

         //4、集合如果不指定类型 默认为String
         List<String> testList = new ArrayList<String>();
         testList.add("first");
         testList.add("second");
         String listToJson = gson.toJson(testList);
         System.out.println(listToJson); //["first","second"]

         //5、集合字符串转回来需要指定类型
         List<String> testList2 = (List<String>) gson.fromJson(listToJson,
           new TypeToken<List<String>>() {
           }.getType());
         System.out.println(testList2);

         //6、 将HashMap字符串转换为 JSON
         Map<String, String> testMap = new HashMap<String, String>();
         testMap.put("id", "id.first");
         testMap.put("name", "name.second");
         String mapToJson = gson.toJson(testMap);
         System.out.println(mapToJson); //{"id":"id.first","name":"name.second"}
         //7、stringMap转对象
         Map<String, String> userMap2 = (Map<String, String>) gson.fromJson(mapToJson,
                 new TypeToken<Map<String, String>>() {
             }.getType());
         System.out.println(userMap2); //{id=id.first, name=name.second}

         //8、对象含有普通对象、集合、map情况
         Student user1 = new Student();
         user1.setStudentId(1001);
         user1.setStudentName("张三");

         Student user3 = new Student();
         user3.setStudentId(1002);
         user3.setStudentName("李四");

         Map<String, Student> userMap = new HashMap<String, Student>();
         userMap.put("user1", user1);
         userMap.put("user3", user3);

         List<Student> userList = new ArrayList<Student>();
         userList.add(user1);
         userList.add(user3);

         Teacher groupBean = new Teacher();
         groupBean.setStudent(user1);
         groupBean.setStus(userList);
         groupBean.setMap((HashMap)userMap);
         //groupBean.setUserList(userList);
         Gson gsonGroup = new Gson();

         String sGroupBean = gsonGroup.toJson(groupBean, new TypeToken<Teacher>() {
             }.getType());
         System.out.println(sGroupBean);
         /*{"stus":[{"studentName":"张三","studentId":1001},{"studentName":"李四","studentId":1002}],"student":{"studentName":"张三","studentId":1001},"map":{"user3":{"studentName":"李四","studentId":1002},"user1":{"studentName":"张三","studentId":1001}},"id":0,"age":0}*/

 //9、复杂对象string转对象
 Teacher groupBean2 = (Teacher) gson.fromJson(sGroupBean,
    new TypeToken<Teacher>() {
    }.getType());
 System.out.println(groupBean2);

 

 package com.andtools;

 import com.google.gson.annotations.Expose;

 public class Student {
     @Expose
     private String studentName;
     @Expose
     private int studentId;
     public Student(){}
     public Student(int studentId,String studentName){
         this.setStudentId(studentId);
         this.setStudentName(studentName);
     }
     public String toString(){
         return this.getStudentId() + ":" + this.getStudentName();
     }
     public String getStudentName() {
         return studentName;
     }
     public void setStudentName(String studentName) {
         this.studentName = studentName;
     }
     public int getStudentId() {
         return studentId;
     }
     public void setStudentId(int studentId) {
         this.studentId = studentId;
     }

 }

 

 package com.andtools;

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

 import com.google.gson.annotations.Expose;

 public class Teacher {
     @Expose
     private int id;
     @Expose
     private String name;
     @Expose
     private int age;
     @Expose
     private Student student;
     @Expose
     private List stus;
     @Expose
     private HashMap map;
     public String toString(){
         return this.getId()+":"+this.getName()+":"+this.getAge() +":"+ this.getStudent().toString() + ":" + this.getStus() + ":" + this.getMap();
     }
     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 getStudent() {
         return student;
     }
     public void setStudent(Student student) {
         this.student = student;
     }
     public List getStus() {
         return stus;
     }
     public void setStus(List stus) {
         this.stus = stus;
     }
     public HashMap getMap() {
         return map;
     }
     public void setMap(HashMap map) {
         this.map = map;
     }

 }