- //轉換器
- GsonBuilder builder = new GsonBuilder();
- // 不轉換沒有 @Expose 註解的字段 @Expose的作用是支持序列化,沒有@Expose不會被序列化
- builder.excludeFieldsWithoutExposeAnnotation();
-
Gson gson = builder.create();
-
@Expose註解的作用:區分實體中不想被序列化的屬性,其自身包含兩個屬性deserialize(反序列化)和serialize(序列化),默認都爲true。
使用 new GsonBuilder().excludeFieldsWithoutExposeAnnotation().create();創建Gson對象,沒有@Expose註釋的屬性將不會被序列化.。
private class User{ private int id; @Expose private String name; ....... }
這樣create() gson對象序列化user,只會有name這一個屬性
- //1、對象轉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轉對象
- 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、對象List轉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(); //指定集合對象屬性
- String beanListToJson = gson.toJson(testBeanList, type);
- System.out.println(beanListToJson); //[{"studentName":"552","studentId":555}]
- //集合string轉對象list
- List<Student> testBeanListFromJson = gson.fromJson(beanListToJson, type);
- System.out.println(testBeanListFromJson); //[555:552]
- //4、集合如果不指定類型 默認爲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、集合字符串轉回來需要指定類型
- List<String> testList2 = (List<String>) gson.fromJson(listToJson,
- new TypeToken<List<String>>() {
- }.getType());
- System.out.println(testList2);
- //6、 將HashMap字符串轉換爲 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轉對象
- 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、對象含有普通對象、集合、map情況
- Student user1 = new Student();
- user1.setStudentId(1001);
- user1.setStudentName("張三");
- 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":"張三","studentId":1001},{"studentName":"李四","studentId":1002}],"student":{"studentName":"張三","studentId":1001},"map":{"user3":{"studentName":"李四","studentId":1002},"user1":{"studentName":"張三","studentId":1001}},"id":0,"age":0}*/
- //9、複雜對象string轉對象
- 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;
- }
- }