Android development _ Gson Analysis

// Converter GsonBuilder builder = new GsonBuilder (); // The Field builder without the @ Expose annotation is not converted. excludeFieldsWithoutExposeAnnotation (); Gson gson = builder. create (); // 1. Convert the object to 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. The string object is 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. Convert Object List to 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 = new TypeToken <List <Student> (){}. getType (); // specify the property String beanListToJson = gson. toJson (testBeanList, type); System. out. println (beanListToJson); // [{"studentName": "552", "studentId": 555}] // list of conversion objects from a collection string <Student> testBeanListFromJson = gson. fromJson (beanListToJson, type); System. out. println (testBeanListFromJson); // [555: 552] // 4. If the set is not specified, the default type is 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. To return the set String, you must specify the type List <String> testList2 = (List <String>) gson. fromJson (listToJson, new TypeToken <List <String> (){}. getType (); System. out. println (testList2); // 6. convert a HashMap String to a 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 to 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. objects contain common objects, sets, and maps. Student user1 = new Student (); user1.setStudentId (1001); user1.setStudentName ("James "); student user3 = new Student (); user3.setStudentId (1002); user3.setStudentName (""); 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": "Zhang San", "studentId": 1001 },{ "studentName": "Li Si ", "studentId": 1002}], "student": {"studentName": "Zhang San", "studentId": 1001}, "map": {"user3 ": {"studentName": "Li Si", "studentId": 1002}, "user1": {"studentName": "Zhang San", "studentId": 1001 }}, "id": 0, "age": 0} */Java code // 9. the string of a complex object is converted to the Teacher groupBean2 = (Teacher) gson. fromJson (sGroupBean, new TypeToken <Teacher> (){}. getType (); System. out. println (groupBean2); Java code 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;} Java code 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 ;}}