使用GSON库将Java中的map键值对应结构对象转换为JSON
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2024-03-12 16:24:44
map的存储结构式key/value形式,key 和 value可以是普通类型,也可以是自己写的javabean(本文),还可以是带有泛型的list.
(gson的git...
map的存储结构式key/value形式,key 和 value可以是普通类型,也可以是自己写的javabean(本文),还可以是带有泛型的list.
(gson的github项目页:https://github.com/google/gson)
javabean
本例中您要重点看如何将json转回为普通javabean对象时typetoken的定义.
实体类:
public class point { private int x; private int y; public point(int x, int y) { this.x = x; this.y = y; } public int getx() { return x; } public void setx(int x) { this.x = x; } public int gety() { return y; } public void sety(int y) { this.y = y; } @override public string tostring() { return "point [x=" + x + ", y=" + y + "]"; } }
测试类:
import java.util.linkedhashmap; import java.util.map; import com.google.gson.gson; import com.google.gson.gsonbuilder; import com.google.gson.reflect.typetoken; public class gsontest3 { public static void main(string[] args) { gson gson = new gsonbuilder().enablecomplexmapkeyserialization() .create(); map<point, string> map1 = new linkedhashmap<point, string>();// 使用linkedhashmap将结果按先进先出顺序排列 map1.put(new point(5, 6), "a"); map1.put(new point(8, 8), "b"); string s = gson.tojson(map1); system.out.println(s);// 结果:[[{"x":5,"y":6},"a"],[{"x":8,"y":8},"b"]] map<point, string> retmap = gson.fromjson(s, new typetoken<map<point, string>>() { }.gettype()); for (point p : retmap.keyset()) { system.out.println("key:" + p + " values:" + retmap.get(p)); } system.out.println(retmap); system.out.println("----------------------------------"); map<string, point> map2 = new linkedhashmap<string, point>(); map2.put("a", new point(3, 4)); map2.put("b", new point(5, 6)); string s2 = gson.tojson(map2); system.out.println(s2); map<string, point> retmap2 = gson.fromjson(s2, new typetoken<map<string, point>>() { }.gettype()); for (string key : retmap2.keyset()) { system.out.println("key:" + key + " values:" + retmap2.get(key)); } } }
结果:
[[{"x":5,"y":6},"a"],[{"x":8,"y":8},"b"]] key:point [x=5, y=6] values:a key:point [x=8, y=8] values:b {point [x=5, y=6]=a, point [x=8, y=8]=b} ---------------------------------- {"a":{"x":3,"y":4},"b":{"x":5,"y":6}} key:a values:point [x=3, y=4] key:b values:point [x=5, y=6]
泛型list
实体类:
import java.util.date; public class student { private int id; private string name; private date birthday; 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 date getbirthday() { return birthday; } public void setbirthday(date birthday) { this.birthday = birthday; } @override public string tostring() { return "student [birthday=" + birthday + ", id=" + id + ", name=" + name + "]"; } } public class teacher { private int id; private string name; private string title; 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 string gettitle() { return title; } public void settitle(string title) { this.title = title; } @override public string tostring() { return "teacher [id=" + id + ", name=" + name + ", title=" + title + "]"; } }
测试类:
package com.tgb.lk.demo.gson.test4; import java.util.arraylist; import java.util.date; import java.util.linkedhashmap; import java.util.list; import java.util.map; import com.google.gson.gson; import com.google.gson.reflect.typetoken; public class gsontest4 { public static void main(string[] args) { student student1 = new student(); student1.setid(1); student1.setname("李坤"); student1.setbirthday(new date()); student student2 = new student(); student2.setid(2); student2.setname("曹贵生"); student2.setbirthday(new date()); student student3 = new student(); student3.setid(3); student3.setname("柳波"); student3.setbirthday(new date()); list<student> stulist = new arraylist<student>(); stulist.add(student1); stulist.add(student2); stulist.add(student3); teacher teacher1 = new teacher(); teacher1.setid(1); teacher1.setname("米老师"); teacher1.settitle("教授"); teacher teacher2 = new teacher(); teacher2.setid(2); teacher2.setname("丁老师"); teacher2.settitle("讲师"); list<teacher> teacherlist = new arraylist<teacher>(); teacherlist.add(teacher1); teacherlist.add(teacher2); map<string, object> map = new linkedhashmap<string, object>(); map.put("students", stulist); map.put("teachers", teacherlist); gson gson = new gson(); string s = gson.tojson(map); system.out.println(s); system.out.println("----------------------------------"); map<string, object> retmap = gson.fromjson(s, new typetoken<map<string, list<object>>>() { }.gettype()); for (string key : retmap.keyset()) { system.out.println("key:" + key + " values:" + retmap.get(key)); if (key.equals("students")) { list<student> stulist = (list<student>) retmap.get(key); system.out.println(stulist); } else if (key.equals("teachers")) { list<teacher> tchrlist = (list<teacher>) retmap.get(key); system.out.println(tchrlist); } } } }
输出结果:
{"students":[{"id":1,"name":"李坤","birthday":"jun 22, 2012 9:48:19 pm"},{"id":2,"name":"曹贵生","birthday":"jun 22, 2012 9:48:19 pm"},{"id":3,"name":"柳波","birthday":"jun 22, 2012 9:48:19 pm"}],"teachers":[{"id":1,"name":"米老师","title":"教授"},{"id":2,"name":"丁老师","title":"讲师"}]} ---------------------------------- key:students values:[{id=1.0, name=李坤, birthday=jun 22, 2012 9:48:19 pm}, {id=2.0, name=曹贵生, birthday=jun 22, 2012 9:48:19 pm}, {id=3.0, name=柳波, birthday=jun 22, 2012 9:48:19 pm}] [{id=1.0, name=李坤, birthday=jun 22, 2012 9:48:19 pm}, {id=2.0, name=曹贵生, birthday=jun 22, 2012 9:48:19 pm}, {id=3.0, name=柳波, birthday=jun 22, 2012 9:48:19 pm}] key:teachers values:[{id=1.0, name=米老师, title=教授}, {id=2.0, name=丁老师, title=讲师}] [{id=1.0, name=米老师, title=教授}, {id=2.0, name=丁老师, title=讲师}]
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