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.
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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:
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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:
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[[{"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
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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 + ", id="codetool">
测试类:
输出结果:
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