{@code
32 | * abstract class Shape {
33 | * int x;
34 | * int y;
35 | * }
36 | * class Circle extends Shape {
37 | * int radius;
38 | * }
39 | * class Rectangle extends Shape {
40 | * int width;
41 | * int height;
42 | * }
43 | * class Diamond extends Shape {
44 | * int width;
45 | * int height;
46 | * }
47 | * class Drawing {
48 | * Shape bottomShape;
49 | * Shape topShape;
50 | * }
51 | * }
52 | * Without additional type information, the serialized JSON is ambiguous. Is 53 | * the bottom shape in this drawing a rectangle or a diamond?
{@code
54 | * {
55 | * "bottomShape": {
56 | * "width": 10,
57 | * "height": 5,
58 | * "x": 0,
59 | * "y": 0
60 | * },
61 | * "topShape": {
62 | * "radius": 2,
63 | * "x": 4,
64 | * "y": 1
65 | * }
66 | * }}
67 | * This class addresses this problem by adding type information to the
68 | * serialized JSON and honoring that type information when the JSON is
69 | * deserialized: {@code
70 | * {
71 | * "bottomShape": {
72 | * "type": "Diamond",
73 | * "width": 10,
74 | * "height": 5,
75 | * "x": 0,
76 | * "y": 0
77 | * },
78 | * "topShape": {
79 | * "type": "Circle",
80 | * "radius": 2,
81 | * "x": 4,
82 | * "y": 1
83 | * }
84 | * }}
85 | * Both the type field name ({@code "type"}) and the type labels ({@code
86 | * "Rectangle"}) are configurable.
87 | *
88 | * {@code
92 | * RuntimeTypeAdapterFactory shapeAdapterFactory
93 | * = RuntimeTypeAdapterFactory.of(Shape.class, "type");
94 | * }
95 | * Next register all of your subtypes. Every subtype must be explicitly
96 | * registered. This protects your application from injection attacks. If you
97 | * don't supply an explicit type label, the type's simple name will be used.
98 | * {@code
99 | * shapeAdapter.registerSubtype(Rectangle.class, "Rectangle");
100 | * shapeAdapter.registerSubtype(Circle.class, "Circle");
101 | * shapeAdapter.registerSubtype(Diamond.class, "Diamond");
102 | * }
103 | * Finally, register the type adapter factory in your application's GSON builder:
104 | * {@code
105 | * Gson gson = new GsonBuilder()
106 | * .registerTypeAdapterFactory(shapeAdapterFactory)
107 | * .create();
108 | * }
109 | * Like {@code GsonBuilder}, this API supports chaining: {@code
110 | * RuntimeTypeAdapterFactory shapeAdapterFactory = RuntimeTypeAdapterFactory.of(Shape.class)
111 | * .registerSubtype(Rectangle.class)
112 | * .registerSubtype(Circle.class)
113 | * .registerSubtype(Diamond.class);
114 | * }
115 | */
116 | public final class RuntimeTypeAdapterFactory