T - the generic typepublic final class RuntimeTypeAdapterFactory<T> extends Object implements com.google.gson.TypeAdapterFactory
{
@code
abstract class Shape {
int x;
int y;
}
class Circle extends Shape {
int radius;
}
class Rectangle extends Shape {
int width;
int height;
}
class Diamond extends Shape {
int width;
int height;
}
class Drawing {
Shape bottomShape;
Shape topShape;
}
}
Without additional type information, the serialized JSON is ambiguous. Is the bottom shape in this drawing a rectangle or a diamond?
{
"bottomShape": {
"width": 10,
"height": 5,
"x": 0,
"y": 0
},
"topShape": {
"radius": 2,
"x": 4,
"y": 1
}
}
This class addresses this problem by adding type information to the
serialized JSON and honoring that type information when the JSON is
deserialized:
{
"bottomShape": {
"type": "Diamond",
"width": 10,
"height": 5,
"x": 0,
"y": 0
},
"topShape": {
"type": "Circle",
"radius": 2,
"x": 4,
"y": 1
}
}
Both the type field name ("type") and the type labels ("Rectangle") are configurable.
RuntimeTypeAdapterFactory by
passing the base type and type field name to the of(java.lang.Class<T>) factory method.
If you don't supply an explicit type field name, "type" will be used.
{
@code
RuntimeTypeAdapterFactory<Shape$gt; shapeAdapterFactory = RuntimeTypeAdapterFactory.of(Shape.class, "type");
}
Next register all of your subtypes. Every subtype must be explicitly
registered. This protects your application from injection attacks. If you
don't supply an explicit type label, the type's simple name will be used.
shapeAdapter.registerSubtype(Rectangle.class, "Rectangle");
shapeAdapter.registerSubtype(Circle.class, "Circle");
shapeAdapter.registerSubtype(Diamond.class, "Diamond");
Finally, register the type adapter factory in your application's GSON
builder:
{
@code
Gson gson = new GsonBuilder().registerTypeAdapterFactory(shapeAdapterFactory).create();
}
Like GsonBuilder, this API supports chaining:
{
@code
RuntimeTypeAdapterFactory shapeAdapterFactory = RuntimeTypeAdapterFactory.of(Shape.class).registerSubtype(Rectangle.class).registerSubtype(Circle.class).registerSubtype(Diamond.class);
}
| Modifier and Type | Method and Description |
|---|---|
<R> com.google.gson.TypeAdapter<R> |
create(com.google.gson.Gson gson,
com.google.gson.reflect.TypeToken<R> type) |
static <T> RuntimeTypeAdapterFactory<T> |
of(Class<T> baseType)
Creates a new runtime type adapter for
baseType using
"type" as the type field name. |
static <T> RuntimeTypeAdapterFactory<T> |
of(Class<T> baseType,
String typeFieldName)
Creates a new runtime type adapter using for
baseType using typeFieldName as the type field name. |
RuntimeTypeAdapterFactory<T> |
registerSubtype(Class<? extends T> type)
Registers
type identified by its simple
name. |
RuntimeTypeAdapterFactory<T> |
registerSubtype(Class<? extends T> type,
String label)
Registers
type identified by label. |
public static <T> RuntimeTypeAdapterFactory<T> of(Class<T> baseType)
baseType using
"type" as the type field name.T - the generic typebaseType - the base typepublic static <T> RuntimeTypeAdapterFactory<T> of(Class<T> baseType, String typeFieldName)
baseType using typeFieldName as the type field name. Type field names are case sensitive.T - the generic typebaseType - the base typetypeFieldName - the type field namepublic <R> com.google.gson.TypeAdapter<R> create(com.google.gson.Gson gson,
com.google.gson.reflect.TypeToken<R> type)
create in interface com.google.gson.TypeAdapterFactorypublic RuntimeTypeAdapterFactory<T> registerSubtype(Class<? extends T> type)
type identified by its simple
name. Labels are case sensitive.type - the typeIllegalArgumentException - if either type or its simple name
have already been registered on this type adapter.public RuntimeTypeAdapterFactory<T> registerSubtype(Class<? extends T> type, String label)
type identified by label. Labels are case
sensitive.type - the typelabel - the labelIllegalArgumentException - if either type or label
have already been registered on this type adapter.Copyright © 2018. All rights reserved.