java.lang.Objectcom.google.gson.internal.bind.MapTypeAdapterFactory
public final class MapTypeAdapterFactory
Adapts maps to either JSON objects or JSON arrays.
Maps
to JSON Objects. This requires that map keys
can be serialized as strings; this is insufficient for some key types. For
example, consider a map whose keys are points on a grid. The default JSON
form encodes reasonably: Map<Point, String> original = new LinkedHashMap<Point, String>();
original.put(new Point(5, 6), "a");
original.put(new Point(8, 8), "b");
System.out.println(gson.toJson(original, type));
The above code prints this JSON object: {
"(5,6)": "a",
"(8,8)": "b"
}
But GSON is unable to deserialize this value because the JSON string name is
just the toString()
of the map key. Attempting to
convert the above JSON to an object fails with a parse exception:
com.google.gson.JsonParseException: Expecting object found: "(5,6)" at com.google.gson.JsonObjectDeserializationVisitor.visitFieldUsingCustomHandler at com.google.gson.ObjectNavigator.navigateClassFields ...
Register this adapter when you are creating your GSON instance.
Gson gson = new GsonBuilder()
.registerTypeAdapter(Map.class, new MapAsArrayTypeAdapter())
.create();
This will change the structure of the JSON emitted by the code above. Now we
get an array. In this case the arrays elements are map entries:
[
[
{
"x": 5,
"y": 6
},
"a",
],
[
{
"x": 8,
"y": 8
},
"b"
]
]
This format will serialize and deserialize just fine as long as this adapter
is registered.
Constructor Summary | |
---|---|
MapTypeAdapterFactory(ConstructorConstructor constructorConstructor,
boolean complexMapKeySerialization)
|
Method Summary | ||
---|---|---|
|
create(Gson gson,
TypeToken<T> typeToken)
Returns a type adapter for type , or null if this factory doesn't
support type . |
Methods inherited from class java.lang.Object |
---|
equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait |
Constructor Detail |
---|
public MapTypeAdapterFactory(ConstructorConstructor constructorConstructor, boolean complexMapKeySerialization)
Method Detail |
---|
public <T> TypeAdapter<T> create(Gson gson, TypeToken<T> typeToken)
TypeAdapterFactory
type
, or null if this factory doesn't
support type
.
create
in interface TypeAdapterFactory