/*
* Copyright (C) 2008 Google Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.smartandroid.sa.json;
import java.lang.reflect.Type;
/**
* Context for deserialization that is passed to a custom deserializer during
* invocation of its
* {@link JsonDeserializer#deserialize(JsonElement, Type, JsonDeserializationContext)}
* method.
*
* @author Inderjeet Singh
* @author Joel Leitch
*/
public class JsonDeserializationContext {
private final ObjectNavigator objectNavigator;
private final FieldNamingStrategy2 fieldNamingPolicy;
private final ParameterizedTypeHandlerMap<JsonDeserializer<?>> deserializers;
private final MappedObjectConstructor objectConstructor;
JsonDeserializationContext(ObjectNavigator objectNavigator,
FieldNamingStrategy2 fieldNamingPolicy,
ParameterizedTypeHandlerMap<JsonDeserializer<?>> deserializers,
MappedObjectConstructor objectConstructor) {
this.objectNavigator = objectNavigator;
this.fieldNamingPolicy = fieldNamingPolicy;
this.deserializers = deserializers;
this.objectConstructor = objectConstructor;
}
JsonDeserializationContext() {
this(null, null, null, null);
}
@SuppressWarnings("unchecked")
public <T> T construct(Type type) {
Object instance = objectConstructor.construct(type);
return (T) instance;
}
public Object constructArray(Type type, int length) {
return objectConstructor.constructArray(type, length);
}
private <T> T fromJsonArray(Type arrayType, JsonArray jsonArray,
JsonDeserializationContext context, boolean systemOnly)
throws JsonParseException {
JsonArrayDeserializationVisitor<T> visitor = new JsonArrayDeserializationVisitor<T>(
jsonArray, arrayType, objectNavigator, fieldNamingPolicy,
objectConstructor, deserializers, context);
objectNavigator.accept(new ObjectTypePair(null, arrayType, true,
systemOnly), visitor);
return visitor.getTarget();
}
private <T> T fromJsonObject(Type typeOfT, JsonObject jsonObject,
JsonDeserializationContext context, boolean systemOnly)
throws JsonParseException {
JsonObjectDeserializationVisitor<T> visitor = new JsonObjectDeserializationVisitor<T>(
jsonObject, typeOfT, objectNavigator, fieldNamingPolicy,
objectConstructor, deserializers, context);
objectNavigator.accept(new ObjectTypePair(null, typeOfT, true,
systemOnly), visitor);
return visitor.getTarget();
}
@SuppressWarnings("unchecked")
private <T> T fromJsonPrimitive(Type typeOfT, JsonPrimitive json,
JsonDeserializationContext context, boolean systemOnly)
throws JsonParseException {
JsonObjectDeserializationVisitor<T> visitor = new JsonObjectDeserializationVisitor<T>(
json, typeOfT, objectNavigator, fieldNamingPolicy,
objectConstructor, deserializers, context);
objectNavigator.accept(new ObjectTypePair(json.getAsObject(), typeOfT,
true, systemOnly), visitor);
Object target = visitor.getTarget();
return (T) target;
}
/**
* Invokes default deserialization on the specified object. It should never
* be invoked on the element received as a parameter of the
* {@link JsonDeserializer#deserialize(JsonElement, Type, JsonDeserializationContext)}
* method. Doing so will result in an infinite loop since Gson will in-turn
* call the custom deserializer again.
*
* @param json
* the parse tree.
* @param typeOfT
* type of the expected return value.
* @param <T>
* The type of the deserialized object.
* @return An object of type typeOfT.
* @throws JsonParseException
* if the parse tree does not contain expected data.
*/
@SuppressWarnings("unchecked")
public <T> T deserialize(JsonElement json, Type typeOfT)
throws JsonParseException {
if (json == null || json.isJsonNull()) {
return null;
} else if (json.isJsonArray()) {
Object array = fromJsonArray(typeOfT, json.getAsJsonArray(), this,
false);
return (T) array;
} else if (json.isJsonObject()) {
Object object = fromJsonObject(typeOfT, json.getAsJsonObject(),
this, false);
return (T) object;
} else if (json.isJsonPrimitive()) {
Object primitive = fromJsonPrimitive(typeOfT,
json.getAsJsonPrimitive(), this, false);
return (T) primitive;
} else {
throw new JsonParseException("Failed parsing JSON source: " + json
+ " to Json");
}
}
@SuppressWarnings("unchecked")
public <T> T deserializeDefault(JsonElement json, Type typeOfT)
throws JsonParseException {
if (json == null || json.isJsonNull()) {
return null;
} else if (json.isJsonArray()) {
Object array = fromJsonArray(typeOfT, json.getAsJsonArray(), this,
true);
return (T) array;
} else if (json.isJsonObject()) {
Object object = fromJsonObject(typeOfT, json.getAsJsonObject(),
this, true);
return (T) object;
} else if (json.isJsonPrimitive()) {
Object primitive = fromJsonPrimitive(typeOfT,
json.getAsJsonPrimitive(), this, true);
return (T) primitive;
} else {
throw new JsonParseException("Failed parsing JSON source: " + json
+ " to Json");
}
}
}