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JsonAdapterAnnotationTypeAdapterFactory.java
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JsonAdapterAnnotationTypeAdapterFactory.java
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/*
* Copyright (C) 2014 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.google.gson.internal.bind;
import com.google.gson.Gson;
import com.google.gson.JsonDeserializer;
import com.google.gson.JsonSerializer;
import com.google.gson.TypeAdapter;
import com.google.gson.TypeAdapterFactory;
import com.google.gson.annotations.JsonAdapter;
import com.google.gson.internal.ConstructorConstructor;
import com.google.gson.reflect.TypeToken;
/**
* Given a type T, looks for the annotation {@link JsonAdapter} and uses an instance of the
* specified class as the default type adapter.
*
* @since 2.3
*/
public final class JsonAdapterAnnotationTypeAdapterFactory implements TypeAdapterFactory {
private final ConstructorConstructor constructorConstructor;
public JsonAdapterAnnotationTypeAdapterFactory(ConstructorConstructor constructorConstructor) {
this.constructorConstructor = constructorConstructor;
}
@SuppressWarnings("unchecked")
@Override
public <T> TypeAdapter<T> create(Gson gson, TypeToken<T> targetType) {
Class<? super T> rawType = targetType.getRawType();
JsonAdapter annotation = rawType.getAnnotation(JsonAdapter.class);
if (annotation == null) {
return null;
}
return (TypeAdapter<T>) getTypeAdapter(constructorConstructor, gson, targetType, annotation);
}
@SuppressWarnings({ "unchecked", "rawtypes" }) // Casts guarded by conditionals.
TypeAdapter<?> getTypeAdapter(ConstructorConstructor constructorConstructor, Gson gson,
TypeToken<?> type, JsonAdapter annotation) {
Object instance = constructorConstructor.get(TypeToken.get(annotation.value())).construct();
TypeAdapter<?> typeAdapter;
boolean nullSafe = annotation.nullSafe();
if (instance instanceof TypeAdapter) {
typeAdapter = (TypeAdapter<?>) instance;
} else if (instance instanceof TypeAdapterFactory) {
typeAdapter = ((TypeAdapterFactory) instance).create(gson, type);
} else if (instance instanceof JsonSerializer || instance instanceof JsonDeserializer) {
JsonSerializer<?> serializer = instance instanceof JsonSerializer
? (JsonSerializer) instance
: null;
JsonDeserializer<?> deserializer = instance instanceof JsonDeserializer
? (JsonDeserializer) instance
: null;
typeAdapter = new TreeTypeAdapter(serializer, deserializer, gson, type, null, nullSafe);
nullSafe = false;
} else {
throw new IllegalArgumentException("Invalid attempt to bind an instance of "
+ instance.getClass().getName() + " as a @JsonAdapter for " + type.toString()
+ ". @JsonAdapter value must be a TypeAdapter, TypeAdapterFactory,"
+ " JsonSerializer or JsonDeserializer.");
}
if (typeAdapter != null && nullSafe) {
typeAdapter = typeAdapter.nullSafe();
}
return typeAdapter;
}
}