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/*
* ============LICENSE_START=======================================================
* ONAP
* ================================================================================
* Copyright (C) 2019 AT&T Intellectual Property. All rights reserved.
* ================================================================================
* 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.
* ============LICENSE_END=========================================================
*/
package org.onap.policy.common.gson;
import com.google.gson.Gson;
import com.google.gson.JsonElement;
import com.google.gson.JsonObject;
import com.google.gson.TypeAdapter;
import com.google.gson.TypeAdapterFactory;
import com.google.gson.reflect.TypeToken;
import com.google.gson.stream.JsonReader;
import com.google.gson.stream.JsonWriter;
import java.io.IOException;
import java.lang.reflect.Field;
import java.util.ArrayList;
import java.util.List;
import org.onap.policy.common.gson.internal.ClassWalker;
import org.onap.policy.common.gson.internal.Deserializer;
import org.onap.policy.common.gson.internal.FieldDeserializer;
import org.onap.policy.common.gson.internal.FieldSerializer;
import org.onap.policy.common.gson.internal.Serializer;
/**
* Factory that serializes/deserializes class fields following the normal behavior of
* jackson. Supports the following annotations:
* <ul>
* <li>GsonJsonIgnore</li>
* <li>GsonJsonProperty</li>
* </ul>
*
* <p>Note: {@link JacksonExclusionStrategy} must also be registered with the gson object.
*/
public class JacksonFieldAdapterFactory implements TypeAdapterFactory {
@Override
public <T> TypeAdapter<T> create(Gson gson, TypeToken<T> type) {
Class<? super T> clazz = type.getRawType();
if (!JacksonExclusionStrategy.isManaged(clazz)) {
return null;
}
ClassWalker data = new ClassWalker();
data.walkClassHierarchy(clazz);
if (data.getInProps(Field.class).isEmpty() && data.getOutProps(Field.class).isEmpty()) {
// no fields to serialize
return null;
}
return new JacksonFieldAdapter<>(gson, data, gson.getDelegateAdapter(this, type));
}
/**
* Adapter for a single class.
*
* @param <T> type of class on which the adapter works
*/
private static class JacksonFieldAdapter<T> extends TypeAdapter<T> {
/**
* Used to create an object of the given class.
*/
private final TypeAdapter<T> delegate;
/**
* Used to serialize/deserialize a JsonElement.
*/
private final TypeAdapter<JsonElement> elementAdapter;
/**
* Serializers for each item within the object.
*/
private final Serializer[] serializers;
/**
* Deserializers for each item within the object.
*/
private final Deserializer[] deserializers;
/**
* Constructs the object.
*
* @param gson the associated gson object
* @param data data used to configure the adapter
* @param delegate default constructor for the type
*/
public JacksonFieldAdapter(Gson gson, ClassWalker data, TypeAdapter<T> delegate) {
this.delegate = delegate;
this.elementAdapter = gson.getAdapter(JsonElement.class);
// create serializers
this.serializers = makeSerializers(gson, data).toArray(new Serializer[0]);
// create deserializers
this.deserializers = makeDeserializers(gson, data).toArray(new Deserializer[0]);
}
/**
* Creates a complete list of serializers.
*
* @param gson the associated gson object
* @param data data used to configure the serializers
* @return a list of all serializers
*/
private List<Serializer> makeSerializers(Gson gson, ClassWalker data) {
List<Serializer> ser = new ArrayList<Serializer>();
data.getOutProps(Field.class).forEach(field -> ser.add(new FieldSerializer(gson, field)));
return ser;
}
/**
* Creates a complete list of deserializers.
*
* @param gson the associated gson object
* @param data data used to configure the deserializers
* @return a list of all deserializers
*/
private List<Deserializer> makeDeserializers(Gson gson, ClassWalker data) {
List<Deserializer> deser = new ArrayList<Deserializer>();
data.getInProps(Field.class).forEach(field -> deser.add(new FieldDeserializer(gson, field)));
return deser;
}
@Override
public void write(JsonWriter out, T value) throws IOException {
JsonElement tree = delegate.toJsonTree(value);
if (tree.isJsonObject()) {
JsonObject jsonObj = tree.getAsJsonObject();
// serialize each item from the value into the target tree
for (Serializer serializer : serializers) {
serializer.addToTree(value, jsonObj);
}
}
elementAdapter.write(out, tree);
}
@Override
public T read(JsonReader in) throws IOException {
JsonElement tree = elementAdapter.read(in);
T object = delegate.fromJsonTree(tree);
if (tree.isJsonObject()) {
JsonObject jsonObj = tree.getAsJsonObject();
// deserialize each item from the tree into the target object
for (Deserializer dser : deserializers) {
dser.getFromTree(jsonObj, object);
}
}
return object;
}
}
}
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