/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You 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 org.apache.zeppelin.json;
import java.io.IOException;
import org.apache.zeppelin.socket.NotebookServer;
import com.google.gson.Gson;
import com.google.gson.JsonElement;
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;
/**
* Custom adapter type factory
* Modify the jsonObject before serailaization/deserialization
* Check sample implementation at {@link NotebookServer}
* @param <C> the type whose json is to be customized for serialization/deserialization
*/
public class NotebookTypeAdapterFactory<C> implements TypeAdapterFactory {
private final Class<C> customizedClass;
public NotebookTypeAdapterFactory(Class<C> customizedClass) {
this.customizedClass = customizedClass;
}
@SuppressWarnings("unchecked")
// we use a runtime check to guarantee that 'C' and 'T' are equal
public final <T> TypeAdapter<T> create(Gson gson, TypeToken<T> type) {
return type.getRawType() == customizedClass ? (TypeAdapter<T>) customizeTypeAdapter(gson,
(TypeToken<C>) type) : null;
}
private TypeAdapter<C> customizeTypeAdapter(Gson gson, TypeToken<C> type) {
final TypeAdapter<C> delegate = gson.getDelegateAdapter(this, type);
final TypeAdapter<JsonElement> elementAdapter = gson.getAdapter(JsonElement.class);
return new TypeAdapter<C>() {
@Override
public void write(JsonWriter out, C value) throws IOException {
JsonElement tree = delegate.toJsonTree(value);
beforeWrite(value, tree);
elementAdapter.write(out, tree);
}
@Override
public C read(JsonReader in) throws IOException {
JsonElement tree = elementAdapter.read(in);
afterRead(tree);
return delegate.fromJsonTree(tree);
}
};
}
/**
* Override this to change {@code toSerialize} before it is written to the
* outgoing JSON stream.
*/
protected void beforeWrite(C source, JsonElement toSerialize) {
}
/**
* Override this to change {@code deserialized} before it parsed into the
* application type.
*/
protected void afterRead(JsonElement deserialized) {
}
}