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/*
* ============LICENSE_START===================================================
* Copyright (c) 2018 Amdocs
* ============================================================================
* 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.aai.validation.util;
import com.google.gson.Gson;
import com.google.gson.GsonBuilder;
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.JsonToken;
import com.google.gson.stream.JsonWriter;
import java.io.IOException;
import java.lang.reflect.ParameterizedType;
import java.lang.reflect.Type;
import java.util.Optional;
/**
* Static utility class
*
*/
public class GsonUtil {
/**
* All methods are static.
*/
private GsonUtil() {
// Do not instantiate
}
/**
* Tell Gson how to handle Optional fields. This factory builds a Type Adapter for a class wrapped with Optional
*
*/
public static class OptionalTypeAdapterFactory implements TypeAdapterFactory {
@SuppressWarnings({ "unchecked", "rawtypes" })
@Override
public <T> TypeAdapter<T> create(Gson gson, TypeToken<T> type) {
Class<T> rawType = (Class<T>) type.getRawType();
if (rawType != Optional.class) {
return null;
}
final ParameterizedType parameterizedType = (ParameterizedType) type.getType();
final Type actualType = parameterizedType.getActualTypeArguments()[0];
return new OptionalTypeAdapter(gson.getAdapter(TypeToken.get(actualType)));
}
}
/**
* Implementation of the Optional Type Adapter
*
* @param <E>
*/
public static class OptionalTypeAdapter<E> extends TypeAdapter<Optional<E>> {
private final TypeAdapter<E> adapter;
public static final TypeAdapterFactory FACTORY = new OptionalTypeAdapterFactory();
/**
* @param adapter
*/
public OptionalTypeAdapter(TypeAdapter<E> adapter) {
this.adapter = adapter;
}
@Override
public void write(JsonWriter out, Optional<E> value) throws IOException {
if (value != null && value.isPresent()) { // NOSONAR
adapter.write(out, value.get());
} else {
boolean nullsAllowed = out.getSerializeNulls();
if (nullsAllowed) {
out.setSerializeNulls(false);
}
out.nullValue();
if (nullsAllowed) {
out.setSerializeNulls(true);
}
}
}
@Override
public Optional<E> read(JsonReader in) throws IOException {
final JsonToken peek = in.peek();
if (peek != JsonToken.NULL) {
return Optional.ofNullable(adapter.read(in));
}
return Optional.empty();
}
}
/**
* @return a new GsonBuilder with standard settings
*/
public static GsonBuilder createGsonBuilder() {
return new GsonBuilder().disableHtmlEscaping().serializeNulls().excludeFieldsWithoutExposeAnnotation()
.registerTypeAdapterFactory(OptionalTypeAdapter.FACTORY);
}
/**
* @return a new Gson instance
*/
public static Gson createGson() {
return createGsonBuilder().create();
}
}
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