SupplierDeserializer.java example

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gerrit-master
// Copyright (C) 2016 The Android Open Source Project
//
// 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.gerrit.server.events;

import static com.google.common.base.Preconditions.checkArgument;

import com.google.common.base.Supplier;
import com.google.common.base.Suppliers;
import com.google.gson.JsonDeserializationContext;
import com.google.gson.JsonDeserializer;
import com.google.gson.JsonElement;
import com.google.gson.JsonParseException;
import java.lang.reflect.ParameterizedType;
import java.lang.reflect.Type;

public class SupplierDeserializer implements JsonDeserializer<Supplier<?>> {

  @Override
  public Supplier<?> deserialize(JsonElement json, Type typeOfT, JsonDeserializationContext context)
      throws JsonParseException {
    checkArgument(typeOfT instanceof ParameterizedType);
    ParameterizedType parameterizedType = (ParameterizedType) typeOfT;
    if (parameterizedType.getActualTypeArguments().length != 1) {
      throw new JsonParseException("Expected one parameter type in Supplier interface.");
    }
    Type supplierOf = parameterizedType.getActualTypeArguments()[0];
    return Suppliers.ofInstance(context.deserialize(json, supplierOf));
  }
}