com.javacreed.examples.gson.part3.AuthorDeserializer.java Source code

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Here is the source code for com.javacreed.examples.gson.part3.AuthorDeserializer.java

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/**
 * Copyright 2012-2014 Java Creed.
 * 
 * Licensed under the Apache License, Version 2.0 (the "<em>License</em>");
 * 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.javacreed.examples.gson.part3;

import java.lang.reflect.Type;
import java.util.HashMap;
import java.util.Map;

import com.google.gson.JsonDeserializationContext;
import com.google.gson.JsonDeserializer;
import com.google.gson.JsonElement;
import com.google.gson.JsonObject;
import com.google.gson.JsonParseException;
import com.google.gson.JsonPrimitive;

public class AuthorDeserializer implements JsonDeserializer<Author> {

    private final ThreadLocal<Map<Integer, Author>> cache = new ThreadLocal<Map<Integer, Author>>() {
        @Override
        protected Map<Integer, Author> initialValue() {
            return new HashMap<>();
        }
    };

    @Override
    public Author deserialize(final JsonElement json, final Type typeOfT, final JsonDeserializationContext context)
            throws JsonParseException {

        // Only the ID is available
        if (json.isJsonPrimitive()) {
            final JsonPrimitive primitive = json.getAsJsonPrimitive();
            return getOrCreate(primitive.getAsInt());
        }

        // The whole object is available
        if (json.isJsonObject()) {
            final JsonObject jsonObject = json.getAsJsonObject();

            final Author author = getOrCreate(jsonObject.get("id").getAsInt());
            author.setName(jsonObject.get("name").getAsString());
            return author;
        }

        throw new JsonParseException("Unexpected JSON type: " + json.getClass().getSimpleName());
    }

    private Author getOrCreate(final int id) {
        Author author = cache.get().get(id);
        if (author == null) {
            author = new Author();
            cache.get().put(id, author);
        }
        return author;
    }
}