org.civilian.content.GsonJsonSerializer.java Source code

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Here is the source code for org.civilian.content.GsonJsonSerializer.java

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/*
 * Copyright (C) 2014 Civilian Framework.
 *
 * Licensed under the Civilian License (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.civilian-framework.org/license.txt
 *
 * 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.civilian.content;

import java.io.Reader;
import java.io.Writer;
import java.lang.reflect.Type;
import com.google.gson.Gson;
import com.google.gson.GsonBuilder;
import com.google.gson.JsonElement;
import com.google.gson.JsonParseException;
import com.google.gson.JsonParser;
import com.google.gson.JsonSyntaxException;
import org.civilian.text.keys.KeyList;
import org.civilian.text.keys.serialize.KeyListSerializer;
import org.civilian.util.Check;
import org.civilian.util.ClassUtil;

/**
 * A ContentSerializer for JSON data based on GSON.
 */
public class GsonJsonSerializer extends ContentSerializer {
    /**
     * Creates a new JsonSerializer.
     */
    public GsonJsonSerializer() {
        this(new GsonBuilder());
    }

    /**
     * Creates a new JsonSerializer. The gson object of the serializer
     * is obtained from the builder
     */
    public GsonJsonSerializer(GsonBuilder builder) {
        Check.notNull(builder, "builder");
        builder.registerTypeHierarchyAdapter(KeyList.class, new KeyListSerializer());
        gson_ = builder.create();
    }

    /**
     * Creates a new JsonSerializer based on the gson object.
        
     */
    public GsonJsonSerializer(Gson gson) {
        Check.notNull(gson, "gson");
        gson_ = gson;
    }

    /**
     * Uses the JsonService of the application to parse the content.    
     */
    @SuppressWarnings("unchecked")
    @Override
    public <T> T read(Class<T> type, Type genericType, Reader reader) throws Exception {
        Check.notNull(type, "type");
        Check.notNull(reader, "reader");

        if (type == JsonElement.class) {
            JsonParser parser = new JsonParser();
            return (T) parser.parse(reader);
        } else if (genericType != null)
            return gson_.fromJson(reader, genericType);
        else
            return gson_.fromJson(reader, type);
    }

    /**
     * Writes the content of the response. 
     */
    @Override
    public void write(Object object, Writer writer) throws Exception {
        if (object instanceof JsonElement)
            gson_.toJson((JsonElement) object, writer);
        else
            gson_.toJson(object, writer);
    }

    /**
     * Returns the gson object if implClass equals Gson.class.
     */
    @Override
    public <T> T unwrap(Class<T> implClass) {
        return ClassUtil.unwrap(gson_, implClass);
    }

    /**
     * Returns the exception message if the exception is a JsonSyntaxException
     * or a JsonParseException, else returns null.
     */
    @Override
    public String describeReadError(Exception e) {
        return (e instanceof JsonSyntaxException) || (e instanceof JsonParseException) ? e.getMessage() : null;
    }

    private Gson gson_;
}