org.jclouds.json.internal.NullHackJsonLiteralAdapter.java Source code

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Here is the source code for org.jclouds.json.internal.NullHackJsonLiteralAdapter.java

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/*
 * 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.jclouds.json.internal;

import java.io.IOException;
import java.io.Writer;
import java.lang.reflect.Field;

import javax.inject.Singleton;

import com.google.common.base.Throwables;
import com.google.gson.TypeAdapter;
import com.google.gson.internal.bind.TypeAdapters;
import com.google.gson.stream.JsonReader;
import com.google.gson.stream.JsonWriter;

/**
 * writes or reads the literal json directly
 * 
 * @see <a href="http://code.google.com/p/google-gson/issues/detail?id=326" />
 */
@Singleton
public abstract class NullHackJsonLiteralAdapter<L> extends TypeAdapter<L> {

    @Override
    public L read(JsonReader reader) throws IOException {
        return createJsonLiteralFromRawJson(TypeAdapters.JSON_ELEMENT.read(reader).toString());
    }

    /**
     * User supplied type that holds json literally. Ex. number as {@code 8}, boolean as {@code true}
     * , string as {@code "value"}, object as {@code , list {@code []}.
     */
    protected abstract L createJsonLiteralFromRawJson(String json);

    // the writer inside JsonWriter is not accessible currently
    private static final Field outField;
    static {
        try {
            outField = JsonWriter.class.getDeclaredField("out");
        } catch (SecurityException e) {
            throw Throwables.propagate(e);
        } catch (NoSuchFieldException e) {
            throw Throwables.propagate(e);
        }
        outField.setAccessible(true);
    }

    @Override
    public void write(JsonWriter jsonWriter, L value) throws IOException {

        Writer writer = getWriter(jsonWriter);
        boolean serializeNulls = jsonWriter.getSerializeNulls();
        try {
            // we are using an implementation hack which depends on replacing null with the raw json
            // supplied as a parameter. In this case, we must ensure we indeed serialize nulls.
            NullReplacingWriter nullReplacingWriter = new NullReplacingWriter(writer, toString(value));
            setWriter(jsonWriter, nullReplacingWriter);
            jsonWriter.setSerializeNulls(true);
            jsonWriter.nullValue();
        } finally {
            setWriter(jsonWriter, writer);
            jsonWriter.setSerializeNulls(serializeNulls);
        }

    }

    protected String toString(L value) {
        return value.toString();
    }

    protected Writer getWriter(JsonWriter arg0) {
        try {
            return Writer.class.cast(outField.get(arg0));
        } catch (IllegalAccessException e) {
            throw Throwables.propagate(e);
        }
    }

    private void setWriter(JsonWriter arg0, Writer arg1) {
        try {
            outField.set(arg0, arg1);
        } catch (IllegalAccessException e) {
            throw Throwables.propagate(e);
        }
    }

    public final class NullReplacingWriter extends Writer {
        private final Writer delegate;
        private final String nullReplacement;

        public NullReplacingWriter(Writer delegate, String nullReplacement) {
            this.delegate = delegate;
            this.nullReplacement = nullReplacement;
        }

        @Override
        public void write(char[] buffer, int offset, int count) throws IOException {
            delegate.write(buffer, offset, count);
        }

        @Override
        public void write(String s) throws IOException {
            if (nullReplacement != null && s.equals("null")) {
                s = nullReplacement;
            }
            super.write(s);
        }

        @Override
        public void flush() throws IOException {
            delegate.flush();
        }

        @Override
        public void close() throws IOException {
            delegate.close();
        }

    }
}