com.google.appengine.tools.mapreduce.ConfigurationXmlUtil.java Source code

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Here is the source code for com.google.appengine.tools.mapreduce.ConfigurationXmlUtil.java

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/*
 * Copyright 2010 Google Inc.
 *
 * 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.appengine.tools.mapreduce;

import com.google.common.base.Preconditions;

import org.apache.hadoop.conf.Configuration;

import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.UnsupportedEncodingException;

/**
 * Utility class for converting between a Configuration and its XML
 * representation.
 *
 *
 */
public class ConfigurationXmlUtil {
    private ConfigurationXmlUtil() {
    }

    /**
     * Reconstitutes a Configuration from an XML string.
     *
     * @param serializedConf an XML document in Hadoop configuration format
     * @return the Configuration corresponding to the XML
     */
    public static Configuration getConfigurationFromXml(String serializedConf) {
        Preconditions.checkNotNull(serializedConf);

        try {
            byte[] serializedConfBytes = serializedConf.getBytes("UTF8");
            ByteArrayInputStream serializedConfStream = new ByteArrayInputStream(serializedConfBytes);

            // false makes Configuration not try to read defaults from the filesystem.
            Configuration conf = new Configuration(false);
            conf.addResource(serializedConfStream);
            return conf;
        } catch (UnsupportedEncodingException e) {
            throw new RuntimeException("JDK doesn't understand UTF8", e);
        }
    }

    /**
     * Serializes a configuration to its corresponding XML document as a string.
     *
     * @param conf the configuration to encode
     * @return the configuration as an XML document
     */
    public static String convertConfigurationToXml(Configuration conf) {
        ByteArrayOutputStream baos = new ByteArrayOutputStream();
        try {
            conf.writeXml(baos);
            return baos.toString("UTF8");
        } catch (IOException e) {
            throw new RuntimeException(
                    "Got an IOException writing to ByteArrayOutputStream. This should never happen.", e);
        }
    }
}