cn.lhfei.hadoop.ch04.SequenceFileReadDemo.java Source code

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Here is the source code for cn.lhfei.hadoop.ch04.SequenceFileReadDemo.java

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/*
 * Copyright 2010-2011 the original author or authors.
 *
 * 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 cn.lhfei.hadoop.ch04;

import java.io.IOException;
import java.net.URI;

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.SequenceFile;
import org.apache.hadoop.io.Writable;
import org.apache.hadoop.util.ReflectionUtils;
import org.apache.zookeeper.common.IOUtils;

/**
 * @version 0.1
 *
 * @author Hefei Li
 *
 * @since Oct 30, 2014
 */

public class SequenceFileReadDemo {

    public static void main(String[] args) {
        String uri = args[0];
        Configuration conf = new Configuration();
        FileSystem fs = null;
        Path path = new Path(uri);

        SequenceFile.Reader reader = null;

        try {
            fs = FileSystem.get(URI.create(uri), conf);

            reader = new SequenceFile.Reader(fs, path, conf);
            Writable key = (Writable) ReflectionUtils.newInstance(reader.getKeyClass(), conf);
            Writable value = (Writable) ReflectionUtils.newInstance(reader.getValueClass(), conf);
            long position = reader.getPosition();
            while (reader.next(key, value)) {
                String syncSeen = reader.syncSeen() ? "*" : "";
                System.out.printf("[%s%s]\t%s\t%s\n", position, syncSeen, key, value);
                position = reader.getPosition(); // beginning of next record
            }
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            IOUtils.closeStream(reader);
        }

    }

}