azkaban.common.web.JsonSequenceFileViewer.java Source code

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Here is the source code for azkaban.common.web.JsonSequenceFileViewer.java

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/*
 * Copyright 2010 LinkedIn, 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 azkaban.common.web;

import java.io.IOException;
import java.io.PrintWriter;

import org.apache.hadoop.io.BytesWritable;
import org.apache.hadoop.io.SequenceFile;
import org.apache.hadoop.io.SequenceFile.Reader;
import org.apache.hadoop.io.Text;
import org.apache.log4j.Logger;

import voldemort.serialization.json.JsonTypeSerializer;

public class JsonSequenceFileViewer extends HdfsSequenceFileViewer {

    private static Logger logger = Logger.getLogger(JsonSequenceFileViewer.class);

    public boolean canReadFile(Reader reader) {
        Text keySchema = reader.getMetadata().get(new Text("key.schema"));
        Text valueSchema = reader.getMetadata().get(new Text("value.schema"));

        return keySchema != null && valueSchema != null;
    }

    public void displaySequenceFile(SequenceFile.Reader reader, PrintWriter output, int startLine, int endLine)
            throws IOException {

        if (logger.isDebugEnabled())
            logger.debug("display json file");

        try {
            BytesWritable keyWritable = new BytesWritable();
            BytesWritable valueWritable = new BytesWritable();
            Text keySchema = reader.getMetadata().get(new Text("key.schema"));
            Text valueSchema = reader.getMetadata().get(new Text("value.schema"));

            JsonTypeSerializer keySerializer = new JsonTypeSerializer(keySchema.toString());
            JsonTypeSerializer valueSerializer = new JsonTypeSerializer(valueSchema.toString());

            // skip lines before the start line
            for (int i = 1; i < startLine; i++)
                reader.next(keyWritable, valueWritable);

            // now actually output lines
            for (int i = startLine; i <= endLine; i++) {
                boolean readSomething = reader.next(keyWritable, valueWritable);
                if (!readSomething)
                    break;
                output.write(safeToString(keySerializer.toObject(keyWritable.getBytes())));
                output.write("\t=>\t");
                output.write(safeToString(valueSerializer.toObject(valueWritable.getBytes())));
                output.write("\n");
                output.flush();
            }
        } finally {
            reader.close();
        }
    }

    private String safeToString(Object value) {
        if (value == null)
            return "null";
        else
            return value.toString();
    }

}