TextFileViewer.java

/*
 * Copyright 2012 LinkedIn Corp.
 *
 * 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.viewer.hdfs;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.PrintWriter;
import java.nio.charset.StandardCharsets;
import java.util.EnumSet;
import java.util.Set;
import java.util.HashSet;

import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.fs.permission.AccessControlException;
import org.apache.log4j.Logger;

public class TextFileViewer extends HdfsFileViewer {

  private static Logger logger = Logger.getLogger(TextFileViewer.class);
  private HashSet<String> acceptedSuffix = new HashSet<String>();

  // only display the first 1M chars. it is used to prevent
  // showing/downloading gb of data
  private static final int BUFFER_LIMIT = 1000000;
  private static final String VIEWER_NAME = "Text";

  public TextFileViewer() {
    acceptedSuffix.add(".txt");
    acceptedSuffix.add(".csv");
    acceptedSuffix.add(".props");
    acceptedSuffix.add(".xml");
    acceptedSuffix.add(".html");
    acceptedSuffix.add(".json");
    acceptedSuffix.add(".log");
  }

  @Override
  public String getName() {
    return VIEWER_NAME;
  }

  @Override
  public Set<Capability> getCapabilities(FileSystem fs, Path path)
      throws AccessControlException {
    return EnumSet.of(Capability.READ);
  }

  @Override
  public void displayFile(FileSystem fs, Path path, OutputStream outputStream,
      int startLine, int endLine) throws IOException {

    if (logger.isDebugEnabled())
      logger.debug("read in uncompressed text file");

    displayFileContent(fs, path, outputStream, startLine, endLine, BUFFER_LIMIT);
  }

  @SuppressWarnings("DefaultCharset")
  static void displayFileContent(FileSystem fs, Path path, OutputStream outputStream,
      int startLine, int endLine, int bufferLimit) throws IOException {

    InputStream inputStream = null;
    BufferedReader reader = null;
    try {
      inputStream = fs.open(path);
      reader = new BufferedReader(new InputStreamReader(inputStream, StandardCharsets.UTF_8));
      PrintWriter output = new PrintWriter(outputStream);
      for (int i = 1; i < startLine; i++) {
        reader.readLine();
      }

      int bufferSize = 0;
      for (int i = startLine; i < endLine; i++) {
        String line = reader.readLine();
        if (line == null)
          break;

        // break if reach the buffer limit
        bufferSize += line.length();
        if (bufferSize >= bufferLimit)
          break;

        output.write(line);
        output.write("\n");
      }
      output.flush();
    } finally {
      if (reader != null) {
        reader.close();
      }
      if (inputStream != null) {
        inputStream.close();
      }
    }
  }
}