FileReadingNioServlet.java

/**
 * Copyright 2015 Google Inc. All Rights Reserved.
 * 
 * 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.apphosting.tests.usercode.testservlets;

import java.io.IOException;
import java.io.File;
import java.io.RandomAccessFile;
import java.nio.ByteBuffer;
import java.nio.channels.ByteChannel;

import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.ServletException;

/**
 * Demonstrates use of {@link FileChannel}.
 *
 */
public class FileReadingNioServlet extends HttpServlet {

  @Override
  protected void doGet(HttpServletRequest request, HttpServletResponse response)
      throws ServletException, IOException {
    String indexHtmlPath = getServletContext().getRealPath("index.html");
    File indexHtml = new File(indexHtmlPath);

    RandomAccessFile raf = new RandomAccessFile(indexHtml, "r");
    ByteChannel channel = raf.getChannel();

    ByteBuffer buffer = ByteBuffer.allocate(8192);
    while (channel.read(buffer) != -1) {
      buffer.flip();
      int len = buffer.remaining();
      byte[] bytes = new byte[len];
      buffer.get(bytes);
      buffer.flip();
      response.getOutputStream().write(bytes, 0, len);
    }

    channel.close();
  }
}