Netty Http File Upload

HttpUploadServerInitializer.java

package my.netty.http.upload;

import io.netty.channel.Channel;
import io.netty.channel.ChannelInitializer;
import io.netty.channel.ChannelPipeline;
import io.netty.channel.EventLoopGroup;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.SocketChannel;
import io.netty.channel.socket.nio.NioServerSocketChannel;
import io.netty.handler.codec.http.HttpRequestDecoder;
import io.netty.handler.codec.http.HttpResponseEncoder;

/**
 * Class for initializing HTTP Handlers.
 */
final class HttpUploadServerInitializer extends ChannelInitializer<SocketChannel> {

  @Override
  protected void initChannel(final SocketChannel socketChannel) throws Exception {
    final ChannelPipeline pipeline = socketChannel.pipeline();
    pipeline.addLast(new HttpRequestDecoder());
    pipeline.addLast(new HttpResponseEncoder());
    pipeline.addLast(new MyHttUploadServerHandler());
  }
}

MyHttUploadServerHandler.java

package my.netty.http.upload;

import io.netty.buffer.ByteBuf;
import io.netty.buffer.Unpooled;
import io.netty.channel.ChannelFutureListener;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.SimpleChannelInboundHandler;
import io.netty.handler.codec.http.DefaultFullHttpResponse;
import io.netty.handler.codec.http.FullHttpResponse;
import io.netty.handler.codec.http.HttpContent;
import io.netty.handler.codec.http.HttpHeaderNames;
import io.netty.handler.codec.http.HttpObject;
import io.netty.handler.codec.http.HttpRequest;
import io.netty.handler.codec.http.HttpResponseStatus;
import io.netty.handler.codec.http.LastHttpContent;
import io.netty.handler.codec.http.multipart.DefaultHttpDataFactory;
import io.netty.handler.codec.http.multipart.FileUpload;
import io.netty.handler.codec.http.multipart.HttpDataFactory;
import io.netty.handler.codec.http.multipart.HttpPostRequestDecoder;
import io.netty.handler.codec.http.multipart.InterfaceHttpData;
import io.netty.util.CharsetUtil;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.net.URI;
import java.nio.channels.FileChannel;

import static io.netty.handler.codec.http.HttpMethod.POST;
import static io.netty.handler.codec.http.HttpResponseStatus.CREATED;
import static io.netty.handler.codec.http.HttpResponseStatus.METHOD_NOT_ALLOWED;
import static io.netty.handler.codec.http.HttpVersion.HTTP_1_1;

/**
 * Handles uploading of file and then saves it to a known location.
 */
public class MyHttUploadServerHandler extends SimpleChannelInboundHandler<HttpObject> {

  // Factory that writes to disk
  private static final HttpDataFactory factory = new DefaultHttpDataFactory(true);
  private static final String FILE_UPLOAD_LOCN = "/tmp/uploads/";
  private HttpRequest httpRequest;
  private HttpPostRequestDecoder httpDecoder;

  @Override
  protected void channelRead0(final ChannelHandlerContext ctx, final HttpObject httpObject)
    throws Exception {
    if (httpObject instanceof HttpRequest) {
      httpRequest = (HttpRequest) httpObject;
      final URI uri = new URI(httpRequest.uri());

      System.out.println("Got URI " + uri);
      if (httpRequest.method() == POST) {
        httpDecoder = new HttpPostRequestDecoder(factory, httpRequest);
        httpDecoder.setDiscardThreshold(0);
      } else {
        sendResponse(ctx, METHOD_NOT_ALLOWED, null);
      }
    }
    if (httpDecoder != null) {
      if (httpObject instanceof HttpContent) {
        final HttpContent chunk = (HttpContent) httpObject;
        httpDecoder.offer(chunk);
        readChunk(ctx);

        if (chunk instanceof LastHttpContent) {
          resetPostRequestDecoder();
        }
      }
    }
  }

  private void readChunk(ChannelHandlerContext ctx) throws IOException {
    while (httpDecoder.hasNext()) {
      InterfaceHttpData data = httpDecoder.next();
      if (data != null) {
        try {
          switch (data.getHttpDataType()) {
            case Attribute:
              break;
            case FileUpload:
              final FileUpload fileUpload = (FileUpload) data;
              final File file = new File(FILE_UPLOAD_LOCN + fileUpload.getFilename());
              if (!file.exists()) {
                file.createNewFile();
              }
              System.out.println("Created file " + file);
              try (FileChannel inputChannel = new FileInputStream(fileUpload.getFile()).getChannel();
                   FileChannel outputChannel = new FileOutputStream(file).getChannel()) {
                outputChannel.transferFrom(inputChannel, 0, inputChannel.size());
                sendResponse(ctx, CREATED, "file name: " + file.getAbsolutePath());
              }
              break;
          }
        } finally {
          data.release();
        }
      }
    }
  }

  /**
   * Sends a response back.
   * @param ctx
   * @param status
   * @param message
   */
  private static void sendResponse(ChannelHandlerContext ctx, HttpResponseStatus status, String message) {
    final FullHttpResponse response;
    String msgDesc = message;
    if (message == null) {
      msgDesc = "Failure: " + status;
    }
    msgDesc += " \r\n";

    final ByteBuf buffer = Unpooled.copiedBuffer(msgDesc, CharsetUtil.UTF_8);
    if (status.code() >= HttpResponseStatus.BAD_REQUEST.code()) {
      response = new DefaultFullHttpResponse(HTTP_1_1, status, buffer);
    } else {
      response = new DefaultFullHttpResponse(HTTP_1_1, status, buffer);
    }
    response.headers().set(HttpHeaderNames.CONTENT_TYPE, "text/plain; charset=UTF-8");

    // Close the connection as soon as the response is sent.
    ctx.writeAndFlush(response).addListener(ChannelFutureListener.CLOSE);
  }

  private void resetPostRequestDecoder() {
    httpRequest = null;
    httpDecoder.destroy();
    httpDecoder = null;
  }

  @Override
  public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
    System.out.println("Got exception " + cause);
    ctx.channel().close();
  }

  @Override
  public void channelInactive(ChannelHandlerContext ctx) throws Exception {
    if (httpDecoder != null) {
      httpDecoder.cleanFiles();
    }
  }

}