Http介绍

Http(超文本传输协议)协议是建立在TCP传输协议之上的应用成协议,Http由于便捷、快速的方式，适用于分布式超媒体信息系统。Http是目前Web开发的主流协议，基于Http的应用非常广泛，因此掌握HTTP的开发非常重要。由于netty的HTTP协议栈是基于netty的NIO通信框架开发的，所以netty的HTTP协议也是异步非阻塞的。

具体的关于HTTP及Netyy的实现细节在以后的章节在写，先上实例代码：

实例代码

服务端：
public class HttpFileServer {

public void run(final int port, final String url) throws InterruptedException {

    EventLoopGroup bossGroup = new NioEventLoopGroup();
    EventLoopGroup workerGroup = new NioEventLoopGroup();

    try {
        ServerBootstrap boot = new ServerBootstrap();

        boot.group(bossGroup, workerGroup).channel(NioServerSocketChannel.class)
                .childHandler(new ChannelInitializer<SocketChannel>() {

                    @Override
                    protected void initChannel(SocketChannel ch) throws Exception {
                        ch.pipeline().addLast("http-decoder", new HttpRequestDecoder());
                        ch.pipeline().addLast("http-aggregator", new HttpObjectAggregator(65536));
                        ch.pipeline().addLast("http-encoder", new HttpResponseEncoder());
                        ch.pipeline().addLast("http-chunked", new ChunkedWriteHandler());
                        ch.pipeline().addLast("fileServerHandler", new HttpFileServerHandler(url));
                    }

                });
        ChannelFuture cf =boot.bind("127.0.0.1",port).sync();
        System.out.println("Http文件目录服务器启动：http://127.0.0.1:"+port+url);
        cf.channel().closeFuture().sync();

    } finally {
        bossGroup.shutdownGracefully();
        workerGroup.shutdownGracefully();

    }

}

public static void main(String[] args) throws InterruptedException {
    String url="/src/main/java/";

    new HttpFileServer().run(8080, url);

}

}

服务端handler

public class HttpFileServerHandler extends SimpleChannelInboundHandler<FullHttpRequest> {

HttpMethod GET = new HttpMethod("GET");

private String url;

private final Pattern ALLOWED_FILE_NAME = Pattern.compile("[A-Za-z0-9][-_A-Za-z0-9\\.]*");

private final Pattern INSECURE_URI = Pattern.compile(".*[<>&\"].*");

public HttpFileServerHandler(String url) {
    this.url = url;
}

@Override
protected void messageReceived(ChannelHandlerContext ctx, FullHttpRequest request) throws Exception {

    if (!request.getDecoderResult().isSuccess()) {
        sendError(ctx, HttpResponseStatus.BAD_REQUEST);
        return;
    }

    if (request.getMethod() != HttpMethod.GET) {
        sendError(ctx, HttpResponseStatus.METHOD_NOT_ALLOWED);
        return;
    }
    final String uri = request.getUri();
    final String path = sanitizeUri(uri);
    if (path == null) {
        sendError(ctx, HttpResponseStatus.FORBIDDEN);
        return;
    }

    File file = new File(path);

    if (file.isHidden() || !file.exists()) {
        sendError(ctx, HttpResponseStatus.NOT_FOUND);
        return;
    }

    if (file.isDirectory()) {
        if (uri.endsWith("/")) {
            sendList(ctx, file);
        } else {
            sendRedirect(ctx, uri + '/');
        }
        return;
    }

    if (!file.isFile()) {
        sendError(ctx, HttpResponseStatus.FORBIDDEN);
        return;
    }

    RandomAccessFile randomAccessFile = null;

    try {
        randomAccessFile = new RandomAccessFile(file, "r");
    } catch (FileNotFoundException e) {
        sendError(ctx, HttpResponseStatus.NO_CONTENT);
        return;
    }
    long fileLength = randomAccessFile.length();
    HttpResponse response = new DefaultHttpResponse(HttpVersion.HTTP_1_1, HttpResponseStatus.OK);
    HttpHeaders.setContentLength(response, fileLength);
    setContentTypeHeader(response, file);

    if (HttpHeaders.isKeepAlive(request)) {
        response.headers().set(HttpHeaders.Names.CONNECTION, HttpHeaders.Values.KEEP_ALIVE);
    }
    ctx.write(response);
    ChannelFuture sendFileFuture;

    sendFileFuture = ctx.write(new ChunkedFile(randomAccessFile, 0, fileLength, 8192), ctx.newProgressivePromise());
    sendFileFuture.addListener(new ChannelProgressiveFutureListener() {

        @Override
        public void operationComplete(ChannelProgressiveFuture future) throws Exception {

            System.err.println(future.channel() + " transfer complete");

        }

        @Override
        public void operationProgressed(ChannelProgressiveFuture future, long progress, long total)
                throws Exception {
            if (total < 0) {
                System.err.println(future.channel() + " transfer progress : " + progress);
            } else {
                System.err.println(future.channel() + " transfer progress : " + progress + " / " + total);
            }
        }
    });

    ChannelFuture lastContentFuture = ctx.writeAndFlush(LastHttpContent.EMPTY_LAST_CONTENT);
    if (!HttpHeaders.isKeepAlive(request)) {
        lastContentFuture.addListener(ChannelFutureListener.CLOSE);
    }

}

@Override
public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {

    cause.printStackTrace();
    if (ctx.channel().isActive()) {
        sendError(ctx, HttpResponseStatus.INTERNAL_SERVER_ERROR);
    }
}

private void sendError(ChannelHandlerContext ctx, HttpResponseStatus status) {
    FullHttpResponse response = new DefaultFullHttpResponse(HttpVersion.HTTP_1_1, status, Unpooled.copiedBuffer(
            "Failure :" + status + "\r\n", CharsetUtil.UTF_8));
    response.headers().set(HttpHeaders.Names.CONTENT_TYPE, "text/plain; charset=UTF-8");
    ctx.writeAndFlush(response).addListener(ChannelFutureListener.CLOSE);
}

public String sanitizeUri(String uri) {

    // Decode the path.
    try {
        uri = URLDecoder.decode(uri, "UTF-8");
    } catch (UnsupportedEncodingException e) {
        throw new Error(e);
    }

    if (uri.isEmpty() || uri.charAt(0) != '/') {
        return null;
    }

    // Convert file separators.
    uri = uri.replace('/', File.separatorChar);

    // Simplistic dumb security check.
    // You will have to do something serious in the production environment.
    if (uri.contains(File.separator + '.') || uri.contains('.' + File.separator) || uri.charAt(0) == '.'
            || uri.charAt(uri.length() - 1) == '.' || INSECURE_URI.matcher(uri).matches()) {
        return null;
    }

    // Convert to absolute path.
    return System.getProperty("user.dir") + File.separator + uri;
}

public final void sendList(ChannelHandlerContext ctx, File file) {
    FullHttpResponse response = new DefaultFullHttpResponse(HttpVersion.HTTP_1_1, HttpResponseStatus.OK);
    response.headers().set(HttpHeaders.Names.CONTENT_TYPE, "text/html; charset=UTF-8");
    StringBuilder sb = new StringBuilder();

    String dirPath = file.getPath();

    sb.append("<!DOCTYPE html>\r\n");
    sb.append("<html><head><title>");
    sb.append(dirPath);
    sb.append("目录：");
    sb.append("</title></head><body>\r\n");
    sb.append("<h3>");
    sb.append(dirPath).append("目录：");
    sb.append("</h3>\r\n");

    sb.append("<ul>");
    sb.append("<li><a href=\"../\">..</a></li>\r\n");

    for (File f : file.listFiles()) {
        if (f.isHidden() || !f.canRead()) {
            continue;
        }
        String name = f.getName();
        if (!ALLOWED_FILE_NAME.matcher(name).matches()) {
            continue;
        }

        sb.append("<li><a href=\"");
        sb.append(name);
        sb.append("\">");
        sb.append(name);
        sb.append("</a></li>\r\n");

    }

    sb.append("</ul></body></html>\r\n");

    ByteBuf buffer = Unpooled.copiedBuffer(sb, CharsetUtil.UTF_8);
    response.content().writeBytes(buffer);
    buffer.release();

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

public void sendRedirect(ChannelHandlerContext ctx, String newUri) {
    FullHttpResponse response = new DefaultFullHttpResponse(HttpVersion.HTTP_1_1, HttpResponseStatus.FOUND);
    response.headers().set(HttpHeaders.Names.LOCATION, newUri);
    ctx.writeAndFlush(response).addListener(ChannelFutureListener.CLOSE);

}

private void setContentTypeHeader(HttpResponse response, File file) {

    MimetypesFileTypeMap mimeTypeMap = new MimetypesFileTypeMap();
    response.headers().set(HttpHeaders.Names.CONTENT_TYPE, mimeTypeMap.getContentType(file.getPath()));
}

}