Netty HTTP 服务端入门开发

一. HTTP 简介

　　HTTP(超文本传输协议) 协议是建立在 TCP 传输协议之上的应用层协议,它的发展是万维网协会和 Internet 工作小组和 IETF 合作的结果. HTTP 是一个属于应用层的面向对象的协议,由于其便捷,快速的方式,适用于分布式超媒体信息系统.

　　HTTP 协议的主要特点如下:

支持 Client/Server 模式.

简单---- 客户端向服务器请求服务时,只需指定服务的 URL, 携带必要的请求参数或者消息体;

灵活---- HTTP 允许传输任意类型的数据对象,传输内容类型有 HTTP 消息头中得 Content-Type 指定.

无状态---- HTTP 协议是无状态协议,无状态是指协议对于会话状态没有记忆功能,缺少状态意味着如果后续处理需要之前的信息,则它必须重传.这样导致每次连接传送的数据量加大另外一方面,在服务器不需要之前的信息时,它的应答就较快,负载较轻.

　　netty 的 Http 协议栈是基于 Netty 的 Nio 通信框架开发的.因此, Netty 的 Http 协议也是异步非阻塞的.

代码如下:

HttpFileServer

package netty.protocol.http;

import io.netty.bootstrap.ServerBootstrap;
import io.netty.channel.ChannelFuture;
import io.netty.channel.ChannelInitializer;
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.HttpObjectAggregator;
import io.netty.handler.codec.http.HttpRequestDecoder;
import io.netty.handler.codec.http.HttpResponseEncoder;
import io.netty.handler.stream.ChunkedWriteHandler;

/**
* TODO
*
* @description
* @author ez
* @time 2015年6月3日 上午10:47:37
*/
public class HttpFileServer {
private static final String DEFAULT_URL = "/src/main/java/netty/protocol/http/";

public void run(final int port, final String url) throws Exception {
EventLoopGroup bossGroup = new NioEventLoopGroup();
EventLoopGroup workerGroup = new NioEventLoopGroup();
try {
ServerBootstrap b = new ServerBootstrap();
b.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()); // http 请求消息解码器,
/*
* httpObject 解码器,
* 它的作用是将多个消息转换为单一的FullHttpRequest或FullHttpResponse
* 对象,原因是HTTP 解码器在每个HTTP消息中会生成多个消息对象 (
* HttpRequest/HttpResponse
* ,HttpContent,LastHttpContent)
*/
ch.pipeline().addLast("http-aggregator",
new HttpObjectAggregator(65536));
/*
* HTTP 响应消息编码器
*/
ch.pipeline().addLast("http-encoder",
new HttpResponseEncoder());
/*
* ChunkedWriteHandler
* 的主要作用是支持异步发送大的码流(例如大文件传输),但不占用过多的内存,防止JAVA内存溢出
*/
ch.pipeline().addLast("http-chunked",
new ChunkedWriteHandler());
/*
* 业务处理类
*/
ch.pipeline().addLast("fileServerHandler",
new HttpFileServerHandler(url));
}
});
ChannelFuture future = b.bind("localhost", port).sync();
System.out.println("HTTP文件目录服务器启动，网址是 : " + "http://localhost:"
+ port + url);
future.channel().closeFuture().sync();
} catch (Exception e) {
e.printStackTrace();
} finally {
bossGroup.shutdownGracefully();
workerGroup.shutdownGracefully();
}
}

public static void main(String[] args) throws Exception {
int port = 8080;
if (args.length > 0) {
try {
port = Integer.parseInt(args[0]);
} catch (NumberFormatException e) {
e.printStackTrace();
}
}
String url = DEFAULT_URL;
if (args.length > 1)
url = args[1];
new HttpFileServer().run(port, url);
}
}

ServerHandler

package netty.protocol.http;

import static io.netty.handler.codec.http.HttpHeaders.isKeepAlive;
import static io.netty.handler.codec.http.HttpHeaders.setContentLength;
import static io.netty.handler.codec.http.HttpHeaders.Names.CONNECTION;
import static io.netty.handler.codec.http.HttpHeaders.Names.CONTENT_TYPE;
import static io.netty.handler.codec.http.HttpHeaders.Names.LOCATION;
import static io.netty.handler.codec.http.HttpMethod.GET;
import static io.netty.handler.codec.http.HttpResponseStatus.BAD_REQUEST;
import static io.netty.handler.codec.http.HttpResponseStatus.FORBIDDEN;
import static io.netty.handler.codec.http.HttpResponseStatus.FOUND;
import static io.netty.handler.codec.http.HttpResponseStatus.INTERNAL_SERVER_ERROR;
import static io.netty.handler.codec.http.HttpResponseStatus.METHOD_NOT_ALLOWED;
import static io.netty.handler.codec.http.HttpResponseStatus.NOT_FOUND;
import static io.netty.handler.codec.http.HttpResponseStatus.OK;
import static io.netty.handler.codec.http.HttpVersion.HTTP_1_1;
import io.netty.buffer.ByteBuf;
import io.netty.buffer.Unpooled;
import io.netty.channel.ChannelFuture;
import io.netty.channel.ChannelFutureListener;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.ChannelProgressiveFuture;
import io.netty.channel.ChannelProgressiveFutureListener;
import io.netty.channel.SimpleChannelInboundHandler;
import io.netty.handler.codec.http.DefaultFullHttpResponse;
import io.netty.handler.codec.http.DefaultHttpResponse;
import io.netty.handler.codec.http.FullHttpRequest;
import io.netty.handler.codec.http.FullHttpResponse;
import io.netty.handler.codec.http.HttpHeaders;
import io.netty.handler.codec.http.HttpResponse;
import io.netty.handler.codec.http.HttpResponseStatus;
import io.netty.handler.codec.http.LastHttpContent;
import io.netty.handler.stream.ChunkedFile;
import io.netty.util.CharsetUtil;

import java.io.File;
import java.io.FileNotFoundException;
import java.io.RandomAccessFile;
import java.io.UnsupportedEncodingException;
import java.net.URLDecoder;
import java.util.regex.Pattern;

import javax.activation.MimetypesFileTypeMap;

public class HttpFileServerHandler extends
SimpleChannelInboundHandler<FullHttpRequest> {
private final String url;

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

@Override
public void messageReceived(ChannelHandlerContext ctx,
FullHttpRequest request) throws Exception {
/*
* 首先对HTTP请求消息的解码结构进行判断,如果解码失败,直接构造HTTP404 错误返回,
*/
if (!request.getDecoderResult().isSuccess()) {
sendError(ctx, BAD_REQUEST);
return;
}
/*
* 如果不是get请求, 则构造 HTTP405 返回
*/
if (request.getMethod() != GET) {
sendError(ctx, METHOD_NOT_ALLOWED);
return;
}
final String uri = request.getUri();
/*
* 对URL进行解码, 使用 UTF-8字符集,解码之后对URI进行合法性判断,
*/
final String path = sanitizeUri(uri);
if (path == null) {
sendError(ctx, FORBIDDEN);
return;
}
File file = new File(path);
if (file.isHidden() || !file.exists()) {
sendError(ctx, NOT_FOUND);
return;
}
if (file.isDirectory()) {
if (uri.endsWith("/")) {
sendListing(ctx, file);
} else {
sendRedirect(ctx, uri + '/');
}
return;
}
if (!file.isFile()) {
sendError(ctx, FORBIDDEN);
return;
}
RandomAccessFile randomAccessFile = null;
try {
randomAccessFile = new RandomAccessFile(file, "r");// 以只读的方式打开文件
} catch (FileNotFoundException fnfe) {
sendError(ctx, NOT_FOUND);
return;
}
long fileLength = randomAccessFile.length();
HttpResponse response = new DefaultHttpResponse(HTTP_1_1, OK);
setContentLength(response, fileLength);
setContentTypeHeader(response, file);
if (isKeepAlive(request)) {
response.headers().set(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() {
public void operationProgressed(ChannelProgressiveFuture future,
long progress, long total) {
if (total < 0) { // total unknown
System.err.println("Transfer progress: " + progress);
} else {
System.err.println("Transfer progress: " + progress + " / "
+ total);
}
}

public void operationComplete(ChannelProgressiveFuture future)
throws Exception {
System.out.println("Transfer complete.");
}
});
/*
* 如果是chunked 编码, 最后需要发送一个编码结束的空消息体,将LastHttpContent的EMPTY_LAST_CONTENT
* 发送到缓存区中,标识所有的消息体已经发送完成,同时调用flush方法将之前在发送缓冲区的消息刷新到SocketChannel中发送给对方
*/
ChannelFuture lastContentFuture = ctx
.writeAndFlush(LastHttpContent.EMPTY_LAST_CONTENT);
/*
* 如果是非 Keep-Alive 的,最后一包消息发送完之后,服务端要主动关闭连接.
*/
if (!isKeepAlive(request)) {
lastContentFuture.addListener(ChannelFutureListener.CLOSE);
}
}

@Override
public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause)
throws Exception {
cause.printStackTrace();
if (ctx.channel().isActive()) {
sendError(ctx, INTERNAL_SERVER_ERROR);
}
}

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

private String sanitizeUri(String uri) {
try {
uri = URLDecoder.decode(uri, "UTF-8");
} catch (UnsupportedEncodingException e) {
try {
uri = URLDecoder.decode(uri, "ISO-8859-1");
} catch (UnsupportedEncodingException e1) {
throw new Error();
}
}
if (!uri.startsWith(url)) {
return null;
}
if (!uri.startsWith("/")) {
return null;
}
uri = uri.replace('/', File.separatorChar);
if (uri.contains(File.separator + '.')
|| uri.contains('.' + File.separator) || uri.startsWith(".")
|| uri.endsWith(".") || INSECURE_URI.matcher(uri).matches()) {
return null;
}
return System.getProperty("user.dir") + File.separator + uri;
}

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

private static void sendListing(ChannelHandlerContext ctx, File dir) {
FullHttpResponse response = new DefaultFullHttpResponse(HTTP_1_1, OK);
response.headers().set(CONTENT_TYPE, "text/html; charset=UTF-8");
StringBuilder buf = new StringBuilder();
String dirPath = dir.getPath();
buf.append("<!DOCTYPE html>\r\n");
buf.append("<html><head><title>");
buf.append(dirPath);
buf.append(" 目录：");
buf.append("</title></head><body>\r\n");
buf.append("<h3>");
buf.append(dirPath).append(" 目录：");
buf.append("</h3>\r\n");
buf.append("<ul>");
buf.append("<li>链接：<a href=\"../\">..</a></li>\r\n");
for (File f : dir.listFiles()) {
if (f.isHidden() || !f.canRead()) {
continue;
}
String name = f.getName();
if (!ALLOWED_FILE_NAME.matcher(name).matches()) {
continue;
}
buf.append("<li>链接：<a href=\"");
buf.append(name);
buf.append("\">");
buf.append(name);
buf.append("</a></li>\r\n");
}
buf.append("</ul></body></html>\r\n");
ByteBuf buffer = Unpooled.copiedBuffer(buf, CharsetUtil.UTF_8);
response.content().writeBytes(buffer);
buffer.release();
ctx.writeAndFlush(response).addListener(ChannelFutureListener.CLOSE);
}

private static void sendRedirect(ChannelHandlerContext ctx, String newUri) {
FullHttpResponse response = new DefaultFullHttpResponse(HTTP_1_1, FOUND);
response.headers().set(LOCATION, newUri);
ctx.writeAndFlush(response).addListener(ChannelFutureListener.CLOSE);
}

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

private static void setContentTypeHeader(HttpResponse response, File file) {
MimetypesFileTypeMap mimeTypesMap = new MimetypesFileTypeMap();
response.headers().set(CONTENT_TYPE,
mimeTypesMap.getContentType(file.getPath()));
}
}

以上内容出自 <netty 权威指南>