下面就让我来详细讲解“如何用Netty实现高效的HTTP服务器”的完整攻略。
1. 引言
Netty是一个高性能、异步的网络编程框架，使用它可以轻松地开发TCP、UDP、HTTP等各种协议的客户端和服务器端。本文将主要讲解如何使用Netty实现高效的HTTP服务器。
2. 环境准备
在开始本篇攻略之前，需要准备如下环境：
1. JDK 8 或以上版本
2. Netty 4.1.x
3. 编写HTTP服务器
下面是一个基本的HTTP服务器的示例。首先我们需要继承ChannelInboundHandlerAdapter类，然后重写channelRead()方法来处理HTTP请求的逻辑。
public class HttpServerHandler extends ChannelInboundHandlerAdapter {
@Override
public void channelRead(ChannelHandlerContext ctx, Object msg) {
if (msg instanceof FullHttpRequest) {
FullHttpRequest request = (FullHttpRequest) msg;
// 处理HTTP请求的逻辑
// ...
}
}
@Override
public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) {
cause.printStackTrace();
ctx.close();
}
}
然后我们需要编写一个包含上述HttpServerHandler的引导程序。这个引导程序的作用是创建一个ServerBootstrap对象并进行一些初始化操作。
public class HttpServer {
public static void main(String[] args) throws Exception {
EventLoopGroup group = new NioEventLoopGroup();
try {
ServerBootstrap b = new ServerBootstrap();
b.group(group)
.channel(NioServerSocketChannel.class)
.localAddress(new InetSocketAddress(8080))
.childHandler(new ChannelInitializer<SocketChannel>() {
@Override
public void initChannel(SocketChannel ch)
throws Exception {
ch.pipeline().addLast(new HttpServerCodec());
ch.pipeline().addLast(new HttpObjectAggregator(65536));
ch.pipeline().addLast(new HttpServerHandler());
}
});
ChannelFuture f = b.bind().sync();
f.channel().closeFuture().sync();
} finally {
group.shutdownGracefully().sync();
}
}
}
在这个引导程序中，我们使用了ServerBootstrap创建了一个NioServerSocketChannel监听8080端口的Socket。然后我们添加了三个ChannelHandler，分别是：
- HttpServerCodec：这个ChannelHandler负责HTTP协议的编码和解码。
- HttpObjectAggregator：这个ChannelHandler将HTTP请求进行聚合。
- HttpServerHandler：这个ChannelHandler是我们自己实现的类，负责处理来自客户端的HTTP请求。
4. 示例
下面是两条示例说明，帮助你更好地理解如何使用Netty实现高效的HTTP服务器。
示例1：返回静态资源
下面的示例演示了如何使用Netty返回一个静态资源（比如html页面）。
public class HttpServerHandler extends ChannelInboundHandlerAdapter {
private static final String HTTP_DATE_FORMAT = "EEE, dd MMM yyyy HH:mm:ss zzz";
private static final String HTTP_DATE_GMT_TIMEZONE = "GMT";
private static final int HTTP_CACHE_SECONDS = 60;
@Override
public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
if (msg instanceof FullHttpRequest) {
FullHttpRequest request = (FullHttpRequest) msg;
String uri = request.uri();
if ("/".equals(uri)) {
uri = "/index.html";
}
String path = "/path/to/static/resources" + uri;
File file = new File(path);
if (file.exists()) {
RandomAccessFile raf = new RandomAccessFile(file, "r");
long fileLength = raf.length();
HttpResponse response = new DefaultHttpResponse(HttpVersion.HTTP_1_1, HttpResponseStatus.OK);
HttpUtil.setContentLength(response, fileLength);
setContentTypeHeader(response, file);
setDateAndCacheHeaders(response, file);
if (HttpUtil.isKeepAlive(request)) {
HttpUtil.setKeepAlive(response, true);
}
ctx.write(response);
ChannelFuture sendFileFuture;
DefaultFileRegion defaultFileRegion = new DefaultFileRegion(raf.getChannel(), 0, fileLength);
sendFileFuture = ctx.write(defaultFileRegion, ctx.newProgressivePromise());
ctx.writeAndFlush(LastHttpContent.EMPTY_LAST_CONTENT);
if (!HttpUtil.isKeepAlive(request)) {
sendFileFuture.addListener(ChannelFutureListener.CLOSE);
}
} else {
// 返回404错误
FullHttpResponse response = new DefaultFullHttpResponse(HttpVersion.HTTP_1_1, HttpResponseStatus.NOT_FOUND);
ctx.write(response);
}
}
}
@Override
public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) {
cause.printStackTrace();
ctx.close();
}
private static void setDateHeader(HttpResponse response) {
SimpleDateFormat dateFormatter = new SimpleDateFormat(HTTP_DATE_FORMAT, Locale.US);
dateFormatter.setTimeZone(TimeZone.getTimeZone(HTTP_DATE_GMT_TIMEZONE));
Calendar time = new GregorianCalendar();
response.headers().set(HttpHeaderNames.DATE, dateFormatter.format(time.getTime()));
}
private static void setDateAndCacheHeaders(HttpResponse response, File fileToCache) {
SimpleDateFormat dateFormatter = new SimpleDateFormat(HTTP_DATE_FORMAT, Locale.US);
dateFormatter.setTimeZone(TimeZone.getTimeZone(HTTP_DATE_GMT_TIMEZONE));
// Add default cache headers.
Calendar time = new GregorianCalendar();
response.headers().set(HttpHeaderNames.DATE, dateFormatter.format(time.getTime()));
time.add(Calendar.SECOND, HTTP_CACHE_SECONDS);
response.headers().set(HttpHeaderNames.EXPIRES, dateFormatter.format(time.getTime()));
response.headers().set(HttpHeaderNames.CACHE_CONTROL, "private, max-age=" + HTTP_CACHE_SECONDS);
response.headers().set(
HttpHeaderNames.LAST_MODIFIED, dateFormatter.format(new Date(fileToCache.lastModified())));
}
private static void setContentTypeHeader(HttpResponse response, File file) {
MimetypesFileTypeMap mimeTypesMap = new MimetypesFileTypeMap();
response.headers().set(
HttpHeaderNames.CONTENT_TYPE,
mimeTypesMap.getContentType(file.getPath()));
}
}
在这个示例中，我们使用了Netty提供的DefaultFileRegion来返回静态资源。
示例2：接收表单数据
下面的示例演示了如何使用Netty接收表单数据并返回处理结果。
public class HttpServerHandler extends SimpleChannelInboundHandler<FullHttpRequest> {
private static final HttpDataFactory factory =
new DefaultHttpDataFactory(DefaultHttpDataFactory.MINSIZE); // Disk if size exceed MINSIZE
private HttpPostRequestDecoder httpDecoder;
@Override
protected void channelRead0(ChannelHandlerContext ctx, FullHttpRequest request) throws Exception {
if (HttpUtil.is100ContinueExpected(request)) {
ctx.write(new DefaultFullHttpResponse(HttpVersion.HTTP_1_1, HttpResponseStatus.CONTINUE));
}
if (!request.decoderResult().isSuccess()) {
FullHttpResponse response = new DefaultFullHttpResponse(
HttpVersion.HTTP_1_1, HttpResponseStatus.BAD_REQUEST,
Unpooled.copiedBuffer("Invalid Request", CharsetUtil.UTF_8));
HttpUtil.setContentLength(response, response.content().readableBytes());
ctx.write(response);
return;
}
if (httpDecoder == null) {
httpDecoder = new HttpPostRequestDecoder(factory, request);
}
if (request instanceof LastHttpContent) {
httpDecoder.offer(request);
List<InterfaceHttpData> postData =
httpDecoder.getBodyHttpDatas();
// 打印表单数据
for (InterfaceHttpData data: postData) {
System.out.println(data.toString());
}
FullHttpResponse response = new DefaultFullHttpResponse(HttpVersion.HTTP_1_1, HttpResponseStatus.OK);
response.content().writeBytes("处理结果".getBytes());
HttpUtil.setContentLength(response, response.content().readableBytes());
ctx.write(response);
httpDecoder.destroy();
httpDecoder = null;
if (HttpUtil.isKeepAlive(request)) {
ctx.write(new DefaultFullHttpResponse(HttpVersion.HTTP_1_1, HttpResponseStatus.OK));
} else {
ctx.writeAndFlush(LastHttpContent.EMPTY_LAST_CONTENT).addListener(ChannelFutureListener.CLOSE);
}
}
}
@Override
public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) {
cause.printStackTrace();
ctx.close();
}
}
在这个示例中，我们使用了Netty提供的HttpPostRequestDecoder来处理表单数据。我们需要在channelRead0()方法中按照如下流程进行处理：
1. 如果请求是100 Continue，则返回HttpResponseStatus.CONTINUE。
2. 如果请求解析出现错误，则返回HttpResponseStatus.BAD_REQUEST。
3. 如果请求是最后一块内容，则调用HttpPostRequestDecoder.getBodyHttpDatas()进行数据处理，并返回结果。
2021年11月4日 更新
本站文章如无特殊说明，均为本站原创，如若转载，请注明出处：如何用Netty实现高效的HTTP服务器 - Python技术站
微信扫一扫 
支付宝扫一扫 