前言
大家好,我是老马。很高兴遇到你。
我们希望实现最简单的 http 服务信息,可以处理静态文件。
如果你想知道 servlet 如何处理的,可以参考我的另一个项目:
手写从零实现简易版 tomcat minicat
netty 相关
如果你对 netty 不是很熟悉,可以读一下
Netty 权威指南-04-为什么选择 Netty?Netty 入门教程
HTTP开发入门-静态文件服务器
netty天生异步事件驱动的架构,无论是在性能上还是在可靠性上,都表现优异,非常适合在非Web容器的场景下应用,相比于传统的Tomcat,Jetty等Web容器,更加的轻量和小巧、灵活性和定制性也更好。
我们以文件服务器为例学习Netty的HTTP服务端入门开发,例程场景如下:
-
文件服务器使用HTTP协议对外提供服务
-
当客户端通过浏览器访问文件服务器时,对访问路径进行检查,检查失败返回403
-
检查通过,以链接的方式打开当前文件目录,每个目录或者都是个超链接,可以递归访问
-
如果是目录,可以继续递归访问它下面的目录或者文件,如果是文件并且可读,则可以在浏览器端直接打开,或者通过[目标另存为]下载
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;
/**
* @version 1.0
* @date 2014年2月14日
*/
public class HttpFileServer {
private static final String DEFAULT_URL = "/";
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()); // 请求消息解码器
ch.pipeline().addLast("http-aggregator",
new HttpObjectAggregator(65536));// 目的是将多个消息转换为单一的request或者response对象
ch.pipeline().addLast("http-encoder",
new HttpResponseEncoder());//响应解码器
ch.pipeline().addLast("http-chunked",
new ChunkedWriteHandler());//目的是支持异步大文件传输()
ch.pipeline().addLast("fileServerHandler",
new HttpFileServerHandler(url));// 业务逻辑
}
});
ChannelFuture future = b.bind("127.0.0.1", port).sync();
System.out.println("HTTP文件目录服务器启动,网址是 : " + "http://127.0.0.1:"
+ 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);
}
}
重点在于编解码器,首先添加的HTTP请求消息解码器HttpRequestDecoder,然后是HttpObjectAggregator解码器,它的作用是将多个消息转换为单一的FullHttpRequest或者FullHttpResponse,原因是HTTP解码器在每个HTTP消息中会生成多个消息对象。
(1) HttpRequest/HttpResponse;
(2) HttpContent;
(3) LastHttpContent;
下面是FileServerHandler:
import io.netty.buffer.ByteBuf;
import io.netty.buffer.Unpooled;
import io.netty.channel.*;
import io.netty.handler.codec.http.*;
import io.netty.handler.stream.ChunkedFile;
import io.netty.util.CharsetUtil;
import javax.activation.MimetypesFileTypeMap;
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 static io.netty.handler.codec.http.HttpMethod.GET;
import static io.netty.handler.codec.http.HttpResponseStatus.*;
import static io.netty.handler.codec.http.HttpVersion.HTTP_1_1;
/**
* @author lilinfeng
* @version 1.0
* @date 2014年2月14日
*/
public class HttpFileServerHandler extends
SimpleChannelInboundHandler<FullHttpRequest> {
private final String url;
public HttpFileServerHandler(String url) {
this.url = url;
}
@Override
protected void channelRead0(ChannelHandlerContext ctx, FullHttpRequest request) throws Exception {
/*如果无法解码400*/
if (!request.decoderResult().isSuccess()) {
sendError(ctx, BAD_REQUEST);
return;
}
/*只支持GET方法*/
if (request.method() != GET) {
sendError(ctx, METHOD_NOT_ALLOWED);
return;
}
final String uri = request.uri();
/*格式化URL,并且获取路径*/
final String path = sanitizeUri(uri);
if (path == null) {
sendError(ctx, FORBIDDEN);
return;
}
File file = new File(path);
/*如果文件不可访问或者文件不存在*/
if (file.isHidden() || !file.exists()) {
sendError(ctx, NOT_FOUND);
return;
}
/*如果是目录*/
if (file.isDirectory()) {
//1. 以/结尾就列出所有文件
if (uri.endsWith("/")) {
sendListing(ctx, file);
} else {
//2. 否则自动+/
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();
//创建一个默认的HTTP响应
HttpResponse response = new DefaultHttpResponse(HTTP_1_1, OK);
//设置Content Length
HttpUtil.setContentLength(response, fileLength);
//设置Content Type
setContentTypeHeader(response, file);
//如果request中有KEEP ALIVE信息
if (HttpUtil.isKeepAlive(request)) {
response.headers().set(HttpHeaderNames.CONNECTION, HttpHeaderValues.KEEP_ALIVE);
}
ctx.write(response);
ChannelFuture sendFileFuture;
//通过Netty的ChunkedFile对象直接将文件写入发送到缓冲区中
sendFileFuture = ctx.write(new ChunkedFile(randomAccessFile, 0,
fileLength, 8192), ctx.newProgressivePromise());
sendFileFuture.addListener(new ChannelProgressiveFutureListener() {
@Override
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);
}
}
@Override
public void operationComplete(ChannelProgressiveFuture future)
throws Exception {
System.out.println("Transfer complete.");
}
});
ChannelFuture lastContentFuture = ctx
.writeAndFlush(LastHttpContent.EMPTY_LAST_CONTENT);
//如果不支持keep-Alive,服务器端主动关闭请求
if (!HttpUtil.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(HttpHeaderNames.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(HttpHeaderNames.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(HttpHeaderNames.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(HttpHeaderNames.CONTENT_TYPE,
mimeTypesMap.getContentType(file.getPath()));
}
}
上面的代码注释相对详细,这里大致梳理一下。
(1) 不能解码返回400,只支持GET请求,否则返回405.
(2) 对url包装,使用UTF-8字符集,转换为绝对path
(3) 如果是目录,创建一个html页面
(4) 如果是文件,设置content-type和content-length,使用netty的chunkedfile直接写到缓冲,异步的方式
(5) 如果是非keepalived的,服务器端主动关闭,否则等待客户端主动关闭。
参考资料
https://www.cnblogs.com/luxiaoxun/p/3959450.html
https://www.cnblogs.com/carl10086/p/6185095.html
https://blog.csdn.net/suifeng3051/article/details/22800171
https://blog.csdn.net/sinat_34163739/article/details/108820355
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