7.3 .Netty 初认识 --http 服务端开发示例

浏览器请求,根据地址,列出本地目录,点击具体文件可以查看右键另存为下载。，示例可以直接运行,只需要添加对应的 netty 包就可以,

注意: DEFAULT_URL 这个值是需要根据自己电脑目录进行修改的。

HttpFileServer.java

package club.wujingjian.com.wujingjian.netty.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;

public class HttpFileServer {
    private static final String DEFAULT_URL = "/accumulate-common/src/main/";

    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 socketChannel) throws Exception {
                            socketChannel.pipeline().addLast("http-decoder", new HttpRequestDecoder());
                            //HttpObjectAggregator 作用是将多个消息转换为单一的FullHttpRequest或者FullHttpResponse,原因是Http解码器会在每个HTTP消息中会生成多个消息对象
                            //1. HttpRequest / HttpResponse
                            //2. HttpContent
                            //3. LastHttpContent
                            socketChannel.pipeline().addLast("http-aggregator", new HttpObjectAggregator(65536));
                            //对HTTP响应消息进行编码
                            socketChannel.pipeline().addLast("http-encoder", new HttpResponseEncoder());
                            //支持异步发送大的码流(例如大的文件传输),但不占用过多的内存,防止发生java内存溢出错误
                            socketChannel.pipeline().addLast("http-chunked", new ChunkedWriteHandler());
                            socketChannel.pipeline().addLast("fileServerHandler", new HttpFileServerHandler(url));
                        }
                    });
            ChannelFuture f = 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);
            f.channel().closeFuture().sync();
        }finally {
            bossGroup.shutdownGracefully();
            workerGroup.shutdownGracefully();
        }
    }

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

}

​

HttpFileServerHandler.java

package club.wujingjian.com.wujingjian.netty.http;

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.HttpHeaders.Names.*;
import static io.netty.handler.codec.http.HttpHeaders.Values.KEEP_ALIVE;
import static io.netty.handler.codec.http.HttpResponseStatus.*;

public class HttpFileServerHandler extends SimpleChannelInboundHandler<FullHttpRequest> {

    private final String url;

    public HttpFileServerHandler(String url) {
        this.url = url;
    }
    @Override
    protected void messageReceived(ChannelHandlerContext ctx, FullHttpRequest fullHttpRequest) throws Exception {
        //首先对HTTP请求消息的解码结果进行判断,如果解码失败,直接构造HTTP400错误返回
        if (!fullHttpRequest.getDecoderResult().isSuccess()) {
            sendError(ctx, BAD_REQUEST);
            return;
        }
        //对请求行中的方法进行判断,如果不是GET请求则构造HTTP405 错误返回
        if(fullHttpRequest.getMethod() != HttpMethod.GET) {
            sendError(ctx, METHOD_NOT_ALLOWED);
            return;
        }
        final String uri = fullHttpRequest.getUri();
        final String path = sanitizeUri(uri); //校验url
        if (path == null) {
            sendError(ctx, FORBIDDEN);
            return;
        }
        File file = new File(path);
        //如果文件不存在或者是系统隐藏文件,则构造HTTP404异常返回
        if (file.isHidden() || !file.exists()) {
            sendError(ctx, NOT_FOUND);
            return;
        }

        //如果文件是目录,则发送目录的链接给客户端浏览器
        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 e) {
            sendError(ctx, NOT_FOUND);
	    return;
        }
        long fileLength = randomAccessFile.length();
        HttpResponse response = new DefaultHttpResponse(HttpVersion.HTTP_1_1, OK);
        setContentLength(response, fileLength);
        setContentTypeHeader(response, file);
        if (isKeepAlive(fullHttpRequest)) {
            response.headers().set(CONNECTION, 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 operationProgressed(ChannelProgressiveFuture future, long progress, long total) throws Exception {
                if (total < 0) {
                    System.err.println("Transfer progress: " + progress);
                } else {
                    System.err.println("Transfer progress: " + progress + "/" + total);
                }
            }

            @Override
            public void operationComplete(ChannelProgressiveFuture channelProgressiveFuture) throws Exception {
                System.out.println("Transfer complete");
            }

        });

        ChannelFuture lastContentFuture = ctx.writeAndFlush(LastHttpContent.EMPTY_LAST_CONTENT);
        if (!isKeepAlive(fullHttpRequest)) {
            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(HttpVersion.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")
                .append("<html><head><title>")
                .append(dirPath)
                .append(" 目录: ")
                .append("</title></head><body>\r\n")
                .append("<h3>")
                .append(dirPath).append("目录: ")
                .append("</h3>\r\n")
                .append("<ul>")
                .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=\"")
                    .append(name)
                    .append("\">")
                    .append(name)
                    .append("</a></li>\r\n");
        }
        buf.append("</ul></body></html>\r\n");
        ByteBuf buffer = Unpooled.copiedBuffer(buf, CharsetUtil.UTF_8);
        //将构造好的缓冲区中的响应消息存放到HTTP应答消息中
        response.content().writeBytes(buffer);
        //然后释放缓冲区
        buffer.release();
        //将响应消息发送到缓冲区并刷新到SocketChannel中
        ctx.writeAndFlush(response).addListener(ChannelFutureListener.CLOSE);
    }

    private static void sendRedirect(ChannelHandlerContext ctx, String newUri) {
        FullHttpResponse response = new DefaultFullHttpResponse(HttpVersion.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(HttpVersion.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 mimetypesFileTypeMap = new MimetypesFileTypeMap();
        response.headers().set(CONTENT_TYPE, mimetypesFileTypeMap.getContentType(file.getPath()));
    }

    private static void setContentLength(HttpResponse response,long length){
        response.headers().set(CONTENT_LENGTH, length);
    }

    private static boolean isKeepAlive(FullHttpRequest fullHttpRequest) {
        if(HttpHeaders.isKeepAlive(fullHttpRequest)){
            return true;
        }
        return false;
    }
}

​

运行效果:

注意：
单机某个文件可以进行下载了，之前不可以，是因为把下面的 DefaultHttpResponse 写成了 DefaultFullHttpResponse 了。

long fileLength = randomAccessFile.length();
HttpResponse response = new DefaultHttpResponse(HttpVersion.HTTP_1_1, OK);