Java 实现HTTP协议

Bertha 。 2022-06-07 13:57 206阅读 0赞

# 实例 #

import java.io.IOException;
    import java.net.InetSocketAddress;
    import java.nio.ByteBuffer;
    import java.nio.channels.SelectionKey;
    import java.nio.channels.Selector;
    import java.nio.channels.ServerSocketChannel;
    import java.nio.channels.SocketChannel;
    import java.nio.charset.Charset;
    import java.util.Iterator;
    
    public class HttpServer { 
    
        public static void main(String[] args) throws Exception {
            // 创建ServerSocketChannel，监听8080端口
            ServerSocketChannel ssc = ServerSocketChannel.open();
            ssc.socket().bind(new InetSocketAddress(8080));
            // 设置为非阻塞模式
            ssc.configureBlocking(false);
            // 为ssc注册选择器
            Selector selector = Selector.open();
            ssc.register(selector, SelectionKey.OP_ACCEPT);
            // 创建处理器
            while (true) {
                // 等待请求，每次等待阻塞3s，超过3s后线程继续向下运行，如果传入0或者不传参数将一直阻塞
                if (selector.select(3000) == 0) {
                    continue;
                }
                // 获取待处理的SelectionKey
                Iterator<SelectionKey> keyIter = selector.selectedKeys().iterator();
    
                while (keyIter.hasNext()) {
                    SelectionKey key = keyIter.next();
                    // 启动新线程处理SelectionKey
                    new Thread(new HttpHandler(key)).run();
                    // 处理完后，从待处理的SelectionKey迭代器中移除当前所使用的key
                    keyIter.remove();
                }
            }
        }
    
        private static class HttpHandler implements Runnable { 
            private int bufferSize = 1024;
            private String localCharset = "UTF-8";
            private SelectionKey key;
    
            public HttpHandler(SelectionKey key) {
                this.key = key;
            }
    
            public void handleAccept() throws IOException {
                SocketChannel clientChannel = ((ServerSocketChannel) key.channel()).accept();
                clientChannel.configureBlocking(false);
                clientChannel.register(key.selector(), SelectionKey.OP_READ, ByteBuffer.allocate(bufferSize));
            }
    
            public void handleRead() throws IOException {
                // 获取channel
                SocketChannel sc = (SocketChannel) key.channel();
                // 获取buffer并重置
                ByteBuffer buffer = (ByteBuffer) key.attachment();
                buffer.clear();
                // 没有读到内容则关闭
                if (sc.read(buffer) == -1) {
                    sc.close();
                } else {
                    // 接收请求数据
                    buffer.flip();
                    String receivedString = Charset.forName(localCharset).newDecoder().decode(buffer).toString();
    
                    // 控制台打印请求报文头
                    String[] requestMessage = receivedString.split("\r\n");
                    for (String s : requestMessage) {
                        System.out.println(s);
                        // 遇到空行说明报文头已经打印完
                        if (s.isEmpty()) {
                            break;
                        }
                    }
    
                    // 控制台打印首行信息
                    String[] firstLine = requestMessage[0].split(" ");
                    System.out.println();
                    System.out.println("Method:\t" + firstLine[0]);
                    System.out.println("url:\t" + firstLine[1]);
                    System.out.println("HTTP Version:\t" + firstLine[2]);
                    System.out.println();
    
                    // 返回客户端
                    StringBuilder sendString = new StringBuilder();
                    sendString.append("HTTP/1.1 200 OK\r\n");//响应报文首行，200表示处理成功
                    sendString.append("Content-Type:text/html;charset=" + localCharset + "\r\n");
                    sendString.append("\r\n");// 报文头结束后加一个空行
    
                    sendString.append("<!DOCTYPE html>");
                    sendString.append("<html lang=\"en\">");
                    sendString.append("<head>");
                    sendString.append(" <meta charset=\"UTF-8\">");
                    sendString.append(" <title>Title</title>");
                    sendString.append("</head>");
                    sendString.append("<body>");
                    sendString.append(" <h4>hello world! </h4>");
                    sendString.append("</body>");
                    sendString.append("</html>");
    
                    buffer = ByteBuffer.wrap(sendString.toString().getBytes(localCharset));
                    sc.write(buffer);
                    sc.close();
                }
            }
    
            @Override
            public void run() {
                try {
                    // 接收到连接请求时
                    if (key.isAcceptable()) {
                        handleAccept();
                    }
                    // 读数据
                    if (key.isReadable()) {
                        handleRead();
                    }
                } catch (IOException ex) {
                    ex.printStackTrace();
                }
            }
        }
    }

# 测试 #

GET: [http://localhost:8080][http_localhost_8080]

![这里写图片描述][SouthEast]

[http_localhost_8080]: http://localhost:8080
[SouthEast]: /images/20220607/35f0748776bc4b8aa41c2b5e7a736fa4.png