Java NioSocket 的用法

分手后的思念是犯贱 2022-06-07 13:50 183阅读 0赞

# 说明 #

从 JDK1.4 开始， Java增加了新的 io 模式，nio(new IO), nio在底层采用了新的处理方式，极大地提高了IO的效率。

nio与原来的io对比：

<table> 
 <thead> 
  <tr> 
   <th>io</th> 
   <th>nio</th> 
  </tr> 
 </thead> 
 <tbody> 
  <tr> 
   <td>ServerSocket</td> 
   <td>ServerSocketChannel</td> 
  </tr> 
  <tr> 
   <td>Socket</td> 
   <td>SocketChannel</td> 
  </tr> 
 </tbody> 
</table>

要理解 NioSocket 的使用必须要理解三个概念：

1.  Buffer
2.  Channel
3.  Selector

类比快递：

1.  Buffer(要送的货物)
2.  Channel(送货员)
3.  Selector(中转站的分拣员)

NioSocket 中服务端的处理过程分5步：

1.  创建 ServerSocketChannel 并设置相应参数
2.  创建 Selector 并注册到 ServerSocketChannel 上。
3.  调用 Selector 的 select 方法等待请求。
4.  Selector 接收请求后使用 selectedKeys 返回 SelectionKey 集合。
5.  使用 SelectionKey 获取到 Channel、Selector 和操作类型并进行具体操作。

# 实例 #

NIOServer.java

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;
    
    /** * @author : xiao * @date : 17/10/23 下午3:14 * @description : */
    public class NIOServer { 
    
        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
            Handler handler = new Handler(1024);
            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) {
                    System.out.println("等待请求超时。。。");
                    continue;
                }
                System.out.println("处理请求。。。");
                // 获取待处理的SelectionKey
                Iterator<SelectionKey> keyIter = selector.selectedKeys().iterator();
    
                while (keyIter.hasNext()) {
                    SelectionKey key = keyIter.next();
                    try {
                        // 接收到连接请求时
                        if (key.isAcceptable()) {
                            handler.handleAccept(key);
                        }
                        // 读数据
                        if (key.isReadable()) {
                            handler.handleRead(key);
                        }
                    } catch (IOException ex) {
                        keyIter.remove();
                        continue;
                    }
                    // 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 Handler { 
            private int bufferSize = 1024;
            private String localCharset = "UTF-8";
    
            public Handler() {
            }
    
            public Handler(int bufferSize) {
                this(bufferSize, null);
            }
    
            public Handler(String LocalCharset) {
                this(-1, LocalCharset);
            }
    
            public Handler(int bufferSize, String localCharset) {
                if (bufferSize > 0) {
                    this.bufferSize = bufferSize;
                }
                if (localCharset != null) {
                    this.localCharset = localCharset;
                }
            }
    
            public void handleAccept(SelectionKey key) throws IOException {
                SocketChannel sc = ((ServerSocketChannel) key.channel()).accept();
                sc.configureBlocking(false);
                sc.register(key.selector(), SelectionKey.OP_READ, ByteBuffer.allocate(bufferSize));
            }
    
            public void handleRead(SelectionKey key) throws IOException {
                // 获取channel
                SocketChannel socketChannel = (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 (socketChannel.read(buffer) == -1) {
                    socketChannel.close();
                } else {
                    // 将buffer转换为读状态
                    buffer.flip();
                    // 将buffer中接收到的值按localCharset格式编码后保存到receivedString
                    String receivedString = Charset.forName(localCharset).newDecoder().decode(buffer).toString();
                    System.out.println("received from client: " + receivedString);
    
                    // 返回数据给客户端
                    StringBuilder sendString = new StringBuilder();
                    // 响应报文首行，200表示处理成功
                    sendString.append("HTTP/1.1 200 OK\r\n");
                    sendString.append("Content-Type:text/html;charset=" + localCharset + "\r\n");
                    // 报文头结束后加一个空行
                    sendString.append("\r\n");
    
                    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));
                    socketChannel.write(buffer);
                    // 关闭Socket
                    socketChannel.close();
                }
            }
        }
    }

# 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/20220607/7756a4f80bcf4bb0852082b6aee5d712.png