nio编程service

 public static void main(String[] args) throws IOException {
    
        // 创建select
        Selector selector = Selector.open();

        ServerSocketChannel ssc = ServerSocketChannel.open();
        ssc.configureBlocking(false);
        // 注册 select和channel联系
        // SelectionKey是事件发生后,可以得到事件和哪个channel的事件
        // 四中事件
        // accept -连接请求时触发
        // connect -连接一旦建立触发
        // read -可读事件
        // write -可写事件
        SelectionKey sscKey = ssc.register(selector, 0, null);
        // 只关注accept事件
        sscKey.interestOps(SelectionKey.OP_ACCEPT);
        System.out.println("register key:"+sscKey);

        ssc.bind(new InetSocketAddress(8888));
        while (true){
    
            // 没有事件,则阻塞线程,歇着;有事件才会恢复
            selector.select();
            // 处理事件,包含了所有发生的事件
            // selector会向集合中添加key,但是不会主动删除事件
            Set<SelectionKey> selectionKeys = selector.selectedKeys();
            Iterator<SelectionKey> iterator = selectionKeys.iterator();
            while (iterator.hasNext()){
    
                SelectionKey key = iterator.next();
                System.out.println("key:"+key);
                if(key.isAcceptable()){
    
                    try {
    
                        // 事件不处理会一直加入事件
                        ServerSocketChannel channel = (ServerSocketChannel)key.channel();
                        // 没有连接建立会返回null
                        SocketChannel sc = channel.accept();
                        sc.configureBlocking(false);

                        ByteBuffer bf = ByteBuffer.allocate(2);
                        SelectionKey scKey = sc.register(selector, 0, bf);

                        scKey.interestOps(SelectionKey.OP_READ);
                        System.out.println("sc, "+sc);
                        // 一定要删除处理的事件
                        iterator.remove();
                    }catch (Exception e){
    
                        // 强制断开,关闭连接
                        key.cancel();
                    }

                }else if(key.isReadable()){
    
                    try {
    
                        SocketChannel readChannel = (SocketChannel)key.channel();
                        ByteBuffer buffer1 = (ByteBuffer)key.attachment();
                        int read = readChannel.read(buffer1);
                        if(read == -1){
    
                            // 正常断开,也会触发一次读事件
                            key.cancel();
                        }else {
    
                            split(buffer1);
                            if(buffer1.position() == buffer1.limit()){
    
                                ByteBuffer newBuffer = ByteBuffer.allocate(buffer1.capacity()*2);
                                buffer1.flip();
                                newBuffer.put(buffer1);
                                key.attach(newBuffer);
                            }
                        }
                        iterator.remove();
                    }catch (Exception e){
    

                    }

                }
            }
        }
    }

    private static void split(ByteBuffer source) {
    
        source.flip();
        for(int i=0;i<source.limit();i++){
    
            //
            if(source.get(i)=='\n'){
    
                int length = i+1-source.position();
                ByteBuffer target = ByteBuffer.allocate(length);
                for(int j=0;j<length;j++){
    
                    target.put(source.get());

                }
                target.flip();
                while (target.hasRemaining()){
    
                    char b = (char)target.get();
                    System.out.print(b);
                }
                System.out.println();
            }
        }
        source.compact();
    }