Java 非阻塞式NIO 案例（实现多人聊天功能）

一、使用java nio完成网络通信的三个核心

　　1.通道（channel）：负责连接

　　      java.nio.channels.channel 接口：
              |--selectablechannel
                  |--socketchannel
                  |--serversocketchannel
                  |--datagramchannel
 
                  |--pipe.sinkchannel
                  |--pipe.sourcechannel

　　2.缓冲区（buffer）：负责数据存取

　　3.选择器（selector）:是selectablechannel 的多路复用器，用来检测selectablechannel的io状态

 

案例：使用非阻塞式实现简单的群聊天系统

一、实现客户端

 1     public static void main(string[] args) throws exception {
 2         socketchannel schannel = socketchannel.open(new inetsocketaddress("127.0.0.1", 8989));
 3 
 4         //2. 切换非阻塞模式
 5         schannel.configureblocking(false);
 6 
 7         //3. 分配指定大小的缓冲区
 8         bytebuffer buf = bytebuffer.allocate(1024);
 9 
10         //4. 发送数据给服务端
11         scanner scan = new scanner(system.in);
12 
13         while (scan.hasnext()) {
14             string str = scan.next();
15             buf.put((new date().tostring() + "\n" + str).getbytes());
16             buf.flip();
17             schannel.write(buf);
18             buf.clear();
19         }
20 
21         //5. 关闭通道
22         schannel.close();
23     }

二、实现服务端

    @test
    public void server() {
        serversocketchannel sschannel = null;
        try {
            sschannel = serversocketchannel.open();
            //配置非阻塞
            sschannel.configureblocking(false);
            //绑定连接
            sschannel.bind(new inetsocketaddress(8989));

            selector selector = selector.open();

            //将通道注册到监听器中，并且制定监听器的监听模式为“接受”
            sschannel.register(selector, selectionkey.op_accept);

            //轮询的选择已经就绪的事件
            while (selector.select() > 0) {
                //获取当前监听
                iterator<selectionkey> it = selector.selectedkeys().iterator();

                while (it.hasnext()) {
                    //获取准备就绪的事件
                    selectionkey sk = it.next();
                    if (sk.isacceptable()) {
                        //如果接受就绪，则获取客户端的连接
                        socketchannel clientchannel = sschannel.accept();

                        //同样配置成非阻塞式
                        clientchannel.configureblocking(false);

                        //把客户端的连接注册到选择器上
                        clientchannel.register(selector, selectionkey.op_read);
                    } else if (sk.isreadable()) {
                        //如果读取就绪，则获取读取的通道
                        socketchannel socketchannel = (socketchannel) sk.channel();

                        //配置成非阻塞模式
                        socketchannel.configureblocking(false);

                        //读取数据

                        bytebuffer bytebuffer = bytebuffer.allocate(1024);

                        int len = 0;
                        while ((len = socketchannel.read(bytebuffer)) > 0) {
                            bytebuffer.flip();
                            system.out.println(new string(bytebuffer.array(), 0, len));
                            bytebuffer.clear();
                        }
                    }
                    it.remove();
                }
            }
        } catch (ioexception e) {
            e.printstacktrace();
        } finally {
            if(sschannel!=null){
                try {
                    sschannel.close();
                } catch (ioexception e) {
                    e.printstacktrace();
                }
            }
        }
    }

注意：这里服务端用到的org.junit.test;这个包方便测试，客户端因为需要读取输入所以写在main函数中（@test方法中测试出来好像不能读取输入）

需要下载包的地址如下：

链接：https://pan.baidu.com/s/14zhhonad3ldnvca3pmcojq
提取码：uqd9

datagramchannel（udp）的使用方法（和上个案例大同小异）

public static void main(string args[]) {
        datagramchannel datagramchannel = null;
        try {
            datagramchannel = datagramchannel.open();

            datagramchannel.configureblocking(false);

            bytebuffer bytebuffer = bytebuffer.allocate(1024);

            scanner scanner = new scanner(system.in);

            while (scanner.hasnext()) {
                string str = scanner.next();
                bytebuffer.put(str.getbytes());
                bytebuffer.flip();
                datagramchannel.send(bytebuffer, new inetsocketaddress("127.0.0.1", 9897));
                bytebuffer.clear();
            }
        } catch (ioexception e) {
            e.printstacktrace();
        }
        finally {
            if(datagramchannel!=null){
                try {
                    datagramchannel.close();
                } catch (ioexception e) {
                    e.printstacktrace();
                }
            }
        }
    }

    @test
    public void server(){
        datagramchannel datagramchannel = null;
        try {
            datagramchannel=datagramchannel.open();
            datagramchannel.bind(new inetsocketaddress(9897));

            datagramchannel.configureblocking(false);

            selector selector = selector.open();
            datagramchannel.register(selector, selectionkey.op_read);

            while(selector.select()>0){
                iterator<selectionkey> st=selector.selectedkeys().iterator();

                while(st.hasnext()){
                    selectionkey sk=st.next();

                    if(sk.isreadable()){
                        bytebuffer btf=bytebuffer.allocate(1024);

                        datagramchannel.receive(btf);

                        btf.flip();

                        system.out.println(new string(btf.array(),0,btf.limit()));
                        btf.clear();
                    }
                }
                st.remove();
            }
        } catch (ioexception e) {
            e.printstacktrace();
        } finally {
            if(datagramchannel!=null){
                try {
                    datagramchannel.close();
                } catch (ioexception e) {
                    e.printstacktrace();
                }
            }
        }
    }

 

pipe简介

pipe是两个线程之间单项数据连接，pipe有两个数据通道，sign通道负责写入，source通道负责读取。
案例如下：

    @test
    public void test() throws exception {
        pipe pipe = pipe.open();

        bytebuffer bytebuffer = bytebuffer.allocate(1024);

        bytebuffer.put("hello world".getbytes());

        pipe.sinkchannel sinkchannel=pipe.sink();
        bytebuffer.flip();
        sinkchannel.write(bytebuffer);


        //读取

        pipe.sourcechannel sourcechannel =pipe.source();
        bytebuffer.flip();
        int len=sourcechannel.read(bytebuffer);

        system.out.println("sourcechanel:"+new string(bytebuffer.array(),0,len));
        bytebuffer.clear();

        sinkchannel.close();

        sourcechannel.close();

    }

 

谢谢浏览，如有问题直接评论，我会及时更改我的错误。