diff --git a/src/doc/selector.md b/src/doc/selector.md new file mode 100644 index 0000000..61655a9 --- /dev/null +++ b/src/doc/selector.md @@ -0,0 +1,71 @@ +# Selector +多路复用器，用来检查一个或多个NIO Channel是否处于可读、可写 + +如此实现单线程管理多个channels +## 可选通道 SelectableChannel +不是所有的Channel都可被Selector复用如，FileChannel + +取决于是否继承了抽象类SelectableChannel + +SelectableChannel可选择监指定通道是可读或者可写 + +## 注册 Channel Selector +`Channel.register(Selector sel,int ops)` +第一个参数指定要注册的选择器，第二个参数指定选择器需要查询的通道操作 +- 可读：SelectionKey.OP_READ +- 可写：SelectionKey.OP_WRITE +- 连接：SelectionKey.OP_CONNECT +- 接收：SelectionKey.OP_ACCEPT + +若Selector对一个通道的多种操作感兴趣，可使用： +`int key = SelectionKey.OP_READ | SelectionKey.OP_WRITE;` +## SelectionKey +Channel注册后，若通道处于以上几种状态，就可以被选择器查询到，使用Selector中的select()，对感兴趣的通道进行操作 + +Selector可以不断查询Channel的状态，一旦有Channel进入Selector监听的就绪状态，就会被Selector选中放入选择键集合中 + +一个选择键包含注册Selector的通道操作类型，如绑定SelectionKey.OP_READ，也包含特定Channel与Selector之间的注册关系 + +## 使用方法 + +### 创建 +```java + //Channel与Selector使用时必须属于非阻塞模式 + //这意味着FileChannel不能和Selector使用 + //create selector + Selector selector = Selector.open(); + ServerSocketChannel serverSocketChannel = ServerSocketChannel.open(); + serverSocketChannel.configureBlocking(false); + //bind + serverSocketChannel.bind(new InetSocketAddress(9999)); + //register channel and listener Accept + serverSocketChannel.register(selector, SelectionKey.OP_ACCEPT); + System.out.println(serverSocketChannel.validOps()==SelectionKey.OP_WRITE); +``` +### 轮询查询就绪操作 +- select():阻塞到至少有一个通道在你注册的事件上生效了 +- select(long timeout):与select一致，但最长阻塞事件为timeout毫秒 +- selectNow():非阻塞，只要有通道准备就绪立即返回 + +select返回int，表示自前一次select到这个之间有多少个通道变为就绪状态 +```java + Selector open = Selector.open(); + Set selectionKeys = open.selectedKeys(); + Iterator iterator = selectionKeys.iterator(); + while (iterator.hasNext()){ + SelectionKey next = iterator.next(); + if(next.isAcceptable()){ + + }else if (next.isConnectable()){ + + } + //... + } +``` +### 停止选择的方法 +选择器执行选择过程中，系统底层会依次询问每个通道是否已经准备就绪，这个过程可能会造调用线程进入阻塞状态 + +有几种方式唤醒在select()方法中阻塞的线程 + +- wakeup()：通过Selector中的方法让处于阻塞状态中的select()方法立即返回；若本次未生效，则下一次select时立即返回 +- close()：通过close关闭Selector，能使唤醒，但会让这个Selector注销，所有的键被唤醒 \ No newline at end of file diff --git a/src/main/java/com/louzin/niodemo/selecter/selectorcrud.java b/src/main/java/com/louzin/niodemo/selecter/selectorcrud.java new file mode 100644 index 0000000..3ecca93 --- /dev/null +++ b/src/main/java/com/louzin/niodemo/selecter/selectorcrud.java @@ -0,0 +1,103 @@ +package com.louzin.niodemo.selecter; + +import org.junit.jupiter.api.Test; + +import java.io.IOException; +import java.net.InetSocketAddress; +import java.nio.ByteBuffer; +import java.nio.channels.*; +import java.nio.charset.StandardCharsets; +import java.util.Date; +import java.util.Iterator; +import java.util.Set; + +public class selectorcrud { + //Channel与Selector使用时必须属于非阻塞模式 + //这意味着FileChannel不能和Selector使用 + + @Test + public void createSelector() throws IOException { + //create selector + Selector selector = Selector.open(); + ServerSocketChannel serverSocketChannel = ServerSocketChannel.open(); + serverSocketChannel.configureBlocking(false); + //bind + serverSocketChannel.bind(new InetSocketAddress(9999)); + //register channel and listener Accept + serverSocketChannel.register(selector, SelectionKey.OP_ACCEPT); + System.out.println(serverSocketChannel.validOps()==SelectionKey.OP_WRITE); + serverSocketChannel.close(); + selector.close(); + + } + @Test + public void cycleSelector() throws IOException { + Selector open = Selector.open(); + Set selectionKeys = open.selectedKeys(); + Iterator iterator = selectionKeys.iterator(); + while (iterator.hasNext()){ + SelectionKey next = iterator.next(); + if(next.isAcceptable()){ + + }else if (next.isConnectable()){ + + } + //... + } + } + @Test + public void serverDemo() throws IOException { + ServerSocketChannel serverSocketChannel = ServerSocketChannel.open(); + serverSocketChannel.bind(new InetSocketAddress("localhost",8000)); + serverSocketChannel.configureBlocking(false); + + Selector selector = Selector.open(); + //register channel and listen accept + serverSocketChannel.register(selector,SelectionKey.OP_ACCEPT); + while (selector.select()>0){ + Set selectionKeys = selector.selectedKeys(); + Iterator iterator = selectionKeys.iterator(); + while (iterator.hasNext()){ + SelectionKey next = iterator.next(); + //judgement operation + if(next.isAcceptable()){ + //get connect + SocketChannel accept = serverSocketChannel.accept(); + //change to nio + accept.configureBlocking(false); + //register + accept.register(selector,SelectionKey.OP_READ); + }else if(next.isReadable()){ + SocketChannel channel = (SocketChannel) next.channel(); + ByteBuffer allocateinno = ByteBuffer.allocate(1024); + int length = 0; + while ((length = channel.read(allocateinno))>0){ + allocateinno.flip(); + System.out.println(new String(allocateinno.array(),0,length)); + allocateinno.clear(); + } + + } + + } + iterator.remove(); + } + } + @Test + public void clientDemo() throws IOException { + //get channel and bind port + SocketChannel so = SocketChannel.open(new InetSocketAddress("localhost",8000)); + //change to nio + so.configureBlocking(false); + //create buffer + ByteBuffer allocate = ByteBuffer.allocate(64); + //write buffer + allocate.put(new Date().toString().getBytes(StandardCharsets.UTF_8)); + //mode change + allocate.flip(); + //write into channel + so.write(allocate); + //clear buffer and close connect + allocate.clear(); + } +}