文章目录
- 1 阻塞式服务端
- 1.1 服务端
- 1.2 测试
- 2 非阻塞式服务端
- 2.1 处理连接事件
- 2.2 处理读就绪事件
- 2.3 处理写就绪事件
- 2.4 测试
- 2.5 完整代码
- 3 混合用阻塞模式与非阻塞模式
使用nio包下的类简单实现一个服务端代码熟悉前面介绍的API
- 采用阻塞式
- 采用非阻塞
- 阻塞和非阻塞混用
1 阻塞式服务端
1.1 服务端
采用阻塞模式，用线程池中的工作线程处理每个客户连接。
- 当ServerSocketChannel与SocketChannel采用默认的阻塞模式时，为了同时处理多个客户的连接，必须使用多个线程。在EchoServer类中，利用java.util.concurrent包中提供的线程池ExecutorService来处理与客户的连接。
- EchoServer类的构造方法负责创建线程池，启动服务器，把它绑定到一个本地端口。EchoServer类的service()方法负责接收客户的连接。每接收到一个客户连接，就把它交给线程池来处理，线程池取出一个空闲的线程，来执行Handler对象的run()方法。Handler类的handle()方法负责与客户通信。该方法先获得与SocketChannel关联的Socket对象，然后从Socket对象中得到输入流与输出流，再接收和发送数据。
package study.wyy.net.nio.server;
import lombok.extern.slf4j.Slf4j;
import study.wyy.net.nio.thread.RequestHandler;
import java.io.IOException;
import java.net.InetSocketAddress;
import java.net.ServerSocket;
import java.nio.channels.ServerSocketChannel;
import java.nio.channels.SocketChannel;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
/**
* @author wyaoyao
* @date 2021/3/17 17:12
* 阻塞式服务端示例
*/
@Slf4j
public class BlockEchoServer {
/**
* 服务端口号
*/
private final int port;
private final ServerSocketChannel serverSocketChannel;
private final ServerSocket serverSocket;
private final ExecutorService executorService;
/**
* 线程池中工作的线程数目
*/
private final int POOL_MULTIPLE = 4;
public BlockEchoServer(int port) throws IOException {
this.port = port;
executorService = Executors.newFixedThreadPool(
// ava.lang.Runtime.availableProcessors() 方法: 返回可用处理器的Java虚拟机的数量。
Runtime.getRuntime().availableProcessors() * POOL_MULTIPLE
);
// 打开通道
this.serverSocketChannel = ServerSocketChannel.open();
// 返回与ServerSocketChannel关联的ServerSocket对象，每个ServerSocketChannel对象都与一个ServerSocket对象关联
serverSocket = serverSocketChannel.socket();
// 使得在同一个主机上关闭了服务器，紧接着再启动服务器程序时，可以顺利绑定相同的端口
serverSocket.setReuseAddress(true);
// 与本地的端口绑定
serverSocket.bind(new InetSocketAddress(port));
log.info("the server has bind address is {}:{}", this.serverSocket.getInetAddress().getHostAddress(), this.port);
}
public void service() {
while (true) {
SocketChannel socketChannel;
try {
// 等待接收客户端连接，一旦有客户端连接，就会返会与当前客户端连接的SocketChannel的对象
socketChannel = serverSocketChannel.accept();
// 开启一个线程去处理当前客户端连接
executorService.submit(new RequestHandler(socketChannel));
} catch (IOException e) {
e.printStackTrace();
}
}
}
}package study.wyy.net.nio.thread;
import lombok.extern.slf4j.Slf4j;
import java.io.*;
import java.net.Socket;
import java.nio.channels.SocketChannel;
/**
* @author wyaoyao
* @date 2021/3/17 17:35
*/
@Slf4j
public class RequestHandler implements Runnable {
private final SocketChannel socketChannel;
private Socket socket;
public RequestHandler(SocketChannel socketChannel) {
this.socketChannel = socketChannel;
}
@Override
public void run() {
try {
// 获得与socketChannel关联的Socket对象
socket = socketChannel.socket();
log.info("new client connection from {}:{} accept", socket.getInetAddress(), socket.getPort());
// 获取输入流
BufferedReader reader = getReader(socket);
// 获取输出流
PrintWriter writer = getWriter(socket);
String msg = null;
while ((msg = reader.readLine()) != null) {
log.info("accept message from client is {}", msg);
// 返回响应给客户端
writer.println("echo: " + msg);
if (msg.contains("bye")) {
// 如果客户端发来的是bye，则退出当前会话
break;
}
}
} catch (Exception e) {
e.printStackTrace();
} finally {
if (socketChannel != null){
try {
socketChannel.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
}
public BufferedReader getReader(Socket socket) throws IOException {
InputStream inputStream = socket.getInputStream();
return new BufferedReader(new InputStreamReader(inputStream));
}
public PrintWriter getWriter(Socket socket) throws IOException {
return new PrintWriter(socket.getOutputStream(), true);
}
}1.2 测试
- 为了测试先写一个客户端: 采用阻塞式
package study.wyy.net.nio.client;
import lombok.Builder;
import lombok.extern.slf4j.Slf4j;
import java.io.*;
import java.net.InetSocketAddress;
import java.net.Socket;
import java.net.SocketAddress;
import java.nio.channels.SocketChannel;
/**
* @author wyaoyao
* @date 2021/3/17 17:59
*/
@Slf4j
public class BlockEchoClient {
private final SocketChannel socketChannel;
private final String serverHost;
private final int serverPort;
public BlockEchoClient(String serverHost, int serverPort) throws IOException {
this.serverHost = serverHost;
this.serverPort = serverPort;
this.socketChannel = SocketChannel.open();
// 连接服务器
SocketAddress remote = new InetSocketAddress(serverHost, serverPort);
socketChannel.connect(remote);
log.info("connect echo server success");
}
public void send(String message) {
try {
BufferedReader reader = getReader(socketChannel.socket());
PrintWriter writer = getWriter(socketChannel.socket());
// 发送数据
writer.println(message);
log.info("send request success; content is {}", message);
// 读取服务端的响应
String s1 = reader.readLine();
log.info("get response success; response is {}", s1);
} catch (Exception e) {
e.printStackTrace();
}
}
public void close() throws IOException {
if(socketChannel != null){
socketChannel.close();
}
}
public BufferedReader getReader(Socket socket) throws IOException {
InputStream inputStream = socket.getInputStream();
return new BufferedReader(new InputStreamReader(inputStream));
}
public PrintWriter getWriter(Socket socket) throws IOException {
return new PrintWriter(socket.getOutputStream(), true);
}
}- 启动服务端
public class BlockEchoServerTest {
public static void main(String[] args) throws IOException {
BlockEchoServer server = new BlockEchoServer(10010);
// 等待客户端连接
server.service();
}
}- 启动客户端，模拟3个客户端同时访问
public static void main(String[] args) throws IOException {
Arrays.asList(1,2,3).stream().forEach(i->{
new Thread(()->{
BlockEchoClient client = null;
try {
client = new BlockEchoClient("localhost", 10010);
client.send("hello! from " + Thread.currentThread().getName());
client.send("你好! from " + Thread.currentThread().getName());
client.send("bye! from " + Thread.currentThread().getName());
} catch (IOException e) {
e.printStackTrace();
} finally {
if(client != null){
try {
client.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
},"client" +i).start();
});
}测试客户端输出结果：
07:56:29.945 [client1] INFO study.wyy.net.nio.client.BlockEchoClient - connect echo server success
07:56:29.945 [client3] INFO study.wyy.net.nio.client.BlockEchoClient - connect echo server success
07:56:29.945 [client2] INFO study.wyy.net.nio.client.BlockEchoClient - connect echo server success
07:56:29.949 [client1] INFO study.wyy.net.nio.client.BlockEchoClient - send request success; content is hello! from client1
07:56:29.949 [client2] INFO study.wyy.net.nio.client.BlockEchoClient - send request success; content is hello! from client2
07:56:29.949 [client3] INFO study.wyy.net.nio.client.BlockEchoClient - send request success; content is hello! from client3
07:56:29.981 [client1] INFO study.wyy.net.nio.client.BlockEchoClient - get response success; response is echo: hello! from client1
07:56:29.981 [client1] INFO study.wyy.net.nio.client.BlockEchoClient - send request success; content is 你好! from client1
07:56:30.993 [client1] INFO study.wyy.net.nio.client.BlockEchoClient - get response success; response is echo: 你好! from client1
07:56:30.993 [client1] INFO study.wyy.net.nio.client.BlockEchoClient - send request success; content is bye! from client1
07:56:31.981 [client3] INFO study.wyy.net.nio.client.BlockEchoClient - get response success; response is echo: hello! from client3
07:56:31.981 [client3] INFO study.wyy.net.nio.client.BlockEchoClient - send request success; content is 你好! from client3
07:56:32.002 [client3] INFO study.wyy.net.nio.client.BlockEchoClient - get response success; response is echo: 你好! from client3
07:56:32.003 [client3] INFO study.wyy.net.nio.client.BlockEchoClient - send request success; content is bye! from client3
07:56:32.016 [client1] INFO study.wyy.net.nio.client.BlockEchoClient - get response success; response is echo: bye! from client1
07:56:32.017 [client3] INFO study.wyy.net.nio.client.BlockEchoClient - get response success; response is echo: bye! from client3
07:56:32.982 [client2] INFO study.wyy.net.nio.client.BlockEchoClient - get response success; response is echo: hello! from client2
07:56:32.983 [client2] INFO study.wyy.net.nio.client.BlockEchoClient - send request success; content is 你好! from client2
07:56:33.004 [client2] INFO study.wyy.net.nio.client.BlockEchoClient - get response success; response is echo: 你好! from client2
07:56:33.005 [client2] INFO study.wyy.net.nio.client.BlockEchoClient - send request success; content is bye! from client2
07:56:37.027 [client2] INFO study.wyy.net.nio.client.BlockEchoClient - get response success; response is echo: bye! from client2由于采用多线程的方式，使得可以同时处理多个客户的连接。
如果服务端修改为不采用多线程：
public void service() {
while (true) {
SocketChannel socketChannel;
try {
// 等待接收客户端连接，一旦有客户端连接，就会返会与当前客户端连接的SocketChannel的对象
socketChannel = serverSocketChannel.accept();
// 开启一个线程去处理当前客户端连接
// executorService.submit(new RequestHandler(socketChannel));
// 这里不开启线程
new RequestHandler(socketChannel).run();
} catch (IOException e) {
e.printStackTrace();
}
}
}在测试：
08:12:59.029 [client1] INFO study.wyy.net.nio.client.BlockEchoClient - connect echo server success
08:12:59.029 [client2] INFO study.wyy.net.nio.client.BlockEchoClient - connect echo server success
08:12:59.029 [client3] INFO study.wyy.net.nio.client.BlockEchoClient - connect echo server success
08:12:59.036 [client3] INFO study.wyy.net.nio.client.BlockEchoClient - send request success; content is hello! from client3
08:12:59.036 [client2] INFO study.wyy.net.nio.client.BlockEchoClient - send request success; content is hello! from client2
08:12:59.036 [client1] INFO study.wyy.net.nio.client.BlockEchoClient - send request success; content is hello! from client1
08:12:59.049 [client2] INFO study.wyy.net.nio.client.BlockEchoClient - get response success; response is echo: hello! from client2
08:12:59.049 [client2] INFO study.wyy.net.nio.client.BlockEchoClient - send request success; content is 你好! from client2
08:12:59.051 [client2] INFO study.wyy.net.nio.client.BlockEchoClient - get response success; response is echo: 你好! from client2
08:12:59.051 [client2] INFO study.wyy.net.nio.client.BlockEchoClient - send request success; content is bye! from client2
08:12:59.053 [client2] INFO study.wyy.net.nio.client.BlockEchoClient - get response success; response is echo: bye! from client2
08:12:59.065 [client1] INFO study.wyy.net.nio.client.BlockEchoClient - get response success; response is echo: hello! from client1
08:12:59.065 [client1] INFO study.wyy.net.nio.client.BlockEchoClient - send request success; content is 你好! from client1
08:12:59.096 [client1] INFO study.wyy.net.nio.client.BlockEchoClient - get response success; response is echo: 你好! from client1
08:12:59.096 [client1] INFO study.wyy.net.nio.client.BlockEchoClient - send request success; content is bye! from client1
08:12:59.107 [client1] INFO study.wyy.net.nio.client.BlockEchoClient - get response success; response is echo: bye! from client1
08:12:59.119 [client3] INFO study.wyy.net.nio.client.BlockEchoClient - get response success; response is echo: hello! from client3
08:12:59.119 [client3] INFO study.wyy.net.nio.client.BlockEchoClient - send request success; content is 你好! from client3
08:12:59.140 [client3] INFO study.wyy.net.nio.client.BlockEchoClient - get response success; response is echo: 你好! from client3
08:12:59.140 [client3] INFO study.wyy.net.nio.client.BlockEchoClient - send request success; content is bye! from client3
08:12:59.151 [client3] INFO study.wyy.net.nio.client.BlockEchoClient - get response success; response is echo: bye! from client3三个客户端同时发送了是第一个请求，但是服务端只能依次一个客户端处理，比如这里先处理client2，直到把client2的三个请求（hello，你好,bye）才会去处理下一个客户端。
2 非阻塞式服务端
在非阻塞模式下，EchoServer只需要启动一个主线程，就能同时处理三件事：
- 接收客户的连接。
- 接收客户发送的数据。
- 向客户发回响应数据。
EchoServer委托Selector来负责监控接收连接就绪事件、读就绪事件和写就绪事件，如果有特定事件发生，就处理该事件。 EchoServer类的构造方法负责启动服务器，把它绑定到一个本地端口，代码如下：
- 构造方法
@Slf4j
public class NoBlockEchoServer {
/**
* 委托给Selector来负责接收连接就绪事件，读就绪事件，写就绪事件
*/
private final Selector selector;
private final ServerSocketChannel serverSocketChannel;
private final ServerSocket serverSocket;
private final int port;
public NoBlockEchoServer(int port) throws IOException {
// 创建一个Selector对象
this.selector = Selector.open();
// 创建一个ServerSocketChannel对象
serverSocketChannel = ServerSocketChannel.open();
// 返回与ServerSocketChannel关联的ServerSocket对象，每个ServerSocketChannel对象都与一个ServerSocket对象关联
serverSocket = serverSocketChannel.socket();
// 使得在同一个主机上关闭了服务器，紧接着再启动服务器程序时，可以顺利绑定相同的端口
serverSocket.setReuseAddress(true);
// 设置serverSocketChannel为非阻塞工作模式
serverSocketChannel.configureBlocking(false);
// 绑定本地端口
this.port = port;
serverSocketChannel.bind(new InetSocketAddress(port));
log.info("the server has bind address is {}:{}", this.serverSocket.getInetAddress().getHostAddress(), this.port);
}
}- service()方法负责处理本节开头所说的三件事，体现其主要流程的代码如下：
public void service() throws IOException {
// 注册一个连接事件
serverSocketChannel.register(selector, SelectionKey.OP_ACCEPT);
// select()返回已经发生的SelectionKey对象的数量，该方法是阻塞的，如果一个也没有就进入阻塞，
while (selector.select() > 0) {
// 进入循环就说明事件发生
// 获取相关事件已经被Selector捕获的SelectionKey的集合
Set<SelectionKey> readyKes = selector.selectedKeys();
// 遍历处理这些已经捕获到的事件
Iterator<SelectionKey> iterator = readyKes.iterator();
while (iterator.hasNext()) {
SelectionKey key = null;
try {
// 取出一个SelectionKey，进行处理
key = iterator.next();
// 既然取出来，就可以从集合中删除了
iterator.remove();
// 判断事件类型
if (key.isAcceptable()) {
// 处理连接就绪事件
}
if (key.isReadable()) {
// 处理读就绪事件
}
if (key.isWritable()) {
// 处理写就绪事件
}
} catch (Exception e) {
e.printStackTrace();
if (null != null) {
// 失效掉这个key, selector不再感兴趣这个SelectionKey感兴趣的事件
key.cancel();
// 关闭与这个key关联的socketChannel
key.channel().close();
}
}
}
}
}service方法中，首先由serverSocketChannel向Selector 注册连接就绪事件。如果Selector监控到该事件发生，就会把相应的SelectionKey对象加入到selected-keys集合中（相关事件已经被Selector捕获的SelectionKey的集合）。接下来第一层while循环，会不断的询问Selector已经发生的事件，然后依次处理这些事件。
其中获取已经发生的事件的SelectionKey个数，如果当前没有任何事件发生，这个方法就会阻塞下去，直到至少一件事情发生。selector.selectedKeys()这个方法返回已经被Selector捕获的SelectionKey的集合（selected-keys集合），selected-keys集合存放了相关事件已经发生的SelectionKey对象。
接下来就是遍历selected-keys集合，处理这些已经捕获到的事件。如果出现异常，就会失效这个SelectionKey，并且关闭与之关联的channel
2.1 处理连接事件
刚刚service方法已经通过if留出了每个事件类型处理的地方，现在就先处理连接事件，代码如下：
private void handleAcceptable(SelectionKey selectionKey) throws IOException {
// 获取与SelectionKey关联的serverSocketChannel，就是通过serverSocketChannel来传输数据的
ServerSocketChannel serverSocketChannel = (ServerSocketChannel) selectionKey.channel();
// 获取与客户端连接的SocketChannel
SocketChannel socketChannel = serverSocketChannel.accept();
log.info("accept client connection from {}:{} accept", socketChannel.socket().getInetAddress(), socketChannel.socket().getPort());
// 设置socketChannel为非阻塞
socketChannel.configureBlocking(false);
// 创建一个缓冲区，用于存放客户端发来的数据
ByteBuffer byteBuffer = ByteBuffer.allocate(1024);
// SocketChannel向selector注册读就绪事件和写就绪事件
// 并把byteBuffer作为附件注册进去，在读写事件发生的时候获取byteBuffer，进行数据读写
socketChannel.register(selector,SelectionKey.OP_READ | SelectionKey.OP_WRITE,byteBuffer);
}如果isAcceptable方法返回true，就表示这个SelectionKey所有感兴趣的接收连接就绪事件已经发生了
首先通过SelectionKey的channel()方法获的与之关联的ServerSocketChannel，然后调用ServerSocketChannel的accpet方法获取与客户端连接的SocketChannel对象。这个SocketChannel对象默认是阻塞模式的，所以首先调用configureBlocking(fasle)方法将其设置为非阻塞模式。
SocketChannel调用register方法向selector注册读就绪事件和写就绪事件，并把byteBuffer作为附件与新建的这个SelectionKey关联。
2.2 处理读就绪事件
如果isReadable方法返回true，就表示这个SelectionKey所有感兴趣的读就绪事件已经发生了
private void handleReadable(SelectionKey selectionKey) throws IOException {
// 获取关联的的附件
ByteBuffer buffer = (ByteBuffer) selectionKey.attachment();
// 获取与当前SelectionKey关联的SocketChannel
SocketChannel socketChannel = (SocketChannel) selectionKey.channel();
// 创建ByteBuffer字节缓冲区，用于存放读取到的数据
ByteBuffer readBuffer = ByteBuffer.allocate(32);
socketChannel.read(readBuffer);
// flip()：把极限设为位置，再把位置设为0
readBuffer.flip();
// 把buffer的极限设置为容量
buffer.limit(buffer.capacity());
// 把readBuffer中的数据拷贝到buffer中
// 假定buffer的容量足够大，不会出现缓冲区溢出的情况
buffer.put(readBuffer);
}- 先获得与这个SelectionKey关联的buffer 和SocketChannel。
- SocketChannel每次读到的数据都被放到这个buffer 中
- 在非阻塞式下，socketChannel.read(readBuffer)方法读取到多少数据是不确定的。假定读取到的数据是n，那么0<=n<=readBuffer的容量。
- 无法保证读取的数据用户一次完整的请求数据，所以只好下把每次读取到的数据放到buffer ，当这个buffer中的数据满足一行数据的时候就，返回给用户，这就是为何之前要在注册读写事件的时候要加入这个一个附件的原因。
这个方法涉及到了ByteBuffer三个属性的变化，特此画了个图，来展示一下三个属性的变化过程：假定socketChannel.read方法读入了
6个字节，放在了readBuffer中，并假定buffer中原先就有10个字节
2.3 处理写就绪事件
如果isWritable方法返回true，就表示这个SelectionKey所有感兴趣的写就绪事件已经发生了
private final Charset charset = Charset.forName("UTF-8");
private void handleWritable(SelectionKey selectionKey) throws IOException {
// 获取关联的的ByteBuffer
ByteBuffer buffer = (ByteBuffer) selectionKey.attachment();
// 获取与当前SelectionKey关联的SocketChannel
SocketChannel socketChannel = (SocketChannel) selectionKey.channel();
// flip()：把极限设为位置，再把位置设为0
buffer.flip();
// 解码，将buffer中的字节转为字符串
String data = decode(buffer);
// 如果buffer中的数据不足用户一次请求（这里就指一行）,就返回
if (data.indexOf("\r\n") == -1) {
return;
}
// 截取一行数据
String req = data.substring(0, data.indexOf("\n") + 1);
// 将字符串进行编码
ByteBuffer responseBuffer = encode("echo:" + req);
// 输出responseBuffer中的所有字节
while (responseBuffer.hasRemaining()){
socketChannel.write(responseBuffer);
}
ByteBuffer temp = encode(req);
// 把buffer的位置设置为temp的极限
buffer.position(temp.limit());
// 删除buffer中已经处理的数据
buffer.compact();
if(req.contains("bye")){
// 如果客户端发来的是bye，则退出当前会话, 失效这个key
selectionKey.cancel();
socketChannel.close();
}
}
/**
* 解码
*
* @param byteBuffer
* @return
*/
private String decode(ByteBuffer byteBuffer) {
CharBuffer decode = charset.decode(byteBuffer);
return decode.toString();
}
/**
* 编码
*/
private ByteBuffer encode(String content) {
ByteBuffer encode = charset.encode(content);
return encode;
}在处理写事件的时候，会把读入的数据放到一个ByteBuffer 中，在我们写数据时候就是从这个ByteBuffer取出处理读事件时候读取的数据。
这里特别说明删除已经处理的数据这部分代码：
ByteBuffer temp = encode(req);
// 把buffer的位置设置为temp的极限
buffer.position(temp.limit());
// 删除buffer中已经处理的数据
buffer.compact();假设buffer中一共16个字节，而temp中是10个字节：这里对compact方法不了解参考：非阻塞通信的API基本介绍
2.4 测试
- 启动服务
public class NoBlockEchoServerTest {
public static void main(String[] args) throws IOException {
NoBlockEchoServer server = new NoBlockEchoServer(10010);
// 等待客户端连接
server.service();
}
}- 运行之前的客户端代码:
17:35:05.122 [client1] INFO study.wyy.net.nio.client.BlockEchoClient - connect echo server success
17:35:05.122 [client3] INFO study.wyy.net.nio.client.BlockEchoClient - connect echo server success
17:35:05.124 [client2] INFO study.wyy.net.nio.client.BlockEchoClient - connect echo server success
17:35:05.128 [client1] INFO study.wyy.net.nio.client.BlockEchoClient - send request success; content is hello! from client1
17:35:05.129 [client3] INFO study.wyy.net.nio.client.BlockEchoClient - send request success; content is hello! from client3
17:35:05.128 [client2] INFO study.wyy.net.nio.client.BlockEchoClient - send request success; content is hello! from client2
17:35:05.144 [client1] INFO study.wyy.net.nio.client.BlockEchoClient - get response success; response is echo:hello! from client1
17:35:05.144 [client1] INFO study.wyy.net.nio.client.BlockEchoClient - send request success; content is 你好! from client1
17:35:05.145 [client3] INFO study.wyy.net.nio.client.BlockEchoClient - get response success; response is echo:hello! from client3
17:35:05.145 [client3] INFO study.wyy.net.nio.client.BlockEchoClient - send request success; content is 你好! from client3
17:35:05.145 [client2] INFO study.wyy.net.nio.client.BlockEchoClient - get response success; response is echo:hello! from client2
17:35:05.145 [client2] INFO study.wyy.net.nio.client.BlockEchoClient - send request success; content is 你好! from client2
17:35:05.146 [client1] INFO study.wyy.net.nio.client.BlockEchoClient - get response success; response is echo:你好! from client1
17:35:05.146 [client1] INFO study.wyy.net.nio.client.BlockEchoClient - send request success; content is bye! from client1
17:35:05.158 [client3] INFO study.wyy.net.nio.client.BlockEchoClient - get response success; response is echo:你好! from client3
17:35:05.158 [client2] INFO study.wyy.net.nio.client.BlockEchoClient - get response success; response is echo:你好! from client2
17:35:05.158 [client3] INFO study.wyy.net.nio.client.BlockEchoClient - send request success; content is bye! from client3
17:35:05.158 [client2] INFO study.wyy.net.nio.client.BlockEchoClient - send request success; content is bye! from client2
17:35:05.158 [client1] INFO study.wyy.net.nio.client.BlockEchoClient - get response success; response is echo:bye! from client1
17:35:05.159 [client2] INFO study.wyy.net.nio.client.BlockEchoClient - get response success; response is echo:bye! from client2
17:35:05.159 [client3] INFO study.wyy.net.nio.client.BlockEchoClient - get response success; response is echo:bye! from client32.5 完整代码
package study.wyy.net.nio.server;
import lombok.extern.slf4j.Slf4j;
import java.io.IOException;
import java.net.InetSocketAddress;
import java.net.ServerSocket;
import java.nio.ByteBuffer;
import java.nio.CharBuffer;
import java.nio.channels.*;
import java.nio.charset.Charset;
import java.util.Iterator;
import java.util.Set;
/**
* @author wyaoyao
* @date 2021/3/18 8:50
* 非阻塞式
*/
@Slf4j
public class NoBlockEchoServer {
/**
* 委托给Selector来负责接收连接就绪事件，读就绪事件，写就绪事件
* 只要ServerSocketChannel以及SocketChannel向Selector注册了特定事件，
* Selector就会监控这些事件是否发生。
*/
private final Selector selector;
private final ServerSocketChannel serverSocketChannel;
private final ServerSocket serverSocket;
private final int port;
private final Charset charset = Charset.forName("UTF-8");
public NoBlockEchoServer(int port) throws IOException {
// 创建一个Selector对象
this.selector = Selector.open();
// 创建一个ServerSocketChannel对象
serverSocketChannel = ServerSocketChannel.open();
// 返回与ServerSocketChannel关联的ServerSocket对象，每个ServerSocketChannel对象都与一个ServerSocket对象关联
serverSocket = serverSocketChannel.socket();
// 使得在同一个主机上关闭了服务器，紧接着再启动服务器程序时，可以顺利绑定相同的端口
serverSocket.setReuseAddress(true);
// 设置serverSocketChannel为非阻塞工作模式
serverSocketChannel.configureBlocking(false);
// 绑定本地端口
this.port = port;
serverSocketChannel.bind(new InetSocketAddress(port));
log.info("the server has bind address is {}:{}", this.serverSocket.getInetAddress().getHostAddress(), this.port);
}
public void service() throws IOException {
// 注册一个连接事件
serverSocketChannel.register(selector, SelectionKey.OP_ACCEPT);
// select()返回已经发生的SelectionKey对象的数量，该方法是阻塞的，如果一个也没有就进入阻塞，
while (selector.select() > 0) {
// 进入循环就说明事件发生
// 获取相关事件已经被Selector捕获的SelectionKey的集合
Set<SelectionKey> readyKes = selector.selectedKeys();
// 遍历处理这些已经捕获到的事件
Iterator<SelectionKey> iterator = readyKes.iterator();
while (iterator.hasNext()) {
SelectionKey key = null;
try {
// 取出一个SelectionKey，进行处理
key = iterator.next();
// 既然取出来，就可以从集合中删除了
iterator.remove();
// 判断事件类型
if (key.isAcceptable()) {
// 处理连接就绪事件
handleAcceptable(key);
}
if (key.isReadable()) {
// 处理读就绪事件
handleReadable(key);
}
if (key.isWritable()) {
// 处理写就绪事件
handleWritable(key);
}
} catch (Exception e) {
e.printStackTrace();
if (null != null) {
// 失效掉这个key, selector不再感兴趣这个SelectionKey感兴趣的事件
key.cancel();
// 关闭与这个key关联的socketChannel
key.channel().close();
}
}
}
}
}
private void handleAcceptable(SelectionKey selectionKey) throws IOException {
// 获取与SelectionKey关联的serverSocketChannel，就是通过serverSocketChannel来传输数据的
ServerSocketChannel serverSocketChannel = (ServerSocketChannel) selectionKey.channel();
// 获取与客户端连接的SocketChannel
SocketChannel socketChannel = serverSocketChannel.accept();
log.info("accept client connection from {}:{} accept", socketChannel.socket().getInetAddress(), socketChannel.socket().getPort());
// 设置socketChannel为非阻塞
socketChannel.configureBlocking(false);
// 创建一个缓冲区，用于存放客户端发来的数据
ByteBuffer byteBuffer = ByteBuffer.allocate(1024);
// SocketChannel向selector注册读就绪事件和写就绪事件
// 并把byteBuffer作为附件注册进去，在读写事件发生的时候获取byteBuffer，进行数据读写
socketChannel.register(selector, SelectionKey.OP_READ | SelectionKey.OP_WRITE, byteBuffer);
}
private void handleReadable(SelectionKey selectionKey) throws IOException {
// 获取关联的的附件
ByteBuffer buffer = (ByteBuffer) selectionKey.attachment();
// 获取与当前SelectionKey关联的SocketChannel
SocketChannel socketChannel = (SocketChannel) selectionKey.channel();
// 创建ByteBuffer字节缓冲区，用于存放读取到的数据
ByteBuffer readBuffer = ByteBuffer.allocate(32);
socketChannel.read(readBuffer);
// flip()：把极限设为位置，再把位置设为0
readBuffer.flip();
// 把buffer的极限设置为容量
buffer.limit(buffer.capacity());
// 把readBuffer中的数据拷贝到buffer中
// 假定buffer的容量足够大，不会出现缓冲区溢出的情况
buffer.put(readBuffer);
}
private void handleWritable(SelectionKey selectionKey) throws IOException {
// 获取关联的的ByteBuffer
ByteBuffer buffer = (ByteBuffer) selectionKey.attachment();
// 获取与当前SelectionKey关联的SocketChannel
SocketChannel socketChannel = (SocketChannel) selectionKey.channel();
// flip()：把极限设为位置，再把位置设为0
buffer.flip();
// 解码，将buffer中的字节转为字符串
String data = decode(buffer);
// 如果buffer中的数据不足用户一次请求（这里就指一行）,就返回
if (data.indexOf("\r\n") == -1) {
return;
}
// 截取一行数据
String req = data.substring(0, data.indexOf("\n") + 1);
// 将字符串进行编码
ByteBuffer responseBuffer = encode("echo:" + req);
// 输出responseBuffer中的所有字节
while (responseBuffer.hasRemaining()){
socketChannel.write(responseBuffer);
}
ByteBuffer temp = encode(req);
// 把buffer的位置设置为temp的极限
buffer.position(temp.limit());
// 删除buffer中已经处理的数据
buffer.compact();
if(req.contains("bye")){
// 如果客户端发来的是bye，则退出当前会话, 失效这个key
selectionKey.cancel();
socketChannel.close();
}
}
/**
* 解码
*
* @param byteBuffer
* @return
*/
private String decode(ByteBuffer byteBuffer) {
CharBuffer decode = charset.decode(byteBuffer);
return decode.toString();
}
/**
* 编码
*/
private ByteBuffer encode(String content) {
ByteBuffer encode = charset.encode(content);
return encode;
}
}3 混合用阻塞模式与非阻塞模式
第二节，接收连接，接收数据，发送数据都是非阻塞式的，采用一个线程完成的。假如由许多客户端连接，为了提高服务的并发性能，可以考虑，把接收连接单独由一个线程完成，把接收数据和发送数据由另一个线程完成。
- 负责接收客户连接的线程按照阻塞模式工作，如果收到客户连接，就向Selector注册读就绪和写就绪事件，否则进入阻塞状态，直到接收到了客户的连接。
- 负责接收数据和发送数据的线程按照非阻塞模式工作，只有在读就绪或写就绪事件发生时，才执行相应的接收数据和发送数据操作。
package study.wyy.net.nio.server;
import lombok.extern.slf4j.Slf4j;
import java.io.IOException;
import java.net.InetSocketAddress;
import java.net.ServerSocket;
import java.nio.ByteBuffer;
import java.nio.CharBuffer;
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;
import java.util.Set;
/**
* @author wyaoyao
* @date 2021/3/18 8:50
* 混合用阻塞模式与非阻塞模式
*/
@Slf4j
public class MixEchoServer {
/**
* 委托给Selector来负责接收连接就绪事件，读就绪事件，写就绪事件
* 只要ServerSocketChannel以及SocketChannel向Selector注册了特定事件，
* Selector就会监控这些事件是否发生。
*/
private final Selector selector;
private final ServerSocketChannel serverSocketChannel;
private final ServerSocket serverSocket;
private final int port;
private final Charset charset = Charset.forName("UTF-8");
private final Object LOCK = new Object();
public MixEchoServer(int port) throws IOException {
// 创建一个Selector对象
this.selector = Selector.open();
// 创建一个ServerSocketChannel对象
serverSocketChannel = ServerSocketChannel.open();
// 返回与ServerSocketChannel关联的ServerSocket对象，
// 每个ServerSocketChannel对象都与一个ServerSocket对象关联
serverSocket = serverSocketChannel.socket();
// 使得在同一个主机上关闭了服务器，紧接着再启动服务器程序时，可以顺利绑定相同的端口
serverSocket.setReuseAddress(true);
// 负责接收客户连接的线程按照阻塞模式
serverSocketChannel.configureBlocking(true);
// 绑定本地端口
this.port = port;
serverSocketChannel.bind(new InetSocketAddress(port));
log.info("the server has bind address is {}:{}", this.serverSocket.getInetAddress().getHostAddress(), this.port);
}
/**
* 接收客户端连接
*/
public void accept() throws IOException {
// 开启一个线程处理
new Thread(() -> {
while (true) {
SocketChannel socketChannel = null;
try {
socketChannel = serverSocketChannel.accept();
// 但是接收数据和响应结果要非阻塞
socketChannel.configureBlocking(false);
// 创建一个缓冲区，用于存放客户端发来的数据
ByteBuffer byteBuffer = ByteBuffer.allocate(1024);
// SocketChannel向selector注册读就绪事件和写就绪事件
// 并把byteBuffer作为附件注册进去，在读写事件发生的时候获取byteBuffer，进行数据读写
// 需要加锁，因为这个方法时操作的selector的all-keys集合
synchronized (LOCK) {
// 防止死锁：当获取已经捕获的事件的SelectionKey的selector.select()方法会阻塞
// 如果在调用register方法的时，正好阻塞了，register也就会阻塞在这
// 所以调用wakeup唤醒selector
selector.wakeup();
socketChannel.register(selector, SelectionKey.OP_READ | SelectionKey.OP_WRITE, byteBuffer);
}
} catch (IOException e) {
e.printStackTrace();
}
log.info("accept client connection from {}:{} accept", socketChannel.socket().getInetAddress(), socketChannel.socket().getPort());
}
},
"accept").start();
}
/**
* 负责接收数据和响应结果
*
* @throws IOException
*/
public void service() throws IOException {
// 不断轮询
while (true) {
// 需要加锁，因为selector.select();这个方法时操作的selector的all-keys集合
synchronized (LOCK) {
}
int select = selector.select();
if (select == 0) {
// 如果没有捕获到事件，那就继续轮询
continue;
}
// 获取已经捕获到的事件的SelectionKey的集合
Set<SelectionKey> readyKes = selector.selectedKeys();
// 遍历readyKes，挨个处理
Iterator<SelectionKey> iterator = readyKes.iterator();
while (iterator.hasNext()) {
SelectionKey key = null;
try {
// 取出一个key
key = iterator.next();
iterator.remove();
// 判断事件类型
if (key.isReadable()) {
// 处理读就绪事件
handleReadable(key);
}
if (key.isWritable()) {
// 处理写就绪事件
handleWritable(key);
}
} catch (Exception e) {
e.printStackTrace();
if (null != null) {
// 失效掉这个key, selector不再感兴趣这个SelectionKey感兴趣的事件
key.cancel();
// 关闭与这个key关联的socketChannel
key.channel().close();
}
}
}
}
}
private void handleAcceptable(SelectionKey selectionKey) throws IOException {
// 获取与SelectionKey关联的serverSocketChannel，就是通过serverSocketChannel来传输数据的
ServerSocketChannel serverSocketChannel = (ServerSocketChannel) selectionKey.channel();
// 获取与客户端连接的SocketChannel
SocketChannel socketChannel = serverSocketChannel.accept();
log.info("accept client connection from {}:{} accept", socketChannel.socket().getInetAddress(), socketChannel.socket().getPort());
// 设置socketChannel为非阻塞
socketChannel.configureBlocking(false);
// 创建一个缓冲区，用于存放客户端发来的数据
ByteBuffer byteBuffer = ByteBuffer.allocate(1024);
// SocketChannel向selector注册读就绪事件和写就绪事件
// 并把byteBuffer作为附件注册进去，在读写事件发生的时候获取byteBuffer，进行数据读写
socketChannel.register(selector, SelectionKey.OP_READ | SelectionKey.OP_WRITE, byteBuffer);
}
private void handleReadable(SelectionKey selectionKey) throws IOException {
// 获取关联的的附件
ByteBuffer buffer = (ByteBuffer) selectionKey.attachment();
// 获取与当前SelectionKey关联的SocketChannel
SocketChannel socketChannel = (SocketChannel) selectionKey.channel();
// 创建ByteBuffer字节缓冲区，用于存放读取到的数据
ByteBuffer readBuffer = ByteBuffer.allocate(32);
socketChannel.read(readBuffer);
// flip()：把极限设为位置，再把位置设为0
readBuffer.flip();
// 把buffer的极限设置为容量
buffer.limit(buffer.capacity());
// 把readBuffer中的数据拷贝到buffer中
// 假定buffer的容量足够大，不会出现缓冲区溢出的情况
buffer.put(readBuffer);
}
private void handleWritable(SelectionKey selectionKey) throws IOException {
// 获取关联的的ByteBuffer
ByteBuffer buffer = (ByteBuffer) selectionKey.attachment();
// 获取与当前SelectionKey关联的SocketChannel
SocketChannel socketChannel = (SocketChannel) selectionKey.channel();
// flip()：把极限设为位置，再把位置设为0
buffer.flip();
// 解码，将buffer中的字节转为字符串
String data = decode(buffer);
// 如果buffer中的数据不足用户一次请求（这里就指一行）,就返回
if (data.indexOf("\r\n") == -1) {
return;
}
// 截取一行数据
String req = data.substring(0, data.indexOf("\n") + 1);
// 将字符串进行编码
ByteBuffer responseBuffer = encode("echo:" + req);
// 输出responseBuffer中的所有字节
while (responseBuffer.hasRemaining()) {
socketChannel.write(responseBuffer);
}
ByteBuffer temp = encode(req);
// 把buffer的位置设置为temp的极限
buffer.position(temp.limit());
// 删除buffer中已经处理的数据
buffer.compact();
if (req.contains("bye")) {
// 如果客户端发来的是bye，则退出当前会话, 失效这个key
selectionKey.cancel();
socketChannel.close();
}
}
private String decode(ByteBuffer byteBuffer) {
CharBuffer decode = charset.decode(byteBuffer);
return decode.toString();
}
private ByteBuffer encode(String content) {
ByteBuffer encode = charset.encode(content);
return encode;
}
}accept方法开启一个线程负责接收客户端连接，并且serverSocketChannel的accept方法为阻塞模式，所以如果没有客户端连接，serverSocketChannel的accept方法就会进入阻塞，直到接收到客户端连接，将代表客户端连接的SocketChannel设置为非阻塞模式，然后在向Selector注册读就绪和写就绪事件。
service方法负责接收数据和响应数据，在一个无限循环中，不断的调用selector.selectedKeys()方法，轮询是否有事件发生，然后做出相应处理。
死锁问题： 这里有这两个地方会进入阻塞：
- accept方法获取客户连接时候的，serverSocketChannel.accept()
- 调用selector.selectedKeys()方法，轮询是否有事件发生 这两个方法又在不同的线程中，当两个方法都进入阻塞的时候就有可能导致死锁。比如主线程在 调用selector.selectedKeys()方法，尚没有没有事件，就会进入阻塞，只有当accept方法的线程向Selector注册事件，并且有事件发生，才会返回；假如就在此时Selector没有事件，selector.selectedKeys()方法进入阻塞，同时只有当accept方法的线程正在向Selector注册事件（socketChannel.register方法）由于主线程正在selector.selectedKeys()方法中阻塞，这使得accept方法的线程也在socketChannel.register方法中阻塞，无法注册事件，这两个线程就会永远阻塞下去。为了避免死锁，当当accept方法的线程正在向Selector注册事件时候，先调用selector.wakeup()方法唤醒主线程，让主线程立刻退出selector.selectedKeys()方法。为了保证让accept方法的线程先执行socketChannel.register方法，再让主线程执行selector.selectedKeys()方法，就要加同步锁，当让accept方法的线程准备先执行socketChannel.register方法时，先获取锁，这样主线程就无法拿到锁，只能等到accept方法的线程注册完事件
另外，selector.selectedKeys()方法和socketChannel.register方法都对selector的all-keys集合这个共享资源进行操作，加同步锁也对共享资源进行了保护，没有并发问题
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