各I/O模型优缺点
- BIO通信模型
BIO主要的问题在于每当有一个新的客户端请求接入时，服务端必须创建一个新的线程处理新接入的客户端链路，一个线程只能处理一个客户端连接 - 线程池I/O编程
假如所有可用线程都被阻塞，后续I/O都将在队列中排队
线程池采用阻塞队列实现，队列积满之后，后续入队列操作将被阻塞，新的客户端请求被拒绝，发生大量连接超时 - NIO编程
- 缓冲区Buffer
每一种Java基本类型都有对一种缓冲区
大多数标准I/O使用ByteBuffer - 通道Channel
Channel分为两大类：用于网络读写的SelectableChannel和用于文件操作的FileChannel - 多路复用器Selector
多路复用器提供选择已经就绪的任务的能力
- NIO2.0 AIO
异步套接字通道不需要通过多路复用器(Selector)对注册的通道进行轮询操作即可实现异步读写
NIO实例分析
- NIO服务端序列
- 步骤一：打开ServerSocketChannel，用于监听客户端的连接
- 步骤二：绑定监听端口，设置连接为非阻塞模式
- 步骤三：创建Reactor线程，创建多路复用器并启动线程
- 步骤四：将ServerSocketChannel注册到Reactor线程的多路复用器Selector上，监听ACCEPT事件
- 步骤五：多路复用器在线程run方法的无限循环体内轮休准备就绪的Key
- 步骤六：多路复用器监听到有新的客户端接入，处理新的计入请求，完成TCP三次握手，建立物理链路
- 步骤七：设置客户端链路为非阻塞模式
- 步骤八：将新接入的客户端连接注册到Reactor线程的多路复用器上，监听读操作
- 步骤九：异步读取客户端请求消息到缓冲区
- 步骤十：对ByteBuffer进行编解码，如果有半包消息指针reset，继续读取后续的报文，将解码成功的消息封装成Task，投递到业务线程池中
- 步骤十一：将POJO对象encode成ByteBuffer，调用SocketChannel的异步write接口，将消息异步发送给客户端
- NIO客户端序列
- 步骤一：打开SocketChannel，绑定客户端本机地址
- 步骤二：设置SocketChannel为非阻塞模式，设置客户端连接的TCP参数
- 步骤三：异步连接服务器
- 步骤四：判断是否连接成功，如果连接成功，则直接注册读状态位到多路复用器中，如果当前没有连接成功
- 步骤五：向Reactor线程的多路复用器注册OP_CONNECT状态位，监听服务端的TCP ACK应答
- 步骤六：创建Reactor线程，创建多路复用器并启动线程
- 步骤七：多路复用器在线程run方法的无限循环体内轮询准备就绪的Key
- 步骤八：接收connect事件进行处理
- 步骤九：判断连接结果，如果连接成功，注册读事件到多路复用器
- 步骤十：注册读事件到多路复用器
- 步骤十一：异步读客户端请求消息到缓冲区
- 步骤十二：对ByteBuffer进行编解码，如果有半包消息接收缓冲区Reset，继续读取后续的报文，将解码成功的消息封装成Task，投递到业务线程池中，进行业务逻辑编排。
- 步骤十三：将POJO对象encode成ByteBuffer，调用SocketChannel的异步write接口，将消息异步发送给客户端
NIO实例代码
- 服务端
/**
*
* @param args
* @throws IOException
*/
public static void main(String[] args) throws IOException{
int port = 8080;
if(args != null &&args.length >0){
try{
port = Integer.valueOf(args[0]);
}catch (NumberFormatException ex){
//采用默认值
}
}
MultiplexerTimeServer timeServer = new MultiplexerTimeServer(port);
new Thread(timeServer,"NIO-MultiplexerTimeServer-001").start();
}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.util.Iterator;
import java.util.Set;
public class MultiplexerTimeServer implements Runnable {
private Selector selector;
private ServerSocketChannel serverChannel;
private volatile boolean stop;
/**
* 初始化多路复用器，绑定监听端口
* @param port
*/
public MultiplexerTimeServer(int port){
try{
selector = Selector.open();//创建多路复用器
serverChannel = ServerSocketChannel.open();
serverChannel.configureBlocking(false);//设置为异步非阻塞模式
serverChannel.socket().bind(new InetSocketAddress(port),1024);//绑定端口
serverChannel.register(selector,SelectionKey.OP_ACCEPT);//注册到Selector
System.out.println("The time server is start in port:" + port);
}catch (IOException e){
e.printStackTrace();
System.exit(1);
}
}
public void stop(){
this.stop = true;
}
public void run(){
while(!stop){
try{
selector.select(1000);//selector每隔1s都被唤醒一次
Set<SelectionKey> selectedKeys = selector.selectedKeys();
Iterator<SelectionKey> it = selectedKeys.iterator();
SelectionKey key = null;
while(it.hasNext()){
key = it.next();
it.remove();
try{
handleInput(key);
}catch (Exception e){
if(key !=null){
key.cancel();
if(key.channel() !=null)
key.channel().close();
}
}
}
}catch (Throwable t){
t.printStackTrace();
}
}
//多路复用器关闭后，所有注册在上面的Channel和Pipe等资源都会被自动去注册并关闭，所以不需要重复释放资源
if(selector != null){
try{
selector.close();
}catch (IOException e){
e.printStackTrace();
}
}
}
private void handleInput(SelectionKey key) throws IOException{
if(key.isValid()){
//处理新接入的请求消息
if(key.isAcceptable()){
//Accept the new connection
ServerSocketChannel ssc = (ServerSocketChannel)key.channel();
SocketChannel sc = ssc.accept();//接收客户端的连接请求，完成TCP三次握手
sc.configureBlocking(false);//设置为异步非阻塞
//Add the new connection to the selector
sc.register(selector,SelectionKey.OP_READ);
}
if(key.isReadable()){
//Read the data
SocketChannel sc = (SocketChannel)key.channel();
ByteBuffer readBuffer = ByteBuffer.allocate(1024);
int readBytes = sc.read(readBuffer);
if(readBytes > 0 ){
readBuffer.flip();//将缓冲区当前的limit设置为position,position设置为0
byte[] bytes = new byte[readBuffer.remaining()];
readBuffer.get(bytes);
String body = new String(bytes,"UTF-8");
System.out.println("The time server receive order :" + body);
String currentTime = "QUERY TIME ORDER".equalsIgnoreCase(body)?new java.util.Date(System.currentTimeMillis()).toString():"BAD ORDER";
doWrite(sc,currentTime);
}else if(readBytes <0){
//对端链路关闭
key.cancel();
sc.close();
}else{
//读到0字节，忽略
}
}
}
}
/**
* 将应答消息异步发送给客户端
* @param channel
* @param response
* @throws IOException
*/
private void doWrite(SocketChannel channel,String response) throws IOException{
if(response !=null && response.trim().length() >0){
byte[] bytes = response.getBytes();
ByteBuffer writeBuffer = ByteBuffer.allocate(bytes.length);
writeBuffer.put(bytes);
writeBuffer.flip();
channel.write(writeBuffer);
}
}
}- 客户端
/**
*
* @param args
* @throws IOException
*/
public static void main(String[] args) throws IOException{
int port = 8080;
if(args != null &&args.length >0){
try{
port = Integer.valueOf(args[0]);
}catch (NumberFormatException ex){
//采用默认值
}
}
new Thread(new TimeClientHandle("127.0.0.1",port),"TimeClient-001").start();
}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.SocketChannel;
import java.util.Iterator;
import java.util.Set;
public class TimeClientHandle implements Runnable{
private String host;
private int port;
private Selector selector;
private SocketChannel socketChannel;
private volatile boolean stop;
public TimeClientHandle(String host,int port){
this.host = host == null?"127.0.0.1":host;
this.port = port;
try{
selector = Selector.open();
socketChannel = SocketChannel.open();
socketChannel.configureBlocking(false);
}catch (IOException e){
e.printStackTrace();
System.exit(1);
}
}
public void run(){
try{
doConnect();
}catch (IOException e){
e.printStackTrace();
System.exit(1);
}
while(!stop){
try{
selector.select(1000);
Set<SelectionKey> selectionKeys = selector.selectedKeys();
Iterator<SelectionKey> it = selectionKeys.iterator();
SelectionKey key = null;
while(it.hasNext()){
key = it.next();
it.remove();
try{
handleInput(key);
}catch (Exception e){
if(key != null){
key.cancel();
if(key.channel() !=null)
key.channel().close();
}
}
}
}catch (Exception e){
e.printStackTrace();
System.exit(1);
}
}
if(selector !=null){
try{
selector.close();
}catch (IOException e){
e.printStackTrace();
}
}
}
private void handleInput(SelectionKey key) throws IOException{
if(key.isValid()){
//判断是否连接成功
SocketChannel sc = (SocketChannel)key.channel();
if(key.isConnectable()){
if(sc.finishConnect()){
sc.register(selector,SelectionKey.OP_READ);
doWrite(sc);
}else{
System.exit(1);//连接失败，进程退出
}
}
if(key.isReadable()) {
ByteBuffer readBuffer = ByteBuffer.allocate(1024);
int readBytes = sc.read(readBuffer);
if (readBytes > 0) {
readBuffer.flip();//将缓冲区当前的limit设置为position,position设置为0
byte[] bytes = new byte[readBuffer.remaining()];
readBuffer.get(bytes);
String body = new String(bytes, "UTF-8");
System.out.println("The time server receive order :" + body);
this.stop = true;
} else if (readBytes < 0) {
//对端链路关闭
key.cancel();
sc.close();
} else {
//读到0字节，忽略
}
}
}
}
private void doConnect() throws IOException{
if(socketChannel.connect(new InetSocketAddress(host,port))){
socketChannel.register(selector,SelectionKey.OP_READ);
doWrite(socketChannel);
}else{
socketChannel.register(selector,SelectionKey.OP_CONNECT);
}
}
private void doWrite(SocketChannel sc) throws IOException {
byte[] bytes = "QUERY TIME ORDER".getBytes();
ByteBuffer writeBuffer = ByteBuffer.allocate(bytes.length);
writeBuffer.put(bytes);
writeBuffer.flip();
sc.write(writeBuffer);
if (!writeBuffer.hasRemaining())
System.out.println("Send order 2 server succeed.");
}
}先启动服务端，再启动客户端运行实例。
NIO2.0 AIO实例代码
- 服务端
/**
*
* @param args
* @throws IOException
*/
public static void main(String[] args) throws IOException {
int port = 8080;
if(args != null &&args.length >0){
try{
port = Integer.valueOf(args[0]);
}catch (NumberFormatException ex){
//采用默认值
}
}
AsyncTimeServerHandler timeServer = new AsyncTimeServerHandler(port);
new Thread(timeServer,"AIO-AsyncTimeServerHandler-001").start();
}import java.io.IOException;
import java.net.InetSocketAddress;
import java.nio.channels.AsynchronousServerSocketChannel;
import java.util.concurrent.CountDownLatch;
public class AsyncTimeServerHandler implements Runnable {
private int port;
CountDownLatch latch;
AsynchronousServerSocketChannel asynchronousServerSocketChannel;
public AsyncTimeServerHandler(int port){
this.port = port;
try{
//创建一个异步的服务端通道
asynchronousServerSocketChannel = AsynchronousServerSocketChannel.open();
//绑定端口
asynchronousServerSocketChannel.bind(new InetSocketAddress(port));
System.out.println("The time server is start in port:"+ port);
}catch (IOException e){
e.printStackTrace();
}
}
public void run(){
latch = new CountDownLatch(1);
doAccept();
try{
latch.await();//允许当前线程阻塞，防止服务端执行完退出
}catch (InterruptedException e){
e.printStackTrace();
}
}
public void doAccept(){
//传递一个CompletionHandler实例来接收通知
asynchronousServerSocketChannel.accept(this,new AcceptCompletionHandler());
}
}import java.nio.ByteBuffer;
import java.nio.channels.AsynchronousSocketChannel;
import java.nio.channels.CompletionHandler;
public class AcceptCompletionHandler implements CompletionHandler<AsynchronousSocketChannel, AsyncTimeServerHandler> {
@Override
public void completed(AsynchronousSocketChannel result, AsyncTimeServerHandler attachment) {
//继续接收
attachment.asynchronousServerSocketChannel.accept(attachment, this);
ByteBuffer buffer = ByteBuffer.allocate(1024);
result.read(buffer, buffer, new ReadCompletionHandler(result));
}
@Override
public void failed(Throwable exc, AsyncTimeServerHandler attachment) {
exc.printStackTrace();
attachment.latch.countDown();
}
}import java.io.IOException;
import java.io.UnsupportedEncodingException;
import java.nio.ByteBuffer;
import java.nio.channels.AsynchronousSocketChannel;
import java.nio.channels.CompletionHandler;
public class ReadCompletionHandler implements CompletionHandler<Integer, ByteBuffer> {
private AsynchronousSocketChannel channel;
public ReadCompletionHandler(AsynchronousSocketChannel channel){
if(this.channel == null){
this.channel = channel;
}
}
@Override
public void completed(Integer result,ByteBuffer attachment){
attachment.flip();
byte[] body = new byte[attachment.remaining()];
attachment.get(body);
try{
String req = new String(body,"UTF-8");
System.out.println("The time server receive order:"+req);
String currentTime = "QUERY TIME ORDER".equalsIgnoreCase(req)?
new java.util.Date(System.currentTimeMillis()).toString():"BAD ORDER";
doWrite(currentTime);
}catch (UnsupportedEncodingException e){
e.printStackTrace();
}
}
private void doWrite(String currentTime){
if(currentTime !=null && currentTime.trim().length()>0){
byte[] bytes = (currentTime).getBytes();
final ByteBuffer writeBuffer = ByteBuffer.allocate(bytes.length);
writeBuffer.put(bytes);
writeBuffer.flip();
channel.write(writeBuffer, writeBuffer, new CompletionHandler<Integer, ByteBuffer>() {
@Override
public void completed(Integer result, ByteBuffer buffer) {
//如果没有发送完成，继续发送
if(buffer.hasRemaining())
channel.write(buffer,buffer,this);
}
@Override
public void failed(Throwable exc, ByteBuffer attachment) {
try{
channel.close();
}catch (IOException e){
//ingnore on close
}
}
});
}
}
public void failed(Throwable exc,ByteBuffer attachment){
try{
this.channel.close();
}catch (IOException e){
e.printStackTrace();
}
}
}- 客户端
/**
*
* @param args
* @throws IOException
*/
public static void main(String[] args) throws IOException {
int port = 8080;
if(args != null &&args.length >0){
try{
port = Integer.valueOf(args[0]);
}catch (NumberFormatException ex){
//采用默认值
}
}
new Thread(new AsyncTimeClientHandler("127.0.0.1",port),"AIO-AsyncTimeClientHandler-001").start();
}import java.io.IOException;
import java.io.UnsupportedEncodingException;
import java.net.InetSocketAddress;
import java.nio.ByteBuffer;
import java.nio.channels.AsynchronousSocketChannel;
import java.nio.channels.CompletionHandler;
import java.util.concurrent.CountDownLatch;
public class AsyncTimeClientHandler implements CompletionHandler<Void,AsyncTimeClientHandler>,Runnable {
private AsynchronousSocketChannel client;
private String host;
private int port;
private CountDownLatch latch;
public AsyncTimeClientHandler(String host,int port){
this.host = host;
this.port = port;
try{
client = AsynchronousSocketChannel.open();
}catch (IOException e){
e.printStackTrace();
}
}
@Override
public void run(){
latch = new CountDownLatch(1);
client.connect(new InetSocketAddress(host,port),this,this);
try{
latch.await();
}catch (InterruptedException el){
el.printStackTrace();
}
try{
client.close();
}catch (IOException e){
e.printStackTrace();
}
}
@Override
public void completed(Void result,AsyncTimeClientHandler attachment){
byte[] req = "QUERY TIME ORDER".getBytes();
ByteBuffer writeBuffer = ByteBuffer.allocate(req.length);
writeBuffer.put(req);
writeBuffer.flip();
client.write(writeBuffer, writeBuffer,
new CompletionHandler<Integer, ByteBuffer>() {
@Override
public void completed(Integer result, final ByteBuffer buffer) {
if(buffer.hasRemaining()){
client.write(buffer,buffer,this);
}else{
ByteBuffer readBuffer = ByteBuffer.allocate(1024);
client.read(
readBuffer,
readBuffer,
new CompletionHandler<Integer, ByteBuffer>() {
@Override
public void completed(Integer result, ByteBuffer attachment) {
attachment.flip();
byte[] bytes = new byte[attachment.remaining()];
attachment.get(bytes);
String body;
try{
body = new String(bytes,"UTF-8");
System.out.println("Now is:"+body);
latch.countDown();
}catch (UnsupportedEncodingException e){
e.printStackTrace();
}
}
@Override
public void failed(Throwable exc, ByteBuffer attachment) {
try{
client.close();
latch.countDown();
}catch (IOException e){
//ingnore on close
}
}
}
);
}
}
@Override
public void failed(Throwable exc, ByteBuffer attachment) {
try{
client.close();
latch.countDown();
}catch (IOException e){
//ingnore on close
}
}
});
}
@Override
public void failed(Throwable exc,AsyncTimeClientHandler attachment){
exc.printStackTrace();
try{
client.close();
latch.countDown();
}catch (IOException e){
e.printStackTrace();
}
}
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