Foreword
Above [from entry to abandon -SpringBoot] SpringBoot source code analysis - request process , we learned, tomcat receiving, returns the requested process is based NIO implementation. There are a lot of daily work based on the use NIO, we know NIO can improve concurrency of the system, the next series we have to learn in depth at NIO, use paper begins with a brief overview on.
NIO Overview
That NIO non-blocking (New IO), refers to the new api jdk1.4 and above in the offer.
NIO and IO biggest difference: IO is streamed processing data, NIO is a block of data handled; IO handling of the incident is blocked, is non-blocking NIO
NIO's core components:
- Channel
- Buffer
- Selector
NIO divided into standard input and output network requests
Standard input and output NIO
Read
private static void readNio() {
try {
//1、开启文件读取流
FileInputStream fileInputStream = new FileInputStream("/Users/my/Desktop/123.txt");
//2、获取fileChannel
FileChannel channel = fileInputStream.getChannel();
//3、设置ByteBuffer大小，一次能容纳capacity字节
int capacity = 9;
ByteBuffer bf = ByteBuffer.allocate(capacity);
//4、当read返回-1时，表示文件读取完毕
int length = -1;
while ((length = channel.read(bf)) != -1) {
byte[] bytes = bf.array();
System.out.println(new String(bytes, 0, length));
//4、将bf position置为0，方便下次读取
bf.clear();
}
channel.close();
fileInputStream.close();
} catch (IOException e) {
e.printStackTrace();
}
}Write
private static void writeNio() {
try {
//1、打开文件写入流
FileOutputStream fileOutputStream = new FileOutputStream("/Users/my/Desktop/123.txt");
//2、获取fileChannel
FileChannel channel = fileOutputStream.getChannel();
//3、初始化byteBuffer
String str = "萨达案发生大大sdada34;sdds'";
ByteBuffer bf = ByteBuffer.allocate(1024);
//4、将bf position置为0，方便下次读取
bf.clear();
//5、从byteBuffer的position位置填充byte
bf.put(str.getBytes());
//6、将bf position置为0，limit设置为position避免写入内容过多
bf.flip();
int length = 0;
//7、如果position小于limit即未写入完毕
while (bf.hasRemaining()) {
//8、将buffer内容写入channel
length = channel.write(bf);
System.out.println(bf);
}
channel.close();
fileOutputStream.close();
} catch (IOException e) {
e.printStackTrace();
}
}NIO network
Server
package com.my.tools.nio;
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;
public class ServerSocket {
private static ServerSocket serverSocket;
private Selector selector;
public static void main(String[] args) throws Exception {
ServerSocket.getInstance().init(8001).listen();
}
public static ServerSocket getInstance() {
if (serverSocket == null) {
synchronized (ServerSocket.class) {
if (serverSocket == null) {
serverSocket = new ServerSocket();
}
}
}
return serverSocket;
}
public ServerSocket init(int port) throws IOException {
//初始化channel
ServerSocketChannel server = ServerSocketChannel.open();
//绑定本机8001端口
server.socket().bind(new InetSocketAddress(8001));
//设置为非阻塞模式
server.configureBlocking(false);
//开启selector管理器
selector = Selector.open();
//将selector注册至server，并设置只处理accept事件
server.register(selector, SelectionKey.OP_ACCEPT);
return this;
}
public void listen() throws Exception {
System.out.println("server start");
//无限循环持续监听
while (true) {
//会阻塞 直到监听到注册的事件
selector.select();
//获取唤醒的事件
Iterator<SelectionKey> selectorKeys = selector.selectedKeys().iterator();
while (selectorKeys.hasNext()) {
SelectionKey key = selectorKeys.next();
//将已取出的SelectionKey删除，防止重复处理
selectorKeys.remove();
if (key.isAcceptable()) {
//获取到服务端的socket
ServerSocketChannel serverSocketChannel = (ServerSocketChannel) key.channel();
//获取接收到的客户端socket
SocketChannel socketChannel = serverSocketChannel.accept();
socketChannel.configureBlocking(false);
//向客户端写消息
socketChannel.write(ByteBuffer.wrap(new String("hello, this is server").getBytes()));
//注册监听read事件
socketChannel.register(selector, SelectionKey.OP_READ);
System.out.println("accept");
} else if (key.isReadable()) {
//使用selector获取channel
SocketChannel socketChannel = (SocketChannel) key.channel();
socketChannel.configureBlocking(false);
ByteBuffer buffer = ByteBuffer.allocate(1024);
//读消息
int length = socketChannel.read(buffer);
String string = new String(buffer.array(), 0 , length);
System.out.println("read:" + socketChannel + string);
//写消息
socketChannel.write(ByteBuffer.wrap(("server " + System.currentTimeMillis()).getBytes()));
Thread.sleep(10000);
}
}
}
}
}
Client
package com.my.tools.nio;
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;
public class ClientSocket {
public static ClientSocket clientSocket;
private static Selector selector;
public static void main(String[] args) throws Exception {
ClientSocket.getInstance().init("localhost", 8001).listen();
}
public static ClientSocket getInstance() {
if (clientSocket == null) {
synchronized (ClientSocket.class) {
if (clientSocket == null) {
clientSocket = new ClientSocket();
}
}
}
return clientSocket;
}
public ClientSocket init(String ip, int port) throws IOException {
SocketChannel socketChannel = SocketChannel.open();
socketChannel.connect(new InetSocketAddress(ip, port));
socketChannel.configureBlocking(false);
selector = Selector.open();
socketChannel.register(selector, SelectionKey.OP_CONNECT | SelectionKey.OP_READ);
return this;
}
public void listen() throws Exception {
System.out.println("client start");
while (true) {
selector.select();
Iterator<SelectionKey> selectionKeys = selector.selectedKeys().iterator();
while (selectionKeys.hasNext()) {
SelectionKey selectionKey = selectionKeys.next();
selectionKeys.remove();
if (selectionKey.isConnectable()) {
SocketChannel socketChannel = (SocketChannel) selectionKey.channel();
socketChannel.configureBlocking(false);
ByteBuffer buffer = ByteBuffer.wrap(new String("hello, this is client").getBytes());
socketChannel.write(buffer);
socketChannel.register(selector, SelectionKey.OP_READ);
System.out.println("client write");
} else if (selectionKey.isReadable()) {
SocketChannel socketChannel = (SocketChannel) selectionKey.channel();
socketChannel.configureBlocking(false);
ByteBuffer buffer = ByteBuffer.allocate(1024);
int length = socketChannel.read(buffer);
System.out.println("client read: " + socketChannel + new String(buffer.array(), 0, length));
socketChannel.write(ByteBuffer.wrap(("client " + System.currentTimeMillis()).getBytes()));
Thread.sleep(10000);
}
}
}
}
}
to sum up
These examples have shown the most simple file NIO NIO and network usage, the next will be in-depth analysis of the source code of each method, and performance tuning.