1.java nio 网络编程 Server端
程序员文章站
2022-03-20 20:56:47
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最近一段时间看了下java nio，对于它的实际用途还有待继续研究，也看了网上很多人的文章博客等，收益颇多，但是还是自己动手才能知道自己是否真的会写了，会写与是否理解nio工作机制还有一定距离。我又不是一个理论派，主要还是讲究实战的，好，废话不多说，直接准备动作写。
首先你需要了解几个nio网络编程中会用到的组件(类)：
1.ByteBuffer
2.Selector
3.ServerSocketChannel
4.SocketChannel
5.SelectionKey
说一下nio server的整体实现思路：
打开Selector--》 打开ServerSocketChannel --> 配置ServerSocketChannel是否阻塞 --》 绑定ServerSocketChannel到某个主机以及端口 --》给ServerSocketChannel注册一个Selector --》 ServerSocketChannel监听accept事件 --》 客户端连接后获取SocketChannel --》 响应SocketChannel上的read/write事件
我写的可能和网络上一些人写的稍微有点不太一样，这也没办法，网络上打开10篇nio相关文章，有好几篇都是一样的，你抄我，我抄你的。个个图文并茂，个个都是架构师，分析reactor设计模式，多路复用，高性能，讲的头头是道，不过这和我没什么关系，我体会不到，应该是我太菜了。所以还是来点简单的，基础打好，总归不会有害处。
下面是具体实现代码：把这个代码拷贝到你的ide中，然后运行，用tcp连接工具，比如putty，cmd也行，不过cmd没有那么好用。有两个例子，第一个是只能少量字符传输，第二个支持大文本传输。
demo1:
package com.govert.project;
import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
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.Random;
import java.util.Set;
/**
* 少量字符传输
*/
public class NioServer {
public static void main(String[] args) throws IOException {
// read and write byte buffer
ByteBuffer rb = ByteBuffer.allocate(1024);
ByteBuffer wb = ByteBuffer.allocate(1024);
// listen hostname and port
String hostname = "127.0.0.1";
int port = 9000;
// open Selector & check
Selector selector = Selector.open();
if (selector.isOpen()) {
System.err.println("selector open success.");
}
// open ServerSocketChannel & check
ServerSocketChannel serverSocketChannel = ServerSocketChannel.open();
if (serverSocketChannel.isOpen()) {
System.err.println("serverSocketChannel open success.");
}
// ServerSocketChannel config non-block & bind hostname and port
serverSocketChannel.configureBlocking(false);
// serverSocketChannel.socket().bind(new InetSocketAddress(hostname, port));// old way bind
serverSocketChannel.bind(new InetSocketAddress(hostname, port));// 1.7+
// ServerSocketChannel register selector
serverSocketChannel.register(selector, SelectionKey.OP_ACCEPT);
// handle event loop
while (true) {
selector.select();
Set<SelectionKey> keys = selector.selectedKeys();
Iterator<SelectionKey> kit = keys.iterator();
while (kit.hasNext()) {
SelectionKey key = kit.next();
// read event
if (key.isReadable()) {
SocketChannel socketChannel = (SocketChannel) key.channel();
rb.clear();
socketChannel.read(rb);
rb.flip();
System.err.println("client request data: " + new String(rb.array(), 0, rb.limit(), "utf-8"));
//
key.interestOps(SelectionKey.OP_WRITE);
}
// write event
else if (key.isWritable()) {
SocketChannel socketChannel = (SocketChannel) key.channel();
String resp = "server response data: " + new Random().nextInt(1000) + 1 + "\r\n";
wb.clear();
wb.put(resp.getBytes("utf-8"));
wb.flip();
socketChannel.write(wb);
//
key.interestOps(SelectionKey.OP_READ);
}
// accept event
else if (key.isAcceptable()) {
SocketChannel socketChannel = serverSocketChannel.accept();
socketChannel.configureBlocking(false);
socketChannel.register(selector, SelectionKey.OP_READ);
}
}
// clear keys
keys.clear();
}
}
}
demo2:
package com.govert.project;
import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.net.InetSocketAddress;
import java.nio.ByteBuffer;
import java.nio.channels.*;
import java.util.Iterator;
import java.util.Random;
import java.util.Set;
/**
* 大文本传输
*/
public class NioServer {
public static void main(String[] args) throws IOException {
// read and write byte buffer
ByteBuffer rb = ByteBuffer.allocate(1024);
ByteBuffer wb = ByteBuffer.allocate(1024);
// listen hostname and port
String hostname = "127.0.0.1";
int port = 9000;
// open Selector & check
Selector selector = Selector.open();
if (selector.isOpen()) {
System.err.println("Selector open success.");
}
// open ServerSocketChannel & check
ServerSocketChannel serverSocketChannel = ServerSocketChannel.open();
if (serverSocketChannel.isOpen()) {
System.err.println("ServerSocketChannel open success.");
}
// ServerSocketChannel config non-block & bind hostname and port
serverSocketChannel.configureBlocking(false);
// serverSocketChannel.socket().bind(new InetSocketAddress(hostname, port));// old way bind
serverSocketChannel.bind(new InetSocketAddress(hostname, port));// 1.7+
// ServerSocketChannel register selector
serverSocketChannel.register(selector, SelectionKey.OP_ACCEPT);
// handle event loop
while (true) {
selector.select();
Set<SelectionKey> keys = selector.selectedKeys();
Iterator<SelectionKey> kit = keys.iterator();
while (kit.hasNext()) {
SelectionKey key = kit.next();
// read event
if (key.isReadable()) {
SocketChannel socketChannel = (SocketChannel) key.channel();
// large text
ByteArrayOutputStream baos = new ByteArrayOutputStream();
StringBuilder sb = new StringBuilder();
while (true) {
if (socketChannel.read(rb) < 1 && rb.hasRemaining()) break;
rb.flip();
baos.write(rb.array(), 0, rb.limit());
rb.clear();
}
//
System.err.println("client request data: " + new String(baos.toByteArray(), 0, baos.size(), "utf-8"));
//
key.interestOps(SelectionKey.OP_WRITE);
}
// write event
else if (key.isWritable()) {
SocketChannel socketChannel = (SocketChannel) key.channel();
// large response
StringBuilder sb = new StringBuilder();
for (int i = 1; i < 1001; i++) {
sb.append("server respnse data: 第" + i + "条响应结果.\r\n");
}
byte[] bytes = sb.toString().getBytes("utf-8");
int length = bytes.length;
int loop = (length + 1023) / 1024;
int lastLoop = loop - 1;
int len;
for (int i = 0; i < loop; i++) {
if (i == lastLoop) len = length - i * 1024;
else len = 1024;
wb.put(bytes, i * 1024, len);
wb.flip();
socketChannel.write(wb);
wb.clear();
}
//
key.interestOps(SelectionKey.OP_READ);
}
// accept event
else if (key.isAcceptable()) {
SocketChannel socketChannel = serverSocketChannel.accept();
socketChannel.configureBlocking(false);
socketChannel.register(selector, SelectionKey.OP_READ);
}
}
// clear keys
keys.clear();
}
}
}