基於Java回想之收集通訊的運用剖析。本站提示廣大學習愛好者:(基於Java回想之收集通訊的運用剖析)文章只能為提供參考,不一定能成為您想要的結果。以下是基於Java回想之收集通訊的運用剖析正文
TCP銜接
TCP的基本是Socket,在TCP銜接中,我們會應用ServerSocket和Socket,當客戶端和辦事器樹立銜接今後,剩下的根本就是對I/O的掌握了。
我們先來看一個簡略的TCP通訊,它分為客戶端和辦事器端。
客戶端代碼以下:
簡略的TCP客戶端
import java.net.*;
import java.io.*;
public class SimpleTcpClient {
public static void main(String[] args) throws IOException
{
Socket socket = null;
BufferedReader br = null;
PrintWriter pw = null;
BufferedReader brTemp = null;
try
{
socket = new Socket(InetAddress.getLocalHost(), 5678);
br = new BufferedReader(new InputStreamReader(socket.getInputStream()));
pw = new PrintWriter(socket.getOutputStream());
brTemp = new BufferedReader(new InputStreamReader(System.in));
while(true)
{
String line = brTemp.readLine();
pw.println(line);
pw.flush();
if (line.equals("end")) break;
System.out.println(br.readLine());
}
}
catch(Exception ex)
{
System.err.println(ex.getMessage());
}
finally
{
if (socket != null) socket.close();
if (br != null) br.close();
if (brTemp != null) brTemp.close();
if (pw != null) pw.close();
}
}
}
辦事器端代碼以下:
簡略版本TCP辦事器端
import java.net.*;
import java.io.*;
public class SimpleTcpServer {
public static void main(String[] args) throws IOException
{
ServerSocket server = null;
Socket client = null;
BufferedReader br = null;
PrintWriter pw = null;
try
{
server = new ServerSocket(5678);
client = server.accept();
br = new BufferedReader(new InputStreamReader(client.getInputStream()));
pw = new PrintWriter(client.getOutputStream());
while(true)
{
String line = br.readLine();
pw.println("Response:" + line);
pw.flush();
if (line.equals("end")) break;
}
}
catch(Exception ex)
{
System.err.println(ex.getMessage());
}
finally
{
if (server != null) server.close();
if (client != null) client.close();
if (br != null) br.close();
if (pw != null) pw.close();
}
}
}
這裡的辦事器的功效異常簡略,它吸收客戶端發來的新聞,然後將新聞“原封不動”的前往給客戶端。當客戶端發送“end”時,通訊停止。
下面的代碼根本上勾畫了TCP通訊進程中,客戶端和辦事器真個重要框架,我們可以發明,上述的代碼中,辦事器端在任什麼時候刻,都只能處置來自客戶真個一個要求,它是串行處置的,不克不及並行,這和我們印象裡的辦事器處置方法不太雷同,我們可認為辦事器添加多線程,當一個客戶真個要求進入後,我們就創立一個線程,來處置對應的要求。
改良後的辦事器端代碼以下:
多線程版本的TCP辦事器端
import java.net.*;
import java.io.*;
public class SmartTcpServer {
public static void main(String[] args) throws IOException
{
ServerSocket server = new ServerSocket(5678);
while(true)
{
Socket client = server.accept();
Thread thread = new ServerThread(client);
thread.start();
}
}
}
class ServerThread extends Thread
{
private Socket socket = null;
public ServerThread(Socket socket)
{
this.socket = socket;
}
public void run() {
BufferedReader br = null;
PrintWriter pw = null;
try
{
br = new BufferedReader(new InputStreamReader(socket.getInputStream()));
pw = new PrintWriter(socket.getOutputStream());
while(true)
{
String line = br.readLine();
pw.println("Response:" + line);
pw.flush();
if (line.equals("end")) break;
}
}
catch(Exception ex)
{
System.err.println(ex.getMessage());
}
finally
{
if (socket != null)
try {
socket.close();
} catch (IOException e1) {
e1.printStackTrace();
}
if (br != null)
try {
br.close();
} catch (IOException e) {
e.printStackTrace();
}
if (pw != null) pw.close();
}
}
}
修正後的辦事器端,便可以同時處置來自客戶真個多個要求了。
在編程的進程中,我們會有“資本”的概念,例如數據庫銜接就是一個典范的資本,為了晉升機能,我們平日不會直接燒毀數據庫銜接,而是應用數據庫銜接池的方法來對多個數據庫銜接停止治理,已完成重用的目標。關於Socket銜接來講,它也是一種資本,當我們的法式須要年夜量的Socket銜接時,假如每一個銜接都須要從新樹立,那末將會是一件異常沒有用率的做法。
和數據庫銜接池相似,我們也能夠設計TCP銜接池,這裡的思緒是我們用一個數組來保持多個Socket銜接,別的一個狀況數組來描寫每一個Socket銜接能否正在應用,當法式須要Socket銜接時,我們遍歷狀況數組,掏出第一個沒被應用的Socket銜接,假如一切銜接都在應用,拋出異常。這是一種很直不雅簡略的“調劑戰略”,在許多開源或許貿易的框架中(Apache/Tomcat),都邑有相似的“資本池”。
TCP銜接池的代碼以下:
一個簡略的TCP銜接池
import java.net.*;
import java.io.*;
public class TcpConnectionPool {
private InetAddress address = null;
private int port;
private Socket[] arrSockets = null;
private boolean[] arrStatus = null;
private int count;
public TcpConnectionPool(InetAddress address, int port, int count)
{
this.address = address;
this.port = port;
this .count = count;
arrSockets = new Socket[count];
arrStatus = new boolean[count];
init();
}
private void init()
{
try
{
for (int i = 0; i < count; i++)
{
arrSockets[i] = new Socket(address.getHostAddress(), port);
arrStatus[i] = false;
}
}
catch(Exception ex)
{
System.err.println(ex.getMessage());
}
}
public Socket getConnection()
{
if (arrSockets == null) init();
int i = 0;
for(i = 0; i < count; i++)
{
if (arrStatus[i] == false)
{
arrStatus[i] = true;
break;
}
}
if (i == count) throw new RuntimeException("have no connection availiable for now.");
return arrSockets[i];
}
public void releaseConnection(Socket socket)
{
if (arrSockets == null) init();
for (int i = 0; i < count; i++)
{
if (arrSockets[i] == socket)
{
arrStatus[i] = false;
break;
}
}
}
public void reBuild()
{
init();
}
public void destory()
{
if (arrSockets == null) return;
for(int i = 0; i < count; i++)
{
try
{
arrSockets[i].close();
}
catch(Exception ex)
{
System.err.println(ex.getMessage());
continue;
}
}
}
}
UDP銜接
UDP是一種和TCP分歧的銜接方法,它平日運用在對及時性請求很高,瞄准肯定請求不高的場所,例如在線視頻。UDP會有“丟包”的情形產生,在TCP中,假如Server沒有啟動,Client發新聞時,會報出異常,但對UDP來講,不會發生任何異常。
UDP通訊應用的兩個類時DatagramSocket和DatagramPacket,後者寄存了通訊的內容。
上面是一個簡略的UDP通訊例子,同TCP一樣,也分為Client和Server兩部門,Client端代碼以下:
UDP通訊客戶端
import java.net.*;
import java.io.*;
public class UdpClient {
public static void main(String[] args)
{
try
{
InetAddress host = InetAddress.getLocalHost();
int port = 5678;
BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
while(true)
{
String line = br.readLine();
byte[] message = line.getBytes();
DatagramPacket packet = new DatagramPacket(message, message.length, host, port);
DatagramSocket socket = new DatagramSocket();
socket.send(packet);
socket.close();
if (line.equals("end")) break;
}
br.close();
}
catch(Exception ex)
{
System.err.println(ex.getMessage());
}
}
}
Server端代碼以下:
UDP通訊辦事器端
import java.net.*;
import java.io.*;
public class UdpServer {
public static void main(String[] args)
{
try
{
int port = 5678;
DatagramSocket dsSocket = new DatagramSocket(port);
byte[] buffer = new byte[1024];
DatagramPacket packet = new DatagramPacket(buffer, buffer.length);
while(true)
{
dsSocket.receive(packet);
String message = new String(buffer, 0, packet.getLength());
System.out.println(packet.getAddress().getHostName() + ":" + message);
if (message.equals("end")) break;
packet.setLength(buffer.length);
}
dsSocket.close();
}
catch(Exception ex)
{
System.err.println(ex.getMessage());
}
}
}
這裡,我們也假定和TCP一樣,當Client收回“end”新聞時,以為通訊停止,但其實如許的設計不是需要的,Client端可以隨時斷開,其實不須要關懷Server端狀況。
多播(Multicast)
多播采取和UDP相似的方法,它會應用D類IP地址和尺度的UDP端標語,D類IP地址是指224.0.0.0到239.255.255.255之間的地址,不包含224.0.0.0。
多播會應用到的類是MulticastSocket,它有兩個辦法須要存眷:joinGroup和leaveGroup。
上面是一個多播的例子,Client端代碼以下:
多播通訊客戶端
import java.net.*;
import java.io.*;
public class MulticastClient {
public static void main(String[] args)
{
BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
try
{
InetAddress address = InetAddress.getByName("230.0.0.1");
int port = 5678;
while(true)
{
String line = br.readLine();
byte[] message = line.getBytes();
DatagramPacket packet = new DatagramPacket(message, message.length, address, port);
MulticastSocket multicastSocket = new MulticastSocket();
multicastSocket.send(packet);
if (line.equals("end")) break;
}
br.close();
}
catch(Exception ex)
{
System.err.println(ex.getMessage());
}
}
}
辦事器端代碼以下:
多播通訊辦事器端
import java.net.*;
import java.io.*;
public class MulticastServer {
public static void main(String[] args)
{
int port = 5678;
try
{
MulticastSocket multicastSocket = new MulticastSocket(port);
InetAddress address = InetAddress.getByName("230.0.0.1");
multicastSocket.joinGroup(address);
byte[] buffer = new byte[1024];
DatagramPacket packet = new DatagramPacket(buffer, buffer.length);
while(true)
{
multicastSocket.receive(packet);
String message = new String(buffer, packet.getLength());
System.out.println(packet.getAddress().getHostName() + ":" + message);
if (message.equals("end")) break;
packet.setLength(buffer.length);
}
multicastSocket.close();
}
catch(Exception ex)
{
System.err.println(ex.getMessage());
}
}
}
NIO(New IO)
NIO是JDK1.4引入的一套新的IO API,它在緩沖區治理、收集通訊、文件存取和字符集操作方面有了新的設計。關於收集通訊來講,NIO應用了緩沖區和通道的概念。
上面是一個NIO的例子,和我們下面提到的代碼作風有很年夜的分歧。
NIO例子
import java.io.*;
import java.nio.*;
import java.nio.channels.*;
import java.nio.charset.*;
import java.net.*;
public class NewIOSample {
public static void main(String[] args)
{
String host="127.0.0.1";
int port = 5678;
SocketChannel channel = null;
try
{
InetSocketAddress address = new InetSocketAddress(host,port);
Charset charset = Charset.forName("UTF-8");
CharsetDecoder decoder = charset.newDecoder();
CharsetEncoder encoder = charset.newEncoder();
ByteBuffer buffer = ByteBuffer.allocate(1024);
CharBuffer charBuffer = CharBuffer.allocate(1024);
channel = SocketChannel.open();
channel.connect(address);
String request = "GET / \r\n\r\n";
channel.write(encoder.encode(CharBuffer.wrap(request)));
while((channel.read(buffer)) != -1)
{
buffer.flip();
decoder.decode(buffer, charBuffer, false);
charBuffer.flip();
System.out.println(charBuffer);
buffer.clear();
charBuffer.clear();
}
}
catch(Exception ex)
{
System.err.println(ex.getMessage());
}
finally
{
if (channel != null)
try {
channel.close();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
}
上述代碼會試圖拜訪一個當地的網址,然後將其內容打印出來。