Java核心技术卷Ⅱ高级特性(原书第8版) XSL、网络

来源：互联网发布：人事考勤软件编辑：程序博客网时间：2024/05/16 10:19

XSL转换机制可以指定将XML文档转换成其他格式的规则，例如，纯文本、XHTML或其他任何XML格式。

因特网地址
InetAddress address = InnetAddress.getByName(“www.baidu.com”);
一个InetAddress 对象封装了一个4字节的序列，如132.163.2.104，可以用getAddress方法来访问这些字节。
byte[] addressBytes = address.getAddress();
InetAddress[] addresses=InetAddress.getAllByName(host);获取所有主机
InetAddress address = InetAddress.getLocalHost();获取本地主机的地址

半关闭
指套接字连接的一端可以终止其输出，同时仍可以接收来自另一端的数据。可以通过关闭一个套接字的输出流来表示发送给服务器的请求数据已经结束，但是必须保持输入流处于打开的状态。
“socket.shutdownOutput();”
三) 可中断套接字

当连接到一个套接字时，当前线程将会被阻塞知道建立连接或产生超时位置。同样地，当通过套接字读写数据时，当前线程也会被阻塞知道操作成功或产生超时为止。
在交互式的应用中，也许会考虑为用户提供一个功能，用以取消那些不会成功的连接。但是当线程因套接字长时间无法响应而发生阻塞时，无法通过调用interrupt来接触阻塞。
为了中断套接字操作，可以使用java.nio包提供的一个特性 SocketChannel 类。
例: 打开SocketChannel

SocketChannel channe = SocketChannel.open(new InetSocketAddress(host, port));

通道(Channel)并没有与之相关联的流。实际上，它所拥有的read和write方法都是通过调用buffer对象来实现的。ReadableByteChannel接口和WritableByteChannel接口都继承了Channel。
如果不想处理缓存，可以使用Scanner类来读取信息，因为Scanner有一个带有ReadableByteChannel参数的构造器:
例:Scanner(ReadableByteChannel source)构造一个新的 Scanner，它生成的值是从指定信道扫描的。

Scanner in = new Scanner(channel);

通过调用静态方法Channels.newOutputStream()，可以从通道中获取输出流。

OutputStream outStream = Channels.newOutputStream(channel);

上述操作都是必须做的，假设线程正在执行打开、读取或写入操作，此时如果线程发生中断，那么这些操作将不会陷入阻塞，而是以抛出异常的方式结束。

例：分别通过SocketChannel和InputStream读取
SocketChannel:

    messages.append("Blocking:\n");    SocketChannel channel = SocketChannel.open(            new InetSocketAddress("localhost", 8189));    try{        in = new Scanner(channel);        while(!Thread.currentThread().isInterrupted()){            if(in.hasNextLine()){                String line = in.nextLine();            }        }    }finally{        channel.close();    }

InputStream:

    Socket socket = new Socket("localhost", 8189);    try{        in = new Scanner(socket.getInputStream());        while(!Thread.currentThread().isInterrupted()){            if(in.hasNextLine()){                String line = in.nextLine();            }        }    }finally{        socket.close();    }

DEMO

import java.awt.EventQueue;

import javax.swing.JFrame;

public class InterruptibleSocketTest {
public static void main(String[] args) {
EventQueue.invokeLater(new Runnable(){
public void run(){
JFrame frame = new InterruptibleSocketFrame();
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setVisible(true);
}
});
}
}

import java.awt.BorderLayout;
import java.awt.EventQueue;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.io.IOException;
import java.io.OutputStream;
import java.io.PrintWriter;
import java.net.InetSocketAddress;
import java.net.ServerSocket;
import java.net.Socket;
import java.nio.channels.SocketChannel;
import java.util.Scanner;

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;

public class InterruptibleSocketFrame extends JFrame {

public static final int WIDTH = 300;public static final int HEIGHT = 300;private Scanner in;private JButton interruptibleButton;private JButton blockingButton;private JButton cancelButton;private JTextArea messages;private TestServer server;private Thread connectThread;public InterruptibleSocketFrame(){    setSize(WIDTH, HEIGHT);    setTitle("InterruptibleSocketTest");    JPanel northPanel = new JPanel();    add(northPanel, BorderLayout.NORTH);    messages = new JTextArea();    add(new JScrollPane(messages));    interruptibleButton = new JButton("Interruptible");    blockingButton = new JButton("Blocking");    northPanel.add(interruptibleButton);    northPanel.add(blockingButton);    interruptibleButton.addActionListener(new ActionListener(){        public void actionPerformed(ActionEvent event){            interruptibleButton.setEnabled(false);            blockingButton.setEnabled(false);            cancelButton.setEnabled(true);            connectThread = new Thread(new Runnable(){                public void run(){                    try{                        connectInterruptibly();                    }catch(Exception e){                        messages.append("\nInterruptibleSocketTest.connectInterruptible" + e);                    }                }            });            connectThread.start();        }    });    blockingButton.addActionListener(new ActionListener(){        public void actionPerformed(ActionEvent event){            interruptibleButton.setEnabled(false);            blockingButton.setEnabled(false);            cancelButton.setEnabled(true);            connectThread = new Thread(new Runnable(){                public void run(){                    try{                        connectBlocking();                    }catch(IOException e){                        e.printStackTrace();                        messages.append("\nInterruptibleSocketTest.connectInterruptible" + e);                    }                }            });            connectThread.start();        }    });    cancelButton = new JButton("Cancel");    cancelButton.setEnabled(false);    northPanel.add(cancelButton);    cancelButton.addActionListener(new ActionListener(){        public void actionPerformed(ActionEvent event){            connectThread.interrupt();            cancelButton.setEnabled(false);        }    });    server = new TestServer();    new Thread(server).start();}public void connectInterruptibly() throws IOException{    messages.append("Blocking:\n");    SocketChannel channel = SocketChannel.open(            new InetSocketAddress("localhost", 8189));    try{        in = new Scanner(channel);        while(!Thread.currentThread().isInterrupted()){            messages.append("Reading ");            if(in.hasNextLine()){                String line = in.nextLine();                messages.append(line);                messages.append("\n");            }        }    }finally{        channel.close();        EventQueue.invokeLater(new Runnable(){            public void run(){                messages.append("Channel closed\n");                interruptibleButton.setEnabled(true);                blockingButton.setEnabled(true);            }        });    }}public void connectBlocking() throws IOException{    messages.append("Blocking:\n");    Socket socket = new Socket("localhost", 8189);    try{        in = new Scanner(socket.getInputStream());        while(!Thread.currentThread().isInterrupted()){            messages.append("Reading ");            if(in.hasNextLine()){                String line = in.nextLine();                messages.append(line);                messages.append("\n");            }        }    }finally{        socket.close();        EventQueue.invokeLater(new Runnable(){            public void run(){                messages.append("Socket closed\n");                interruptibleButton.setEnabled(true);                blockingButton.setEnabled(true);            }        });    }}class TestServer implements Runnable{    public void run(){        try{            ServerSocket s = new ServerSocket(8189);            while(true){                Socket incoming = s.accept();                Runnable r = new TestServerHandler(incoming);                Thread t = new Thread(r);                t.start();            }        }catch(IOException e){            messages.append("\nTestServer.run: " + e);        }    }}class TestServerHandler implements Runnable{    private Socket incoming;    private int counter;    public TestServerHandler(Socket i){        incoming = i;    }    public void run(){        try{            OutputStream outStream = incoming.getOutputStream();            PrintWriter out = new PrintWriter(outStream, true);            while(counter<100){                counter++;                if(counter <= 10){                    out.println(counter);                }                Thread.sleep(100);                incoming.close();                messages.append("Closing server\n");            }        }catch(Exception e){            messages.append("\nTestServerHandler.run: " + e);        }    }}

}

java.net包对统一资源定位符（ uniform resource locator, URL）和统一资源标识符（uiform resource identifier,URI)作了非常有用的区分。URL是URI的一个特例，它包含了用于定位Web资源的的足够信息。在Java类库中，URI类不包含任何用于访问资源的方法，它唯一的作用就是解析。相反的是，URL类可以打开一个到达资源的流。

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