viewremotefile.java

此源码为机械工业出版社出版的《Java语言程序设计》第三版所配套的书中所有源代码。

// ViewRemoteFile.java: Retrieve remote files
import java.awt.*;
import java.awt.event.*;
import java.io.*;
import java.net.*;
import javax.swing.*;

public class ViewRemoteFile extends JApplet
  implements ActionListener
{
  // Button to view the file
  private JButton jbtView = new JButton("View");

  // Text field to receive file name
  private JTextField jtfURL = new JTextField(12);

  // Text area to store file
  private JTextArea jtaFile = new JTextArea();

  // Label to display status
  private JLabel jlblStatus = new JLabel();

  // Initialize the applet
  public void init()
  {
    // Create a panel to hold a label, a text field, and a button
    Panel p1 = new Panel();
    p1.setLayout(new BorderLayout());
    p1.add(new JLabel("Filename"), BorderLayout.WEST);
    p1.add(jtfURL, BorderLayout.CENTER);
    p1.add(jbtView, BorderLayout.EAST);

    // Place text area and panel p to the applet
    getContentPane().setLayout(new BorderLayout());
    getContentPane().add(new JScrollPane(jtaFile),
      BorderLayout.CENTER);
    getContentPane().add(p1, BorderLayout.NORTH);
    getContentPane().add(jlblStatus, BorderLayout.SOUTH);

    // Register listener
    jbtView.addActionListener(this);
  }

  // Handle the "View" button
  public void actionPerformed(ActionEvent e)
  {
    if (e.getSource() == jbtView)
      showFile();
  }

  private void showFile()
  {
    // Declare buffered stream
    BufferedReader infile = null;

    // Get file name from the text field
    String inLine;

    URL url = null;

    try
    {
      // Sample URL
      String urlString =
        "http://www.geocities.com/liangjava/index.html";
        //"file:/C:\\Book\\ViewRemoteFile.java";
        //"http://www.geocities.com/liangjava/introjava" + filename;

      urlString = jtfURL.getText().trim();
      url = new URL(urlString);
      InputStream is = url.openStream();

      // Create a buffered stream
      infile = new BufferedReader(new InputStreamReader(is));

      // Read a line and append the line to the text area
      while ((inLine = infile.readLine()) != null)
      {
        jtaFile.append(inLine + '\n');
      }

      jlblStatus.setText("File loaded successfully");
    }
    catch (FileNotFoundException e)
    {
      jlblStatus.setText("URL not found: " + url);
    }
    catch (IOException e)
    {
      jlblStatus.setText(e.getMessage());
    }
    finally
    {
      try
      {
        if (infile != null) infile.close();
      }
      catch (IOException e) {}
    }
  }

  // Main method
  public static void main(String[] args)
  {
    // Create a frame
    JFrame frame = new JFrame("View File From a Web Server");

    // Create an instance of MortgageApplet
    ViewRemoteFile applet = new ViewRemoteFile();

    // Add the applet instance to the frame
    frame.getContentPane().add(applet, BorderLayout.CENTER);

    // Invoke init() and start()
    applet.init();
    applet.start();

    // Display the frame
    frame.setSize(300, 300);
    frame.setVisible(true);
  }
}