sendpost.java

servlet与jsp核心编程 书籍源码 部分

import java.applet.Applet;
import java.awt.*;
import java.awt.event.*;
import java.net.*;
import java.io.*;

/** Applet that reads firstName, lastName, and
 *  emailAddress parameters and sends them via
 *  POST to the host, port, and URI specified.
 *  <P>
 *  Taken from Core Servlets and JavaServer Pages
 *  from Prentice Hall and Sun Microsystems Press,
 *  http://www.coreservlets.com/.
 *  &copy; 2000 Marty Hall; may be freely used or adapted.
 */

public class SendPost extends Applet
                      implements ActionListener {
  private LabeledTextField firstNameField, lastNameField,
                           emailAddressField, hostField,
                           portField, uriField;
  private Button sendButton;
  private TextArea resultsArea;
  URL currentPage;
  
  public void init() {
    setBackground(Color.white);
    setLayout(new BorderLayout());
    Panel inputPanel = new Panel();
    inputPanel.setLayout(new GridLayout(9, 1));
    inputPanel.setFont(new Font("Serif", Font.BOLD, 14));
    firstNameField =
      new LabeledTextField("First Name:", 15);
    inputPanel.add(firstNameField);
    lastNameField =
      new LabeledTextField("Last Name:", 15);
    inputPanel.add(lastNameField);
    emailAddressField =
      new LabeledTextField("Email Address:", 25);
    inputPanel.add(emailAddressField);
    Canvas separator1 = new Canvas();
    inputPanel.add(separator1);
    hostField =
      new LabeledTextField("Host:", 15);
    
    // Applets loaded over the network can only connect
    // to the server from which they were loaded.
    hostField.getTextField().setEditable(false);
    
    currentPage = getCodeBase();
    // getHost returns empty string for applets from local disk.
    String host = currentPage.getHost();
    String resultsMessage = "Results will be shown here...";
    if (host.length() == 0) {
      resultsMessage = "Error: you must load this applet\n" +
                       "from a real Web server via HTTP,\n" +
                       "not from the local disk using\n" +
                       "a 'file:' URL. It is fine,\n" +
                       "however, if the Web server is\n" +
                       "running on your local system.";
      setEnabled(false);
    }
    hostField.getTextField().setText(host);
    inputPanel.add(hostField);
    portField =
      new LabeledTextField("Port (-1 means default):", 4);
    String portString = String.valueOf(currentPage.getPort());
    portField.getTextField().setText(portString);
    inputPanel.add(portField);
    uriField =
      new LabeledTextField("URI:", 40);
    String defaultURI = "/servlet/coreservlets.ShowParameters";
    uriField.getTextField().setText(defaultURI);
    inputPanel.add(uriField);
    Canvas separator2 = new Canvas();
    inputPanel.add(separator2);
    sendButton = new Button("Submit Data");
    sendButton.addActionListener(this);
    Panel buttonPanel = new Panel();
    buttonPanel.add(sendButton);
    inputPanel.add(buttonPanel);
    add(inputPanel, BorderLayout.NORTH);
    resultsArea = new TextArea();
    resultsArea.setFont(new Font("Monospaced", Font.PLAIN, 14));
    resultsArea.setText(resultsMessage);
    add(resultsArea, BorderLayout.CENTER);
  }

  public void actionPerformed(ActionEvent event) {
    try {
      String protocol = currentPage.getProtocol();
      String host = hostField.getTextField().getText();
      String portString = portField.getTextField().getText();
      int port;
      try {
        port = Integer.parseInt(portString);
      } catch(NumberFormatException nfe) {
        port = -1; // I.e., default port of 80
      }
      String uri = uriField.getTextField().getText();
      URL dataURL = new URL(protocol, host, port, uri);
      URLConnection connection = dataURL.openConnection();
      
      // Make sure browser doesn't cache this URL.
      connection.setUseCaches(false);
      
      // Tell browser to allow me to send data to server.
      connection.setDoOutput(true);
      
      ByteArrayOutputStream byteStream =
        new ByteArrayOutputStream(512); // Grows if necessary
      // Stream that writes into buffer
      PrintWriter out = new PrintWriter(byteStream, true);
      String postData =
        "firstName=" + encodedValue(firstNameField) +
        "&lastName=" + encodedValue(lastNameField) +
        "&emailAddress=" + encodedValue(emailAddressField);
      
      // Write POST data into local buffer
      out.print(postData);
      out.flush(); // Flush since above used print, not println

      // POST requests are required to have Content-Length
      String lengthString =
        String.valueOf(byteStream.size());
      connection.setRequestProperty
        ("Content-Length", lengthString);
      
      // Netscape sets the Content-Type to multipart/form-data
      // by default. So, if you want to send regular form data,
      // you need to set it to
      // application/x-www-form-urlencoded, which is the
      // default for Internet Explorer. If you send
      // serialized POST data with an ObjectOutputStream,
      // the Content-Type is irrelevant, so you could
      // omit this step.
      connection.setRequestProperty
        ("Content-Type", "application/x-www-form-urlencoded");
      
      // Write POST data to real output stream
      byteStream.writeTo(connection.getOutputStream());

      BufferedReader in =
        new BufferedReader(new InputStreamReader
                             (connection.getInputStream()));
      String line;
      String linefeed = "\n";
      resultsArea.setText("");
      while((line = in.readLine()) != null) {
        resultsArea.append(line);
        resultsArea.append(linefeed);
      }
    } catch(IOException ioe) {
      // Print debug info in Java Console
      System.out.println("IOException: " + ioe);
    }
  }
  
  // LabeledTextField is really a Panel with a Label and
  // TextField inside it. This extracts the TextField part,
  // gets the text inside it, URL-encodes it, and
  // returns the result.
  
  private String encodedValue(LabeledTextField field) {
    String rawValue = field.getTextField().getText();
    return(URLEncoder.encode(rawValue));
  }
    
}