applet调用servlet的问题

DaytimeApplet的代码如下
import java.applet.*;
import java.awt.*;
import java.io.*;
import java.net.*;
import java.rmi.*;
import java.rmi.registry.*;
import java.util.*;import com.oreilly.servlet.HttpMessage;public class DaytimeApplet extends Applet {  static final int DEFAULT_PORT = 1313;

  TextField httpText, httpObject, socketText, socketObject, RMIObject;
  Button refresh;  public void init() {
    // Construct the user interface    setLayout(new BorderLayout());    // On the left create labels for the various communication
    // mechanisms
    Panel west = new Panel();
    west.setLayout(new GridLayout(5, 1));
    west.add(new Label("HTTP text: ", Label.RIGHT));
    west.add(new Label("HTTP object: ", Label.RIGHT));
    west.add(new Label("Socket text: ", Label.RIGHT));
    west.add(new Label("Socket object: ", Label.RIGHT));
    west.add(new Label("RMI object: ", Label.RIGHT));
    add("West", west);
    // On the right create text fields to display the retrieved time values
    Panel center = new Panel();
    center.setLayout(new GridLayout(5, 1));    httpText = new TextField();
    httpText.setEditable(false);
    center.add(httpText);    httpObject = new TextField();
    httpObject.setEditable(false);
    center.add(httpObject);    socketText = new TextField();
    socketText.setEditable(false);
    center.add(socketText);    socketObject = new TextField();
    socketObject.setEditable(false);
    center.add(socketObject);    RMIObject = new TextField();
    RMIObject.setEditable(false);
    center.add(RMIObject);    add("Center", center);    // On the bottom create a button to update the times
    Panel south = new Panel();
    refresh = new Button("Refresh");
    south.add(refresh);
    add("South", south);
  }  public void start() {
    refresh();
  }  private void refresh() {
    // Fetch and display the time values
    httpText.setText(getDateUsingHttpText());
    httpObject.setText(getDateUsingHttpObject());
    socketText.setText(getDateUsingSocketText());
    socketObject.setText(getDateUsingSocketObject());
    RMIObject.setText(getDateUsingRMIObject());
  }  private String getDateUsingHttpText() {
    try {
      // Construct a URL referring to the servlet
      URL url = new URL(getCodeBase(), "/servlet/DaytimeServlet");      // Create a com.oreilly.servlet.HttpMessage to communicate with that URL
      HttpMessage msg = new HttpMessage(url);      // Send a GET message to the servlet, with no query string
      // Get the response as an InputStream
      InputStream in = msg.sendGetMessage();      // Wrap the InputStream with a DataInputStream
      DataInputStream result =
        new DataInputStream(new BufferedInputStream(in));      // Read the first line of the response, which should be
      // a string representation of the current time
      String date = result.readLine();      // Close the InputStream
      in.close();      // Return the retrieved time
      return date;
    }
    catch (Exception e) {
      // If there was a problem, print to System.out
      // (typically the Java console) and return null
      e.printStackTrace();
      return null;
    }
  }  private String getDateUsingHttpObject() {
    try {
      // Construct a URL referring to the servlet
      URL url = new URL(getCodeBase(), "/servlet/DaytimeServlet");

      // Create a com.oreilly.servlet.HttpMessage to communicate with that URL
      HttpMessage msg = new HttpMessage(url);

      // Construct a Properties list to say format=object
      Properties props = new Properties();
      props.put("format", "object");

      // Send a GET message to the servlet, passing "props" as a query string
      // Get the response as an ObjectInputStream
      InputStream in = msg.sendGetMessage(props);
      ObjectInputStream result = new ObjectInputStream(in);

      // Read the Date object from the stream
      Object obj = result.readObject();
      Date date = (Date)obj;

      // Return the string representation of the Date
      return date.toString();
    }
    catch (Exception e) {
      // If there was a problem, print to System.out
      // (typically the Java console) and return null
      e.printStackTrace();
      return null;
    }
  }  private int getSocketPort() {
    try { return Integer.parseInt(getParameter("socketPort")); }
    catch (NumberFormatException e) { return DEFAULT_PORT; }
  }

  private String getDateUsingSocketText() {
    InputStream in = null;
    try {
      // Establish a socket connection with the servlet
      Socket socket = new Socket(getCodeBase().getHost(), getSocketPort());

      // Print an empty line, indicating we want the time as plain text
      PrintStream out = new PrintStream(socket.getOutputStream());
      out.println();
      out.flush();

      // Read the first line of the response
      // It should contain the current time
      in = socket.getInputStream();
      DataInputStream result =
        new DataInputStream(new BufferedInputStream(in));
      String date = result.readLine();

      // Return the retrieved string
      return date;
    }
    catch (Exception e) {
      // If there was a problem, print to System.out
      // (typically the Java console) and return null
      e.printStackTrace();
      return null;
    }
    finally {
      // Always close the connection
      // This code executes no matter how the try block completes
      if (in != null) {
        try { in.close(); }
        catch (IOException ignored) { }
      }
    }
  }

  private String getDateUsingSocketObject() {
    InputStream in = null;
    try {
      // Establish a socket connection with the servlet
      Socket socket = new Socket(getCodeBase().getHost(), getSocketPort());

      // Print a line saying "object", indicating we want the time as
      // a serialized Date object
      PrintStream out = new PrintStream(socket.getOutputStream());
      out.println("object");
      out.flush();

      // Create an ObjectInputStream to read the response
      in = socket.getInputStream();
      ObjectInputStream result =
        new ObjectInputStream(new BufferedInputStream(in));

      // Read an object, and cast it to be a Date
      Object obj = result.readObject();
      Date date = (Date)obj;

      // Return a string representation of the retrieved Date
      return date.toString();
    }
    catch (Exception e) {
      // If there was a problem, print to System.out
      // (typically the Java console) and return null
      e.printStackTrace();
      return null;
    }
    finally {
      // Always close the connection
      // This code executes no matter how the try block completes
      if (in != null) {
        try { in.close(); }
        catch (IOException ignored) { }
      }
    }
  }  private String getRegistryHost() {
    return getCodeBase().getHost();
  }

  private int getRegistryPort() {
    try { return Integer.parseInt(getParameter("registryPort")); }
    catch (NumberFormatException e) { return Registry.REGISTRY_PORT; }
  }

  private String getRegistryName() {
    String name = getParameter("registryName");
    if (name == null) {
      name = "DaytimeServlet";  // default
    }
    return name;
  }

  private String getDateUsingRMIObject() {
    try {
      Registry registry =
        LocateRegistry.getRegistry(getRegistryHost(), getRegistryPort());
      DaytimeServer daytime =
        (DaytimeServer)registry.lookup(getRegistryName());
      return daytime.getDate().toString();
    }
    catch (ClassCastException e) {
      System.out.println("Retrieved object was not a DaytimeServer: " +
                         e.getMessage());
    }
    catch (NotBoundException e) {
      System.out.println(getRegistryName() + " not bound: " + e.getMessage());
    }
    catch (RemoteException e) {
      System.out.println("Hit remote exception: " + e.getMessage());
    }
    catch (Exception e) {
      System.out.println("Problem getting DaytimeServer reference: " +
                         e.getClass().getName() + ": " + e.getMessage());
    }
    return null;
  }  public boolean handleEvent(Event event) {
    // When the refresh button is pushed, refresh the display
    // Use JDK 1.0 events for maximum portability
    switch (event.id) {
      case Event.ACTION_EVENT:
        if (event.target == refresh) {
          refresh();
          return true;
        }
    }
    return false;
  }
}

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applet调用servlet的问题

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