sendapplet.java

java网络高级编程的配套源码,java网络高级编程为清华出版社出版.

/*程序清单5-19*/

import java.awt.*;
import java.awt.event.*;
import java.applet.*;
import javax.swing.*;
import com.borland.jbcl.layout.*;
import java.io.*;
import java.net.*;

public class SendApplet extends JApplet
{
  boolean isStandalone = false;
  //用于提醒用户输入
  Label sendLabel = new Label();
  XYLayout xYLayout1 = new XYLayout();
  //用于返回用户输入
  Label messageInfo = new Label();
  //用于发送用户的输入信息
  Button sendButton = new Button();
  TextField sendText = new TextField();
  TextField messageText = new TextField();
  //用于与Servlet连接
  URLConnection connect;
  //用于保存用户的输入信息
  String message;
  URL chatURL;

  /**Get a parameter value*/
  public String getParameter(String key, String def)
  {
    return isStandalone ? System.getProperty(key, def) :
      (getParameter(key) != null ? getParameter(key) : def);
  }

  /**Construct the applet*/
  public SendApplet()
  {
  }

  /**Initialize the applet*/
  public void init()
  {
    try
    {
      jbInit();
    }
    catch(Exception e)
    {
      e.printStackTrace();
    }
  }

  /**Component initialization*/
  private void jbInit() throws Exception
  {
    sendLabel.setText("请输入信息：");
    this.getContentPane().setLayout(xYLayout1);
    messageInfo.setText("您输入的信息是：");
    sendButton.setLabel("发送");
    sendButton.addActionListener(new java.awt.event.ActionListener() {
      public void actionPerformed(ActionEvent e) {
        sendButton_actionPerformed(e);
      }
    });
    messageText.setEditable(false);
    xYLayout1.setWidth(400);
    xYLayout1.setHeight(129);
    sendText.addActionListener(new java.awt.event.ActionListener() {
      public void actionPerformed(ActionEvent e) {
        sendText_actionPerformed(e);
      }
    });
    this.getContentPane().add(sendLabel, new XYConstraints(0, 0, 400, -1));
    this.getContentPane().add(messageInfo, new XYConstraints(9, 58, 388, 19));
    this.getContentPane().add(sendText, new XYConstraints(6, 24, 205, -1));
    this.getContentPane().add(sendButton, new XYConstraints(210, 24, 187, 22));
    this.getContentPane().add(messageText, new XYConstraints(5, 89, 400, -1));
    chatURL = getCodeBase();
  }

  /**Get Applet information*/
  public String getAppletInfo()
  {
    return "Applet Information";
  }

  /**Get parameter info*/
  public String[][] getParameterInfo()
  {
    return null;
  }

  public synchronized void start()
  {
  }

  public synchronized void stop()
  {
  }

  public synchronized void destroy()
  {
  }

  //方法Send把用户在Applet中输入的字符串送给Servlet
  //然后将Servlet的处理结果显示
  void Send()
  {
    message = sendText.getText();
    //清除用户的输入信息
    sendText.setText("");
    showStatus("Message sent!");
    //把输入的字符转化为x-www-form-urlencode格式
    String queryString = "servlet/ReceiveServlet?message=" + URLEncoder.encode(message);
    //建立与Servlet的连接，并取得Servlet的输出信息
    try
    {
	connect = (new URL(chatURL,queryString)).openConnection();
	showStatus("Open Connection!");
	//下次连接不用Cache
	connect.setDefaultUseCaches(false);
	//这次连接不用Cache
	connect.setUseCaches(false);
	//打开的流用于读取数据
	connect.setDoInput(true);
	//不能用于些数据
	connect.setDoOutput(false);
	//服务器与客户的连接
	connect.connect();
	showStatus("打开流！");
	DataInputStream in = new DataInputStream(connect.getInputStream());
	showStatus("读数据！");
	message = in.readLine();
	//接收Servlet的输出信息
	while (message!=null)
	{
  	  messageText.setText(message);
	  message = in.readLine();
	}
    }
    catch (MalformedURLException e2)
    {
      System.err.println("MalformedURLException!");
      e2.printStackTrace(System.err);
      showStatus("MalformedURLException!");
    }
    catch (IOException e1)
    {
      System.err.println("IOException!");
      e1.printStackTrace(System.err);
      showStatus("IOException!");
    }
   }

  void sendButton_actionPerformed(ActionEvent e)
  {
    Send();
  }

  void sendText_actionPerformed(ActionEvent e)
  {
    Send();
  }
}