bjtapplet.java

《JAVA网络编程实例》源代码

import java.sql.*;
import java.awt.*;
import java.awt.event.*;
import java.applet.*;

/**
 * File:        bjtApplet.java  主程序
 * Title:       小型数据库查寻系统
 * Description: 查寻北京市区范围内任意两个公交车站之间的乘坐路线。
 * Copyright:   Copyright (c) 2002
 * Company:     中国科学院
 * @author      李小满
 * @version 1.0 由于教程需要，此版本仅仅提供了简单的直达和一次转乘查询。
 */

public class bjtApplet extends Applet {

  String mystat1=new String("");
  String mystat2=new String("");

  boolean isStandalone = false;
  Button button1 = new Button();
  TextField user_mystat1 = new TextField();
  TextField user_mystat2 = new TextField();
  List line_list = new List();
  Button button2 = new Button();
  Label label1 = new Label();

  /**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 bjtApplet() {
  }

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

  /**Component initialization*/
  private void jbInit() throws Exception {
    button1.setLabel("查询");
    button1.setBounds(new Rectangle(28, 206, 176, 24));
    button1.addActionListener(new java.awt.event.ActionListener() {
      public void actionPerformed(ActionEvent e) {
        button1_actionPerformed(e);
      }
    });
    this.setLayout(null);
    user_mystat1.setText("出发站");
    user_mystat1.setBounds(new Rectangle(28, 176, 116, 23));
    user_mystat2.setText("到达站");
    user_mystat2.setBounds(new Rectangle(154, 176, 121, 26));
    button2.setLabel("取消");
    button2.setBounds(new Rectangle(216, 206, 60, 24));
    button2.addActionListener(new java.awt.event.ActionListener() {
      public void actionPerformed(ActionEvent e) {
        button2_actionPerformed(e);
      }
    });
    line_list.setMultipleMode(true);
    line_list.setBounds(new Rectangle(28, 30, 243, 92));
    label1.setText("请在下面两个文本框分别填写入出发站和到达站：");
    label1.setBounds(new Rectangle(27, 151, 296, 19));
    this.add(button1, null);
    this.add(user_mystat1, null);
    this.add(user_mystat2, null);
    this.add(button2, null);
    this.add(line_list, null);
    this.add(label1, null);
  }
  /**Start the applet*/
  public void start() {
  }
  /**Stop the applet*/
  public void stop() {
  }
  /**Destroy the applet*/
  public void destroy() {
  }
  /**Get Applet information*/
  public String getAppletInfo() {
    return "Applet Information";
  }
  /**Get parameter info*/
  public String[][] getParameterInfo() {
    return null;
  }
  /**Main method*/
  public static void main(String[] args) {
    bjtApplet applet = new bjtApplet();
    applet.isStandalone = true;
    Frame frame;
    frame = new Frame() {
      protected void processWindowEvent(WindowEvent e) {
        super.processWindowEvent(e);
        if (e.getID() == WindowEvent.WINDOW_CLOSING) {
          System.exit(0);
        }
      }
      public synchronized void setTitle(String title) {
        super.setTitle(title);
        enableEvents(AWTEvent.WINDOW_EVENT_MASK);
      }
    };
    frame.setTitle("北京市区公交查寻系统");
    frame.add(applet, BorderLayout.CENTER);
    applet.init();
    applet.start();
    frame.setSize(400,320);
    Dimension d = Toolkit.getDefaultToolkit().getScreenSize();
    frame.setLocation((d.width - frame.getSize().width) / 2, (d.height - frame.getSize().height) / 2);
    frame.setVisible(true);
  }

  void button1_actionPerformed(ActionEvent e) {

  /////////////////////////////////////////////////////
  //查寻两站之间的可行乘车路线，如果存在直达线路则显示直达路线，
  //反之，则进一步提示用户寻找转乘路线。
  //////////////////////////////////////////////////////

    mystat1=user_mystat1.getText();
    mystat2=user_mystat2.getText();


    String driverName = "sun.jdbc.odbc.JdbcOdbcDriver";
    String databaseURL = "jdbc:odbc:bjtdb";
    String user = "bjtdb";
    String password = "bjtdb";

    String sqlStr="SELECT DISTINCT line FROM stat_line WHERE stat='"+mystat1+"' and line in (SELECT line FROM stat_line where stat='"+mystat2+"')";

   try {
        Class.forName (driverName);
        System.out.println ("成功加载JDBC-ODBC驱动程序！");
    }
    catch (java.lang.ClassNotFoundException ex) {
        System.out.println ("加载JDBC-ODBC驱动程序失败！");
        System.out.println (ex.getMessage ());
        return;
    }
    try {
          Connection con = DriverManager.getConnection (databaseURL, user, password);
          System.out.println ("连接bjtdb数据库成功！");
          Statement stmt = con.createStatement();
          try{
            ResultSet result = stmt.executeQuery(sqlStr);

            //初始化（清空）路线列表.
            line_list.clear();

            //判断是否得到直达路线
            if (!result.next()) {
               //没有直达路线，提示用户进行下一步查找（查寻是否可以通过转乘站到达目的站）
               step1_Frame f1=new step1_Frame("没有直达路线。点击<<下一步>>寻找转车车站。");
               f1.mystat1=this.mystat1;
               f1.mystat2=this.mystat2;
               f1.show();
            } else {
                //有直达路线，直接给出直达路线。
                line_list.clear();
                line_list.add("OK，这里是所有的可直达路线：");
                msgFrame msgframe=new msgFrame("查询到了可以直达的路线，请看“直达路线列表”。");
                msgframe.show();

                //由于前面判断语句中使用了result.next()，
                //这个函数不仅返回了一个Boolean的判断，
                //而且把结果集合指针向后移动了一个纪录。
                //所以这里先用result.getString(1)方法读出当前的记录。
                //后面的while循环将不在能读到头条记录.
                line_list.add(result.getString(1));

                //循环读出剩下的所有记录.
                while (result.next()) {
                      String returnInfo = result.getString(1);
                      line_list.add(returnInfo);
                }       // end while

            };

          }
          catch(SQLException ex){
            System.out.println ("查询数据库数据失败！");
            System.err.println("SQLException: " + ex.getMessage());
          }
          con.close();
   }
          catch(SQLException ex) {
            System.out.println ("连接bjtdb数据库失败！");
            System.err.println("SQLException: " + ex.getMessage());
            return;
   }//end try

 }//end void

  void button2_actionPerformed(ActionEvent e) {
      this.hide();
  }
}