paraqueryframe.java

JAVA数据库编程实例随书源码

package paraquery;
import com.borland.jbcl.layout.*;
import java.awt.*;
import java.awt.event.*;
import java.sql.*;
import javax.swing.*;

/**
   * Title:				使用参数查询数据库程序
   * Description:			教学示范
   * Copyright:				Copyright (c) 2003
   * Company:				北京师范大学计算机系
   * @author				孙一林
   * @version				1.0
   */

public class ParaQueryFrame extends JFrame {
  private JPanel contentPane;
  private XYLayout xYLayout1 = new XYLayout();// 构造XYLayout布局管理器
  // 创建显示信息用的组件
  private Label label1 = new Label();
  private TextField numberField = new TextField();
  private Button queryButton = new Button();

  Connection connection = null;                // 定义与数据库进行连接的Connection对象
  ResultSet rSet = null;                       // 定义数据库查询的结果集
  Statement statement = null;                  // 定义查询数据库的Statement对象

  public ParaQueryFrame() {
    enableEvents(AWTEvent.WINDOW_EVENT_MASK);
    try {
      jbInit();
    }
    catch(Exception e) {
      e.printStackTrace();
    }
  }

  private void jbInit() throws Exception  {
    contentPane = (JPanel) this.getContentPane();
    // 初始化组件
    label1.setText("查询学号");
    contentPane.setLayout(xYLayout1);
    this.setSize(new Dimension(400, 300));
    this.setTitle("使用参数查询数据库");
    queryButton.setLabel("查询");
    queryButton.addActionListener(new java.awt.event.ActionListener() {  // 设置queryButton按钮监听器
      public void actionPerformed(ActionEvent e) {
        queryButton_actionPerformed(e);
      }
    });
    contentPane.add(label1, new XYConstraints(72, 106, 65, 30));
    contentPane.add(numberField, new XYConstraints(154, 109, 90, 29));
    contentPane.add(queryButton, new XYConstraints(154, 186, 92, 33));
  }

  protected void processWindowEvent(WindowEvent e) {
    super.processWindowEvent(e);
    if (e.getID() == WindowEvent.WINDOW_CLOSING) {
      System.exit(0);
    }
  }

  void queryButton_actionPerformed(ActionEvent e) {           // 处理queryButton的ActionEvent
    try {
      Class.forName("sun.jdbc.odbc.JdbcOdbcDriver");          // 实例化JDBC-ODBC桥的驱动
      String url = "jdbc:odbc:TestDbStu";                     // 设置连接字符串
      connection = DriverManager.getConnection(url);          // 连接数据库
      // 创建Statement接口对象
      statement = connection.createStatement(ResultSet.TYPE_SCROLL_SENSITIVE, ResultSet.CONCUR_UPDATABLE);
      String sql = "select * from studentbase where 学号="+Integer.parseInt(numberField.getText()) ;
      rSet = statement.executeQuery(sql);                     // 执行学号为输入学号的查询语句
      if (rSet.next()==false) {                               // 判断数据库中是否有要查询学号的记录，如没有则输出提示框
        JOptionPane msg = new JOptionPane();
        JOptionPane.showMessageDialog(ParaQueryFrame.this, "数据库中没有您查询的学号", "数据库中没有您查询的学号！", 1);
      }
      else {
        rSet.previous() ;                                     // 使指针返回到ResultSet对象的开始
        ResultSetMetaData data = rSet.getMetaData();          // 定义ResultSetMetaData对象data
        numberField.setText("") ;                             // 清空学号文本框
        int col = data.getColumnCount();                      // 获取列数
        for (int i=1; i<=col; i++) {                          // 打印列名
          if (i<col) {
          System.out.print(data.getColumnName(i) + "  ");
          }
          else {
            System.out.println(data.getColumnName(i));
          }
        }
        while(rSet.next()) {                                  // 打印数据
          for (int i=1; i<=col; i++) {
            if (i<col)
            {
              System.out.print(rSet.getString(i) + "  ");
            }
            else {
              System.out.println(rSet.getString(i));
            }
          }
        }
        rSet.close();                                         // 关闭结果集
      }
    }
    catch(SQLException ex){                                   // 捕捉异常
      System.out.println("\nERROR:----- SQLException -----\n");
      while (ex != null) {
        System.out.println("Message:   " + ex.getMessage());
        System.out.println("SQLState:  " + ex.getSQLState());
        System.out.println("ErrorCode: " + ex.getErrorCode());
        ex = ex.getNextException();
      }
    }
    catch(Exception ex ) {
      ex.printStackTrace();
    }
    finally {
      try {
        if(statement != null) {
          statement.close();                                  // 关闭Statement接口实例
        }
        if(connection != null) {
          connection.close();                                 // 关闭Connection接口实例
        }
      }
      catch (SQLException ex)  {
        System.out.println("\nERROR:----- SQLException -----\n");
        System.out.println("Message:   " + ex.getMessage( ));
        System.out.println("SQLState:  " + ex.getSQLState());
        System.out.println("ErrorCode: " + ex.getErrorCode());
      }
    }
  }
}