displayqueryresults.java

java 数据库编程源代码

package displayqueryresults;

import java.applet.*;
import java.sql.*;
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
import java.util.*;

/**
 * Title:        显示查询数据库结果
 * Description:  Java语言演示程序：显示查询数据库结果，用于北京师范大学计算机系Java课程教学示范。
 * Copyright:    Copyright (c) 2002
 * Company:      北京师范大学计算机系
 * @author 孙一林
 * @version 1.0
 */
 public class DisplayQueryResults extends JFrame {
   private Connection connection;         // 数据库变量定义
   private Statement statement;
   private ResultSet resultSet;
   private ResultSetMetaData rsMetaData;
   private JTable table;
   private JTextArea inputQuery;
   private JButton submitQuery;
   public DisplayQueryResults() {
      super( "输入SQL语句，按查询按钮查看结果。" );      //标题
      String url = "jdbc:odbc:student";
      String username = "xiao";
      String password = "1978";
      try {
         Class.forName( "sun.jdbc.odbc.JdbcOdbcDriver" );
         connection = DriverManager.getConnection(url, username, password );
      }
      catch ( ClassNotFoundException cnfex ) {
         System.err.println( "装载 JDBC/ODBC 驱动程序失败。" );
         cnfex.printStackTrace();
         System.exit( 1 );
      }
      catch ( SQLException sqlex ) {
         System.err.println( "无法连接数据库" );
         sqlex.printStackTrace();
         System.exit( 1 );
      }
      String test="select * from test where 性别 = '女'";
      inputQuery = new JTextArea( test, 4, 30 );
      submitQuery = new JButton( "查询" );
      submitQuery.addActionListener(              // 定义Button事件
         new ActionListener() {
            public void actionPerformed( ActionEvent e )
            {
               getTable();
            }
         }
      );
      JPanel topPanel = new JPanel();             // 创建界面
      topPanel.setLayout( new BorderLayout() );
      topPanel.add( new JScrollPane( inputQuery), BorderLayout.CENTER );
      topPanel.add( submitQuery, BorderLayout.SOUTH );
      table = new JTable();
      Container c = getContentPane();
      c.setLayout( new BorderLayout() );
      c.add( topPanel, BorderLayout.NORTH );
      c.add( table, BorderLayout.CENTER );
      getTable();
      setSize( 500, 300 );
      show();                               // 显示窗口
   }
   private void getTable() {
      try {
         String query = inputQuery.getText();
         statement = connection.createStatement();
         resultSet = statement.executeQuery( query );    //执行SQL语句
         displayResultSet( resultSet );                 // 显示查询结果
      }
      catch ( SQLException sqlex ) {
         sqlex.printStackTrace();
      }
   }
   private void displayResultSet( ResultSet rs ) throws SQLException {
      boolean moreRecords = rs.next();      // 定位到第一条记录
      if ( ! moreRecords ) {                // 如果没有记录，则显示一条消息
         JOptionPane.showMessageDialog( this,"结果集中无记录" );
         setTitle( "无记录显示" );
         return;
      }
      Vector columnHeads = new Vector();    // 声明向量对象并实例化向量
      Vector rows = new Vector();
      try {
         ResultSetMetaData rsmd = rs.getMetaData();         // 获取字段的名称
         for ( int i = 1; i <= rsmd.getColumnCount(); ++i )
            columnHeads.addElement( rsmd.getColumnName( i ) );
         do {                                               // 获取记录集
            rows.addElement( getNextRow( rs, rsmd ) );
         } while ( rs.next() );
         table = new JTable( rows, columnHeads );           // 显示查询结果
         JScrollPane scroller = new JScrollPane( table );
         Container c = getContentPane();
         c.remove(1);
         c.add( scroller, BorderLayout.CENTER );
         c.validate();
      }
      catch ( SQLException sqlex ) {
         sqlex.printStackTrace();
      }
   }
   private Vector getNextRow( ResultSet rs,ResultSetMetaData rsmd ) throws SQLException{
      Vector currentRow = new Vector();
      for ( int i = 1; i <= rsmd.getColumnCount(); ++i )
         currentRow.addElement( rs.getString( i ) );
      return currentRow;      //返回一条记录
   }
   public void shutDown()  {
      try {
         connection.close();        	 //断开数据库连接
      }
      catch ( SQLException sqlex ) {
         System.err.println( "不能断开数据库连接" );
         sqlex.printStackTrace();
      }
   }
   public static void main( String args[] ) {
      final DisplayQueryResults app = new DisplayQueryResults();
      app.addWindowListener(
         new WindowAdapter() {
            public void windowClosing( WindowEvent e ) {
               app.shutDown();
               System.exit( 0 );
            }
         }
      );
   }
}