一个通用的SQL客户程序

能够与任何关系数据库建立连接，并且交互地执行SQL命令，该客户程序能够连接任何jdbc数据源，也可以提交要执行的sqlSELECT命令和非SELECT命令。对于SELECT查询命令，显示执行结果；对于非select命令，显示执行状态。（我的电脑上只有mysql，所以只测了mysql，没有问题）

如下图所示：

代码实现：

import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.sql.*;
import javax.swing.*;
import javax.swing.border.*;


public class SQLClient extends JApplet{
    //连接数据库
    private Connection connection;
    //执行sql命令
    private Statement statement;
    //输入sql命令 的文本框
    private JTextArea jtaSQLCommand=new JTextArea();
    //显示sql命令的执行结果的文本框
    private JTextArea jtaSQLResult=new JTextArea();
    //连接数据库的JDBC相关信息，包括用户名,密码,数据库url，数据库驱动器
    JTextField jtfUserName=new JTextField();
    JPasswordField jpfPassword=new JPasswordField();
    JComboBox jcboURL=new JComboBox(new String[]{
            "jdbc:mysql://localhost/world",
            "jdbc:odbc:exampleMDBDataSource",
            "jdbc:oracle:thin:@liang.armstrong.edu:1521:orcl"
    });
    JComboBox jcboDriver = new JComboBox(new String[]{
            "com.mysql.jdbc.Driver",
            "sun.jdbc.odbc.jdbcOdbcDriver",
            "oracle.jdbc.driver.OracleDriver"
    });
    
    JButton jbtExecuteSQL =new JButton("Execute SQL Command");
    JButton jbtClearSQLCommand=new JButton("Clear");
    JButton jbtConnectDB1=new JButton("Connect to DataBase");
    JButton jbtClearSQLResult=new JButton("Clear Result");
    
    //create titled borders
    Border titledBorder1=new TitledBorder("Enter an SQL Command");
    Border titledBorder2=new TitledBorder("SQL Execute Result");
    Border titledBorder3=new TitledBorder("Enter Database Information");
    
    JLabel jlblConnectionStatus=new JLabel("No connection now");
    
    public void init(){
        JScrollPane jScrollPane1=new JScrollPane(jtaSQLCommand);
        jScrollPane1.setBorder(titledBorder1);
        JScrollPane jScrollPane2=new JScrollPane(jtaSQLResult);
        jScrollPane2.setBorder(titledBorder2);
        
        JPanel jPanel1=new JPanel(new FlowLayout(FlowLayout.RIGHT));
        jPanel1.add(jbtClearSQLCommand);
        jPanel1.add(jbtExecuteSQL);
        
        JPanel jPanel2=new JPanel();
        jPanel2.setLayout(new BorderLayout());
        jPanel2.add(jScrollPane1,BorderLayout.CENTER);
        jPanel2.add(jPanel1,BorderLayout.SOUTH);
        jPanel2.setPreferredSize(new Dimension(100,100));
        
        JPanel jPanel3=new JPanel();
        jPanel3.setLayout(new BorderLayout());
        jPanel3.add(jlblConnectionStatus,BorderLayout.CENTER);
        jPanel3.add(jbtConnectDB1,BorderLayout.EAST);
        
        JPanel jPanel4=new JPanel();
        jPanel4.setLayout(new GridLayout(4,1,10,5));
        jPanel4.add(jcboDriver);
        jPanel4.add(jcboURL);
        jPanel4.add(jtfUserName);
        jPanel4.add(jpfPassword);
        
        JPanel jPanel5=new JPanel();
        jPanel5.setLayout(new GridLayout(4,1,10,5));
        jPanel5.add(new JLabel("JDBC Driver"));
        jPanel5.add(new JLabel("Database URL"));
        jPanel5.add(new JLabel("UserName"));
        jPanel5.add(new JLabel("Password"));
        
        JPanel jPanel6 = new JPanel();
        jPanel6.setLayout(new BorderLayout());
        jPanel6.setBorder(titledBorder3);
        jPanel6.add(jPanel4,BorderLayout.CENTER);
        jPanel6.add(jPanel5,BorderLayout.WEST);
        
        JPanel jPanel7 = new JPanel();
        jPanel7.setLayout(new BorderLayout());
        jPanel7.add(jPanel3,BorderLayout.SOUTH);
        jPanel7.add(jPanel6,BorderLayout.CENTER);
        
        JPanel jPanel8 = new JPanel();
        jPanel8.setLayout(new BorderLayout());
        jPanel8.add(jPanel2,BorderLayout.CENTER);
        jPanel8.add(jPanel7,BorderLayout.WEST);
        
        JPanel jPanel9=new JPanel(new FlowLayout(FlowLayout.LEFT));
        jPanel9.add(jbtClearSQLCommand);
        
        jcboURL.setEditable(true);
        jcboDriver.setEditable(true);
        
        add(jPanel8,BorderLayout.NORTH);
        add(jScrollPane2,BorderLayout.CENTER);
        add(jPanel9,BorderLayout.SOUTH);
        //点击execute按钮执行sql语句
        jbtExecuteSQL.addActionListener(new ActionListener(){
            public void actionPerformed(ActionEvent arg0) {
                executeSQL();
            }
        });
        //连接数据库
        jbtConnectDB1.addActionListener(new ActionListener(){
            public void actionPerformed(ActionEvent e) {
                // TODO Auto-generated method stub
                connectToDB();
            }
        });
        //中兴清除命令的
        jbtClearSQLCommand.addActionListener(new ActionListener(){
            public void actionPerformed(ActionEvent e) {
                jtaSQLCommand.setText(null);
            }
        });
        
        jbtClearSQLResult.addActionListener(new ActionListener(){
            public void actionPerformed(ActionEvent e){
                jtaSQLResult.setText(null);
            }
        });
    }
    
    private void connectToDB(){
        String driver=(String)jcboDriver.getSelectedItem();
        String url=(String)jcboURL.getSelectedItem();
        String userName=jtfUserName.getText().trim();
        String password=new String(jpfPassword.getPassword());
        
        //连接数据库
        try{
            Class.forName(driver);
            connection=DriverManager.getConnection(url,userName,password);
            jlblConnectionStatus.setText("Connected to "+url);
        }catch(java.lang.Exception ex){
            ex.printStackTrace();
        }
    }
    
    private void executeSQL(){
        if(connection==null){
            jtaSQLResult.setText("Please connect to a database first");
            return;
        }else{
            String sqlCommands=jtaSQLCommand.getText().trim();
            //trim返回字符串的副本，忽略前导空白和尾部空白。
            String[] commands=sqlCommands.replace('\n', ' ').split(";");
            
            for(String aCommand: commands){
                if(aCommand.trim().toUpperCase().startsWith("SELECT")){
                    //是否以前缀SELECT开始
                    processSQLSelect(aCommand);
                }
                else{
                    processSQLNonSelect(aCommand);
                }
            }
        }
    }
//执行选择命令
    private void processSQLSelect(String sqlCommand) {
        
        try{
            statement = connection.createStatement();
            ResultSet resultSet=statement.executeQuery(sqlCommand);
            
            int columnCount=resultSet.getMetaData().getColumnCount();
            String row=" ";
            for(int i=1;i<=columnCount;++i)
                row+=resultSet.getMetaData().getColumnName(i)+"\t";
            
            jtaSQLResult.append(row+"\n");
            while(resultSet.next()){
                row=" ";
                for(int i=1;i<=columnCount;++i)
                    row+=resultSet.getString(i)+"\t";
                jtaSQLResult.append(row+'\n');
            }
        }catch(SQLException ex){
            jtaSQLResult.setText(ex.toString());
        }
    }
    //执行非选择命令
    private void processSQLNonSelect(String sqlCommand) {
        try{
            statement=connection.createStatement();
            statement.executeUpdate(sqlCommand);
            jtaSQLResult.setText("SQL command excuted");
        }catch(SQLException ex){
            jtaSQLResult.setText(ex.toString());
        }
    }
    
}