package db;

 import java.awt.BorderLayout;

 import java.awt.event.ActionEvent;

 import java.awt.event.ActionListener;

 import java.io.FileInputStream;

 import java.sql.Connection;

 import java.sql.DriverManager;

 import java.sql.ResultSet;

 import java.sql.ResultSetMetaData;

 import java.sql.SQLException;

 import java.sql.Statement;

 import java.util.Properties;

 import java.util.Vector;

 import javax.swing.JButton;

 import javax.swing.JFrame;

 import javax.swing.JLabel;

 import javax.swing.JPanel;

 import javax.swing.JScrollPane;

 import javax.swing.JTable;

 import javax.swing.JTextField;

 public class QueryExecutor {

     JFrame jf = new JFrame("查询执行器");

     private JScrollPane scrollPane;

     private JButton execBn = new JButton("查询");

     //用来输入查询语句的文本框

     private JTextField sqlField = new JTextField(45);

     private static Connection conn;

     private static Statement stmt;

     //用静态初始化块来初始化Connection和Statement对象

     static {

         try {

             //用Properties类加载属性文件

             Properties prop = new Properties();

             prop.load(new FileInputStream("mysql.ini"));

             String drivers = prop.getProperty("driver");

             String url = prop.getProperty("url");

             String user = prop.getProperty("user");

             String pass = prop.getProperty("pass");

             Class.forName(drivers);

             conn = DriverManager.getConnection(url, user, pass);

             stmt = conn.createStatement();

         } catch (Exception e) {

             e.printStackTrace();

         }

     }

     //初始化界面

     public void init() {

         JPanel top = new JPanel();

         top.add(new JLabel("输入查询语句"));

         top.add(sqlField);

         top.add(execBn);

         //为执行按钮，单行文本框添加事件监听器

         execBn.addActionListener(new ExceListener());

         sqlField.addActionListener(new ExceListener());

         jf.add(top, BorderLayout.NORTH);

         jf.setSize(680, 480);

         jf.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

         jf.setVisible(true);

     }

     //定义监听器

     class ExceListener implements ActionListener {

         @Override

         public void actionPerformed(ActionEvent evt) {

             //删除原来的JTable(JTable使用scrollPane来包装)

             if (scrollPane != null) {

                 jf.remove(scrollPane);

             }

             try (

                     ResultSet rs = stmt.executeQuery(sqlField.getText())) {

                 //取出ResultSet的MetaData

                 ResultSetMetaData rsmd = rs.getMetaData();

                 Vector<String> columnNames = new Vector<>();

                 Vector<Vector<String>> data = new Vector<>();

                 //把ResultSet的所有列名添加到vector里

                 for (int i = 0; i < rsmd.getColumnCount(); i++) {

                     columnNames.add(rsmd.getColumnName(i+1));

                 }

                 //把ResultSet的所有记录添加到vector里

                 while (rs.next()) {

                     Vector<String> v = new Vector<>();

                     for (int i = 0; i < rsmd.getColumnCount(); i++) {

                         v.add(rs.getString(i+1));

                     }

                     data.add(v);

                 }

                 //创建新的JTable

                 JTable table = new JTable(data, columnNames);

                 scrollPane = new JScrollPane(table);

                 //添加新的table

                 jf.add(scrollPane);

                 //更新主窗口

                 jf.validate();

             } catch (SQLException e) {

                 // TODO Auto-generated catch block

                 e.printStackTrace();

             }

         }

     }

     public static void main(String[] args) {

         new QueryExecutor().init();

     }

 }