Mysql数据库 (JTree应用)

package com.databases.jtree;

import java.awt.FlowLayout;
import java.awt.GridLayout;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;
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.ArrayList;

import javax.swing.JFrame;
import javax.swing.JOptionPane;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTable;
import javax.swing.JTree;
import javax.swing.plaf.PanelUI;
import javax.swing.table.DefaultTableModel;
import javax.swing.tree.DefaultMutableTreeNode;
import javax.swing.tree.TreePath;

public class MainFrame extends JFrame {
    private Connection conn; // 数据库连接对象
    ResultSet rs;
    Statement st;
    private JTree tree;
    ArrayList<String> list = new ArrayList<>();
    private DefaultMutableTreeNode databases;
    public static JTable jtable;
    public static JScrollPane jScrollPane;

    public static JPanel p1 = new JPanel();
    public static JPanel p2 = new JPanel();
    public static JPanel p3 = new JPanel();
    
    public static void main(String[] args) throws SQLException {
        new MainFrame();
    }

    public MainFrame() throws SQLException {
        super("数据库管理");
        this.setBounds(400, 300, 780, 480);
        this.setDefaultCloseOperation(EXIT_ON_CLOSE);
        this.getContentPane().setLayout(new FlowLayout(FlowLayout.LEFT));
        databases = new DefaultMutableTreeNode("数据库管理                         ");
        tree = new JTree(databases);
        tree.setSize(600, 600);
        tree.setLocation(400, 300);

        p2.add(new JScrollPane(tree));
        p3.add(jScrollPane = new JScrollPane(jtable));
        p1.setLayout(new GridLayout(1, 2));
        p1.add(p2);
        p1.add(p3);
        this.add(p1);

        conDB("information_schema");
        String sql = "SELECT SCHEMA_NAME FROM information_schema.SCHEMATA";
        rs = st.executeQuery(sql);
        while (rs.next()) {
            System.out.println(rs.getString("SCHEMA_NAME"));
            list.add(rs.getString("SCHEMA_NAME"));
        }
        closeDB();

        for (int i = 0; i < list.size(); i++) {
            DefaultMutableTreeNode roots = new DefaultMutableTreeNode(list.get(i));
            databases.add(roots);
            conDB("information_schema");
            String sql1 = "SELECT TABLE_NAME FROM INFORMATION_SCHEMA.TABLES WHERE TABLE_SCHEMA = '" + list.get(i)
                    + "';";
            rs = st.executeQuery(sql1);
            while (rs.next()) {
                System.out.println(rs.getString("TABLE_NAME"));
                DefaultMutableTreeNode tables = new DefaultMutableTreeNode(rs.getString("TABLE_NAME"));
                roots.add(tables);
            }
            closeDB();
        }
        MouseListener ml = new MouseAdapter() {
            public void mousePressed(MouseEvent e) {
                int selRow = tree.getRowForLocation(e.getX(), e.getY());
                TreePath selPath = tree.getPathForLocation(e.getX(), e.getY());
                if (selRow != -1) {
                    if (e.getClickCount() == 1) {
                        try {
                            mySingleClick(selRow, selPath);
                        } catch (SQLException e1) {
                            e1.printStackTrace();
                        }
                        System.out.println("长度" + selPath.getPathCount());
                    }
                }
            }
        };
        
        tree.addMouseListener(ml);
        this.setVisible(true);
    }
    public void mySingleClick(int selRow, TreePath selPath) throws SQLException {
        if (selPath.getPathCount() == 3) {
            String tableName = selPath.getLastPathComponent().toString();
            String databasesName = selPath.getPathComponent(1).toString();
            conDB(databasesName);
            JTable jtable = new JTable();
            jtable= query(tableName);
            p3.removeAll();
            jScrollPane = new JScrollPane(jtable);
            p3.add(MainFrame.jScrollPane);
            p3.updateUI();
            closeDB();
        }
    }
    // 以下是连接数据库
    public void conDB(String DBName) {
        try {
            // 加载数据库驱动
            Class.forName("com.mysql.jdbc.Driver");
        } catch (ClassNotFoundException e) {
            JOptionPane.showMessageDialog(null, "数据库加载失败！");
        }
        try {
            // 连接数据库
            String url = "jdbc:mysql://localhost:3306/" + DBName + "";
            System.out.println(url);
            String user = "root";
            String passwd = "10521";
            conn = DriverManager.getConnection(url, user, passwd);
            st = conn.createStatement();
        } catch (SQLException e) {
            JOptionPane.showMessageDialog(null, "数据库连接失败！");
        }
    }

    // 以下是关闭数据库
    public void closeDB() {
        try {
            conn.close();
        } catch (SQLException e) {
            JOptionPane.showMessageDialog(null, "数据库关闭失败！");
        }
    }

    public JTable query(String table) throws SQLException {
        DefaultTableModel tablemodel = new DefaultTableModel();
        String sql = "SELECT * FROM " + table + ";";
        Statement stmt = this.conn.createStatement(); // 创建语句对象
        ResultSet rest = stmt.executeQuery(sql); // 执行数据查询SELECT语句
        ResultSetMetaData rsmd = rest.getMetaData(); // 返回表属性对象
        int count = rsmd.getColumnCount(); // 获得列数
        for (int j = 1; j <= count; j++) // 将各列名添加到表格模型作为标题，列序号>=1
            tablemodel.addColumn(rsmd.getColumnLabel(j)); // 将结果集中各行数据添加到表格模型
        Object[] columns = new Object[count]; // 创建对象数组，数组长度为列数
        while (rest.next()) // 迭代遍历结果集，从前向后访问每行
        {
            for (int j = 1; j <= columns.length; j++) // 获得每行各列值
                columns[j - 1] = rest.getString(j);
            tablemodel.addRow(columns); // 表格模型添加一行，参数指明各列值
        }
        rest.close();
        stmt.close();
        return new JTable(tablemodel);
    }
}