通过JApplet连接derby数据库

import java.awt.BorderLayout;import java.awt.Dimension;import java.awt.Font;import java.awt.event.ActionEvent;import java.awt.event.ActionListener;import java.awt.event.WindowAdapter;import java.awt.event.WindowEvent;import java.io.UnsupportedEncodingException;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 javax.swing.JApplet;import javax.swing.JButton;import javax.swing.JComboBox;import javax.swing.JFrame;import javax.swing.JLabel;import javax.swing.JOptionPane;import javax.swing.JPanel;import javax.swing.JScrollPane;import javax.swing.JTextArea;import javax.swing.JTextField;import javax.swing.SwingUtilities;public class JDBC_Applet extends JApplet{private JScrollPane jScrollPane;private JTextArea taResponse;private JPanel jPanel1,jPanel2,jPanel3,jPanel4;private JLabel jLabel3,jLabel6,jLabel7,jLabel9,jLabel10;private JTextField tfSql,tfUrl,tfUser,tfPassword;private JButton btnExecute,btnConnect,btnDisconnect;private JComboBox cbDriver;//-----------------------------------------------------------------------------------final static private String[] jdbcDriver = { "com.mysql.jdbc.Driver","com.informix.jdbc.IfxDriver", "sun.jdbc.odbc.JdbcOdbcDriver","com.borland.datastore.jdbc.DataStoreDriver","org.apache.derby.jdbc.EmbeddedDriver","com.sybase.jdbc.SybDriver", "oracle.jdbc.driver.OracleDriver","COM.ibm.db2.jdbc.net.DB2Driver", "interbase.interclient.Driver","weblogic.jdbc.mssqlserver4.Driver" };private boolean connected = false;//初始连接为假private Connection con = null;//连接对像private ResultSet rs = null;//结果private String query = null;//查询private String rsLine = null;//结果集的行private String driver = null;private String url = null;private String user = null;private String password = null;//-----------------------------------------------------------------------------------public JDBC_Applet(){Com_init();//窗体内容Post_init();//下拉菜单}public void Post_init(){//下拉菜单的内容for(int i= 0; i < jdbcDriver.length; i++){cbDriver.addItem(jdbcDriver[i]);}}private void Com_init() {jScrollPane = new JScrollPane();//面板taResponse = new JTextArea();//response:响应  文本域// 显示sql查询结果的文本区域jPanel2 = new JPanel();jPanel1 = new JPanel();jLabel6 = new JLabel();tfSql = new JTextField();// 输入sql语句的文本区域。btnExecute = new JButton();// sql执行按钮jPanel3 = new JPanel();jLabel3 = new JLabel();jPanel4 = new JPanel();cbDriver = new JComboBox();// 数据库驱动下拉框jLabel7 = new JLabel();tfUrl = new JTextField();// 连接数据库的urljLabel9 = new JLabel();tfUser = new JTextField();// 录入用户名的文本框jLabel10 = new JLabel();tfPassword = new JTextField();// 录入用户密码的文本框btnConnect = new JButton();// 连接buttonbtnDisconnect = new JButton();// 释放数据库连接的buttonsetFont(new Font("Verdana", 0, 25));// 设置字体jScrollPane.setViewportView(taResponse);getContentPane().add(jScrollPane, BorderLayout.CENTER);getContentPane().add(jPanel2, BorderLayout.EAST);jLabel6.setText("SQL:");// label Sql:jPanel1.add(jLabel6);tfSql.setPreferredSize(new Dimension(300, 21));jPanel1.add(tfSql);btnExecute.setText("执行语句");btnExecute.addActionListener(new ActionListener() {public void actionPerformed(ActionEvent evt) {btnExecuteActionPerformed(evt);}});jPanel1.add(btnExecute);// 将jPanel1放到上边getContentPane().add(jPanel1, BorderLayout.SOUTH);jPanel3.setPreferredSize(new Dimension(550, 100));jPanel3.setMinimumSize(new Dimension(550, 100));jPanel3.setMaximumSize(new Dimension(550, 100));jLabel3.setText("JDBC 驱动:");jPanel3.add(jLabel3);// label JDBC Driver:jPanel3.add(jPanel4);cbDriver.setPreferredSize(new Dimension(450, 26));cbDriver.setMinimumSize(new Dimension(100, 26));jPanel3.add(cbDriver);jLabel7.setText("数据库地址:");jPanel3.add(jLabel7);// label Database URL:tfUrl.setPreferredSize(new Dimension(450, 21));jPanel3.add(tfUrl);jLabel9.setText("用户名:");jPanel3.add(jLabel9);// label User:tfUser.setPreferredSize(new Dimension(100, 21));jPanel3.add(tfUser);jLabel10.setText("密码:");jPanel3.add(jLabel10);tfPassword.setPreferredSize(new Dimension(100, 21));jPanel3.add(tfPassword);btnConnect.setPreferredSize(new Dimension(89, 27));btnConnect.setMaximumSize(new Dimension(89, 27));btnConnect.setText("连接");btnConnect.setMinimumSize(new Dimension(89, 27));btnConnect.addActionListener(new ActionListener() {//连接按钮事件public void actionPerformed(ActionEvent evt) {btnConnectActionPerformed(evt);}});jPanel3.add(btnConnect);btnDisconnect.setText("断开");btnDisconnect.addActionListener(new ActionListener() {//断开按钮事件public void actionPerformed(ActionEvent evt) {btnDisconnectActionPerformed(evt);}});jPanel3.add(btnDisconnect);// 放在布局管理器的北边getContentPane().add(jPanel3, BorderLayout.NORTH);}//-----------------------------------------------------------------------------------private void btnConnectActionPerformed(ActionEvent be){//连接事件细节if(connected){taResponse.append("数据库已连接.\n");}else{driver = (String)cbDriver.getSelectedItem();//把下拉菜单的内容赋值给driverurl = tfUrl.getText();//用户输入数据库地址user = tfUser.getText();password = tfPassword.getText();try{SwingUtilities.invokeLater(new Runnable(){public void run(){taResponse.append("Using JDBC driver: " + driver + "\n");}});// 注册数据库驱动 通过jdbc的方式连接数据库Class.forName(driver).newInstance();//con = DriverManager.getConnection(url,user,password);con = DriverManager.getConnection(url);if(con != null){SwingUtilities.invokeLater(new Runnable(){public void run(){taResponse.append("数据库 " + url + " 已经连接.\n");}});connected = true;}}catch(ClassNotFoundException e){SwingUtilities.invokeLater(new Runnable(){public void run(){taResponse.append("不能加载驱动.\n");}});e.printStackTrace();}catch(SQLException se){SwingUtilities.invokeLater(new Runnable(){public void run(){taResponse.append("不能连接数据库.\n");}});se.printStackTrace();}catch(Exception e){e.printStackTrace();}}}//-----------------------------------------------------------------------------------private void btnDisconnectActionPerformed(ActionEvent e){//断开事件细节if(connected){try{if(con != null){con.close();con = null;SwingUtilities.invokeLater(new Runnable(){public void run(){taResponse.append("数据库断开.\n");}});}}catch(SQLException se){SwingUtilities.invokeLater(new Runnable(){public void run(){taResponse.append("数据库断开错误.\n");}});se.printStackTrace();}connected = false;driver = null;url = null;user = null;password = null;}else{SwingUtilities.invokeLater(new Runnable(){public void run(){taResponse.append("数据库已断开.\n");}});}}//-----------------------------------------------------------------------------------private void btnExecuteActionPerformed(ActionEvent evt) {//执行SQL语句处理if(!connected){//没有连接的情况SwingUtilities.invokeLater(new Runnable(){public void run(){taResponse.append("没有可连接的数据库.\n");}});}else{if(con == null){//con为空的情况SwingUtilities.invokeLater(new Runnable() {public void run() {taResponse.append("连接数据库错误.\n");}});}else{try{query = tfSql.getText();//从文本域里获得用户输入Statement stmt = con.createStatement();//创建一个声明SwingUtilities.invokeLater(new Runnable(){public void run(){taResponse.append("正在查询:" + query + "\n");}});rs = stmt.executeQuery(query);ResultSetMetaData rsmd = rs.getMetaData();//获得结果集以便更多使用方法int count = rsmd.getColumnCount();//获得列数int i;rsLine = "\n 表的结构如下：\n";for(int it = 1; it <= count; it++){rsLine += rsmd.getColumnName(it) + " ";//获得所有列名}rsLine += "\n";while(rs.next()){for(i = 1; i <= count; i++){String s;try{s = new String(rs.getString(i).getBytes("ISO-8859-1"),"GBK");rsLine += s;}catch (UnsupportedEncodingException e) {JOptionPane.showMessageDialog(null, "系统不支持的字符");}}rsLine += "\n";}rsLine += "\n";stmt.close();SwingUtilities.invokeLater(new Runnable(){public void run(){taResponse.append(rsLine);}});}catch (SQLException e) {SwingUtilities.invokeLater(new Runnable() {public void run() {taResponse.append("查询失败.\n");}});e.printStackTrace();}}}}public static void main(String[] args) {JFrame frame = new JFrame("通过JApplet连接数据库...");JDBC_Applet applet = new JDBC_Applet();frame.addWindowListener(new WindowAdapter() {public void windowClosing(WindowEvent e) {System.exit(0);}});frame.getContentPane().add(applet);applet.init();frame.setSize(400, 300);frame.setVisible(true);}}