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applet中使用JDBC访问数据库
摘要: applet中使用JDBC访问数据库
最近，在这里看到了几篇关于在applet中使用JDBC访问数据库的帖子，觉得大侠们有的回复很绝对，说applet不能访问数据库，不敢苟同，于是参照Sun的网上教程"[url=http://cn.sun.com/developers/onlineTraining/Programming/BasicJava1/data.html]Java程序设计语言基础: 实践指南，第1部分[/url]"，做了一些实验，总结出来与大家分享，也请多多指教。
实验环境 DB Server #1: Solairs 8 + Oracle 8.1.7 + apache DB Server #2: Solairs 8 + Oracle 8.1.7 Client: Windows2000 SP4 + J2SE1.4.1 + Oracle JDBC Driver
实验中使用的数据表的结构 [code:1:8c94ca30e9] TABLE DBA ( TEXT varchar2(100), primary key (TEXT) ) [/code:1:8c94ca30e9]
applet的源代码 [code:1:8c94ca30e9] import java.awt.Color; import java.awt.BorderLayout; import java.awt.event.*; import java.applet.Applet; import javax.swing.*; import java.sql.*; import java.net.*; import java.io.*;
public class DbaAppl extends Applet implements ActionListener {
JLabel text, clicked; JButton button, clickButton; JTextField textField; private boolean _clickMeMode = true; private Connection c;
final static private String _driver = "oracle.jdbc.driver.OracleDriver"; final static private String _url = "jdbc:oracle:thin:username/password@(description=(address_list=(address=(protocol=tcp)(host=developer)(port=1521)))(source_route=yes)(connect_data=(sid=ansid)))";
public void init(){ setBackground(Color.white); text = new JLabel("Text to save to file:"); clicked = new JLabel("Text retrieved from file:"); button = new JButton("Click Me"); button.addActionListener(this); clickButton = new JButton("Click Again"); clickButton.addActionListener(this); textField = new JTextField(20); setLayout(new BorderLayout()); setBackground(Color.white); add(BorderLayout.NORTH, text); add(BorderLayout.CENTER, textField); add(BorderLayout.SOUTH, button); }
public void start(){ System.out.println("Applet starting."); } public void stop(){ System.out.println("Applet stopping."); }
public void destroy(){ System.out.println("Destroy method called."); }
public void actionPerformed(ActionEvent event){ try{ Class.forName (_driver); c = DriverManager.getConnection(_url); }catch (java.lang.ClassNotFoundException e){ System.out.println("Cannot find driver"); System.out.println(e.getMessage()); }catch (java.sql.SQLException e){ System.out.println("Cannot get connection"); System.out.println(e.getMessage()); }
Object source = event.getSource(); if(source == button){ if(_clickMeMode){ JTextArea displayText = new JTextArea(); try{ //Write to database String theText = textField.getText(); Statement stmt = c.createStatement(); String updateString = "INSERT INTO dba VALUES ('" + theText + "')"; int count = stmt.executeUpdate(updateString); //Read from database ResultSet results = stmt.executeQuery("SELECT TEXT FROM dba "); while(results.next()){ String s = results.getString("TEXT"); displayText.append(s + "\n"); } stmt.close(); }catch(java.sql.SQLException e){ System.out.println("Cannot create SQL statement"); System.out.println(e.getMessage()); }
//Display text read from database text.setText("Text retrieved from file:"); button.setText("Click Again"); _clickMeMode = false; //Display text read from database } else { text.setText("Text to save to file:"); textField.setText(""); button.setText("Click Me"); _clickMeMode = true; } } } } [/code:1:8c94ca30e9]
运行此applet的html文件DbaAppl.html [code:1:8c94ca30e9] <body>