带有JDBC的Applet – java.security.AccessControlException：访问被拒绝

//JDBC using Applet /*   */ import javax.swing.*; //JApplet,JLabel,JButton import java.applet.*; //Applet import java.awt.*; //Layout import java.awt.event.*; //Events import java.sql.*; //JDBC public class JDBC1 extends Applet implements Runnable,ActionListener { JFrame frame ; JPanel panel1; JLabel lblNo,lblName,lblBdate ; JTextField txtNo,txtName,txtBdate; JButton btn; Statement st1; Connection cn; ResultSet rs; public JDBC1() { try { panel1 = new JPanel (); panel1.setLayout(new GridLayout(0,2)); lblNo = new JLabel ("Roll No : "); panel1.add(lblNo); txtNo = new JTextField(15); panel1.add(txtNo); lblName = new JLabel ("Name : "); panel1.add(lblName); txtName = new JTextField(15); panel1.add(txtName); lblBdate = new JLabel ("Birth Date : "); panel1.add(lblBdate); txtBdate = new JTextField(15); panel1.add(txtBdate); //Add textarea to the panel. add(panel1); //Add panel to the aaplet. btn = new JButton ("First"); add(btn); //Add button to the applet. btn.addActionListener(this); btn = new JButton ("Next"); add(btn); btn.addActionListener(this); btn = new JButton ("Last"); add(btn); btn.addActionListener(this); btn = new JButton ("Prev"); add(btn); btn.addActionListener(this); btn = new JButton ("Save"); add(btn); btn.addActionListener(this); btn = new JButton ("Reset"); add(btn); btn.addActionListener(this); btn = new JButton ("Delete"); add(btn); btn.addActionListener(this); btn = new JButton ("Update"); add(btn); btn.addActionListener(this); Class.forName("sun.jdbc.odbc.JdbcOdbcDriver"); //Load the JDBC-ODBC bridge driver cn = DriverManager.getConnection("jdbc:odbc:STUDENT_MYDSN"); // conection to databse st1 = cn.createStatement(ResultSet.TYPE_SCROLL_SENSITIVE,ResultSet.CONCUR_UPDATABLE); String query = "select * from Student"; rs = st1.executeQuery(query); } catch (Exception e) { e.printStackTrace(); } } public void init() { try { Thread th = new Thread (this); th.start(); } catch(Exception ex) { System.out.println(ex.toString()); } } public void run () { try { while(true) { JDBC1 my = new JDBC1(); repaint(); Thread.sleep(1000); } } catch(Exception ex) { System.out.println(ex.toString()); } } public void paint (Graphics g) { super.paint(g); java.util.Date dt = new java.util.Date(); String myDate = dt+""; g.drawString(myDate,100,150); } void getRecord() { try { txtNo.setText((String) rs.getObject(1)); } catch (Exception e) { System.out.println(e.toString()); } } public void actionPerformed(ActionEvent e) { try { String name = ((JButton) e.getSource()).getText(); if (name == "First") { System.out.println("First"); } if (name == "Prev") { System.out.println("Prev"); } if (name == "Next") { System.out.println("Next"); } if (name == "Last") { System.out.println("First"); } if (name == "Save") { System.out.println("First"); } if (name == "Delete") { System.out.println("First"); } if (name == "Update") { System.out.println("First"); } if (name == "Reset") { System.out.println("First"); } } catch (Exception ex) { System.out.println(ex.toString()); ex.printStackTrace(); } } } 

通过将此Applet与JDBC一起使用，我将得到以下错误

 java.security.AccessControlException: access denied ("java.util.PropertyPermission" "file.encoding" at java.security.AccessControlContext.checkPermission(AccessControlContext.java:366) at java.security.AccessController.checkPermission(AccessController.java:560) at java.lang.SecurityManager.checkPermission(SecurityManager.java:549) at java.lang.SecurityManager.checkPropertyAccess(SecurityManager.java:1302) at java.lang.System.getProperty(System.java:706) at sun.jdbc.odbc.JdbcOdbcConnection.initialize(JdbcOdbcConnection.java:142) at sun.jdbc.odbc.JdbcOdbcDriver.connect(JdbcOdbcDriver.java:174) at java.sql.DriverManager.getConnection(DriverManager.java:579) at java.sql.DriverManager.getConnection(DriverManager.java:243) at JDBC1.(JDBC1.java:87) at JDBC1.run(JDBC1.java:123) at java.lang.Thread.run(Thread.java:722) 

Answer 1

如果不采取措施为applet提供适当的权限，您将无法在applet中运行JDBC。 Oracle的本教程详细介绍了该主题。

Answer 2

您将无法从（不受信任的）applet访问ODBC驱动程序，就像您无法读取本地文件系统一样。

有“纯Java”JDBC驱动程序只需要套接字权限。 如果数据库服务器通过与提供applet的Web服务器相同的源（“同源策略”）可用（并且没有任何干扰网络），这将起作用。

但是，通过网络向最终用户公开数据库可能是个坏主意。 通常，您将通过Web服务器公开安全接口。 此外，如果通过网络加载applet，则您不太可能想要选择本地配置的数据库。

（与表达问题的最小完整程序相比，问题中的代码似乎非常长，但我可以继续批评代码。）