java删除mysql数据错误
java.lang.NullPointerException
at stuframe.actionPerformed(stuframe.java:87)
at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:1995)
at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2318)
at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:387)
at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:242)
at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonListener.java:236)
at java.awt.Component.processMouseEvent(Component.java:6216)
at javax.swing.JComponent.processMouseEvent(JComponent.java:3265)
at java.awt.Component.processEvent(Component.java:5981)
at java.awt.Container.processEvent(Container.java:2041)
at java.awt.Component.dispatchEventImpl(Component.java:4583)
at java.awt.Container.dispatchEventImpl(Container.java:2099)
at java.awt.Component.dispatchEvent(Component.java:4413)
at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4556)
at java.awt.LightweightDispatcher.processMouseEvent(Container.java:4220)
at java.awt.LightweightDispatcher.dispatchEvent(Container.java:4150)
at java.awt.Container.dispatchEventImpl(Container.java:2085)
at java.awt.Window.dispatchEventImpl(Window.java:2475)
at java.awt.Component.dispatchEvent(Component.java:4413)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:599)
at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:269)
at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:184)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:174)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:169)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:161)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:122)
Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at stuframe.actionPerformed(stuframe.java:97)
at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:1995)
at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2318)
at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:387)
at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:242)
at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonListener.java:236)
at java.awt.Component.processMouseEvent(Component.java:6216)
at javax.swing.JComponent.processMouseEvent(JComponent.java:3265)
at java.awt.Component.processEvent(Component.java:5981)
at java.awt.Container.processEvent(Container.java:2041)
at java.awt.Component.dispatchEventImpl(Component.java:4583)
at java.awt.Container.dispatchEventImpl(Container.java:2099)
at java.awt.Component.dispatchEvent(Component.java:4413)
at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4556)
at java.awt.LightweightDispatcher.processMouseEvent(Container.java:4220)
at java.awt.LightweightDispatcher.dispatchEvent(Container.java:4150)
at java.awt.Container.dispatchEventImpl(Container.java:2085)
at java.awt.Window.dispatchEventImpl(Window.java:2475)
at java.awt.Component.dispatchEvent(Component.java:4413)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:599)
at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:269)
at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:184)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:174)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:169)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:161)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:122)
是将数据库删除数据时的报错，请教啊。。。。。。
Connection ct = null;
PreparedStatement ps = null;
String sql = "delete from stubase where stuid='" + id + "'";
// 连接数据库,完成删除任务
try {
// 加载驱动
Class.forName("com.mysql.jdbc.Driver");
// 得到连接
ct = DriverManager.getConnection(
"jdbc:mysql://localhost:3306/studentmanagement",
"root", "lhsu");
ps = ct.prepareStatement(sql);
ps.executeUpdate();
} catch (Exception ex) {
ex.printStackTrace();
} finally {
try {
if (ps != null)
ps.close();
if (ct != null)
ps.close();
} catch (SQLException e1) {
// TODO Auto-generated catch block
e1.printStackTrace();
}
}
mytablemodel mtm = new mytablemodel(sql);
jt1.setModel(mtm);
}
[解决办法]
at stuframe.actionPerformed(stuframe.java:97)
这一行是哪行
[解决办法]
finally {
try {
if (ps != null)
ps.close();
if (ct != null)
ps.close(); // 这里不是ps，应该是ct，上面你已经把ps关闭了！
} catch (SQLException e1) {
// TODO Auto-generated catch block
e1.printStackTrace();
}
}
[解决办法]
mytablemodel mtm = new mytablemodel(sql);
jt1.setModel(mtm);
这两句是什么 ？
finally {
try {
if (ps != null)
ps.close();
if (ct != null)
ps.close();
} catch (SQLException e1) {
// TODO Auto-generated catch block
e1.printStackTrace();
}
}
finally {
if (ct!= null){
try {
ct.close();
} catch (SQLException e1) {
e1.printStackTrace();
ct = null ;
}
}
