经典的【AWT-EventQueue-0】异常问题！求解 eclipse

[小小刚]

我用的是eclipse做一个登陆界面。

Loginfrm.java文件如下：

NetConn sql;
Statement sqll;
ResultSet rs;
（省略部分代码）
sqll=sql.connect();
rs=sqll.executeQuery("SELECT * FROM users where username="+"'"+t_name.getText()+"'");


编译后代码没有问题，但是当我输入用户名和密码登陆的时候，上面那句 rs=……就报了如下的错误。

Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at Loginfrm.actionPerformed(Loginfrm.java:87)
at javax.swing.AbstractButton.fireActionPerformed(Unknown Source)
at javax.swing.AbstractButton$Handler.actionPerformed(Unknown Source)
at javax.swing.DefaultButtonModel.fireActionPerformed(Unknown Source)
at javax.swing.DefaultButtonModel.setPressed(Unknown Source)
at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(Unknown Source)
at java.awt.Component.processMouseEvent(Unknown Source)
at javax.swing.JComponent.processMouseEvent(Unknown Source)
at java.awt.Component.processEvent(Unknown Source)
at java.awt.Container.processEvent(Unknown Source)
at java.awt.Component.dispatchEventImpl(Unknown Source)
at java.awt.Container.dispatchEventImpl(Unknown Source)
at java.awt.Component.dispatchEvent(Unknown Source)
at java.awt.LightweightDispatcher.retargetMouseEvent(Unknown Source)
at java.awt.LightweightDispatcher.processMouseEvent(Unknown Source)
at java.awt.LightweightDispatcher.dispatchEvent(Unknown Source)
at java.awt.Container.dispatchEventImpl(Unknown Source)
at java.awt.Window.dispatchEventImpl(Unknown Source)
at java.awt.Component.dispatchEvent(Unknown Source)
at java.awt.EventQueue.dispatchEvent(Unknown Source)
at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.run(Unknown Source)

[小小刚]

没人收吗？这100分？

[billpu]

来了 可以结贴了

[水族杰纶]

[Quote=引用 3 楼 billpu 的回复:]
来了 可以结贴了
[/Quote]
...

[王向飞]

恭喜 这次真的可以结贴

[飘零一叶]

SELECT * FROM users where username='"+t_name.getText()+"'

这样就可以了

[abuying]

java.lang.NullPointerException
你的t_name.getText()确定没有问题吗?单步调试时的值是什么?可能为null
再把t_name.getText()转成字符串吗?t_name.getText().ToString()

rs=sqll.executeQuery("SELECT * FROM [users] where [username]='"+t_name.getText()+"'");
//如果不行,改写成like ,当然只是测试,like不可用于登录
rs=sqll.executeQuery("SELECT * FROM [users] where [username] like '%"+t_name.getText()+"%'");

[Andy__Huang]

你直接用这个语句
("SELECT * FROM users where username='xxxx'");
代替你的语句，就知道你的诗句是否有误了
xxxx为测试用代号

[dawugui]

非SQL内容,友情帮顶.