怎么解决，java里rs赋值为null

[Ynagman]

严重: Servlet.service() for servlet [jsp] in context with path [/dear] threw exception [An exception occurred processing JSP page /validate.jsp at line 19

16: MySqlBean.OpenConn();
17: ResultSet rs=MySqlBean.executeQuery(sql);
18: while(rs.next()){
19: if((rs.getString("username").compareTo(usr)==0)
20: &&(rs.getString("password").compareTo(pwd)==0)){vaildate=true;}
21: }
22: rs.close();


Stacktrace:] with root cause
java.lang.NullPointerException
at java.lang.String.compareTo(String.java:1139)
at org.apache.jsp.validate_jsp._jspService(validate_jsp.java:88)
at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:727)
at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:432)
at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:395)
at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:339)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:727)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:303)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:220)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:122)
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:503)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:170)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:103)
at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:950)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:116)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:421)
at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1070)
at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:611)
at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:316)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
at java.lang.Thread.run(Thread.java:744)

[Ynagman]

引用 1 楼 usecf 的回复:

数据库连接不成功，检查下你连接数据库那块的代码或者配置

我debug了，能接收到密码的值，但是不能接收到用户名的值

[usecf]

数据库连接不成功，检查下你连接数据库那块的代码或者配置

[Ynagman]

可以了，谢谢各位大大

[nayi_224]

19行报错，应该是username属性为空，检查下大小写

[usecf]

密码可以的话 那你看看username属性字段大小写

[bcsflilong]

rs.getString("username").compareTo(usr)==0

改成

usr.equals(rs.getString("username"))

是不是能好点

[cc_sha_9999]

第19行写反了容易造成空指针异常，compareTo前面那个对象不能为null啊，改成usr.equals(rs.getString("username"))就可以啦