严重: Servlet.service() for servlet [jsp] in context with path [/Article] threw exception [An exception occurred processing [/controller/loginController.jsp] at line [15]

//初始化LoginService
            LoginService loginService = new LoginService();
            //接下来判断用户名是否存在
            User user = loginService.getUser(username);
            if(user == null){
                out.print("-2");//错误码-2 :   用户名不存在！
            }else
                //如果用户名存在，那么验证用户名和密码是否匹配
                if(!username.equals(user.getUsername()) || !password.equals(user.getPassword())){
                    out.print("-3");//错误码-3 :   用户名或密码错误！
                }else{
                    //如果能到这一步，就说明用户的确存在，而且账号密码也正确。那么就把user放在session中

Stacktrace:] with root cause
java.lang.NullPointerException
    at util.DataBaseUtils.queryForBean(DataBaseUtils.java:237)
    at service.LoginService.getUser(LoginService.java:9)
    at org.apache.jsp.controller.loginController_jsp._jspService(loginController_jsp.java:132)
    at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:741)
    at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:444)
    at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:385)
    at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:329)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:741)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
    at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:199)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96)
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:475)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:140)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:81)
    at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:651)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:87)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:342)
    at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:500)
    at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66)
    at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:754)
    at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1376)
    at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
    at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
    at java.lang.Thread.run(Thread.java:748)