求助：看看jsp的javaBean对象跳转页面哪里出错了，代码如下

Question

十一月 10, 2016 9:16:13 下午 org.apache.catalina.core.StandardWrapperValve invoke严重: Servlet.service() for servlet jsp threw exceptionorg.apache.jasper.JasperException: file:/qq.jsp(35,5) jsp:getProperty for bean with name 'username'. Name was not previously introduced as per JSP.5.3 at org.apache.jasper.compiler.Generator$GenerateVisitor.visit(Generator.java:1099) at org.apache.jasper.compiler.Node$GetProperty.accept(Node.java:1124) at org.apache.jasper.compiler.Node$Nodes.visit(Node.java:2361) at org.apache.jasper.compiler.Node$Visitor.visitBody(Node.java:2411) at org.apache.jasper.compiler.Node$Visitor.visit(Node.java:2417) at org.apache.jasper.compiler.Node$Root.accept(Node.java:495) at org.apache.jasper.compiler.Node$Nodes.visit(Node.java:2361) at org.apache.jasper.compiler.Generator.generate(Generator.java:3459) at org.apache.jasper.compiler.Compiler.generateJava(Compiler.java:231) at org.apache.jasper.compiler.Compiler.compile(Compiler.java:354) at org.apache.jasper.compiler.Compiler.compile(Compiler.java:334) at org.apache.jasper.compiler.Compiler.compile(Compiler.java:321) at org.apache.jasper.JspCompilationContext.compile(JspCompilationContext.java:592) at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:328) at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:313) at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:260) at javax.servlet.http.HttpServlet.service(HttpServlet.java:717) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233) at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191) at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127) at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102) at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109) at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:293) at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:859) at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:602) at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:489) at java.lang.Thread.run(Thread.java:722)