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 exception

org.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)