JSP中使用JavaBeans时出错

type Exception report

message

description The server encountered an internal error () that prevented it from fulfilling this request.

exception

org.apache.jasper.JasperException: /tt/next.jsp(2,0) The value for the useBean class attribute User is invalid.
	org.apache.jasper.compiler.DefaultErrorHandler.jspError(DefaultErrorHandler.java:39)
	org.apache.jasper.compiler.ErrorDispatcher.dispatch(ErrorDispatcher.java:409)
	org.apache.jasper.compiler.ErrorDispatcher.jspError(ErrorDispatcher.java:150)
	org.apache.jasper.compiler.Generator$GenerateVisitor.visit(Generator.java:1227)
	org.apache.jasper.compiler.Node$UseBean.accept(Node.java:1116)
	org.apache.jasper.compiler.Node$Nodes.visit(Node.java:2163)
	org.apache.jasper.compiler.Node$Visitor.visitBody(Node.java:2213)
	org.apache.jasper.compiler.Node$Visitor.visit(Node.java:2219)
	org.apache.jasper.compiler.Node$Root.accept(Node.java:456)
	org.apache.jasper.compiler.Node$Nodes.visit(Node.java:2163)
	org.apache.jasper.compiler.Generator.generate(Generator.java:3272)
	org.apache.jasper.compiler.Compiler.generateJava(Compiler.java:244)
	org.apache.jasper.compiler.Compiler.compile(Compiler.java:495)
	org.apache.jasper.compiler.Compiler.compile(Compiler.java:476)
	org.apache.jasper.compiler.Compiler.compile(Compiler.java:464)
	org.apache.jasper.JspCompilationContext.compile(JspCompilationContext.java:511)
	org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:295)
	org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:292)
	org.apache.jasper.servlet.JspServlet.service(JspServlet.java:236)
	javax.servlet.http.HttpServlet.service(HttpServlet.java:802)

note The full stack trace of the root cause is available in the Apache Tomcat/5.0.30 logs

用JavaBeans，<jsp:useBean ******></jsp:useBean>
出现异常，有什么解决方法吗????????