在servlet里创建了javabean对象，并且保存到session里，代码如下
Lefttopbean lt=new Lefttopbean();
session.setAttribute("lefttopbean",lt);
在jsp页面上引用javabean，代码如下
<jsp:useBean id="lefttopbean" type="user.yourbean.Lefttopbean" scope="session" />
结果上面这句话报错，报错如下
注意，有的人可能会说，把type换成class属性就没事了，我试过了，如果换成class属性，运行没错，但是bean对象是jsp页面执行时新创建的，不是在servlet里创建的，所以jsp页面获取的bean的方法的数据会有问题，不合逻辑
HTTP Status 500 - An exception occurred processing JSP page /lefttopback.jsp at line 4
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type Exception report
message An exception occurred processing JSP page /lefttopback.jsp at line 4
description The server encountered an internal error that prevented it from fulfilling this request.
exception
org.apache.jasper.JasperException: An exception occurred processing JSP page /lefttopback.jsp at line 4
1: <%@ page import="user.yourbean.Lefttopbean" %>
2: <html>
3: <%@ page contentType="text/html; charset=utf-8" %>
4: <jsp:useBean id="lefttopbean" type="user.yourbean.Lefttopbean" scope="session" />
5: <body>
6: <jsp:getProperty name="lefttopbean" property="information" />
7: <%
Stacktrace:
org.apache.jasper.servlet.JspServletWrapper.handleJspException(JspServletWrapper.java:568)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:455)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:390)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:334)
javax.servlet.http.HttpServlet.service(HttpServlet.java:728)
user.yourservlet.Lefttop.doPost(Lefttop.java:88)
user.yourservlet.Lefttop.doGet(Lefttop.java:91)
javax.servlet.http.HttpServlet.service(HttpServlet.java:621)
javax.servlet.http.HttpServlet.service(HttpServlet.java:728)
root cause
javax.servlet.ServletException: java.lang.InstantiationException: bean lefttopbean not found within scope
org.apache.jasper.runtime.PageContextImpl.doHandlePageException(PageContextImpl.java:912)
org.apache.jasper.runtime.PageContextImpl.handlePageException(PageContextImpl.java:841)
org.apache.jsp.lefttopback_jsp._jspService(lefttopback_jsp.java:105)
org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
javax.servlet.http.HttpServlet.service(HttpServlet.java:728)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:432)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:390)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:334)
javax.servlet.http.HttpServlet.service(HttpServlet.java:728)
user.yourservlet.Lefttop.doPost(Lefttop.java:88)
user.yourservlet.Lefttop.doGet(Lefttop.java:91)
javax.servlet.http.HttpServlet.service(HttpServlet.java:621)
javax.servlet.http.HttpServlet.service(HttpServlet.java:728)
root cause
java.lang.InstantiationException: bean lefttopbean not found within scope
org.apache.jsp.lefttopback_jsp._jspService(lefttopback_jsp.java:70)
org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
javax.servlet.http.HttpServlet.service(HttpServlet.java:728)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:432)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:390)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:334)
javax.servlet.http.HttpServlet.service(HttpServlet.java:728)
user.yourservlet.Lefttop.doPost(Lefttop.java:88)
user.yourservlet.Lefttop.doGet(Lefttop.java:91)
javax.servlet.http.HttpServlet.service(HttpServlet.java:621)
javax.servlet.http.HttpServlet.service(HttpServlet.java:728)
note The full stack trace of the root cause is available in the Apache Tomcat/7.0.40 logs.
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Apache Tomcat/7.0.40
------解决方案--------------------
我没大看明白,竟然你要在servlet里面创建对象,你直接在servlet方法里面把对象放入session里面啊，干嘛要在jsp里面写,而且你type肯定是个错的.
------解决方案--------------------
这种情况应该取出来直接用,比如用jstl输出${lefttopbean.xxxxx}，而不是使用useBean.