[1]Servlet代码

        if(pageObj==null){
            pb=new PageBean(request.getRequestURI());
        }else{
            pb = (PageBean)pageObj;
        }

        request.getSession().setAttribute("ARTICAL_LIST_PAGE", pb);

这个地方把对象pb 放到session里面，变量的名字是ARTICAL_LIST_PAGE

[2]jsp里面的代码

    <jsp:useBean id="ARTICAL_LIST_PAGE" scope="session" type="pagination.PageBean" >
   
    </jsp:useBean>


注意：
    jsp:useBean标签里面的id一定要和Servlet里面的变量名字是一致的。否则的话，就会出现下面的异常：

SEVERE: Servlet.service() for servlet jsp threw exception
java.lang.InstantiationException: ARTICAL_LIST_PAGE
    at org.apache.jsp.jsp.artical.list_jsp._jspService(list_jsp.java:105)
    at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
    at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:374)
    at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:342)
    at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:267)
    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.ApplicationDispatcher.invoke(ApplicationDispatcher.java:646)
    at org.apache.catalina.core.ApplicationDispatcher.processRequest(ApplicationDispatcher.java:436)
    at org.apache.catalina.core.ApplicationDispatcher.doForward(ApplicationDispatcher.java:374)
    at org.apache.catalina.core.ApplicationDispatcher.forward(ApplicationDispatcher.java:302)
    at ccx.ims.core.servlet.BaseHttpServlet.farward(BaseHttpServlet.java:52)
    at ccx.ims.modules.information.servlet.ArticalListServlet.doPost(ArticalListServlet.java:123)
    at ccx.ims.modules.information.servlet.ArticalListServlet.doGet(ArticalListServlet.java:60)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:617)
    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:128)
    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:849)
    at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:583)
    at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:454)
    at java.lang.Thread.run(Thread.java:619)
Mar 2, 2010 8:42:21 AM org.apache.catalina.core.StandardWrapperValve invoke
SEVERE: Servlet.service() for servlet ArticalListServlet threw exception
java.lang.InstantiationException: ARTICAL_LIST_PAGE
    at org.apache.jsp.jsp.artical.list_jsp._jspService(list_jsp.java:105)
    at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
    at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:374)
    at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:342)
    at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:267)
    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.ApplicationDispatcher.invoke(ApplicationDispatcher.java:646)
    at org.apache.catalina.core.ApplicationDispatcher.processRequest(ApplicationDispatcher.java:436)
    at org.apache.catalina.core.ApplicationDispatcher.doForward(ApplicationDispatcher.java:374)
    at org.apache.catalina.core.ApplicationDispatcher.forward(ApplicationDispatcher.java:302)
    at ccx.ims.core.servlet.BaseHttpServlet.farward(BaseHttpServlet.java:52)
    at ccx.ims.modules.information.servlet.ArticalListServlet.doPost(ArticalListServlet.java:123)
    at ccx.ims.modules.information.servlet.ArticalListServlet.doGet(ArticalListServlet.java:60)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:617)
    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:128)
    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:849)
    at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:583)
    at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:454)
    at java.lang.Thread.run(Thread.java:619)

比如，下面的用法就会出现此异常


    <jsp:useBean id="p" scope="session" type="PageBean" beanName="ARTICAL_LIST_PAGE">
   
    </jsp:useBean>

因为在session范围内找不到p变量指向的对象。








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