struts框架下的jfreechart配置问题
Servlet   execution   threw   an   exception   运行后的结果
我在Struts框架下，想用图表方式显示查询结果，配置好后tomcat抛出以上错误
具体的思路：jsp传入查询数据，ACTION调用model的方法得到结果集，然后作为调用一个生成图表类，存入request,之后供结果页面Jsp调用


Q1：Servlet   execution   threw   an   exception   ，我已经在web.xml文件下配置好了文件如下：
<?xml   version= "1.0 "   encoding= "UTF-8 "?>
<web-app   xmlns= "http://java.sun.com/xml/ns/j2ee "   xmlns:xsi= "http://www.w3.org/2001/XMLSchema-instance "   version= "2.4 "   xsi:schemaLocation= "http://java.sun.com/xml/ns/j2ee       http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd ">
    <servlet>
        <servlet-name> action </servlet-name>
        <servlet-class> org.apache.struts.action.ActionServlet </servlet-class>
        <init-param>
            <param-name> config </param-name>
            <param-value> /WEB-INF/struts-config.xml </param-value>
        </init-param>
        <init-param>
            <param-name> debug </param-name>
            <param-value> 3 </param-value>
        </init-param>
        <init-param>
            <param-name> detail </param-name>
            <param-value> 3 </param-value>
        </init-param>
        <load-on-startup> 0 </load-on-startup>
    </servlet>
    <servlet-mapping>
        <servlet-name> action </servlet-name>
        <url-pattern> *.do </url-pattern>
    </servlet-mapping>
    <servlet>
<servlet-name> DisplayChart </servlet-name>
        <servlet-class> org.jfree.chart.servlet.DisplayChart </servlet-class>
</servlet>
<servlet-mapping>
<servlet-name> DisplayChart </servlet-name>
<url-pattern> /servlet/DisplayChart </url-pattern>
</servlet-mapping>
    <welcome-file-list>
    <welcome-file> login.jsp </welcome-file>
    </welcome-file-list>
</web-app>
Q2：   String   filename=ServletUtilities.saveChartAsJPEG（chart,600,400,info,session);
                //设置生成图片，包括图片的大小，长度是300，宽是200
                System.out.println(filename);
                System.out.println(info);
              session.setAttribute( "file_name1 ",filename);
                String   URL=   request.getContextPath()   +   "/servlet/DisplayChart?   filename= "   +   filename;  
                session.setAttribute( "file_url1 ",URL);