strut2声明式异常不能显示

各位大侠好：
     本人用的是struts2拦截器的声明式异常处理，定义如下：
     struts.xml
     配置
     <?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE struts PUBLIC
        "-//Apache Software Foundation//DTD Struts Configuration 2.0//EN"
        "http://struts.apache.org/dtds/struts-2.0.dtd"><struts>
<package name="struts-base" abstract="true" extends="struts-default">
  <interceptors>
     <interceptor name="exceptionInterceptor" class="exceptionInterceptor"/>
    <global-results>     
<result name="error" type="redirect">/common/myerror.jsp</result>     
</global-results>     
<global-exception-mappings>     
<exception-mapping exception="com.hw.exception.SystemException" result="error"/>     
</global-exception-mappings>
</package>
</struts>自定义异常
SystemException：
public class SystemException extends RuntimeException {
  private static final long serialVersionUID = 1L;
    public SystemException(String frdMessage) {
       super(createFriendlyErrMsg(frdMessage));
    }
    public SystemException(Throwable throwable){
       super(throwable);
    }
    public SystemException(Throwable throwable, String frdMessage){
       super(throwable);
    }
    private static String createFriendlyErrMsg(String msgBody) {
       String prefixStr = "抱歉。";
       String suffixStr = "请稍后再试或与管理员联系！";
       StringBuffer friendlyErrMsg = new StringBuffer();
       friendlyErrMsg.append(prefixStr);
       friendlyErrMsg.append(msgBody);
       friendlyErrMsg.append(suffixStr);
       return friendlyErrMsg.toString();
    }
}错误页面：
<%@ page language="java" contentType="text/html;charset=UTF-8" pageEncoding="UTF-8"%>
<%@ page isErrorPage="true"%>
<%@ taglib prefix="s" uri="/struts-tags" %>
<%
    response.setHeader("Cache-Control","no-cache");
    response.setHeader("Cache-Control","no-store");
    response.setDateHeader("Expires",0);
    response.setHeader("Pragma","no-cache");
%>
<html>
<head>
<script language="javascript">
function showContent(){
    if(document.getElementById("errorMessage").style.display == 'block'){
       document.getElementById("errorMessage").style.display = 'none';
    }else{
       document.getElementById("errorMessage").style.display = 'block';
    }
}
</script>
</head>
<body scroll="auto">
<table width="100%" height="100%" border="0" cellpadding="0" cellspacing="0">
<tr>
    <td align="center" class="bg" valign="top">
       <table width="100%" border="0" cellspacing="0" cellpadding="0" style="table-layout:fixed;word-break:break-all;">
           <tr>
              <td align="center" width="100%" height="80">
              </td>
           </tr>
           <tr>
              <td height="30" align="center">
                  <a href="#" onclick="javascript:history.go(-1);"><s:text name="global.return"/></a>&nbsp; &nbsp; 
                  <a href="#" onclick="javascript:showContent();">查看详细信息</a>
              </td>
           </tr>
           <tr>
              <td align="left" valign="top">
                  <!-- 异常堆栈信息(开发人员用) -->
                  <div style="display:none;" id="errorMessage">
                  <pre>   <s:property value="exceptionStack" /></pre>
                  </div>
              </td>
           </tr>
       </table>
    </td>
</tr>
</table>
</body>
</html>拦截器定义：
public class ExceptionInterceptor extends AbstractInterceptor {
private static final long serialVersionUID = -2871235590759171276L;
@Override
public String intercept(ActionInvocation invocation) throws Exception {
String result = "";
       try {
           result = invocation.invoke();
       } catch (DataAccessException ex) {
           throw new SystemException(ex,"数据库操作失败！");
       } catch (NullPointerException ex) {
           throw new SystemException(ex,"空指针，调用了未经初始化或者是不存在的对象！");
       } catch (IOException ex) {
           throw new SystemException(ex,"IO读写异常！");
       } catch (ClassNotFoundException ex) {
           throw new SystemException(ex,"指定的类不存在！");
       } catch (ArithmeticException ex) {
           throw new SystemException(ex,"数学运算异常！");
       } catch (ArrayIndexOutOfBoundsException ex) {
           throw new SystemException(ex,"数组下标越界！");
       } catch (IllegalArgumentException ex) {
           throw new SystemException(ex,"调用方法的参数错误！");
       } catch (ClassCastException ex) {
           throw new SystemException(ex,"类型强制转换错误！");
       } catch (SecurityException ex) {
           throw new SystemException(ex,"违背安全原则异常！");
       } catch (SQLException ex) {
           throw new SystemException(ex,"操作数据库异常！");
       } catch (NoSuchMethodError ex) {
           throw new SystemException(ex,"调用了未定义的方法！");
       } catch (InternalError ex) {
           throw new SystemException(ex,"Java虚拟机发生了内部错误！");
       } catch (Exception ex) {
           throw new SystemException(ex,"程序内部错误，操作失败！");
       }
    System.out.print("===测试数据=====");
    if(StringHelper.isEmpty(result)){
     result = "error";
    }
return result;
}
}
异常抛出后不能显示页码