我曾经只使用可以执行查询的Tomcat和JSP页面，然后将查询结果分配给数组或对象，然后通过响应将数据传递到客户端。

request.setAttribute("errorMessage", "this is error!!");
request.getRequestDispatcher("report.jsp").forward(request, response);

在客户端jsp代码中，我可以执行以下操作：

$ {errorMessage}

然后是“这是错误！” 消息将会显示。

我想对REST JAX-RS GlassFish v3做同样的事情。

    @Path("schedule/test")
    @POST
    @Consumes("application/x-www-form-urlencoded")
    @Produces("application/vnd.ms-excel")
    public Object tmpTest(String content) {
        try {

            //just my method to execute query and get result
            Vector out = (Vector)QueryManager.executeQuery;

            //if query result is empty, I want user to redirect to report.jsp page
            if(out.isEmpty()) {
                request.setAttribute("errorMessage", "This is error!!");
                request.getRequestDispatcher("report.jsp").forward(request, response);
                return null;
            }
        ....continue code......
   }

这导致了我从未见过的神秘异常。

java.lang.ClassCastException: $Proxy109 cannot be cast to org.apache.catalina.core.ApplicationHttpRequest
            at org.apache.catalina.core.ApplicationHttpRequest.getRequestFacade(ApplicationHttpRequest.java:1001)
            at org.apache.catalina.core.ApplicationDispatcher.doDispatch(ApplicationDispatcher.java:472)
            at org.apache.catalina.core.ApplicationDispatcher.dispatch(ApplicationDispatcher.java:379)
            at org.apache.catalina.core.ApplicationDispatcher.dispatch(ApplicationDispatcher.java:336)
            at org.apache.catalina.core.ApplicationDispatcher.forward(ApplicationDispatcher.java:314)

那么，如何将用户重定向到report.jsp并传递“这是错误”之类的消息？

客户端jsp期望错误msg变量具有一个值：

<b>${errorMessage}</b>