在JSP scriptlet中，如何访问从Spring MVC ModelMap传递的java.util.Date值？

Question

FooController.java:

@RequestMapping(value = "/foo", method = RequestMethod.GET)
public final String foo(HttpServletRequest request, ModelMap model)
{
    java.util.Date myDate = new java.util.Date();
    model.addAttribute("myDate", myDate);
    return "foo";
}

foo.jsp:

<%
    java.util.Date myUtilDate = (java.util.Date)request.getParameter("myDate");
    org.joda.time.DateTime myJodaDate = new org.joda.time.DateTime(myUtilDate);
%>

<joda:format value="${myJodaDate}" style="LL"/>

Why does the JSP scriptlet fail to obtain the myDate value that was added to the ModelMap in the FooController ?

Answer 1

You should be able to just access your ModelMap parameter with ${myDate} - see similar questions: How do I access ModelMap in a jsp? and JSPs not displaying objects from model in Spring

Answer 2

The attributes in the ModelMap are stored as request (or session, depending on your declarations) attributes , not parameters. After your controller method finishes execution, Spring forwards to the JSP associated with the returned view name.

So, in your JSP, you must use request.getAttribute("myDate") , not getParameter . Actually, you should stay away from Java code in JSPs, but you should also understand what EL expressions do - in your case, ${myDate} finds the request attribute named "myDate".

PS: There is an existing tag in JSTL for formatting java.util.Date s based on patterns, <fmt:formatDate> .

Answer 3

That's a request parameter, you need to bind appropriately coming off the wire, I wrote a blog post on this last week:

http://linkedjava.blogspot.com/2011/06/spring-controller-with-date-object.html

Answer 4

Answer by Nicolae Albu is right - this is request attribute , not parameter . Attribute is something you associate with request yourself, in code, using API (in this case - Spring MVC does that using Model). Parameters are added by Servlet Container, not you, and they represent URL/POST parameters sent by browser.

The only thing to add is that ${varName} is equivalent to pageContext.findAttribute("varName"); and request.getAttribute("varName") is equivalent to pageContext.getAttribute("varName", PageContext.REQUEST_SCOPE) (if you're not sure what this is about, look up documentation on page, request, session and application scopes in Servlets+JSPs).