简单就是美！

<c:out value='${modelName}'/>
<c:out value='${modelName.keyxxx}'/>

<c:out value='${keyxxx}'/>

package com.simba.test;

import java.util.HashMap;
import java.util.Map;

import junit.framework.TestCase;

import org.springframework.mock.web.MockHttpServletRequest;
import org.springframework.mock.web.MockHttpServletResponse;
import org.springframework.web.servlet.ModelAndView;
import org.springframework.web.servlet.view.RedirectView;

public class TestRedirectView extends TestCase{
	
    protected MockHttpServletRequest request = new MockHttpServletRequest("GET", "");
    protected MockHttpServletResponse response = new MockHttpServletResponse();

	public void testRedirect() throws Exception{
		Map<String, String> map = new HashMap<String, String>();
		map.put("key1", "value1");
		map.put("key2", "value2");
		
		//这种用法,map就是ModelAndView中的Model.
		ModelAndView mv = new ModelAndView(new RedirectView("/foo/bar.jsp"), map);
		
		//这里用getModel()与DispatcherServlet中用getModelInternal是一样的.
		mv.getView().render(mv.getModel(), request, response);
		
		assertEquals(response.getRedirectedUrl(),"/foo/bar.jsp?key1=value1&key2=value2");
	}
	
	public void testWrongRedirect() throws Exception{
		Map<String, String> map = new HashMap<String, String>();
		map.put("key1", "value1");
		map.put("key2", "value2");
		
		//这种用法,map就是ModelAndView中Model的一个key/value对了...
		ModelAndView mv = new ModelAndView(new RedirectView("/foo/bar.jsp"), "model", map);
		
		//这里用getModel()与DispatcherServlet中用getModelInternal是一样的.
		mv.getView().render(mv.getModel(), request, response);
		
		assertTrue(response.getRedirectedUrl().contains("/foo/bar.jsp?model="));
	}
}

new ModelAndView(new RedirectView("xxx.do"),"modelName",modelMap); 

DispatcherServlet.render(ModelAndView mv, HttpServletRequest request, HttpServletResponse response){
...
//call view's render method
view.render(mv.getModelInternal(), request, response);
}
...

AbstractView.render(Map model, HttpServletRequest request, HttpServletResponse response){
...
//the model still here...
renderMergedOutputModel(mergedModel, request, response);
}

RedirectView.renderMergedOutputModel(Map model, HttpServletRequest request, HttpServletResponse response){
...
//Append query properties to the redirect URL. Here, the modelMap represented by url...
appendQueryProperties(targetUrl, model, this.encodingScheme);

//do redirect
sendRedirect(request, response, targetUrl.toString(), this.http10Compatible);
}

new ModelAndView(new RedirectView("xxx.do"),"modelName",modelMap);