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can't not cast to java.util.map

See original GitHub issue

the heml is like this:

<!DOCTYPE html SYSTEM "http://www.thymeleaf.org/dtd/xhtml1-strict-thymeleaf-spring4-4.dtd">
<html>
<head>
<title>tmpl1</title>

</head>
<body>
    <div th:each="item : ${rows}">
        <h1 th:text="${item.title}"></h1>
    </div>
</body>
</html>

and the controller is like this:

@RequestMapping(value="tmpl1")
    public ModelAndView testTmpl1(){

        List<Integer> ids = new ArrayList<Integer>();
        ids.add(100052);
        ids.add(100052);
        ids.add(100052);
        ids.add(100052);
        ids.add(100052);
        List<Item> itemsByIds = itemService.getItemsByIds(ids);
        ModelAndView modelAndView = new ModelAndView("test/tmpl1");
        modelAndView.addObject("rows",itemsByIds);
        return modelAndView;
    }

    @RequestMapping(value="tmpl2")
    public ModelAndView testTmpl2(){
        List<Integer> ids = new ArrayList<Integer>();
        ids.add(100052);
        ids.add(100052);
        ids.add(100052);
        ids.add(100052);
        ids.add(100052);
        List<Item> itemsByIds = itemService.getItemsByIds(ids);
        ModelAndView modelAndView = new ModelAndView("test/tmpl1");
        modelAndView.addObject("rows",JSON.toJSON(itemsByIds));
        return modelAndView;
    }

!!!when i visited tmpl2 , and then i go to visit tmpl1, it will throw a exception , can’t not cast to java.util.map ,

the JSON library is fastjson

<dependency>
                <groupId>com.alibaba</groupId>
                <artifactId>fastjson</artifactId>
                <!-- <version>1.1.35</version> -->
                <version>1.1.46</version>
            </dependency>