FastJson反序列化为什么用TypeReference

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泛型序列化非TypeReference code：

    public static void main(String[] args) {
        Map<String, Person> map = new HashMap<>(16);
        map.put("one", new Person("zhangsan"));
        map.put("two", new Person("lisi"));
        String jsonStr = JSON.toJSONString(map);
        byte[] bytes = jsonStr.getBytes();
        String json = new String(bytes);
        Map<String, Person> res = JSON.parseObject(json, Map.class);
        System.out.println(res.get("one"));
        System.out.println(res.get("one").getName());
    }

输出：

Exception in thread "main" java.lang.reflect.InvocationTargetException
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:498)
	at com.intellij.rt.execution.CommandLineWrapper.main(CommandLineWrapper.java:67)
Caused by: java.lang.ClassCastException: com.alibaba.fastjson.JSONObject cannot be cast to subtitle.io.Person
	at subtitle.io.MyMain.main(MyMain.java:48)
	... 5 more
{"name":"zhangsan"}

泛型序列化TypeReference code：

    public static void main(String[] args) {
        Map<String, Person> map = new HashMap<>(16);
        map.put("one", new Person("zhangsan"));
        map.put("two", new Person("lisi"));
        String jsonStr = JSON.toJSONString(map);
        byte[] bytes = jsonStr.getBytes();
        String json = new String(bytes);
        Map<String, Person> res = JSON.parseObject(json, new TypeReference<Map<String, Person>>(){});
        System.out.println(res.get("one"));
        System.out.println(res.get("one").getName());
    }

输出：

Person{name='zhangsan'}
zhangsan

报错原因：
    反序列化时候，虽然添加Map.class，但是没有办法指定Person类型，导致反序列化后的对象为Map<String, Map<String, String>>,而不是Map<String, Person>，所以针对泛型的反序列化，需要使用TypeReference