[alibaba/fastjson]同一个list多个元素引用同一个HashMap实例，序列化失败

fastjson.version = 1.2.75

1. 创建两个 Person 类实例，并引用同一个 HashMap 实例

        Map<String, String> roles = new HashMap<>();
        roles.put("1", "Master");
        roles.put("2", "Student");

        Person p1 = new Person(roles);
        Person p2 = new Person(roles);

2. 分别序列化，没有问题

       System.out.println(JSON.toJSONString(p1)); 
       System.out.println(JSON.toJSONString(p2));       

   {"roles":{"1":"Master","2":"Student"}}        
   {"roles":{"1":"Master","2":"Student"}}

3. 将两个对象一起放入同一个 LinkedList 之后再序列化，BUG happens...

       List<Person> oneGroupOfPeople = new LinkedList<>();
       oneGroupOfPeople.add(p1);
       oneGroupOfPeople.add(p2);
       System.out.println(JSON.toJSONString(oneGroupOfPeople));

   [{"roles":{"1":"Master","2":"Student"}},{"roles":{"$ref":"$[0].roles"}}]

Person 类的定义

@Data
@AllArgsConstructor
@FieldDefaults(level = AccessLevel.PRIVATE)
static class Person {
    Map<String, String> roles;
}