### Environment

* Dubbo version: 2.7.4.1
* Operating System version: macOS Catalina Version 10.15.3
* Java version: 1.8.0_231

### Steps to reproduce this issue

1. 通过telnet调用接口如下
方法(Method)
`public String convert7(UserInfoCondition userInfoCondition) {  }`
参数(Parameter)
`public class UserInfoCondition {
    private List<Map<Integer, UserInfo>> userList;
}`
`public class UserInfo {
    private String accountMobile;
    private String userPassword;
}`

invoke UsesrInfoFacade.convert7({"userList":[{"1":{"accountMobile":"15052234567"}}]})
or
invoke UsesrInfoFacade.convert7({"userList":[{1:{"accountMobile":"15052234567"}}]})

提示如下错误(has a problem)
![image](https://user-images.githubusercontent.com/17045745/77892951-ebd50d00-72a5-11ea-95b0-dd59a68a83cc.png)

到底如何书写这个入参呢?(How to write the parameters)


person1.setName("person1");
        Person person2 = new Person();
        person2.setName("person2");
        array[0] = person1;
        array[1] = person2;
        Object o = PojoUtils.realize(PojoUtils.generalize(array), LinkedList.class);
        assertTrue(o instanceof LinkedList);
        assertEquals(((List) o).get(0), person1);
        assertEquals(((List) o).get(1), person2);
    }
    @Test
    public void testCollectionToArray() throws Exception {
        Person person1 = new Person();
        person1.setName("person1");
        Person person2 = new Person();
        person2.setName("person2");
        List<Person> list = new LinkedList<Person>();
        list.add(person1);
        list.add(person2);
        Object o = PojoUtils.realize(PojoUtils.generalize(list), Person[].class);
        assertTrue(o instanceof Person[]);
        assertEquals(((Person[]) o)[0], person1);
        assertEquals(((Person[]) o)[1], person2);
    }
    @Test
    public void testMapToEnum() throws Exception {
        Map map = new HashMap();
        map.put("name", "MONDAY");
        Object o = PojoUtils.realize(map, Day.class);
        assertEquals(o, Day.MONDAY);