### 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)


Type gtype = getType("returnListPersonMethod");
        List<Person> list = new ArrayList<Person>();
        list.add(new Person());
        {
            Person person = new Person();
            person.setName("xxxx");
            list.add(person);
        }
        assertObject(list, gtype);
    }
    @Test
    public void test_total() throws Exception {
        Object generalize = PojoUtils.generalize(bigPerson);
        Type gtype = getType("returnBigPersonMethod");
        Object realize = PojoUtils.realize(generalize, BigPerson.class, gtype);
        assertEquals(bigPerson, realize);
    }
    @Test
    public void test_total_Array() throws Exception {
        Object[] persons = new Object[]{bigPerson, bigPerson, bigPerson};
        Object generalize = PojoUtils.generalize(persons);
        Object[] realize = (Object[]) PojoUtils.realize(generalize, Object[].class);
        assertArrayEquals(persons, realize);
    }
    @Test
    public void test_Loop_pojo() throws Exception {
        Parent p = new Parent();
        p.setAge(10);
        p.setName("jerry");
        Child c = new Child();