### 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)


}
    @Test
    public void testGeneralizeEnumArray() throws Exception {
        Object days = new Enum[]{Day.FRIDAY, Day.SATURDAY};
        Object o = PojoUtils.generalize(days);
        assertTrue(o instanceof String[]);
        assertEquals(((String[]) o)[0], "FRIDAY");
        assertEquals(((String[]) o)[1], "SATURDAY");
    }
    @Test
    public void testGeneralizePersons() throws Exception {
        Object persons = new Person[]{new Person(), new Person()};
        Object o = PojoUtils.generalize(persons);
        assertTrue(o instanceof Object[]);
        assertEquals(((Object[]) o).length, 2);
    }
    @Test
    public void testMapToInterface() throws Exception {
        Map map = new HashMap();
        map.put("content", "greeting");
        map.put("from", "dubbo");
        map.put("urgent", true);
        Object o = PojoUtils.realize(map, Message.class);
        Message message = (Message) o;
        assertThat(message.getContent(), equalTo("greeting"));
        assertThat(message.getFrom(), equalTo("dubbo"));
        assertTrue(message.isUrgent());
    }
    @Test
    public void testException() throws Exception {