### 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)


InnerPojo realizeParentList = (InnerPojo) realizeInnerList.get(0);
        Assertions.assertEquals(1, realizeParentList.getList().size());
        assertTrue(realizeParentList.getList().get(0) instanceof Parent);
        Parent realizeParent = (Parent) realizeParentList.getList().get(0);
        Assertions.assertEquals(parent.getName(), realizeParent.getName());
        Assertions.assertEquals(parent.getAge(), realizeParent.getAge());
    }
    @Test
    public void testDateTimeTimestamp() throws Exception {
        String dateStr = "2018-09-12";
        String timeStr = "10:12:33";
        String dateTimeStr = "2018-09-12 10:12:33";
        String[] dateFormat = new String[]{"yyyy-MM-dd HH:mm:ss", "yyyy-MM-dd", "HH:mm:ss"};
        //java.util.Date
        Object date = PojoUtils.realize(dateTimeStr, Date.class, (Type) Date.class);
        assertEquals(Date.class, date.getClass());
        assertEquals(dateTimeStr, new SimpleDateFormat(dateFormat[0]).format(date));
        //java.sql.Time
        Object time = PojoUtils.realize(dateTimeStr, java.sql.Time.class, (Type) java.sql.Time.class);
        assertEquals(java.sql.Time.class, time.getClass());
        assertEquals(timeStr, new SimpleDateFormat(dateFormat[2]).format(time));
        //java.sql.Date
        Object sqlDate = PojoUtils.realize(dateTimeStr, java.sql.Date.class, (Type) java.sql.Date.class);
        assertEquals(java.sql.Date.class, sqlDate.getClass());
        assertEquals(dateStr, new SimpleDateFormat(dateFormat[1]).format(sqlDate));
        //java.sql.Timestamp
        Object timestamp = PojoUtils.realize(dateTimeStr, java.sql.Timestamp.class, (Type) java.sql.Timestamp.class);
        assertEquals(java.sql.Timestamp.class, timestamp.getClass());
        assertEquals(dateTimeStr, new SimpleDateFormat(dateFormat[0]).format(timestamp));
    }