### 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)


map = (Map<Object, Object>) pojo;
                }
            } else {
                map = (Map<Object, Object>) pojo;
            }
            if (Map.class.isAssignableFrom(type) || type == Object.class) {
                final Map<Object, Object> result = createMap(map);
                history.put(pojo, result);
                for (Map.Entry<Object, Object> entry : map.entrySet()) {
                    Type keyType = getGenericClassByIndex(genericType, 0);
                    Type valueType = getGenericClassByIndex(genericType, 1);
                    Class<?> keyClazz;
                    if (keyType instanceof Class) {
                        keyClazz = (Class<?>) keyType;
                    } else if (keyType instanceof ParameterizedType) {
                        keyClazz = (Class<?>) ((ParameterizedType) keyType).getRawType();
                    } else {
                        keyClazz = entry.getKey() == null ? null : entry.getKey().getClass();
                    }
                    Class<?> valueClazz;
                    if (valueType instanceof Class) {
                        valueClazz = (Class<?>) valueType;
                    } else if (valueType instanceof ParameterizedType) {
                        valueClazz = (Class<?>) ((ParameterizedType) valueType).getRawType();
                    } else {
                        valueClazz = entry.getValue() == null ? null : entry.getValue().getClass();
                    }
                    Object key = keyClazz == null ? entry.getKey() : realize0(entry.getKey(), keyClazz, keyType, history);
                    Object value = valueClazz == null ? entry.getValue() : realize0(entry.getValue(), valueClazz, valueType, history);