### 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)


* @return
     */
    private static Object getDefaultValue(Class<?> parameterType) {
        if ("char".equals(parameterType.getName())) {
            return Character.MIN_VALUE;
        }
        if ("bool".equals(parameterType.getName())) {
            return false;
        }
        return parameterType.isPrimitive() ? 0 : null;
    }
    private static Method getSetterMethod(Class<?> cls, String property, Class<?> valueCls) {
        String name = "set" + property.substring(0, 1).toUpperCase() + property.substring(1);
        Method method = NAME_METHODS_CACHE.get(cls.getName() + "." + name + "(" + valueCls.getName() + ")");
        if (method == null) {
            try {
                method = cls.getMethod(name, valueCls);
            } catch (NoSuchMethodException e) {
                for (Method m : cls.getMethods()) {
                    if (ReflectUtils.isBeanPropertyWriteMethod(m) && m.getName().equals(name)) {
                        method = m;
                        break;
                    }
                }
            }
            if (method != null) {
                NAME_METHODS_CACHE.put(cls.getName() + "." + name + "(" + valueCls.getName() + ")", method);
            }
        }
        return method;