### 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)


assertEquals(name, realize.getName());
    }
    @Test
    public void testGenerializeAndRealizeClass() throws Exception {
        Object generalize = PojoUtils.generalize(Integer.class);
        assertEquals(Integer.class.getName(), generalize);
        Object real = PojoUtils.realize(generalize, Integer.class.getClass());
        assertEquals(Integer.class, real);
        generalize = PojoUtils.generalize(int[].class);
        assertEquals(int[].class.getName(), generalize);
        real = PojoUtils.realize(generalize, int[].class.getClass());
        assertEquals(int[].class, real);
    }
    @Test
    public void testPublicField() throws Exception {
        Parent parent = new Parent();
        parent.gender = "female";
        parent.email = "email@host.com";
        parent.setEmail("securityemail@host.com");
        Child child = new Child();
        parent.setChild(child);
        child.gender = "male";
        child.setAge(20);
        child.setParent(parent);
        Object obj = PojoUtils.generalize(parent);
        Parent realizedParent = (Parent) PojoUtils.realize(obj, Parent.class);
        Assertions.assertEquals(parent.gender, realizedParent.gender);
        Assertions.assertEquals(child.gender, parent.getChild().gender);
        Assertions.assertEquals(child.age, realizedParent.getChild().getAge());
        Assertions.assertEquals(parent.getEmail(), realizedParent.getEmail());