### 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)


}
    // java.lang.IllegalArgumentException: argument type mismatch
    @Test
    public void test_realize_LongPararmter_IllegalArgumentException() throws Exception {
        Method method = PojoUtilsTest.class.getMethod("setLong", long.class);
        assertNotNull(method);
        Object value = PojoUtils.realize("563439743927993", method.getParameterTypes()[0], method.getGenericParameterTypes()[0]);
        method.invoke(new PojoUtilsTest(), value);
    }
    // java.lang.IllegalArgumentException: argument type mismatch
    @Test
    public void test_realize_IntPararmter_IllegalArgumentException() throws Exception {
        Method method = PojoUtilsTest.class.getMethod("setInt", int.class);
        assertNotNull(method);
        Object value = PojoUtils.realize("123", method.getParameterTypes()[0], method.getGenericParameterTypes()[0]);
        method.invoke(new PojoUtilsTest(), value);
    }
    @Test
    public void testStackOverflow() throws Exception {
        Parent parent = Parent.getNewParent();
        parent.setAge(Integer.MAX_VALUE);
        String name = UUID.randomUUID().toString();
        parent.setName(name);
        Object generalize = PojoUtils.generalize(parent);
        assertTrue(generalize instanceof Map);
        Map map = (Map) generalize;
        assertEquals(Integer.MAX_VALUE, map.get("age"));
        assertEquals(name, map.get("name"));
        Parent realize = (Parent) PojoUtils.realize(generalize, Parent.class);
        assertEquals(Integer.MAX_VALUE, realize.getAge());