Spring MVC - 如何将继承类型从jsp传递给控制器

Question

I have a controller that gets a certain DTO as a parameter:

@Controller
public class MyController {

   @RequestMapping(value = "/request", method = RequestMethod.POST, consumes = MediaType.APPLICATION_JSON_VALUE)
   @ResponseStatus(value = HttpStatus.OK)
   @ResponseBody
   public int processRequest(@RequestBody BaseRequestDTO baseRequestDTO, HttpServletRequest request) {
       ...
   }

}

BaseRequestDTO has a field, let's say String a .

I have another DTO that extends BaseRequestDTO - MyRequestDTO. MyRequestDTO also has a field, let's say String b . I'm trying to pass a MyRequestDTO from a jsp form to the controller:

$.ajax({
        type : "POST",
        url : URL + "/request",
        data : JSON.stringify(eval({
             "a" : "hello",
             "b" : "world"
        })),
        ...
});

Now when I try to send the parameters I get this error:

Could not read JSON: Unrecognized field "b"

Because obviously BaseRequestDTO doesn't have that field.

EDIT: The message converters that are defined in the application context:

<property name="messageConverters">
        <list>
            <bean
                class="org.springframework.http.converter.json.MappingJacksonHttpMessageConverter">
            </bean>
            <bean class="org.springframework.http.converter.FormHttpMessageConverter" />
            <bean
                class="org.springframework.http.converter.StringHttpMessageConverter" />
        </list>
    </property>

So how can I pass an inheriting type (that has additional fields to the base class) as a parameter to the controller? Does anyone know of a solution to that?

Answer 1

There is support for this in Jackson , try specifying a property in the support class that holds the concrete type information:

@JsonTypeInfo(use=JsonTypeInfo.Id.CLASS, include=JsonTypeInfo.As.PROPERTY, property="@class")
public abstract class BaseRequestDTO {
  ...
} 

And on the JSON, specify the concrete type:

{
  "@class" : "com.yourpackage.MyRequestDTO",
       "a" : "hello",
       "b" : "world"
}