Accept two different subclasses with same @RequestMapping

Question

I have WebDeviceInfo and IOSDeviceInfo classes that are subclasses of DeviceInfo. How can I create a single endpoint in a Spring @RestController that will accept either IOSDeviceInfo or WebDeviceInfo?

Attempt #1

I tried to map the same RequestMapping to two different methods, one that would get called if the RequestBody could be mapped to a WebDeviceInfo and the other that would get called if the RequestBody could be mapped to a IOSDeviceInfo.

@RequestMapping(value = "/register-device", method = RequestMethod.POST, consumes = MediaType.APPLICATION_JSON_VALUE)
public void registerWebDevice(@RequestBody final WebDeviceInfo webDeviceInfo) {
    //register web device
}

@RequestMapping(value = "/register-device", method = RequestMethod.POST, consumes = MediaType.APPLICATION_JSON_VALUE)
public void registerIOSDevice(@RequestBody final IOSDeviceInfo iosDeviceInfo) {
    //register ios device
}

But this does not work, the second RequestMapping does not get registered and the application fails to start up because Spring sees that /register-device with the same RequestMethod and MediaType is already mapped to another method.

Attempt #2

Next, I tried accepting the superclass as the RequestBody and then casting it to the appropriate subclass.

@RequestMapping(value = "/register-device", method = RequestMethod.POST, consumes = MediaType.APPLICATION_JSON_VALUE)
public void registerDevice(@RequestBody final DeviceInfo deviceInfo) {
    if (deviceInfo instanceof WebDeviceInfo) {
        final WebDeviceInfo webDeviceInfo = (WebDeviceInfo) deviceInfo;
        //register web device
    } else if (deviceInfo instanceof IOSDeviceInfo) {
        final IOSDeviceInfo iosDeviceInfo = (IOSDeviceInfo) deviceInfo;
        //register ios device
    } else {
        logger.debug("Could not cast deviceInfo to WebDeviceInfo or IOSDeviceInfo");
    }
}

This does not work either. I always get:

Could not cast deviceInfo to WebDeviceInfo or IOSDeviceInfo

Attempt #3

Finally, I tried just casting to the correct subclass inside a try/catch.

@RequestMapping(value = "/register-device", method = RequestMethod.POST, consumes = MediaType.APPLICATION_JSON_VALUE)
public void registerDevice(@RequestBody final DeviceInfo deviceInfo) {
    try {
        final WebDeviceInfo webDeviceInfo = (WebDeviceInfo) deviceInfo);
        //register web device
    } catch (final ClassCastException ex) {
        try {
            final IOSDeviceInfo iosDeviceInfo = (IOSDeviceInfo) deviceInfo);
            //register ios device
        } catch (final ClassCastException ex2) {
            logger.debug("Could not cast deviceInfo to WebDeviceInfo or IOSDeviceInfo");
        }
    }
}

Again I get error:

Could not cast deviceInfo to WebDeviceInfo or IOSDeviceInfo

Is there any way to accomplish this, or am I going to have to create two separate methods with two different RequestMappings?

user_1032890 · Answer

Attempts #2 and #3 should work when you annotate the base class DeviceInfo with the correct Jackson annotations:

@JsonTypeInfo(
        use = JsonTypeInfo.Id.NAME,
        include = JsonTypeInfo.As.PROPERTY,
        property = "type")
@JsonSubTypes({
        @JsonSubTypes.Type(value = IOSDeviceInfo.class, name = "ios"),
        @JsonSubTypes.Type(value = WebDeviceInfo.class, name = "web")
})
public abstract class DeviceInfo {
    [...]
}

class IOSDeviceInfo extends DeviceInfo {
    [...]
}

class WebDeviceInfo extends DeviceInfo {
    [...]
}

Then when you receive a request, the body will be deserialized into the correct subclass, either a IOSDeviceInfo or a WebDeviceInfo, depending on the 'type' parameter in the JSON body:

{
  type : "ios",
  [...]
}

Now you only need a single @RequestMapping method:

@RequestMapping(value = "/register-device", method = RequestMethod.POST, consumes = MediaType.APPLICATION_JSON_VALUE)
public void registerDevice(@RequestBody final DeviceInfo deviceInfo) {
    if (deviceInfo instanceof WebDeviceInfo) {
        final WebDeviceInfo webDeviceInfo = (WebDeviceInfo) deviceInfo;
        //register web device
    } else if (deviceInfo instanceof IOSDeviceInfo) {
        final IOSDeviceInfo iosDeviceInfo = (IOSDeviceInfo) deviceInfo;
        //register ios device
    } else {
        logger.debug("Could not cast deviceInfo to WebDeviceInfo or IOSDeviceInfo");
    }
}

Accept two different subclasses with same @RequestMapping

3 Answers