Inheritance in Spring RestController

Question

I have a Spring RestController which handles version 1 of API calls.

package rest.v1;

@RestController
@RequestMapping("v1/someResource")
public class Controller_V1 {

    @RequestMapping(value = "/{resourceName}", method = RequestMethod.GET)
    public Object retrieve() throws Exception {
        ....
    }
}

What I want to do is create another controller which handles version 2 requests. At the same time I want to inherit the implementation which are already in version 1 controller. This is because the implementations which are unchanged from v1 to v2 will just be inherited as it is from v1.

So something like this:

package rest.v2;

@RestController("controllerV2")
@RequestMapping("v2/someResource")
public class Controller_v2 extends Controller_v1 {

    @RequestMapping(value = "/{resourceName}", method = RequestMethod.GET)
    public Object retrieve() throws Exception {
        //implementation overridden from v1
    }
}

Doing it results in ConflictingBeanDefinitionException. I am also not sure if extending the controllers like above is supposed to work.

I am aware that I can use multiple paths in RequestMapping of the same controller like this:

@RestController
@RequestMapping(value = { "v1/someResource", "v1/someResource" })
public class Controller_V1 {

}

But the above is not going to work for my scenario.

Here is the stack trace when the controllers are extended:

 [java] org.springframework.beans.factory.BeanDefinitionStoreException: Unexpected exception parsing XML document from class path resource [rest-context.xml]; nested exception is org.springframework.context.annotation.ConflictingBeanDefinitionException: Annotation-specified bean name 'controller_V1' for bean class [rest.v2.Controller_V2] conflicts with existing, non-compatible bean definition of same name and class [rest.v1.Controller_V1]
     [java]     at org.springframework.beans.factory.xml.XmlBeanDefinitionReader.doLoadBeanDefinitions(XmlBeanDefinitionReader.java:413)
     [java]     at org.springframework.beans.factory.xml.XmlBeanDefinitionReader.loadBeanDefinitions(XmlBeanDefinitionReader.java:335)
     [java]     at org.springframework.beans.factory.xml.XmlBeanDefinitionReader.loadBeanDefinitions(XmlBeanDefinitionReader.java:303)
     [java]     at org.springframework.beans.factory.support.AbstractBeanDefinitionReader.loadBeanDefinitions(AbstractBeanDefinitionReader.java:180)
     [java]     at org.springframework.beans.factory.support.AbstractBeanDefinitionReader.loadBeanDefinitions(AbstractBeanDefinitionReader.java:216)
     [java]     at org.springframework.beans.factory.support.AbstractBeanDefinitionReader.loadBeanDefinitions(AbstractBeanDefinitionReader.java:187)
     [java]     at org.springframework.web.context.support.XmlWebApplicationContext.loadBeanDefinitions(XmlWebApplicationContext.java:125)
     [java]     at org.springframework.web.context.support.XmlWebApplicationContext.loadBeanDefinitions(XmlWebApplicationContext.java:94)
     [java]     at org.springframework.context.support.AbstractRefreshableApplicationContext.refreshBeanFactory(AbstractRefreshableApplicationContext.java:129)
     [java]     at org.springframework.context.support.AbstractApplicationContext.obtainFreshBeanFactory(AbstractApplicationContext.java:540)
     [java]     at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:454)
     [java]     at org.springframework.web.servlet.FrameworkServlet.configureAndRefreshWebApplicationContext(FrameworkServlet.java:658)
     [java]     at org.springframework.web.servlet.FrameworkServlet.createWebApplicationContext(FrameworkServlet.java:624)
     [java]     at org.springframework.web.servlet.FrameworkServlet.createWebApplicationContext(FrameworkServlet.java:672)
     [java]     at org.springframework.web.servlet.FrameworkServlet.initWebApplicationContext(FrameworkServlet.java:543)
     [java]     at org.springframework.web.servlet.FrameworkServlet.initServletBean(FrameworkServlet.java:484)
     [java]     at org.springframework.web.servlet.HttpServletBean.init(HttpServletBean.java:136)
     [java]     at javax.servlet.GenericServlet.init(GenericServlet.java:158)

Answer 1

A @RestController extension is currently available. I needed to extend a @RestController due to a new method implementation version. I tried to extend a @RestController and it works perfectly without specifying the name of the spring bean. Here is a simple example:

@RestController
@RequestMapping("/v1/mycontroller")
public class MyControllerV1 {
    
    @RequestMapping("/mymethod1")
    public Object mymethod1(@RequestBody Object myRequest) {
        <my v1 implementation>
        return .....
    }
    
    @RequestMapping("/mymethod2")
    public Object mymethod2(@RequestBody Object myRequest) {
        <my v1 implementation>
        return .....
    }
}



@RestController
@RequestMapping("/v2/mycontroller")
public class MyControllerV2 extends MyControllerV1 {
    
    @RequestMapping("/mymethod1")
    public Object mymethod1(@RequestBody Object myRequest) {
        <my v2 implementation>
        return .....
    }
    
}

In this case you can call "mymethod1" and "mymethod2" in two different ways, which are

http://hostname/v1/mycontroller/mymethod1 <-- first implementation -->

http://hostname/v2/mycontroller/mymethod1 <-- second implementation -->

http://hostname/v1/mycontroller/mymethod2 <-- same implementation -->

http://hostname/v2/mycontroller/mymethod2 <-- same implementation -->

"mymethod1" has two different implementation and "mymethod2" has only one implemation that "MyControllerV1" has inherited from "MyControllerV2"