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Where is databinding mapping stored for a controller?

In the following controller
#Controller
public class MyFormController {
#InitBinder
public void initBinder(WebDataBinder binder) {
SimpleDateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd");
dateFormat.setLenient(false);
binder.registerCustomEditor(Date.class, new CustomDateEditor(dateFormat, false));
}
// ...
}
The class does not inherit any other class or it doesn't have any WebDataBinder instance variable. How come then the custom editors are stored and where?

The Spring MVC infrastructure is complex. There are a lot of pieces that come together to invoke your #Controller handler method. I explain some of it in my answer here.
In summary, Spring MVC scans your #Controller classes for #RequestMapping annotated methods. It creates mappings for these in a RequestMappingHandlerMapping and uses a RequestMappingHandlerAdapter to dispatch to them, ie. invoke your handler methods.
Before it invokes the method, it goes through a couple of housekeeping steps. You can see these in the source code, here. The short version is:
It wraps the HttpServletRequest and HttpServletResponse in an adapter.
It creates factories producing Model and WebDataBinder instances (the latter come from your #InitBinder methods).
It creates a ServletInvocableHandlerMethod which encapsulates the invocation of your handler method with HandlerMethodArgumentResolver to generate arguments for your handler method and HandlerMethodReturnValueHandler to process the return value of your handler method.
It creates a ModelAndViewContainer which will potentially be used to later render a view as the HTTP response.
It prepares an async environment in case the request uses async components.
Then it invokes the method.
That WebDataBinder object you're curious about is stored and used in various places in the execution context described above.

Spring #initBinder method to be called only once inside a controller

I have a class that annotated with #RestController and #ControllerAdvice that has my requests mapped methods (#RequestMapping). Also in this class I added a method public void initBinder(WebDataBinder dataBinder) that is annotated with #InitBinder and responsible to register some custom editor.
Specifically, it is a propertyEditor that convert String to Enum.
I noticed that on every call to #RequestMapping method in my controller, my initBinder method is being called. Since in my opinion this editor registration should happen only once (initialization of controller), I want this to be set (called) only once.
Is there a way to do so?

Alternatively, you can use implementation of BindingInitializer for registering your custom Editor. You have to define a bean of class "org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter" in your app context file and set its "webBindingInitializer" property with your implementation of BindingInitializer.
In any case, scope of WebDataBinder is for a request. Hope this helps.

#Controller annotation and Controller Classes in Spring MVC

When I am using Spring 3.x
While using annotations its difficult for me to know Which type of Controller class we are going to fetch using this #Controller
With reference to
http://docs.spring.io/spring/docs/current/javadoc-api/org/springframework/web/servlet/mvc/Controller.html
These are implementing Controller class
AbstractController
AbstractUrlViewController
MultiActionController
ParameterizableViewController
ServletForwardingController
ServletWrappingController
UrlFilenameViewController
AbstractWizardFormController
SimpleFormController
However when we are using #Controller annotation in our Spring MVC
program how to know that Our #Controller annotation is implementing
any of these controllers, Kindly anyone explain me

I think you are missing the point here. In the old times to register a controller, your class must have implemented controller interface and choose request mapping type. Sometimes you had to implement lots of code to achieve single request mapping.
Nowadays, when we have annotations, the model has changed. We can handle multiple request types per controller class. Because in single #Controller annotated class we can handle many request mappings.
Controller annotation is a specialized #Component, that tells Spring that inside it will find #RequestMapping handlers. Those handlers can be used either for returning Json, HTML or for uploading files.
Now logic connected with same module can be placed under single controller class, you are more flexible in what you want to achieve. Secondly #Controller enables us to reduce code anount significantly.

You aren't using any of those classes. You confuse the Controller interface with the annotation.
The annotation is just a marker that states that your bean is a Spring Controller and can send an receive HTTP requests.
http://docs.spring.io/spring/docs/current/javadoc-api/org/springframework/stereotype/Controller.html
The Controller interface was introduced when there were no annotations in the Java language.

Which type of Controller class we are going to fetch using this
#Controller ?
The #Controller annotation is to tell the web container that this is the controller class for requests with urls specified with #RequestMapping(URI). you are going to fetch no class if you are annotating your class with #Controller , you just need to provide a request handler method within the class and annotate it with #RequestMapping , though the controller class can also be annotated with #RequestMapping and in that case , only method inside the class will work as request handler method.
how to know that Our #Controller annotation is implementing any of
these controllers ?
The names of the classes you have mentioned are implementing Controller interface , not that #Controller annotation is implementing anything .Those controller classes are for specific purposes ,as their names suggest .

Better practice with Spring MVC: Service with non-fixed dependency

I have a requirement of compatibility with a new architecture based in Spring 3.2. The requirement is: a http request will come to a controller with an attribute that defines which kind of object is required. For example ...mycontroller/load?objType='obj1'.
My controller will have this structure:
#Controller
public class myController{
private ObjectService objectService;
#Autowired
public setObjectService(ObjectService objectService){
this.objectService = objectService;
}
}
So after that, I need to check this attribute to decide which service will I use. For example, this case is Obj1Service (method: "load"). All this services are extended from ObjectService, so: It is a good idea to swap objectService dependency to Obj1Service / Obj2Service in each incoming call? For example:
if(objType.equals("obj1")) this.setObjectService(context.getBean("obj1Service"..))
if(objType.equals("obj2")) this.setObjectService(context.getBean("obj2Service"..))
I know that is not a great design, but we need to integrate this new modules with other system that produces this kind of http requests.
It is necessary the inheritance because we have very similar behavior in many service's code, but with modifications in internal methods, so part of the behavior will be placed in ObjectService (it is not abstract) and other portion of the code will be placed in it children. Is there another way, more appropriate, to do this? Or you consider that is an acceptable solution?
Thanks!

You can use a map for all of your services, and get the appropriate service inside each controller method.
Let's say you have two services:
#Service("obj1")
public class ObjectServiceImpl1 implements ObjectService {
...
}
#Service("obj2")
public class ObjectServiceImpl2 implements ObjectService {
...
}
In your controller:
private Map<String, ObjectService> objectServices;
#Autowired
public setObjectServices(Map<String, ObjectService> objectServices){
this.objectServices= objectServices;
}
Spring will inject the map with all the ObjectService beans mapped by their names.
In load?objType=obj1 handler, you would have something like:
objectServices.get("obj1").doSomething(); // will use ObjectServiceImpl1
The same with load?objType=obj2 handler:
objectServices.get("obj2").doSomething(); // will use ObjectServiceImpl2
And so on.

Spring-MVC Problem using #Controller on controller implementing an interface

I'm using spring 2.5 and annotations to configure my spring-mvc web context. Unfortunately, I am unable to get the following to work. I'm not sure if this is a bug (seems like it) or if there is a basic misunderstanding on how the annotations and interface implementation subclassing works.
For example,
#Controller
#RequestMapping("url-mapping-here")
public class Foo {
#RequestMapping(method=RequestMethod.GET)
public void showForm() {
...
}
#RequestMapping(method=RequestMethod.POST)
public String processForm() {
...
}
}
works fine. When the context starts up, the urls this handler deals with are discovered, and everything works great.
This however does not:
#Controller
#RequestMapping("url-mapping-here")
public class Foo implements Bar {
#RequestMapping(method=RequestMethod.GET)
public void showForm() {
...
}
#RequestMapping(method=RequestMethod.POST)
public String processForm() {
...
}
}
When I try to pull up the url, I get the following nasty stack trace:
javax.servlet.ServletException: No adapter for handler [com.shaneleopard.web.controller.RegistrationController#e973e3]: Does your handler implement a supported interface like Controller?
org.springframework.web.servlet.DispatcherServlet.getHandlerAdapter(DispatcherServlet.java:1091)
org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:874)
org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:809)
org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:571)
org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:501)
javax.servlet.http.HttpServlet.service(HttpServlet.java:627)
However, if I change Bar to be an abstract superclass and have Foo extend it, then it works again.
#Controller
#RequestMapping("url-mapping-here")
public class Foo extends Bar {
#RequestMapping(method=RequestMethod.GET)
public void showForm() {
...
}
#RequestMapping(method=RequestMethod.POST)
public String processForm() {
...
}
}
This seems like a bug. The #Controller annotation should be sufficient to mark this as a controller, and I should be able to implement one or more interfaces in my controller without having to do anything else. Any ideas?

What I needed to do was replace
<tx:annotation-driven/>
with
<tx:annotation-driven proxy-target-class="true"/>
This forces aspectj to use CGLIB for doing aspects instead of dynamic proxies - CGLIB doesn't lose the annotation since it extends the class, whereas dynamic proxies just expose the implemented interface.

Ed is right, adding
<bean class="org.springframework.web.servlet.mvc.annotation.DefaultAnnotationHandlerMapping"/>
<bean class="org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter"/>
works fine

If you wish to use interfaces for your Spring MVC controllers then you need to move the annotations around a bit, as mentioned in the Spring docs: http://static.springsource.org/spring/docs/3.1.x/spring-framework-reference/html/mvc.html#mvc-ann-requestmapping
Using #RequestMapping On Interface Methods A common pitfall when
working with annotated controller classes happens when applying
functionality that requires creating a proxy for the controller object
(e.g. #Transactional methods). Usually you will introduce an interface
for the controller in order to use JDK dynamic proxies. To make this
work you must move the #RequestMapping annotations to the interface as
well as the mapping mechanism can only "see" the interface exposed by
the proxy. Alternatively, you could activate proxy-target-class="true"
in the configuration for the functionality applied to the controller
(in our transaction scenario in ). Doing so
indicates that CGLIB-based subclass proxies should be used instead of
interface-based JDK proxies. For more information on various proxying
mechanisms see Section 8.6, “Proxying mechanisms”.
Unfortunately it doesn't give a concrete example of this. I have found a setup like this works:
#Controller
#RequestMapping(value = "/secure/exhibitor")
public interface ExhibitorController {
#RequestMapping(value = "/{id}")
void exhibitor(#PathVariable("id") Long id);
}
#Controller
public class ExhibitorControllerImpl implements ExhibitorController {
#Secured({"ROLE_EXHIBITOR"})
#Transactional(readOnly = true)
#Override
public void exhibitor(final Long id) {
}
}
So what you have here is an interface that declares the #Controller, #PathVariable and #RequestMapping annotations (the Spring MVC annotations) and then you can either put your #Transactional or #Secured annotations for instance on the concrete class. It is only the #Controller type annotations that you need to put on the interface because of the way Spring does its mappings.
Note that you only need to do this if you use an interface. You don't necessarily need to do it if you are happy with CGLib proxies, but if for some reason you want to use JDK dynamic proxies, this might be the way to go.

There's no doubt that annotations and inheritance can get a little tricky, but I think that should work. Try explicitly adding the AnnotationMethodHandlerAdapter to your servlet context.
http://static.springframework.org/spring/docs/2.5.x/reference/mvc.html#mvc-ann-setup
If that doesn't work, a little more information would be helpful. Specifically, are the two annotated controller methods from the interface? Is Foo supposed to be RegistrationController?

I know it is too late but i'm writing this for anyone have this problem
if you are using annotation based configuration... the solution might be like this:
#Configuration
#ComponentScan("org.foo.controller.*")
#EnableAspectJAutoProxy(proxyTargetClass=true)
public class AppConfig { ...}

The true reason you need to use 'proxy-target-class="true"' is in DefaultAnnotationHandlerMapping#determineUrlsForHandler() method: though it uses ListableBeanFactory#findAnnotationOnBean for looking up a #RequestMapping annotation (and this takes care about any proxy issues), the additional lookup for #Controller annotation is done using AnnotationUtils#findAnnotation (which does not handles proxy issues)