@RequestMapping will only be processed if a corresponding HandlerMapping (for type level annotations) and/or HandlerAdapter (for method level annotations) is present in the dispatcher. This is the case by default in both DispatcherServlet and DispatcherPortlet.

However, if you are defining custom HandlerMappings or HandlerAdapters, then you need to make sure that a corresponding custom DefaultAnnotationHandlerMapping and/or AnnotationMethodHandlerAdapter is defined as well - provided that you intend to use @RequestMapping.

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://www.springframework.org/schema/beans
        http://www.springframework.org/schema/beans/spring-beans-3.0.xsd">

    <bean class="org.springframework.web.portlet.mvc.annotation.DefaultAnnotationHandlerMapping"/>

    <bean class="org.springframework.web.portlet.mvc.annotation.AnnotationMethodHandlerAdapter"/>

    // ... (controller bean definitions) ...

</beans>

Defining a DefaultAnnotationHandlerMapping and/or AnnotationMethodHandlerAdapter explicitly also makes sense if you would like to customize the mapping strategy, e.g. specifying a custom WebBindingInitializer (see below).

The @Controller annotation indicates that a particular class serves the role of a controller. There is no need to extend any controller base class or reference the Portlet API. You are of course still able to reference Portlet-specific features if you need to.

The basic purpose of the @Controller annotation is to act as a stereotype for the annotated class, indicating its role. The dispatcher will scan such annotated classes for mapped methods, detecting @RequestMapping annotations (see the next section).

Annotated controller beans may be defined explicitly, using a standard Spring bean definition in the dispatcher's context. However, the @Controller stereotype also allows for autodetection, aligned with Spring 2.5's general support for detecting component classes in the classpath and auto-registering bean definitions for them.

To enable autodetection of such annotated controllers, you have to add component scanning to your configuration. This is easily achieved by using the spring-context schema as shown in the following XML snippet:

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xmlns:p="http://www.springframework.org/schema/p"
    xmlns:context="http://www.springframework.org/schema/context"
    xsi:schemaLocation="
        http://www.springframework.org/schema/beans
        http://www.springframework.org/schema/beans/spring-beans-3.0.xsd
        http://www.springframework.org/schema/context
        http://www.springframework.org/schema/context/spring-context-3.0.xsd">

    <context:component-scan base-package="org.springframework.samples.petportal.portlet"/>

    // ...

</beans>

The @RequestMapping annotation is used to map portlet modes like 'VIEW'/'EDIT' onto an entire class or a particular handler method. Typically the type-level annotation maps a specific mode (or mode plus parameter condition) onto a form controller, with additional method-level annotations 'narrowing' the primary mapping for specific portlet request parameters.

Tip

@RequestMapping at the type level may be used for plain implementations of the Controller interface as well. In this case, the request processing code would follow the traditional handle(Action|Render)Request signature, while the controller's mapping would be expressed through an @RequestMapping annotation. This works for pre-built Controller base classes, such as SimpleFormController, too. In the following discussion, we'll focus on controllers that are based on annotated handler methods.

The following is an example of a form controller from the PetPortal sample application using this annotation:

@Controller
@RequestMapping("EDIT")
@SessionAttributes("site")
public class PetSitesEditController {

    private Properties petSites;

    public void setPetSites(Properties petSites) {
        this.petSites = petSites;
    }

    @ModelAttribute("petSites")
    public Properties getPetSites() {
        return this.petSites;
    }

    @RequestMapping  // default (action=list)
    public String showPetSites() {
        return "petSitesEdit";
    }

    @RequestMapping(params = "action=add")  // render phase
    public String showSiteForm(Model model) {
        // Used for the initial form as well as for redisplaying with errors.
        if (!model.containsAttribute("site")) {
            model.addAttribute("site", new PetSite());
        }
        return "petSitesAdd";
    }

    @RequestMapping(params = "action=add")  // action phase
    public void populateSite(
            @ModelAttribute("site") PetSite petSite, BindingResult result,
            SessionStatus status, ActionResponse response) {

        new PetSiteValidator().validate(petSite, result);
        if (!result.hasErrors()) {
            this.petSites.put(petSite.getName(), petSite.getUrl());
            status.setComplete();
            response.setRenderParameter("action", "list");
        }
    }

    @RequestMapping(params = "action=delete")
    public void removeSite(@RequestParam("site") String site, ActionResponse response) {
        this.petSites.remove(site);
        response.setRenderParameter("action", "list");
    }
}

Handler methods which are annotated with @RequestMapping are allowed to have very flexible signatures. They may have arguments of the following types, in arbitrary order (except for validation results, which need to follow right after the corresponding command object, if desired):

The following return types are supported for handler methods:

The @RequestParam annotation is used to bind request parameters to a method parameter in your controller.

The following code snippet from the PetPortal sample application shows the usage:

@Controller
@RequestMapping("EDIT")
@SessionAttributes("site")
public class PetSitesEditController {

    // ...

    public void removeSite(@RequestParam("site") String site, ActionResponse response) {
        this.petSites.remove(site);
        response.setRenderParameter("action", "list");
    }

    // ...
}

Parameters using this annotation are required by default, but you can specify that a parameter is optional by setting @RequestParam's required attribute to false (e.g., @RequestParam(value="id", required="false")).

@ModelAttribute has two usage scenarios in controllers. When placed on a method parameter, @ModelAttribute is used to map a model attribute to the specific, annotated method parameter (see the processSubmit() method below). This is how the controller gets a reference to the object holding the data entered in the form. In addition, the parameter can be declared as the specific type of the form backing object rather than as a generic java.lang.Object, thus increasing type safety.

@ModelAttribute is also used at the method level to provide reference data for the model (see the populatePetTypes() method below). For this usage the method signature can contain the same types as documented above for the @RequestMapping annotation.

Note: @ModelAttribute annotated methods will be executed before the chosen @RequestMapping annotated handler method. They effectively pre-populate the implicit model with specific attributes, often loaded from a database. Such an attribute can then already be accessed through @ModelAttribute annotated handler method parameters in the chosen handler method, potentially with binding and validation applied to it.

The following code snippet shows these two usages of this annotation:

@Controller
@RequestMapping("EDIT")
@SessionAttributes("site")
public class PetSitesEditController {

    // ...

    @ModelAttribute("petSites")
    public Properties getPetSites() {
        return this.petSites;
    }

    @RequestMapping(params = "action=add")  // action phase
    public void populateSite(
            @ModelAttribute("site") PetSite petSite, BindingResult result,
            SessionStatus status, ActionResponse response) {

        new PetSiteValidator().validate(petSite, result);
        if (!result.hasErrors()) {
            this.petSites.put(petSite.getName(), petSite.getUrl());
            status.setComplete();
            response.setRenderParameter("action", "list");
        }
    }
}

The type-level @SessionAttributes annotation declares session attributes used by a specific handler. This will typically list the names of model attributes which should be transparently stored in the session or some conversational storage, serving as form-backing beans between subsequent requests.

The following code snippet shows the usage of this annotation:

@Controller
@RequestMapping("EDIT")
@SessionAttributes("site")
public class PetSitesEditController {
  // ...
}

To customize request parameter binding with PropertyEditors, etc. via Spring's WebDataBinder, you can either use @InitBinder-annotated methods within your controller or externalize your configuration by providing a custom WebBindingInitializer.

@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));
    }

    // ...
}