Spring MVC : Common param in all requests

Question

I have many controllers in my Spring MVC web application and there is a param mandatoryParam let's say which has to be present in all the requests to the web application.

Now I want to make that param-value available to all the methods in my web-layer and service-layer. How can I handle this scenario effectively?

Currently I am handling it in this way:

... controllerMethod(@RequestParam String mandatoryParam, ...)

and, then passing this param to service layer by calling it's method

Answer 1

@ControllerAdvice("net.myproject.mypackage")
public class MyControllerAdvice {

    @ModelAttribute
    public void myMethod(@RequestParam String mandatoryParam) {

        // Use your mandatoryParam
    }
}

myMethod() will be called for every request to any controller in the net.myproject.mypackage package. (Before Spring 4.0, you could not define a package. @ControllerAdvice applied to all controllers).

See the Spring Reference for more details on @ModelAttribute methods.

Answer 2

Thanks Alexey for leading the way.

His solution is:

• Add a @ControllerAdvice triggering for all controllers, or selected ones
• This @ControllerAdvice has a @PathVariable (for a "/path/{variable}" URL) or a @RequestParam (for a "?variable=..." in URL) to get the ID from the request (worth mentioning both annotations to avoid blind-"copy/past bug", true story ;-) )
• This @ControllerAdvice then populates a model attribute with the data fetched from database (for instance)
• The controllers with uses @ModelAttribute as method parameters to retrieve the data from the current request's model

I'd like to add a warning and a more complete example:

Warning: see JavaDoc for ModelAttribute.name() if no name is provided to the @ModelAttribute annotation (better to not clutter the code):

The default model attribute name is inferred from the declared attribute type (i.e. the method parameter type or method return type), based on the non-qualified class name: e.g. "orderAddress" for class "mypackage.OrderAddress", or "orderAddressList" for "List<mypackage.OrderAddress>".

The complete example:

@ControllerAdvice
public class ParentInjector {

    @ModelAttribute
    public void injectParent(@PathVariable long parentId, Model model) {
        model.addAttribute("parentDTO", new ParentDTO(parentId, "A faked parent"));
    }

}

@RestController
@RequestMapping("/api/parents/{parentId:[0-9]+}/childs")
public class ChildResource {

    @GetMapping("/{childId:[0-9]+}")
    public ChildDTO getOne(@ModelAttribute ParentDTO parent, long childId) {
        return new ChildDTO(parent, childId, "A faked child");
    }

}

To continue about the warning, requests are declaring the parameter "@ModelAttribute ParentDTO parent": the name of the model attribute is not the variable name ("parent"), nor the original "parentId", but the classname with first letter lowerified: "parentDTO", so we have to be careful to use model.addAttribute("parentDTO"...)

Edit: a simpler, less-error-prone, and more complete example:

@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@Documented
@RestController
public @interface ProjectDependantRestController {

    /**
     * The value may indicate a suggestion for a logical component name,
     * to be turned into a Spring bean in case of an autodetected component.
     *
     * @return the suggested component name, if any
     */
    String value() default "";

}

@ControllerAdvice(annotations = ParentDependantRestController.class)
public class ParentInjector {

    @ModelAttribute
    public ParentDTO injectParent(@PathVariable long parentId) {
        return new ParentDTO(parentId, "A faked parent");
    }

}

@ParentDependantRestController
@RequestMapping("/api/parents/{parentId:[0-9]+}/childs")
public class ChildResource {

    @GetMapping("/{childId:[0-9]+}")
    public ChildDTO getOne(@ModelAttribute ParentDTO parent, long childId) {
        return new ChildDTO(parent, childId, "A faked child");
    }

}