Specifying the controller’s method return type (part I)

The controller's method return type can be void, String, Viewable Java type and Response:

·         void - such controller method must be decorated by @View          

·         String - the returned String will be interpreted as a path

·         Viewable - encapsulates a view path as well as additional information related to its processing    

·         Java Type - the method toString() is called on other Java types and the result interpreted as a view path   

·         Response - A JAX-RS Response whose entity’s type is one of the above

Void and String Examples

In the simplest example we return a String (path) from a controller method, so in this section we will focus more on returning void, using @View and exposing the interaction cases between @View and String returning.  Let's suppose that we have a simple controller with a single method that returns void. In such case we need to annotate the method with @View("path"), as below:

// the helloVoidAction() will return the hello.html thanks to @View

@Controller   

@Path("hello")

public class HelloController {

   

 @GET      

 @View("hello.html")

 public void helloVoidAction() {

  // NOPE       

 }

}

In the above example, we can achieve the same behavior by annotating the class with @View. If all the methods of a controller return void then the @View from class level will point out the same returned view for all methods. Further, let's suppose that we have a controller with @View at class level and with different kind of methods, as follows (notice how the returned path is computed based on certain priorities: the String returned by a method has the highest priority, while the @View at class level has the smallest priority):

·         by default, the controller will always return bye.html

@Controller

@Path("bye")

@View("bye.html")

public class ByeController {

 ...

}

·         method that uses @View at class level (returns the bye.html)

@GET

@Path("forever")

public void byeVoidAction() {

 // NOPE       

}

·         method that override the @View from class level with @View at method level (returns the seeyou.html)

@GET

@Path("wasbye")

@View("seeyou.html")

public void wasForeverVoidAction() {

 // NOPE       

}

·         method that override @View from method level by returning a String (path)  (returns the bye.html)

@GET

@Path("stillbye")

@View("seeyou.html")

public String stillByeStringAction() {

 return "bye.html";

}

·         method that returns null will use @View from class level (returns the bye.html)

@GET

@Path("nullbye")

public String nullByeStringAction() {

 return null;       

}

·         method that returns null will use @View from method level (returns the seeyou.html)

@GET

@Path("nullseeyou")

@View("seeyou.html")

public String nullSeeyouStringAction() {

 return null;       

}

·         method that returns String (path) overrides @View from class level (returns the seeyou.html)

@GET

@Path("fornow")

public String seeyouStringAction() {

 return "seeyou.html";

}