How to “throw” JSF2 404 error?

Question

Let\'s say that I have an application which manages users. You can add new user, delete them, edit detail etc. Each user has na ID and has detail page on URL like this:

Answer 1

(I ended up here searching for something similar but here's another pattern I used on a similar problem)

The Validation/ExternalContext response above is a very good way to handle it, alternatively (since you are already inside the context) you can handle the error when parsing in the parameters from the request and deal with it internally. I think it is more of how you want to handle it in your flow than a "here's a better solution"

//Inside "SomeManagedBean"
  public String getParam()
  {
    String value = (String) FacesContext.getCurrentInstance().getExternalContext().getRequestParameterMap().get("key");
    if(value == null)
      return "key not Exist";
    else
      return value;

  }

//JSF 2.0 Source (something.xhtml) ... ...

I think the above is generally easier to work with inside the framework (you don't have to send out to an error page and disrupt the flow), but really it is simply an architectural decision. Both solutions are similar, it is just a question of breaking the flow or internal handling. Either way the ExternalContext is your friend.