Initialize managed bean from request parameters

Question

Hi:
I thought this topic would be on the FAQ, but I couldn't find it. I am looking for a mean to initialize my managed bean from the query string. There must be something like:
<h:form initializeBean=""true"" requestParameter=""id_author"" beanProperty=""#{author.id_author}"" action=""#{author.getFromDB}"" >
</form>
The url would be something like http://localhost:8080/protoJSF/showAuthor.jsf?id_author=5334
And the getFromDB method would be something like
  Public void getFromDB()
     Statement stmt = cn.createStatement( ?SELECT * from author where id_author=? + getId_author() );
     ResultSet rs = stmt.executeQuery();
  }The only way I've found to perform something like this is to present a blank author form with a ''load data'' button: after pressing the button the user can see author's data and edit the data if she wants to. This two-step data screening is annoying, to say the least.
There must be a better way.
I beg for a pointer on how can I achieve the initializing of a managed bean with dynamic data.
Regards
Alberto Gaona

Answer 1

You just have to read carefully the very fun 289 pages
specification :-)Or, if 289 pages of JavaServer Faces is too much, you can get almost all of the same information from the JavaServer Pages 2.0 specification, or even the JSP Standard Tag Libraries specification :-).
More seriously, the standard set of "magic" variable names that JavaServer Faces recognizes is the same as that reognized by the EL implementations in JSP and JSTL. Specifically:
* applicationScope - Map of servlet context attributes
* cooke - Map of cookies in this request
* facesContext - The FacesContext instance for this request
* header - Map of HTTP headers (max one value per header name)
* headerValues - Map of HTTP headers (String array of values per header name)
* initParam - Map of context initialization parameters for this webapp
* param - Map of request parameters (max one value per parameter name)
* paramMap - Map of request parameters (String array of values per parameter name)
* requestScope - Map of request attributes for this request
* sessionScope - Map of session attributes for this request
* view - The UIViewRoot component at the base of the component tree for this view
If you use a simple name other than the ones on this list, JavaServer Faces will search through request attributes, session attributes, and servlet context (application) attributes. If not found, it will then try to use the managed bean facility to create and configure an appropriate bean, and give it back to you.
For extra fun, you can even create your own VariableResolver that can define additional "magic" variable names known to your application, and delegate to the standard VariableResolver for anything else.
Craig McClanahan