supermanhamuerto.com

User Tools

Site Tools

Trace:
java:passparametersamongpages

Differences

This shows you the differences between two versions of the page.

Link to this comparison view

Both sides previous revisionPrevious revision
java:passparametersamongpages [2012/12/09 11:35] – [Step 4: Page 2 receives the parameter] rlunarojava:passparametersamongpages [2022/12/02 21:02] (current) – external edit 127.0.0.1
Line 1: Line 1:
 +====== Pass parameters from one page to another in jsf ======
 +
 +====== Intro ======
 +
 +I've been looking around how to solve this typical problem: to pass one parameter from one page to other (for instance when we prompt the user to select one item on a list and, when clicking a button, switch to another page to edit this very item). 
 +
 +Despite the fact that the Internet is crowded with examples of how to pass parameters to and fro a bean and a page, I've don't see many examples of this, and the solutions I've found didn't satisfy me completely: first, because some of them use the faces-config.xml file and I don't use it much because all my beans are held by Spring, second, because these solution requires a configuration per navigation case, that it isn't very easy to do. 
 +
 +So, I've found this solution reading some hints of [[http://balusc.blogspot.com.es/2006/06/communication-in-jsf.html|this article]].
 +
 +
 +====== Step 1: the idea ======
 +
 +I've avoided to pass the parameters in a request, or something like that: instead of this, I will save them in a session bean devoted to this. 
 +
 +====== Step 2: the bean to save the objects in session ======
 +
 +<code java>
 +public class SessionHelper implements Serializable
 +{
 +    
 +    public static Object getSessionMapValue(String key) 
 +    {
 +        return FacesContext.getCurrentInstance().getExternalContext().getSessionMap().get(key);
 +    }
 +
 +    public static void setSessionMapValue(String key, Object value) 
 +    {
 +    FacesContext.getCurrentInstance().getExternalContext().getSessionMap().put(key, value);
 +    }
 +}
 +
 +</code>
 +
 +====== Step 3: Page 1 saves the parameter ======
 +
 +This is an example in a commandButton of [[http://www.primefaces.org/|Primefaces]], but you can adapt to your library of preference: 
 +
 +<code xml>
 +    <p:commandButton ajax="false"
 +                    type="submit" 
 +                    id="cmdModify" 
 +                    value="Modificar"
 +                    action="#{manageUsersForm.cmdModify}"
 +                    disabled="#{!manageUsersForm.userSelected}"
 +                    styleClass="right">
 +       #{sessionHelper.setSessionMapValue('selectedUser',manageUsersForm.selectedUser)}
 +    </p:commandButton>
 +
 +</code>
 +
 +Yes, I've called the ''sessionHelper.setSessionMapValue'' directly inside the ''commandButton'' tag and it seems to do the work. I thought that you have to use a faces tag or something like that, but it seems that it is not completely neccesary.
 +
 +====== Step 4: Page 2 receives the parameter ======
 +
 +Just simple as this: 
 +
 +<code>
 + <h3><h:outputText value="#{sessionHelper.getSessionMapValue('selectedUser').username}"/></h3>
 +</code>
 +
 +Look that I've passed through the session a complete object. Okay, it's not a recommendable practice unless you are __completely sure__ that the objects implements ''[[http://docs.oracle.com/javase/6/docs/api/java/io/Serializable.html|Serializable]]'' (and the depending objects, of course), because otherwise you would run into problems in a clustered environment. 
 +
 +This particular example the object is an Hibernate entity object... Mmmm I think that if persisted in another computer could lead into problems, but I have to confess that I am not an expert in the field.
 +
 + 
 +