Visual force error message in a new page

Question

I'm creating a custom VF page for the registration of new users.

Page: simple form to get the user's email.

Controller:

public with sharing class SiteRegisterController {

    public SiteRegisterController () {
    }


public String username {get; set;}
public String email {get; set;}
public String password {get; set;}

    public PageReference registerUser() {
       user u = [select id,username from User where username = :email];
           if (u!=null) {
                  //ADD HERE CODE FOR ERROR MESSAGE IN THE PAGE FORGOTPASSWORD
                  PageReference page = System.Page.ForgotPassword;
                page.setRedirect(true);
                return page;
            }
            else {
                PageReference page = new PageReference('http://registration.com/');
                page.setRedirect(true);
                return page;
            }

        return null;
    }
}

If the user is already registered i would like also add a message "You are already registered, Did you forget your password?" on the new page System.Page.ForgotPassword;. I know how to add an eror message in the current page

ApexPages.Message myMsg = new ApexPages.Message(ApexPages.Severity.ERROR,'Error Message.');
ApexPages.addMessage(myMsg); 

but is it also possible add it in a new page(forgotpassword) from the controller of the current page? Of course in the page forgot password there is a tag <apex:pageMessages id="error"/>

Thanks in advantage for any advice.

BR.

Answer 1

PageReference page = new PageReference('http://aapp.salesforce.com/forgotpassword?mess='forgot');
            page.setRedirect(true);
            return page;

Using above code pass the message in mess param to next page as URL parameter

In the forgot password page just get this param value

string errormessge=Apexpages.currentpage().getparameters.get(mess);

if(errormessge=='forgot'){
  ApexPages.Message myMsg = new ApexPages.Message(ApexPages.Severity.ERROR,'Forgot passowrd');//Same old drama 
    ApexPages.addMessage(myMsg); 
}