I am going to bring this post back from the dead.

The whole reason behind this thread is I was looking to build some type of URL shortener. The problem was that if the URL contained an "&" symbol within one of the parameter values it would get all messed up and break, see original post. There is the Link Force app on the AppExchange but from what I can tell that uses a URL field to store the long URL. This has a limit of 255 characters and in my use case this wont work. What did work was using this line of code to add URL params. It did not double encode characters and all was good.

page1.getParameters().put('name','Anderson & Smith');

My use case also had about 20 url params. So how to do this? Let's say we want to create this url http://www.mysite.com?name=jason&company=Cool & Rad.

I created a custom object with two fields, Base URL (Text) and URL Params (Long Text).

The Base URL field would contain this value: http://www.mysite.com

The long text field stores the URL params like this:

name<---------------->jason
company<---------------->Cool & Rad

The code below would contruct this URL:

List<URL_Shortener__c> url = [select Base_URL__c, URL_Parameters__c from URL_Shortener__c where Id = :ApexPages.currentPage().getParameters().get('id')];
        
if(url.size() > 0){
    page = new PageReference(url[0].Base_URL__c);
       
    List<String> paramList = url[0].URL_Parameters__c.split('\n');
             
    //Loop through param and add to page
    for(String s : paramList){
      	List<String> keyValue = s.split('<---------------->');
  	page.getParameters().put(keyValue[0],keyValue[1]);
    }
}

This will break if by some random chance a URL param value contains "<---------------->" but I am willing to bet against this ever happening but you can always make the delimiter something even more random if this is a concern.

-Jason