setting url parameter in an action method in struts

I want to add a URL parameter before forwarding to another action from an action method. Although HttpServletRequest has a getParameter() method, it has no setParameter() method. I know setAttribute() is there but I need the it to be part of the URL (like ?something=something&some2=some2). I know I can do it using filters but that's an overkill for this task.

Basically we have an externally managed filter which will change something on a page when that parameter is开发者_运维技巧 set. Let's say the color of the page will be passed as part of the URL parameter. When that parameter is present a servlet filter picks it up and changes the color of that page. I know it's a very odd way of doing but that's how they have it set up here.

I know how to make it work using java script based form submit by adding the URL parameter to the action url (ie. "/someAction.do?color=red"). But for some of the actions it actually does a action.forward("action_name") in the code. For those I was wondering what to do.

Does anyone know how to do that in struts 1.2?

The short answer is that it isn't possible. Request parameters are supposed to be from the HTTP request. You can fake adding them using a combination of a ServletFilter and an HttpServletRequestWrapper but that is outside of Struts. Depending upon what you are trying to accomplish there may be a better solution. Want to describe that a bit more?

Update

With the additional detail you've added, I think you can try this to see if it meets your needs:

import org.apache.struts.action.ActionRedirect;
...
ActionForward forward = action.forward("action_name");
ActionRedirect redirect = new ActionRedirect(forward);
redirect.addParameter("color", "red");
return redirect;

I know this is an old and accepted post, but If you can't upgrade your struts (like me) then this might be useful http://www.coderanch.com/t/45890/Struts/Adding-parameters-struts-action

import org.apache.struts.action.ActionForward;
public class ParameterizedForward extends ActionForward
{
    public ParameterizedForward(ActionForward forward)
    {
        super(forward.getPath(), forward.getRedirect());
    }
    public void addParameter(String key, String value)
    {
        StringBuffer sb = new StringBuffer(getPath());
        if (key == null || key.length() < 1)
            return;
        if (getPath().indexOf('?') == -1)
            sb.append('?');
        else
            sb.append('&');
        sb.append(key + "=" + value);
        setPath(sb.toString());
    }
}

ParameterizedForward fwd = new ParameterizedForward(mapping.findForward("success"));
fwd.addParameter("name","jason");
fwd.addParameter("userLevel", "god");
return fwd;