Rendering command validation errors across a redirect

I cannot render the errors from my command object. It does the job well but my .gsp view does not render the errors I raise.

Here is my controller action:

def handleModifyProfile2 = { CreditProviderModificationCommand cpmc -> // bind params to the command object
   if (cpmc.hasErrors()) {
      flash.message = "Error modifying your profile:"
      redirect(action: "modifyProfile", params: [creditProvider : cpmc])
   } ...

Here is how I try to render the errors in my .gsp view:

<g:hasErrors bean="${creditProvider}">
   <div class="errors">
       <g:renderErrors bean="${creditProvider}" as="list" />
   </div>
</g:hasErrors>

How can I get the errors to be displayed in the view?

You can't send the command across in a redirect using params. You have a couple options:

• render() in the error condition instead of redirect()ing:

  if(cpmc.hasErrors()) {
      render(view: 'profile', model: [creditProvider: cpmc])
  }
  

  This is the most common idiom for what you're doing.

• Store the command in the session to persist it across the redirect:

  if(cpmc.hasErrors()) {
      session.cpmc = cpmc
      redirect(...)
  }
  
  // and in your action
  def cpmc = session.cpmc ?: null
  render(view: 'profile', model: [creditProvider: cpmc])
  

  This option is somewhat questionable. If not done correctly, you can pollute the session and leave objects hanging around, taking up memory. If done correctly, though, it can be a decent way to implement a post-redirect-get.