I know my opinion doesn't mean much, but here's what I'd do.

Choice #1: I'd tell the shoddy-code guy, "well fuck it. You're the Oracle Portlet expert, let's see what you've got in mind." And try to shift the "primary coding job" over to him. This sounds like a power struggle, and he's just trying to get it done his way. But if he's forced to do the primary coding because he's the one with all the experience with the portlets, then he won't like that, because it'll make him feel like the bitch. While he does all the hard work, you standby and watch.

Choice #2: if choice #1 isn't feasible, or you really want to do the primary coding yourself, then talk directly to your real boss. Tell him how you think it should be done. I'm sure he would understand the situation. If you're the one doing the majority of the work, then it should be up to you how it is done, not up to some dumbass shoddy-code guy.