If you're like many cat owners, you've probably experienced all the "fun" of having a cat for an alarm clock. In some cases, this is beneficial, and a few people even swear their cats are better alarm clocks than their regular alarm clock. Buzzfeed even has a listicle about why cats make such great alarm clocks (with the author's tongue planted firmly in cheek). But what about when you don't want your cat waking you up like that, especially if you're sick or injured, and you need to rest as much as possible?
First off, it's important to understand that cats are crepuscular creatures, meaning they're most active at dawn and dusk. The time of dawn varies throughout the year, and while it might be a comfortable time in, say, fall or winter, it's entirely too early at the summer solstice for many people.
This is where training comes in. When your cat is looking for your attention, either because he's hungry or because he's bored, as soon as you pay attention to him, you've rewarded his behavior. Your cat needs to know that he's not getting anything from you until you're ready to be up, not even a look. So it might be necessary to shut him out of your room, so he can't see you wake up.
But that doesn't solve the issue of meowing loudly at your bedroom door for an hour (or two or three). You can sleep with ear plugs if you have to, but, if he's waking you up for food, you can try feeding your cat right before you go to bed at night, so he's not so hungry so early. If it's not hunger, but boredom, that causes him to wake you up, you might want to get several different types of toys for him that he can play with when he wakes up. Test out the toys to see which ones he likes the most. You might want to rotate through them so he doesn't get bored with any one toy.
Also, playing with him in the evening before you go to bed can help, because if you tire him out, he may want to sleep for longer at night, giving you the extra couple of hours you're not currently getting.
It's extremely important to stop responding to his demands that you get up. If you give him that reward, he'll keep doing it no matter what else you try. And he knows it, which is why he keeps it up. Once he figures out that you won't pay attention when you're trying to sleep, he'll stop. Feeding him later, and giving him things to do while you're sleeping, will aid in that process.