Java annotations in odd places

Question

Browsing through the source of a spring framework project i came across a method that looked like this:

@RequestMapping("primitive")
public @ResponseBody String primitive(@RequestParam Integer value) {
    return "Converted primitive " + value;
}

Being only a casual java user, ive not come across this before. As far as i was aware, the @ symbol preceded java annotations, yet there appear to be annotations in the method signature itself. What are the @ResponseBody and @RequestParam sections doing?

Answer 1

The @ResponseBody is actually just a Plain-Jane Method annotation. You're allowed to put them after the scope keyword.

The @RequestParam annotation isn't part of the method signature. It's a Parameter Annotation.

Answer 2

Those annotations are specific to Spring, so you'll need to dive into Spring to learn all the annotations and what they mean.

Whenever I need to learn something new in Spring, I always jump back to the documentation: http://static.springsource.org/spring/docs/3.1.x/spring-framework-reference/html/

It's good to read through that whole thing at least once in your life, if you plan on using Spring for enterprise development.