注解：RequestBody PathVariable RequestParam的区别

A: GET       http://localhost/getproduct/32

B: GET/POST  http://localhost/getproduct?id=32

C: POST      http://localhost/getproduct

             [POST数据部分内容为:    {id:32}

A:@RequestMapping("/getproduct/{id}")

public Product getProduct(@PathVariable("id") Long id){

  ...

}

B:@RequestMapping("/getproduct")

public Product getProduct(@RequestParam("id") Long id){

  ...

}

C:@RequestMapping("/getproduct")

public Product getProduct(@RequestBody Product product){

 ...//Product包含有一个 名字为 id的属性

}