@RequestPart :看源码备注:

Annotation that can be used to associate the part of a "multipart/form-data" request
 * with a method argument.
 *
 * 
Supported method argument types include {@link MultipartFile} in conjunction with
 * Spring's {@link MultipartResolver} abstraction, {@code javax.servlet.http.Part} in
 * conjunction with Servlet 3.0 multipart requests, or otherwise for any other method
 * argument, the content of the part is passed through an {@link HttpMessageConverter}
 * taking into consideration the 'Content-Type' header of the request part. This is
 * analogous to what @{@link RequestBody} does to resolve an argument based on the
 * content of a non-multipart regular request.
 *
 * 
Note that @{@link RequestParam} annotation can also be used to associate the part
 * of a "multipart/form-data" request with a method argument supporting the same method
 * argument types. The main difference is that when the method argument is not a String
 * or raw {@code MultipartFile} / {@code Part}, {@code @RequestParam} relies on type
 * conversion via a registered {@link Converter} or {@link PropertyEditor} while
 * {@link RequestPart} relies on {@link HttpMessageConverter HttpMessageConverters}
 * taking into consideration the 'Content-Type' header of the request part.
 * {@link RequestParam} is likely to be used with name-value form fields while
 * {@link RequestPart} is likely to be used with parts containing more complex content
 * e.g. JSON, XML).

@RequestPart主要用来处理content-type为 multipart/form-data 或 multipart/mixed stream 发起的请求,可以获取请求中的参数,包括普通文本、文件或复杂对象比如json、xml等,针对json等复杂对象,需要明确对应的content-type,例如:

 发出来的请求头:

Content-Type: multipart/form-data; boundary=xxxxxxxxxx

----xxxxxxxxxxxx

@RequestParam:看源码备注:

Annotation which indicates that a method parameter should be bound to a web
 * request parameter.
 *
 * 
Supported for annotated handler methods in Spring MVC and Spring WebFlux
 * as follows:
 * 

 * 
In Spring MVC, "request parameters" map to query parameters, form data,
 * and parts in multipart requests. This is because the Servlet API combines
 * query parameters and form data into a single map called "parameters", and
 * that includes automatic parsing of the request body.
 * 
In Spring WebFlux, "request parameters" map to query parameters only.
 * To work with all 3, query, form data, and multipart data, you can use data
 * binding to a command object annotated with {@link ModelAttribute}.
 * 
 *
 * 
If the method parameter type is {@link Map} and a request parameter name
 * is specified, then the request parameter value is converted to a {@link Map}
 * assuming an appropriate conversion strategy is available.
 *
 * 
If the method parameter is {@link java.util.Map Map<String, String&gt;} or
 * {@link org.springframework.util.MultiValueMap MultiValueMap<String, String&gt;}
 * and a parameter name is not specified, then the map parameter is populated
 * with all request parameter names and values.

@RequestParam默认主要来处理query parameters, form data,and parts in multipart requests, 且是 key-value键值对这种文本,要区分 

　　Spring MVC:

　　　　会把query parameters, form data,and parts in multipart requests 里面的参数组合到一起存放在一个参数Map里(key相同的参数,值会追加)

　　Spring WebFlux:

　　　　只会处理query parameters

另外  可以看这里