@RequestParam

Reference: Spring Docs - RequestParam

What is @RequestParam?

• An annotation that retrieves parameters passed from external sources to an API

• Used to bind HTTP request parameters to method parameters

• Mainly used when receiving parameter values from client requests as Controller method parameters for processing

• ex)

  @RequestParam("name") String name

  Stores the parameter passed externally with the name "name" into the method parameter name (String name)

Using @RequestParam

• Spring MVC

  • Maps to query parameters, form data, and parts of multipart requests

  • This occurs because the Servlet API combines query parameters and form data into a single map called parameters, which includes automatic parsing of the request body

• Spring WebFlux

  • Maps only to query parameters

  • To handle all three types -- query parameters, form data, and multipart -- you can use data binding to a command object annotated with ModelAttribute

• Things to know

  • If the method parameter type is Map and a request parameter name is specified, the request parameter value is converted to a Map when an appropriate conversion strategy exists

  • If the method parameter is Map<String, String> or MultiValueMap<String, String> and no parameter name is specified, the map parameter is populated with all request parameter names and values

Attributes of @RequestParam

• name

  • Specifies the name of the request parameter

• required

  • Specifies whether the request parameter is required

  • Default value is true

  • If required=true and the parameter is not present in the request, an exception is thrown

• defaultValue

  • Specifies the default value to use when the request parameter is not provided

• value

  • Alias for name()