04_RequestParam.md

@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()