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How to DRY when using Swagger UI and the ApiResponses annotations with Java Spring endpoints?

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I like Swagger because it makes your apis very user friendly. I use Swagger annotations like

  • @ApiParam
  • @ApiResponse | @ApiResponses
  • @ApiOperation
  • Others
  • On endpoints, query params, request params, request body and so on.

    I like to keep my POJO classes clean and in general I try my best to follow DRY rule however, when it comes to swagger I noticed that I keep repeating myself over and over as shown below

    @ApiOperation(value = "Retrieve object by id")
    @ApiResponses(value = {
        @ApiResponse(code = 200, message = "OK"),
        @ApiResponse(code = 404, message = "Not Found"),
        @ApiResponse(code = 400, message = "Bad Request"),
        @ApiResponse(code = 500, message = "ISE")
    public Response retrieveById(@ApiParam(value = "Some id") @PathParam("sid") int id) {       
    @ApiOperation(value = "Create object")
    @ApiResponses(value = {
        @ApiResponse(code = 201, message = "Created"),
        @ApiResponse(code = 404, message = "Not Found"),
        @ApiResponse(code = 400, message = "Bad Request"),
        @ApiResponse(code = 500, message = "ISE")
    public Response create(@ApiParam(value = "Request body") RequestBody body) {
    

    How to avoid repeating yourself with Swagger annotations?

    I did some Googling around and came across this github issue and some other SO questions that are not directly related to ApiResponses annotations and none of them seem to present a working solution.

    Using Swagger UI 2.0 I thought let's give it a try, so I did the following

  • I created a custom annotations GroupedApiResponses..
  • I annotated GroupedApiResponses.. with a group of Swagger annotations
  • I used the GroupedApiResponses.. annotations on top of endpoints
  • Works just like before
  • See below

    package com.raf.annotation;
    import java.lang.annotation.ElementType;
    import java.lang.annotation.Retention;
    import java.lang.annotation.RetentionPolicy;
    import java.lang.annotation.Target;
    import io.swagger.annotations.ApiResponse;
    import io.swagger.annotations.ApiResponses;
    @Retention(RetentionPolicy.RUNTIME)
    @Target(ElementType.METHOD)
    @ApiResponses(value = {
            @ApiResponse(code = 200, message = "Ok"),
            @ApiResponse(code = 404, message = "Not Found"),
            @ApiResponse(code = 400, message = "Bad Request"),
            @ApiResponse(code = 500, message = "ISE") 
    public @interface GroupedApiResponsesAvecOk {
    

    Similarly (you can group annotations as you want in one or more than one custom annotation depending on structure of your endpoints and the response messages it return)

    @Retention(RetentionPolicy.RUNTIME)
    @Target(ElementType.METHOD)
    @ApiResponses(value = {
            @ApiResponse(code = 201, message = "Created"),
            @ApiResponse(code = 404, message = "Not Found"),
            @ApiResponse(code = 400, message = "Bad Request"),
            @ApiResponse(code = 500, message = "ISE") 
    public @interface GroupedApiResponsesAvecCreated {
    

    And then I used the above @GroupedApiResponsesAvecOk on retrieveById and @GroupedApiResponsesAvecCreated on create endpoint in place of @ApiResponses and worked it just like before.

    As shown above, the ApiResponse annotations relating to 400, 404, 500 can now be reused across other endpoints.

    Very nice. Is there anyway to provide an input to the new meta-annotation that allows the user to specify the response type for one of the @ApiResponses? – RocketMan Sep 9, 2021 at 16:50

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