def accessToken()

in plugin-rest/spring-security-rest/grails-app/controllers/grails/plugin/springsecurity/rest/RestOauthController.groovy [127:181]
47 lines of code
10 McCabe index (conditional complexity)

    def accessToken() {
        String grantType = params['grant_type']
        if (!grantType || grantType != 'refresh_token') {
            render status: HttpStatus.BAD_REQUEST, text: "Invalid grant_type"
            return
        }

        String refreshToken = params['refresh_token']
        log.debug "Trying to generate an access token for the refresh token: ${refreshToken}"
        if(!refreshToken) {
            log.debug "Refresh token is missing. Replying with bad request"
            render status: HttpStatus.BAD_REQUEST, text: "Refresh token is required"
            return
        }

        // only JWT tokens can be refreshed
        if(!AbstractJwtTokenGenerator.isAssignableFrom(tokenGenerator.getClass())) {
            log.debug("Token type does not support refresh tokens")
            render status: HttpStatus.FORBIDDEN
            return
        }

        try {
            JWT jwt = jwtService.parse(refreshToken)
            if(!jwt || !jwt.JWTClaimsSet.getBooleanClaim(AbstractJwtTokenGenerator.REFRESH_ONLY_CLAIM)) {
                log.debug("Token ${refreshToken} is not a refresh token")
                render status: HttpStatus.FORBIDDEN
                return
            }
        }
        catch(e) {
            log.debug("Invalid refresh token: ${refreshToken}", e)
            render status: HttpStatus.FORBIDDEN
            return
        }

        try {
            def user = tokenStorageService.loadUserByToken(refreshToken)
            User principal = user ? user as User : null
            log.debug "Principal found for refresh token: ${principal}"

            AccessToken accessToken = (tokenGenerator as AbstractJwtTokenGenerator).generateAccessToken(principal, false)
            accessToken.refreshToken = refreshToken

            tokenStorageService.storeToken(accessToken)
            authenticationEventPublisher.publishTokenCreation(accessToken)

            response.addHeader 'Cache-Control', 'no-store'
            response.addHeader 'Pragma', 'no-cache'
            render contentType: 'application/json', encoding: 'UTF-8',  text:  accessTokenJsonRenderer.generateJson(accessToken)
        } catch (e) {
            log.debug("Could not load by refresh token", e)
            render status: HttpStatus.FORBIDDEN
        }
    }