用Java模拟公共接口，我无法模拟接口

Question

enter code here

我的课程需要测试  公共类FASTapiController; `@RequestMapping（value =“ / downloadAttachments”，方法= RequestMethod.GET，   产生=“应用程序/ pdf”）     公共无效downloadAttachment（HttpServletResponse响应）引发     SpringException {         byte [] bdata = null;         字符串fileName = null;         InputStream myInputStream = null;         BufferedOutputStream fos = null;         尝试{             AttachmentDTO attachmentDTO = manageCampaignServices.downloadAttachment（attachmentIndex）;             长bloblength =附件DTO.getAttachmentContent（）。length（）;             bdata = attachmentDTO.getAttachmentContent（）。getBytes（1，bloblength.intValue（））;             fileName = attachmentDTO.getAttachmentName（）;

response.reset（）;

公共接口ManageCampaignService {     public AttachmentDTO downloadAttachment（String attachmentID）抛出ClipsException; } }