SpringMVC返回图片的几种方式(小结)

@RequestMapping(value = {"/img/render"}, method = {RequestMethod.GET, RequestMethod.POST, RequestMethod.OPTIONS})
@CrossOrigin(origins = "*")
@ResponseBody
public String execute(HttpServletRequest httpServletRequest,
       HttpServletResponse httpServletResponse) {
  // img为图片的二进制流
  byte[] img = xxx;
  httpServletResponse.setContentType("image/png");
  OutputStream os = httpServletResponse.getOutputStream();
  os.write(img);
  os.flush();
  os.close();
  return "success";
}

@Data
public class BaseRequest {
  private static final long serialVersiOnUID= 1146303518394712013L;
  /**
   * 输出图片方式:
   *
   * url : http地址 （默认方式）
   * base64 : base64编码
   * stream : 直接返回图片
   *
   */
  private String outType;
  /**
   * 返回图片的类型
   * jpg | png | webp | gif
   */ 
  private String mediaType;
  public ReturnTypeEnum returnType() {
    return ReturnTypeEnum.getEnum(outType);
  }
  public MediaTypeEnum mediaType() {
    return MediaTypeEnum.getEnum(mediaType);
  }
}

public enum ReturnTypeEnum {
  URL("url"),
  STREAM("stream"),
  BASE64("base");

  private String type;
  ReturnTypeEnum(String type) {
    this.type = type;
  }
  private static Map map;
  static {
    map = new HashMap<>(3);
    for(ReturnTypeEnum e: ReturnTypeEnum.values()) {
      map.put(e.type, e);
    }
  }

  public static ReturnTypeEnum getEnum(String type) {
    if (type == null) {
      return URL;
    }

    ReturnTypeEnum e = map.get(type.toLowerCase());
    return e == null &＃63; URL : e;
  }
}

@Data
public enum MediaTypeEnum {
  ImageJpg("jpg", "image/jpeg", "FFD8FF"),
  ImageGif("gif", "image/gif", "47494638"),
  ImagePng("png", "image/png", "89504E47"),
  ImageWebp("webp", "image/webp", "52494646"),
  private final String ext;
  private final String mime;
  private final String magic;
  MediaTypeEnum(String ext, String mime, String magic) {
    this.ext = ext;
    this.mime = mime;
    this.magic = magic;
  }

  private static Map map;
  static {
    map = new HashMap<>(4);
    for (MediaTypeEnum e: values()) {
      map.put(e.getExt(), e);
    }
  }

  public static MediaTypeEnum getEnum(String type) {
    if (type == null) {
      return ImageJpg;
    }
    MediaTypeEnum e = map.get(type.toLowerCase());
    return e == null &＃63; ImageJpg : e;
  }
}

@Data
public class BaseResponse {

  /**
   * 返回图片的相对路径
   */
  private String path;


  /**
   * 返回图片的https格式
   */
  private String url;


  /**
   * base64格式的图片
   */
  private String base;
}

protected void buildResponse(BaseRequest request,
               BaseResponse response,
               byte[] bytes) throws SelfError {
  switch (request.returnType()) {
    case URL:
      upload(bytes, response);
      break;
    case BASE64:
      base64(bytes, response);
      break;
    case STREAM:
      stream(bytes, request);
  }
}
private void upload(byte[] bytes, BaseResponse response) throws SelfError {
  try {
    // 上传到图片服务器，根据各自的实际情况进行替换
    String path = UploadUtil.upload(bytes);

    if (StringUtils.isBlank(path)) { // 上传失败
      throw new InternalError(null);
    }

    response.setPath(path);
    response.setUrl(CdnUtil.img(path));
  } catch (IOException e) { // cdn异常
    log.error("upload to cdn error! e:{}", e);
    throw new CDNUploadError(e.getMessage());
  }
}

// 返回base64
private void base64(byte[] bytes, BaseResponse response) {
  String base = Base64.getEncoder().encodeToString(bytes);
  response.setBase(base);
}
// 返回二进制图片
private void stream(byte[] bytes, BaseRequest request) throws SelfError {
  try {
    MediaTypeEnum mediaType = request.mediaType();
    HttpServletResponse servletRespOnse= ((ServletRequestAttributes) RequestContextHolder.getRequestAttributes()).getResponse();
    servletResponse.setContentType(mediaType.getMime());
    OutputStream os = servletResponse.getOutputStream();
    os.write(bytes);
    os.flush();
    os.close();
  } catch (Exception e) {
    log.error("general return stream img error! req: {}, e:{}", request, e);
    if (StringUtils.isNotBlank(e.getMessage())) {
      throw new InternalError(e.getMessage());
    } else {
      throw new InternalError(null);
    }
  }
}

@Override
public synchronized Throwable fillInStackTrace() {
  return this;
}