努力的人不一定能成功，但是成功的人，一定都曾努力。努力寫完今天這篇吧！

ok，今天來做下載API 跟 列出資料API吧

1.Service改加上

 public Resource loadFileAsResource(String fileName) throws Exception {
....
    ...

    }

找到filePath
Path filePath = this.fileStoreLocation.resolve(fileName).normalize();
用resource處理url
Resource resource = new UrlResource(filePath.toUri());
判斷存不存在

 if(resource.exists()) {
    return resource;
 } else {
                throw new Exception("找不到file " + fileName);
            }

2. list所有的資料，這裡用另一個model的方式包覆傳回去
   model，裡面放檔案名稱，檔案網址，因為回傳只想看到檔案名稱跟網址給前端(APP)

public class UrLResponse {




    public String getFileName() {
        return fileName;
    }

    public void setFileName(String fileName) {
        this.fileName = fileName;
    }


    private String fileName="";

    public String getFileUrl() {
        return fileUrl;
    }

    public void setFileUrl(String fileUrl) {
        this.fileUrl = fileUrl;
    }

    private String fileUrl="";
}

 public List<UrLResponse> listUserAll(){
        List<UrLResponse> rl=new ArrayList<>();
        List<FileUpDownModel> fileUpDownModel= upLoadRepository.findAll();
        for (FileUpDownModel ff:fileUpDownModel){
            UrLResponse urLResponse=new UrLResponse();
            urLResponse.setFileName(ff.getFileName());
            urLResponse.setFileUrl(ff.getImgurl());
            rl.add(urLResponse);
        }
        return rl;
    }

4.Controller

下載API

載入resource

  Resource resource = fileUpLoadService.loadFileAsResource(fileName);

設定content-type，必須設成application/octet-stream

 String contentType = null;
        try {
            contentType = request.getServletContext().getMimeType(resource.getFile().getAbsolutePath());
        } catch (IOException ex) {

        }

        if(contentType == null) {
            contentType = "application/octet-stream";
        }

回傳ResponseEntity跟header

        return ResponseEntity.ok()
                .contentType(MediaType.parseMediaType(contentType))
                .header(HttpHeaders.CONTENT_DISPOSITION, "attachment; filename=\"" + resource.getFilename() + "\"")
                .body(resource);

 @GetMapping("/downloadFile/{fileName:.+}")
    public ResponseEntity<Resource> downloadFile(@PathVariable String fileName, HttpServletRequest request) throws Exception {

      ....
       
    }

列出所有的資料API
用responseEntity回傳

  @GetMapping("/searchAllFile")
    public ResponseEntity<Object> downloadFile() throws Exception {

        List<UrLResponse> urLResponses=new ArrayList<>();
        for (UrLResponse file:fileUpLoadService.listUserAll()) {
//            UrLResponse urLResponse=new UrLResponse();
//            urLResponse.setFileName(file);
            urLResponses.add(file);
        }
        return new ResponseEntity<Object>(urLResponses, HttpStatus.OK);

    }

POSTMAN測試

postman下載網址
https://www.postman.com/downloads/
上傳圖片

可以看到有傳進去資料夾了

搜尋所有圖片

下載特定圖片