您无法立即看到上传的图片，因为您将图像保存在应用程序的静态文件中.您可以在文件夹中看到保存的图像，但如果您调用 url，则无法看到.如果您在上传文件(项目根目录并按 F5)后刷新正在运行的项目，您应该能够看到它.

You are not able to see the uploaded picture instantly because you save the image in the static files of your application. You are able to see the the saved image in your folder but not if you call your url. If you refresh your running project after uploading the file (project root and hit F5) you should be able to see it.

但更好的解决方案是你有一个 @RequestMapping 来加载图片并在浏览器中显示.

But the better solution would be that you have a @RequestMapping to load the picture and show it in browser.

以您的项目为基础，尝试像这样使用它:

Build on your project, try to use it like this:

import java.io.IOException;
import java.net.MalformedURLException;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.util.stream.Stream;

import org.json.JSONObject;
import org.springframework.core.io.Resource;
import org.springframework.core.io.UrlResource;
import org.springframework.http.ResponseEntity;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.ResponseBody;
import org.springframework.web.multipart.MultipartFile;

@Controller
public class TestingController {

    private final Path p = Paths.get("/Users/devin/Documents/workspace-sts-3.8.1.RELEASE/testing/src/main/resources/static/uploads/images");

    @RequestMapping(value={ "/", "/home"})
    public String home(){
        return "home";
    }

    @RequestMapping(value = "/post_upload_avatar_file", method = RequestMethod.POST)
    @ResponseBody
    public Object uploadAvatarFile(@RequestParam("uploadfile") MultipartFile uploadfile) {
        JSONObject resJsonData=new JSONObject();
        try {
            if(uploadfile.isEmpty()){
                System.out.println("Empty");
            }

            Files.copy(uploadfile.getInputStream(), p.resolve(uploadfile.getOriginalFilename()));

            resJsonData.put("status", 200);
            resJsonData.put("message", "Success!");
            resJsonData.put("data", uploadfile.getOriginalFilename());
        }catch (Exception e) {
            System.out.println(e.getMessage());
            resJsonData.put("status", 400);
            resJsonData.put("message", "Upload Image Error!");
            resJsonData.put("data", "");
        }
        return resJsonData.toString();
    }

    @GetMapping("files/{filename:.+}")
    @ResponseBody
    public ResponseEntity<Resource> serverFile(@PathVariable String filename){
        Resource file = loadAsResource(filename);
        return ResponseEntity
                .ok()
                .body(file);
    }

     public Resource loadAsResource(String filename) {
        try {
            Path file = p.resolve(filename);
            Resource resource = new UrlResource(file.toUri());
            if(resource.exists() || resource.isReadable()) {
                return resource;
            }
            else {
                System.out.println("no file");
            }
        } catch (MalformedURLException e) {
            System.out.println(e);
        }
        return null;
    }

    public Stream<Path> loadAll() {
        try {
            return Files.walk(p, 1)
                    .filter(path -> !path.equals(p))
                    .map(path -> p.relativize(path));
        } catch (IOException e) {
            System.out.println(e);
        }
        return null;
    }
}

在这段代码中，我没有实现异常和错误处理.

In this code I dont implement exception and error handling.

您可以像以前一样上传图片.然后你可以调用另一个 url 在浏览器中接收图片.

You can upload your picture like it was. And then you can call another url to receive the picture in your browser.

http://localhost:8080/files/testing.png

图片应该是回复.

请查看这两个来源以获得完整的解决方案.

Please have a look to those two sources for a complete solution.

Spring 文件上传 - 后端

Spring 文件上传 - 前端