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首先描述一下问题，spring boot 使用的是内嵌的tomcat， 所以不清楚文件上传到哪里去了， 而且spring boot 把静态的文件全部在启动的时候都会加载到classpath的目录下的，所以上传的文件不知相对于应用目录在哪，也不知怎么写访问路径合适，对于新手的自己真的一头雾水。

后面想起了官方的例子，没想到一开始被自己找到的官方例子，后面太依赖百度谷歌了，结果发现只有官方的例子能帮上忙，而且帮上大忙，直接上密码的代码

package hello; 
import static org.springframework.hateoas.mvc.ControllerLinkBuilder.linkTo; 
import static org.springframework.hateoas.mvc.ControllerLinkBuilder.methodOn; 
import java.io.IOException; 
import java.nio.file.Files; 
import java.nio.file.Paths; 
import java.util.stream.Collectors; 
import javax.servlet.http.HttpServletRequest; 
import org.slf4j.Logger; 
import org.slf4j.LoggerFactory; 
import org.springframework.beans.factory.annotation.Autowired; 
import org.springframework.core.io.ResourceLoader; 
import org.springframework.http.ResponseEntity; 
import org.springframework.stereotype.Controller; 
import org.springframework.ui.Model; 
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; 
import org.springframework.web.servlet.mvc.support.RedirectAttributes; 
@Controller 
public class FileUploadController { 
 private static final Logger log = LoggerFactory.getLogger(FileUploadController.class); 
 public static final String ROOT = "upload-dir"; 
 private final ResourceLoader resourceLoader; 
 @Autowired 
 public FileUploadController(ResourceLoader resourceLoader) { 
 this.resourceLoader = resourceLoader; 
 } 
 @RequestMapping(method = RequestMethod.GET, value = "/") 
 public String provideUploadInfo(Model model) throws IOException { 
 model.addAttribute("files", Files.walk(Paths.get(ROOT)) 
  .filter(path -> !path.equals(Paths.get(ROOT))) 
  .map(path -> Paths.get(ROOT).relativize(path)) 
  .map(path -> linkTo(methodOn(FileUploadController.class).getFile(path.toString())).withRel(path.toString())) 
  .collect(Collectors.toList())); 
 return "uploadForm"; 
 } 
//显示图片的方法关键 匹配路径像 localhost:8080/b7c76eb3-5a67-4d41-ae5c-1642af3f8746.png 
 @RequestMapping(method = RequestMethod.GET, value = "/{filename:.+}") 
 @ResponseBody 
 public ResponseEntity<?> getFile(@PathVariable String filename) { 
 
 try { 
  return ResponseEntity.ok(resourceLoader.getResource("file:" + Paths.get(ROOT, filename).toString())); 
 } catch (Exception e) { 
  return ResponseEntity.notFound().build(); 
 } 
 } 
//上传的方法 
 @RequestMapping(method = RequestMethod.POST, value = "/") 
 public String handleFileUpload(@RequestParam("file") MultipartFile file, 
RedirectAttributes redirectAttributes, HttpServletRequest request) { 
 System.out.println(request.getParameter("member")); 
 if (!file.isEmpty()) { 
  try { 
  Files.copy(file.getInputStream(), Paths.get(ROOT, file.getOriginalFilename())); 
  redirectAttributes.addFlashAttribute("message", 
   "You successfully uploaded " + file.getOriginalFilename() + "!"); 
  } catch (IOException|RuntimeException e) { 
  redirectAttributes.addFlashAttribute("message", "Failued to upload " + file.getOriginalFilename() + " => " + e.getMessage()); 
  } 
 } else { 
  redirectAttributes.addFlashAttribute("message", "Failed to upload " + file.getOriginalFilename() + " because it was empty"); 
 } 
 return "redirect:/"; 
 } 
} 

新闻名称：springboot图片上传与显示功能实例详解-创新互联
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