本小节你将建立一个可以接受HTTP multi-part 文件的服务。

你将建立一个后台服务来接收文件以及前台页面来上传文件。

要利用servlet容器上传文件，你要注册一个MultipartConfigElement类，以往需要在web.xml 中配置<multipart-config>，
而在这里，你要感谢SpringBoot，一切都为你自动配置好了。

1、新建一个文件上传的Controller：

应用已经包含一些 存储文件 和 从磁盘中加载文件 的类，他们在cn.tiny77.guide05这个包下。我们将会在FileUploadController中用到这些类。

package cn.tiny77.guide05;import java.io.IOException;import java.util.List;import java.util.stream.Collectors;import org.springframework.beans.factory.annotation.Autowired;import org.springframework.core.io.Resource;import org.springframework.http.HttpHeaders;import org.springframework.http.ResponseEntity;import org.springframework.stereotype.Controller;import org.springframework.ui.Model;import org.springframework.web.bind.annotation.ExceptionHandler;import org.springframework.web.bind.annotation.GetMapping;import org.springframework.web.bind.annotation.PathVariable;import org.springframework.web.bind.annotation.PostMapping;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.method.annotation.MvcUriComponentsBuilder;import org.springframework.web.servlet.mvc.support.RedirectAttributes;@Controllerpublic class FileUploadController { private final StorageService storageService; @Autowired public FileUploadController(StorageService storageService) { this.storageService = storageService; } @GetMapping("/") public String listUploadedFiles(Model model) throws IOException { List<String> paths = storageService.loadAll().map( path -> MvcUriComponentsBuilder.fromMethodName(FileUploadController.class, "serveFile", path.getFileName().toString()).build().toString()) .collect(Collectors.toList()); model.addAttribute("files", paths); return "uploadForm"; } @GetMapping("/files/{filename:.+}") @ResponseBody public ResponseEntity<Resource> serveFile(@PathVariable String filename) { Resource file = storageService.loadAsResource(filename); return ResponseEntity.ok().header(HttpHeaders.CONTENT_DISPOSITION, "attachment; filename=\"" + file.getFilename() + "\"").body(file); } @PostMapping("/") public String handleFileUpload(@RequestParam("file") MultipartFile file, RedirectAttributes redirectAttributes) { storageService.store(file); redirectAttributes.addFlashAttribute("message", "You successfully uploaded " + file.getOriginalFilename() + "!"); return "redirect:/"; } @ExceptionHandler(StorageFileNotFoundException.class) public ResponseEntity<?> handleStorageFileNotFound(StorageFileNotFoundException exc) { return ResponseEntity.notFound().build(); }}

该类用@Controller注解，因此SpringMvc可以基于它设定相应的路由。每一个@GetMapping和@PostMapping注解将绑定对应的请求参数和请求类型到特定的方法。

GET / 通过StorageService 扫描文件列表并 将他们加载到 Thymeleaf 模板中。它通过MvcUriComponentsBuilder来生成资源文件的连接地址。

GET /files/{filename} 当文件存在时候，将加载文件，并发送文件到浏览器端。通过设置返回头"Content-Disposition"来实现文件的下载。

POST / 接受multi-part文件并将它交给StorageService保存起来。

你需要提供一个服务接口StorageService来帮助Controller操作存储层。接口大致如下

package cn.tiny77.guide05;import org.springframework.core.io.Resource;import org.springframework.web.multipart.MultipartFile;import java.nio.file.Path;import java.util.stream.Stream;public interface StorageService { void init(); void store(MultipartFile file); Stream<Path> loadAll(); Path load(String filename); Resource loadAsResource(String filename); void deleteAll();}

以下是接口实现类

package cn.tiny77.guide05;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.nio.file.StandardCopyOption;import java.util.stream.Stream;import org.springframework.beans.factory.annotation.Autowired;import org.springframework.core.io.Resource;import org.springframework.core.io.UrlResource;import org.springframework.stereotype.Service;import org.springframework.util.FileSystemUtils;import org.springframework.util.StringUtils;import org.springframework.web.multipart.MultipartFile;@Servicepublic class FileSystemStorageService implements StorageService { private final Path rootLocation; @Autowired public FileSystemStorageService(StorageProperties properties) { this.rootLocation = Paths.get(properties.getLocation()); } @Override public void store(MultipartFile file) { String filename = StringUtils.cleanPath(file.getOriginalFilename()); try { if (file.isEmpty()) { throw new StorageException("无法保存空文件 " + filename); } if (filename.contains("..")) { // This is a security check throw new StorageException( "无权访问该位置 " + filename); } Files.copy(file.getInputStream(), this.rootLocation.resolve(filename), StandardCopyOption.REPLACE_EXISTING); } catch (IOException e) { throw new StorageException("无法保存文件 " + filename, e); } } @Override public Stream<Path> loadAll() { try { return Files.walk(this.rootLocation, 1) .filter(path -> !path.equals(this.rootLocation)) .map(path -> this.rootLocation.relativize(path)); } catch (IOException e) { throw new StorageException("读取文件异常", e); } } @Override public Path load(String filename) { return rootLocation.resolve(filename); } @Override public Resource loadAsResource(String filename) { try { Path file = load(filename); Resource resource = new UrlResource(file.toUri()); if (resource.exists() || resource.isReadable()) { return resource; } else { throw new StorageFileNotFoundException( "无法读取文件: " + filename); } } catch (MalformedURLException e) { throw new StorageFileNotFoundException("无法读取文件: " + filename, e); } } @Override public void deleteAll() { FileSystemUtils.deleteRecursively(rootLocation.toFile()); } @Override public void init() { try { Files.createDirectories(rootLocation); } catch (IOException e) { throw new StorageException("初始化存储空间出错", e); } }}

2、建立一个Html页面

这里使用Thymeleaf模板

<html xmlns:th="http://mandLineRunner init(StorageService storageService) { return (args) -> { storageService.deleteAll(); storageService.init(); }; }}

5、运行结果

以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持。