接收上传的multi-file的文件(四)

构建工程

为例创建一个springmvc工程你需要spring-boot-starter-thymeleaf和 spring-boot-starter-web的起步依赖。为例能够上传文件在服务器，你需要在web.xml中加入标签做相关的配置，但在sringboot 工程中，它已经为你自动做了，所以不需要你做任何的配置。

<dependencies>
      <dependency>
          <groupId>org.springframework.boot</groupId>
          <artifactId>spring-boot-starter-web</artifactId>
      </dependency>
 
      <dependency>
          <groupId>org.springframework.boot</groupId>
          <artifactId>spring-boot-starter-test</artifactId>
          <scope>test</scope>
      </dependency>
 
      <dependency>
          <groupId>org.springframework.boot</groupId>
          <artifactId>spring-boot-starter-thymeleaf</artifactId>
      </dependency>
  </dependencies>

创建文件上传controller

直接贴代码：

@Controller
public class FileUploadController {
 
    private final StorageService storageService;
 
    @Autowired
    public FileUploadController(StorageService storageService) {
        this.storageService = storageService;
    }
 
    @GetMapping("/")
    public String listUploadedFiles(Model model) throws IOException {
 
        model.addAttribute("files", storageService
                .loadAll()
                .map(path ->
                        MvcUriComponentsBuilder
                                .fromMethodName(FileUploadController.class, "serveFile", path.getFileName().toString())
                                .build().toString())
                .collect(Collectors.toList()));
 
        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();
    }
 
}

这个类通过@Controller注解，表明自己上一个Spring mvc的c。每个方法通过
@GetMapping 或者@PostMapping注解表明自己的 http方法。

GET / 获取已经上传的文件列表
GET /files/{filename} 下载已经存在于服务器的文件
POST / 上传文件给服务器

创建一个简单的 html模板

为了展示上传文件的过程，我们做一个界面：
在src/main/resources/templates/uploadForm.html

<html xmlns:th="http://www.thymeleaf.org">
<body>
 
    <div th:if="${message}">
        <h2 th:text="${message}"/>
    </div>
 
    <div>
        <form method="POST" enctype="multipart/form-data" action="/">
            <table>
                <tr><td>File to upload:</td><td><input type="file" name="file" /></td></tr>
                <tr><td></td><td><input type="submit" value="Upload" /></td></tr>
            </table>
        </form>
    </div>
 
    <div>
        <ul>
            <li th:each="file : ${files}">
                <a th:href="${file}" th:text="${file}" />
            </li>
        </ul>
    </div>
 
</body></html>

上传文件大小限制

如果需要限制上传文件的大小也很简单，只需要在springboot 工程的src/main/resources/application.properties 加入以下：

spring.http.multipart.max-file-size=128KB
spring.http.multipart.max-request-size=128KB