15.上传文件

SpringBoot java

创建时间:2020-03-21 21:47

阅读:

构建

构建

IDEA新建选择 Web Thymeleaf

或者添加POM依赖

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

编码

定义上传的配置

@Configuration
@ConfigurationProperties("storage")
public class StorageProperties {

    /**
     * Folder location for storing files
     */
    private String location = "upload-dir";

    public String getLocation() {
        return location;
    }

    public void setLocation(String location) {
        this.location = location;
    }

}

创建上传的service

public interface StorageService {

    void init();

    void store(MultipartFile file);

    Stream<Path> loadAll();

    Path load(String filename);

    Resource loadAsResource(String filename);

    void deleteAll();
}

实现service

@Service
public 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) {
        try {
            if (file.isEmpty()) {
                throw new StorageException("Failed to store empty file " + file.getOriginalFilename());
            }
            Files.copy(file.getInputStream(), this.rootLocation.resolve(file.getOriginalFilename()));
        } catch (IOException e) {
            throw new StorageException("Failed to store file " + file.getOriginalFilename(), 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("Failed to read stored files", 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("Could not read file: " + filename);

            }
        } catch (MalformedURLException e) {
            throw new StorageFileNotFoundException("Could not read file: " + filename, e);
        }
    }

    @Override
    public void deleteAll() {
        FileSystemUtils.deleteRecursively(rootLocation.toFile());
    }

    @Override
    public void init() {
        try {
            Files.createDirectory(rootLocation);
        } catch (IOException e) {
            throw new StorageException("Could not initialize storage", e);
        }
    }
}

定义可能出现的错误类

public class StorageException extends RuntimeException{

    public StorageException(String message) {
        super(message);
    }

    public StorageException(String message, Throwable cause) {
        super(message, cause);
    }
}

public class StorageFileNotFoundException extends StorageException {

    public StorageFileNotFoundException(String message) {
        super(message);
    }

    public StorageFileNotFoundException(String message, Throwable cause) {
        super(message, cause);
    }
}

创建文件上传controller

@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.servlet.multipart.max-file-size=128KB
spring.servlet.multipart.max-request-size=128KB

测试

访问http://localhost:8080/

官方文档

https://spring.io/guides/gs/uploading-files/

问题1：

官方样例代码里StorageProperties 只有 @ConfigurationProperties
但是IDEA总报错，增加@Configuration后解决

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