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。
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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; @Controller public 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
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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
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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; @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) { 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
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< 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}" rel = "external nofollow" th:text = "${file}" /> </ li > </ ul > </ div > </ body > </ html > |
页面主要分为三部分分
- 顶部展示SpringMvc传过来的信息
- 一个提供用户上传文件的表单
- 一个后台提供的文件列表
3、限制上传文件的大小
在文件上传的应用中通常要设置文件大小的,想象一下后台处理的文件如果是5GB,那得多糟糕!在SpringBoot中,我们可以通过属性文件来控制。
新建一个application.properties,代码如下:
spring.http.multipart.max-file-size=128KB #文件总大小不能超过128kb
spring.http.multipart.max-request-size=128KB #请求数据的大小不能超过128kb
4、应用启动函数
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package cn.tiny77.guide05; import org.springframework.boot.CommandLineRunner; import org.springframework.boot.SpringApplication; import org.springframework.boot.autoconfigure.SpringBootApplication; import org.springframework.boot.context.properties.EnableConfigurationProperties; import org.springframework.context.annotation.Bean; @SpringBootApplication @EnableConfigurationProperties (StorageProperties. class ) public class Application { public static void main(String[] args) { SpringApplication.run(Application. class , args); } @Bean CommandLineRunner 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服务器之家。
原文链接:http://www.cnblogs.com/qins/p/7461464.html