文件上传

SpringBoot中对文件上传做了简化，使文件上传变得非常方便，以下分享前后端分离的情况下单文件上传与多文件上传的写法。

1. 依赖添加（pom.xml）（基本依赖）

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

2. 配置

   ​ Java中文件上传涉及2个组件，其一是基于commons-fileupload的CommonsMutipartResolver来处理multipart请求，其二是基于Servlet 3.0的StandardServletMultipartResolver来处理multipart请求。Tomcat7开始支持Servlet 3.0，所以SpringBoot内嵌了Tomcat，SpringBoot提供的文件上传自动化配置类MultipartAutoConfiguration，如果开发者未提供MultipartResolver，默认也采用StandardServletMultipartResolver组件，所以SpringBoot文件上传可以做到零配置。

   1. application.properties配置（非必需）

      #配置文件上传
      #是否开启文件上传支持，默认true
      spring.servlet.multipart.enabled=true    
      #文件写入磁盘的阈值，默认为0
      spring.servlet.multipart.file-size-threshold=0
      #上传文件的临时保存位置
      spring.servlet.multipart.location=D:\\data
      #上传的单个文件的最大大小，默认1MB
      spring.servlet.multipart.max-file-size=100MB
      #多文件上传时，文件的总大小，默认10MB
      spring.servlet.multipart.max-request-size=100MB
      #表示文件是否延迟解析，默认为false
      spring.servlet.multipart.resolve-lazily=false

3. Controller

   package cn.wsyjlly.controller;
   
   import org.slf4j.Logger;
   import org.slf4j.LoggerFactory;
   import org.springframework.ui.ModelMap;
   import org.springframework.web.bind.annotation.PostMapping;
   import org.springframework.web.bind.annotation.RestController;
   import org.springframework.web.multipart.MultipartFile;
   
   import javax.servlet.http.HttpServletRequest;
   import java.io.File;
   import java.io.IOException;
   import java.text.SimpleDateFormat;
   import java.util.Date;
   import java.util.HashMap;
   import java.util.Map;
   import java.util.UUID;
   
   /**
    * @author wsyjlly
    * @create 2019.06.13 - 17:23
    **/
   @RestController
   public class FileUploadController {
       private String fomartDate = new SimpleDateFormat("yyyy-MM-dd").format(new Date());
       private final String UPLOAD_PATH = "/uploadFiles/";
       private final Integer SUCCESS = 1;
       private final Integer FAILURE = 0;
       private Logger logger = LoggerFactory.getLogger(getClass());
   
       /*
        * 单文件上传
        * */
       @PostMapping("/upload")
       public ModelMap upload(MultipartFile uploadFile, HttpServletRequest request) {
           ModelMap map = new ModelMap();
           if (uploadFile == null){
               map.addAttribute("status",FAILURE);
               map.addAttribute("message","未选择文件");
               return map;
           }
           File folder = getRootPath();
           logger.debug("文件夹路径:"+folder.getAbsolutePath());
           String originalFilename = uploadFile.getOriginalFilename();
           logger.debug("文件原名："+originalFilename);
           String newName = UUID.randomUUID().toString() + originalFilename.substring(originalFilename.lastIndexOf("."), originalFilename.length());
           try {
               uploadFile.transferTo(new File(folder,newName));
               String filePath = request.getScheme() + "://" + request.getServerName() + ":" + request.getServerPort() + UPLOAD_PATH + fomartDate+"/" + newName;
               logger.debug("文件访问路径："+filePath);
               map.addAttribute("filePath",filePath);
               map.addAttribute("status",SUCCESS);
               return map;
           } catch (IOException e) {
               e.printStackTrace();
           }
           map.addAttribute("status",FAILURE);
           return map;
       }
   
       
       /*
        * 多文件上传
        * */
       @PostMapping("/uploads")
       public ModelMap uploads(MultipartFile[] uploadFiles, HttpServletRequest request) {
           ModelMap map = new ModelMap();
           logger.debug("文件个数："+uploadFiles.length);
   
           //String realPath = ResourceUtils.getURL("classpath:").getPath()+UPLOAD_PATH;
           File folder = getRootPath();
           HashMap<String, Map> fileListUploadStatus = new HashMap<>();
           for (MultipartFile file:uploadFiles){
               HashMap<String, Object> item = new HashMap<>();
               String originalFilename = file.getOriginalFilename();
               System.out.println("————————————————————————————————");
   
               logger.debug("————————————————————————————————");
               logger.debug("文件原名："+originalFilename);
               logger.debug("文件大小："+file.getSize());
               logger.debug("文件类型："+file.getContentType());
               String newName = UUID.randomUUID().toString() + originalFilename.substring(originalFilename.lastIndexOf("."), originalFilename.length());
               try {
                   file.transferTo(new File(folder,newName));
                   String filePath = request.getScheme() + "://" + request.getServerName() + ":" + request.getServerPort() + UPLOAD_PATH + fomartDate+"/" + newName;
                   logger.debug("访问地址："+filePath);
                   logger.debug("地址文件名："+newName);
                   item.put("isUpload",true);
                   item.put("url",filePath);
                   fileListUploadStatus.put(originalFilename,item);
               } catch (IOException e) {
                   item.put("isUpload",false);
                   item.put("url","");
                   fileListUploadStatus.put(originalFilename,item);
                   e.printStackTrace();
               }
           }
           map.addAttribute("resultList",fileListUploadStatus);
           return map;
       }
       private File getRootPath(){
           File file = new File(System.getProperty("user.dir")+UPLOAD_PATH);
           if(!file.exists()){//如果文件夹不存在
               file.mkdirs();//创建文件夹
           }
           String rootPath = file.getAbsolutePath();
           File folder = new File(rootPath+'/' + fomartDate);
           if (!folder.isDirectory()){
               folder.mkdirs();
           }
           return folder;
       }
   }

4. 静态资源访问路径配置

   如果上传资源需要被访问，则须配置上传文件路径添加静态资源访问路径。

   注意：在Linux系统和window系统中相对于当前运行位置的盘的根路径都可表示为 ‘/’

   静态资源文件路径分为两种：

   • 相对路径（相对于classes的路径）即：'classpath:'
   • 绝对路径：文件系统路径，配置文件系统静态资源路径时须添加前缀：'file:'

   /**
    * @author wsyjlly
    * @create 2019.06.12 - 16:17
    **/
   @Configuration
   public class WebMvcConfig implements WebMvcConfigurer {
       private Logger logger = LoggerFactory.getLogger(getClass());
       /*
       * 配置静态资源过滤策略
       * 将静态资源路径映射为访问路径
       * */
       @Override
       public void addResourceHandlers(ResourceHandlerRegistry registry) {
           registry.addResourceHandler("/static/**")
       .addResourceLocations("classpath:/");
           String uploadPath = new File(System.getProperty("user.dir"),"uploadFiles")
           .getAbsolutePath().replaceAll("\\\\","/")+"/";
           registry.addResourceHandler("/uploadFiles/**").
           addResourceLocations("file:"+uploadPath);
           logger.info("上传文件路径映射：/uploadFiles/**  ————>>  "+uploadPath);
       }
   }