上传文件（完整代码）

package com.zuoguohui.peis.controller;

import org.springframework.ui.ModelMap;
import org.springframework.web.bind.annotation.*;
import org.springframework.web.multipart.MaxUploadSizeExceededException;
import org.springframework.web.multipart.MultipartFile;
import org.springframework.web.servlet.ModelAndView;
import javax.servlet.http.HttpServletRequest;
import java.io.File;
import java.util.HashMap;
import java.util.Map;

/**Controller层代码
 * @author zuoguohui on 2020/12/19
 */
@RestController
public class FromAction {
    @RequestMapping(value = "/upload",method = RequestMethod.POST)
    public String upload(@RequestParam("file")
                                 MultipartFile file, HttpServletRequest request, ModelMap model)
            throws Exception {

        // 判断提交来的文件是否为空
        if (file.isEmpty()) {
            // model.addAttribute("error", "上传文件不能为空");
            // return "upload";
            throw new RuntimeException("file is null");
        }
        // 获取文件所要保存目录在服务器上所对应的实际路径
        String path="C:/image/";
        // 组成拥有真实路径的一个完整的地址字符串
        String fileUrl = path + "\\" + file.getOriginalFilename();
        // 封装上传文件名称到model对象中
        model.addAttribute("fileName", file.getOriginalFilename());
        // 根据这个完整地址字符串，生成提交文件所要保存到的目标文件或目录的对象
        File targetFile = new File(fileUrl);
        // 判断目标文件或目录的对象是否已经存在
        if (!targetFile.exists()) {
            targetFile.mkdirs();
        }

        // 传送文件到目标对象

        file.transferTo(targetFile);

        System.out.println("已上传文件：" + file);
        return "ok";
    }

    @ExceptionHandler
    public ModelAndView doException(Exception e,HttpServletRequest request) throws Exception {
        Map<String,Object> map = new HashMap<String,Object>();
        if (e instanceof MaxUploadSizeExceededException) {
            long maxSize = ((MaxUploadSizeExceededException) e)
                    .getMaxUploadSize();
            map.put("error", "上传文件太大，不能超过" + maxSize / 1024 + "k");
        }else if(e instanceof RuntimeException){
            map.put("error", "未选中文件");
        }else{
            map.put("error", "上传失败");
        }
        return new ModelAndView("upload",map);

    }

    @GetMapping("/toFromAtion")
    public ModelAndView toFromAtion(ModelAndView modelAndView){
        modelAndView.setViewName("form");
        return modelAndView;
    }
}