java实现文件上传下载功能

本文实例为大家分享了java实现文件上传下载的具体代码，供大家参考，具体内容如下

1.上传单个文件

Controller控制层

import java.io.File;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.multipart.MultipartFile;
import org.springframework.web.servlet.mvc.support.RedirectAttributes;

@Controller
@RequestMapping("testup")
public class UploadController {
   private static Logger LG= LoggerFactory.getLogger(UploadController.class);
   /**
    * 9.①单个文件上传
    * @param file
    * @param redirectAttributes
    * @return
    */
   @RequestMapping(value="/upload",method=RequestMethod.POST,consumes="multipart/form-data")
   public String uploadFile(@RequestParam MultipartFile file,RedirectAttributes redirectAttributes){
       if(file.isEmpty()){
           redirectAttributes.addFlashAttribute("message", "Plse select file");
           return "redirect:/test/index";
       }
       try {
           String fileName=file.getOriginalFilename();
           /*上传文件存储位置*/
           String destFileName="D:\\whupload"+File.separator+fileName;
           File destFile=new File(destFileName);
           file.transferTo(destFile);
           //文件上传成功显示
           //redirectAttributes.addAttribute("message","upload file success.");
           redirectAttributes.addFlashAttribute("message", "upload file success.");
       } catch (Exception e) {
           //文件上传失败显示
           redirectAttributes.addFlashAttribute("message", "upload file fail");
           LG.debug(e.getMessage());
       }
       return "redirect:/test/index";
   }

}

前端页面源码

<p>上传文件，使用multipart/form-data类型</p>
 <form action="/testup/upload" method="post" enctype="multipart/form-data">
       <input type="file" name="file">
       <button type="submit">上传</button>
</form>

2.上传多个文件

Controller控制层

import java.io.File;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.multipart.MultipartFile;
import org.springframework.web.servlet.mvc.support.RedirectAttributes;

@Controller
@RequestMapping("testup")
public class UploadController {
   private static Logger LG= LoggerFactory.getLogger(UploadController.class);

/**
    * 9.②多个文件上传
    */
   @RequestMapping(value="/uploadBatchFile",method=RequestMethod.POST,consumes="multipart/form-data")
   public String uploadBatchFile(@RequestParam MultipartFile[] files,RedirectAttributes redirectAttributes){
       boolean isEmpty=true;
       try {
           for (MultipartFile multipartFile : files) {
               if(multipartFile.isEmpty()){
                   continue;
               }
               String fileName=multipartFile.getOriginalFilename();
               String destFileName="D:\\whupload"+File.separator+fileName;
               File destFile=new File(destFileName);
               multipartFile.transferTo(destFile);
               isEmpty=false;
           }
           //int i=1/0;
           //localhost:8086/test/index?message=upload file success
           //redirectAttributes.addAttribute("message","upload file success.");

} catch (Exception e) {
           // TODO Auto-generated catch block
           redirectAttributes.addFlashAttribute("message", "upload file fail");
           LG.debug(e.getMessage());
           return "redirect:/test/index";
       }
       if(isEmpty){
           redirectAttributes.addFlashAttribute("message", "Plse select file");
       }else{
           redirectAttributes.addFlashAttribute("message", "upload file success.");
       }
       return "redirect:/test/index";
   }

}

前端页面源码

<form action="/testup/uploadBatchFile" method="post" enctype="multipart/form-data">
       <input type="file" name="files">
       <input type="file" name="files">
       <button type="submit">上传</button>
</form>

3.下载文件

Controller控制器

import java.io.File;
import java.net.MalformedURLException;
import java.nio.file.Paths;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.core.io.Resource;
import org.springframework.core.io.UrlResource;
import org.springframework.http.HttpHeaders;
import org.springframework.http.ResponseEntity;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.ResponseBody;

@Controller
@RequestMapping("testup")
public class UploadController {
   private static Logger LG= LoggerFactory.getLogger(UploadController.class);

/**
    * 10.下载文件
    */
   @RequestMapping("/download")
   @ResponseBody
   public ResponseEntity<Resource> downloadFile(@RequestParam String fileName){
       try {
           Resource resource=new UrlResource(
                   //拼接下载的文件的原路径
                   Paths.get("D:/whupload"+File.separator+fileName).toUri());
           if(resource.exists() && resource.isReadable()){
               return ResponseEntity.ok()
                       .header(HttpHeaders.CONTENT_TYPE, "application/octet-stream")
                       .header(HttpHeaders.CONTENT_DISPOSITION,"attachment;filename=\""+
                               resource.getFilename()+"\"").body(resource);

}
       } catch (MalformedURLException e) {
           // TODO Auto-generated catch block
           e.printStackTrace();
           LG.debug(e.getMessage());
       }
       return null;
   }
}

前端页面源码

<p>下载文件，这里设置默认下载文件为Demo.txt,fileName是下载文件名</p>
<a href="/testup/download?fileName=Demo.txt" rel="external nofollow" >download file</a>

运行效果

最后，需要注意的是，文件上传有默认的大小限制
在配置文件中加入，即可消除限制

spring.servlet.multipart.max-file-size=-1
spring.servlet.multipart.max-request-size=-1

来源：https://blog.csdn.net/wh456413/article/details/107302180