java文件上传与下载

不多说，直接上实例代码！！！

我使用的是idea工具，maven管理。

首先，在pom.xml引入上传文件所需要的包。

<!--fileupload-->
    <dependency>
      <groupId>commons-fileupload</groupId>
      <artifactId>commons-fileupload</artifactId>
      <version>1.3.1</version>
    </dependency>

    <dependency>
      <groupId>commons-io</groupId>
      <artifactId>commons-io</artifactId>
      <version>2.2</version>
    </dependency>

单文件上传：

/**
 * Created by 陈 on 2017/9/17.
 */
@Controller
@RequestMapping("/home")
public class UploadController {
    @RequestMapping("/oneUpload")
    public String upload(@RequestParam("file") MultipartFile file, HttpServletRequest request){
        String uploadUrl = request.getSession().getServletContext().getRealPath("/") + "upload/";
        String filename = file.getOriginalFilename();

        //判断相应路径是否存在，不存在则创建
        File dir = new File(uploadUrl);
        if(!dir.exists()){
            dir.mkdir();
        }

        System.out.println("文件上传到：" + uploadUrl + filename);
        File targetFile = new File(uploadUrl + filename);
        if(!targetFile.exists()){
            try {
                targetFile.createNewFile();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
        //移动上传文件
        try {
            file.transferTo(targetFile);
        } catch (IOException e) {
            e.printStackTrace();
        }

        System.out.println("http://127.0.0.1:8080/study2/upload/" + filename);
        return null;
    }
}

多文件上传：

 @RequestMapping("/moreUpload")
    public String moreUpload(HttpServletRequest request){
        MultipartHttpServletRequest multipartHttpServletRequest = (MultipartHttpServletRequest) request;
        Map<String, MultipartFile> files = multipartHttpServletRequest.getFileMap();

        String uploadUrl = request.getSession().getServletContext().getRealPath("/") + "upload/";

        //判断相应路径是否存在，不存在则创建
        File dir = new File(uploadUrl);
        if(!dir.exists()){
            dir.mkdir();
        }

        List<String> fileList = new ArrayList<String>();
        for(MultipartFile file : files.values()){
            File targetFile = new File(uploadUrl + file.getOriginalFilename());
            if(!targetFile.exists()){
                try {
                    targetFile.createNewFile();
                } catch (IOException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }

                try {
                    file.transferTo(targetFile);
                    fileList.add("http://localhost:8080/study2/upload/" + file.getOriginalFilename());
                } catch (IllegalStateException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                } catch (IOException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }
            }
        }

        request.setAttribute("files",fileList);
        System.out.println(files.size());
        return null;
    }

文件下载：

@Controller

public class downLoadController {
    @RequestMapping("/downLoad")
    public String downLoad(String fileName, HttpServletRequest request, HttpServletResponse response){
        response.setContentType("text/html;charset=utf-8");
        try {
            request.setCharacterEncoding("UTF-8");
        } catch (UnsupportedEncodingException e) {
            e.printStackTrace();
        }

        BufferedInputStream bis = null;
        BufferedOutputStream bos = null;

        String ctxPath = request.getSession().getServletContext().getRealPath("/") + "upload/";
        String downLoadPath = ctxPath + fileName;
        System.out.println(downLoadPath);

        try {
            long fileLength = new java.io.File(downLoadPath).length();
            response.setContentType("application/x-msdownload;");
            response.setHeader("Content-disposition", "attachment; filename=" + new String(fileName.getBytes("utf-8"), "ISO8859-1"));
            response.setHeader("Content-Length", String.valueOf(fileLength));
            bis = new BufferedInputStream(new FileInputStream(downLoadPath));
            bos = new BufferedOutputStream(response.getOutputStream());
            byte[] buff = new byte[2048];
            int bytesRead;
            while ((bytesRead = bis.read(buff, 0, buff.length)) != -1) {
                bos.write(buff, 0, bytesRead);
            }
        }catch (Exception e){
            e.printStackTrace();
        }finally {
            try {
                bis.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
            try {
                bos.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }

        return null;
    }
}