springmvc(七)文件上传和下载

SpringMVC为文件上传提供了直接支持，这种支持是通过即插即用MultipartResolver实现的。

Spring中有一个MultipartResolver实现类：CommonsMultipartResolver

Spring上下文中默认没有装配MultipartResolver，因此默认情况下不能处理文件上传工作。想要使用上传功能，需要在上下文中装配MultipartResolver。

    
            commons-fileupload
            commons-fileupload
            1.3.1
        

<%@ page contentType="text/html;charset=UTF-8" language="java" %>


    



    

    上传文件

@Controller
@RequestMapping("file")
public class FileController {

    @RequestMapping("upload")
    public String upload(@RequestParam("myFile")MultipartFile myFile, HttpServletRequest request){
        String originalFilename = myFile.getOriginalFilename();
        String fileName = UUID.randomUUID().toString().replace("-", "") + originalFilename.substring(originalFilename.lastIndexOf("."));
        System.out.println(fileName);
        String realPath=request.getServletContext().getRealPath("/uploadFile")+"/";
        try {
            myFile.transferTo(new File(realPath+fileName));
            System.out.println("上传成功"+realPath+fileName);
        } catch (IOException e) {
            e.printStackTrace();
        }
        return "ok";
    }

    @RequestMapping("hello")
    public String hello(){
        return "/jsp/fileHandle";
    } 
}

1、添加过滤器 FileInterceptor

public class FileInterceptor implements HandlerInterceptor {

    
    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
        boolean result=true;
        //判断是否是文件上传请求
        if(request instanceof MultipartHttpServletRequest){
            //获取文件对象map
            MultipartHttpServletRequest multipartRequest= (MultipartHttpServletRequest) request;
            Map fileMap = multipartRequest.getFileMap();
            //遍历map集合中的file
            for(Map.Entry map: fileMap.entrySet()){
                //获取文件名中的后缀
                MultipartFile file = map.getValue();
                String originalFilename = file.getOriginalFilename();
                String suffix=originalFilename.substring(originalFilename.lastIndexOf("."));
                //判断后缀是否满足要求
                if(!suffix.equalsIgnoreCase(".png")&&!suffix.equalsIgnoreCase(".jpg")
                        &&!suffix.equalsIgnoreCase(".gif")&&!suffix.equalsIgnoreCase(".jpeg")){
                    request.getRequestDispatcher("/jsp/fileError.jsp").forward(request,response);
                    result=false;
                }
            }
        }
        return result;
    }

    @Override
    public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {

    }

    @Override
    public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {

    }
}

2、配置过滤器到springmvc.xml

3、添加上传错误页面

<%@ page contentType="text/html;charset=UTF-8" language="java" %>


    


文件类型上传错误，文件必须是.png、.jpg、.jpeg、.gif格式

    下载图片-a6a9ac28393742358b33582d69ee497e.jpg

    @RequestMapping("download")
    public ResponseEntity download(HttpServletRequest request) throws IOException {
        //指定文件路径
        String fileName="a6a9ac28393742358b33582d69ee497e.jpg";
        String filePath=request.getServletContext().getRealPath("/uploadFile")+"/"+fileName;
        File file=new File(filePath);
        //创建响应的头信息
        HttpHeaders headers=new HttpHeaders();
        //标记以流的形式作出响应
        headers.setContentType(MediaType.APPLICATION_OCTET_STREAM);
        //以附件形式响应给用户
        headers.setContentDispositionFormData("attachment", URLEncoder.encode(fileName,"UTF-8"));
        ResponseEntity resp=new ResponseEntity<> (FileUtils.readFileToByteArray(file),headers, HttpStatus.CREATED);
        return resp;
    }