springmvc 文件上传与下载

springmvc上传与下载

必须导入jar包

如果是maven项目导入依赖包

<!-- 文件上传 -->  
<dependency>  
<groupId>commons-fileupload</groupId>  
<artifactId>commons-fileupload</artifactId>  
<version>1.3</version>  
</dependency>  

在spring的servlet视图解析器下面定义CommonsMultipartResolver文件解析器，就是加入这个的时候运行项目，如果没有fileuload相关的jar包就会报错。

在spring mvc 的配置文件中书写xml配置

<!-- 定义文件解释器 -->  
<bean id="multipartResolver" class="org.springframework.web.multipart.commons.CommonsMultipartResolver">    
    <!-- 设置默认编码 -->  
    <property name="defaultEncoding" value="utf-8"></property>  
    <!-- 上传图片最大大小5M-->   
    <property name="maxUploadSize" value="5242440"></property>    
</bean>  

代码演示

@RequestMapping("file")  
@Controller  
public class FileController {  
    /**  
     * 文件上传功能  
     * @param file  
     * @return  
     * @throws IOException   
     */  
    @RequestMapping(value="/upload",method=RequestMethod.POST)  
    @ResponseBody  
    public String upload(MultipartFile file,HttpServletRequest request) throws IOException{  
        String path = request.getSession().getServletContext().getRealPath("upload");  
        String fileName = file.getOriginalFilename();    
        File dir = new File(path,fileName);          
        if(!dir.exists()){  
            dir.mkdirs();  
        }  
        //MultipartFile自带的解析方法  
        file.transferTo(dir);  
        return "ok!";  
    }  
      
    /**  
     * 文件下载功能  
     * @param request  
     * @param response  
     * @throws Exception  
     */  
    @RequestMapping("/down")  
    public void down(HttpServletRequest request,HttpServletResponse response) throws Exception{  
        //模拟文件，myfile.txt为需要下载的文件  
        String fileName = request.getSession().getServletContext().getRealPath("upload")+"/myfile.txt";  
        //获取输入流  
        InputStream bis = new BufferedInputStream(new FileInputStream(new File(fileName)));  
        //假如以中文名下载的话  
        String filename = "下载文件.txt";  
        //转码，免得文件名中文乱码  
        filename = URLEncoder.encode(filename,"UTF-8");  
        //设置文件下载头  
        response.addHeader("Content-Disposition", "attachment;filename=" + filename);    
        //1.设置文件ContentType类型，这样设置，会自动判断下载文件类型    
        response.setContentType("multipart/form-data");   
        BufferedOutputStream out = new BufferedOutputStream(response.getOutputStream());  
        int len = 0;  
        while((len = bis.read()) != -1){  
            out.write(len);  
            out.flush();  
        }  
        out.close();  
    }  
}  

 

from表单提交时一定要设置文件上传属性

上传时的文件名name  一定要与方法中的形参一致

 enctype="multipart/form-data"

<form action="http://localhost:8080/uploadDemo/rest/file/upload" method="post" enctype="multipart/form-data">  
        选择文件:<input type="file" name="file">  
        <input type="submit" value="上传">  
    </form>  
    
    <form action="http://localhost:8080/uploadDemo/rest/file/down" method="get">  
        <input type="submit" value="下载">  
    </form>