springmvc文件上传和文件下载

1.首先springMVC的配置文件：

<!-- 配置 MultipartResolver 文件上传-->
<bean id="multipartResolver" class="org.springframework.web.multipart.commons.CommonsMultipartResolver">
<property name="defaultEncoding" value="UTF-8"/>
<property name="maxUploadSize" value="1024000000"/>
</bean>
<!-- SpringMVC在超出上传文件限制时,会抛出org.springframework.web.multipart.MaxUploadSizeExceededException -->
<!-- 该异常是SpringMVC在检查上传的文件信息时抛出来的,而且此时还没有进入到Controller方法中 -->
<bean id="exceptionResolver" class="org.springframework.web.servlet.handler.SimpleMappingExceptionResolver">
<property name="exceptionMappings">
<props>
<!-- 遇到MaxUploadSizeExceededException异常时,自动跳转到/WEB-INF/jsp/error_fileupload.jsp页面 -->
<prop key="org.springframework.web.multipart.MaxUploadSizeExceededException">error_fileupload</prop>
</props>
</property>
</bean>

导需要的入包

<!-- commons包 -->
<dependency>
<groupId>commons-fileupload</groupId>
<artifactId>commons-fileupload</artifactId>
<version>1.3.2</version>
</dependency>

<dependency>
<groupId>commons-io</groupId>
<artifactId>commons-io</artifactId>
<version>2.4</version>
</dependency>

2.前端页面

<form name="form4" action="/fileupload" method="post" enctype="multipart/form-data">
<input type="file" name="file">
<input type="submit" value="upload"/>
</form>

3.后端接收代码：
/**
* 上传文件
*/
@RequestMapping(value = "/fileupload",method = RequestMethod.POST)
public ModelAndView fileUpload(@RequestParam(value = "file") MultipartFile multipartFile) throws IOException {
String tempPath = "d://temp" + File.separator;
File dir = new File(tempPath);
if (!dir.exists()) {
dir.mkdirs();
}
String storageFilePath = null;//文件路径
String originalFilename = null;//原文件
if (multipartFile.isEmpty()) {
throw new RuntimeException("文件不存在");
} else {
originalFilename = multipartFile.getOriginalFilename();

if (null != originalFilename && originalFilename.length() > 0) {
storageFilePath = tempPath + originalFilename;
try {
Files.copy(multipartFile.getInputStream(), Paths.get(storageFilePath));
} catch (IOException e) {
e.printStackTrace();
throw new RuntimeException("文件上传失败，请重试！！");
}

}
}
return new ModelAndView("success");
}4.后端下载代码：
/**
* 文件下载
* @param response
* @throws Exception
*/
@RequestMapping(value = "/downFile")
public void downFile(HttpServletResponse response)throws Exception{
String pdfPath = "d:"+File.separator+ "temp" + File.separator + "aa.pdf";
response.setContentType("application/octet-stream");
response.setHeader("Content-Disposition", "attachment;filename=aa.pdf");
ServletOutputStream output = response.getOutputStream();

BufferedOutputStream bufferOut = new BufferedOutputStream(output);
InputStream inputStream = new FileInputStream(pdfPath);

byte[] buffer = new byte[5 * 1024];
int length = 0;
while ((length = inputStream.read(buffer, 0, buffer.length)) != -1) {
bufferOut.write(buffer, 0, length);
}
bufferOut.flush();
bufferOut.close();
output.close();
inputStream.close();
}