以下是获取servletContext:

import javax.servlet.ServletContext;import org.springframework.web.context.ContextLoader;
import org.springframework.web.context.WebApplicationContext;/*** ServletContext辅助类。提供springmvc获取servletContext对象及项目真实路径的静态方法* @author Administrator**/
public class ServletContextUtils {private ServletContextUtils() {}/*** 获取ServletContext对象* @return ServletContext对象*/public static ServletContext getServletContext() {WebApplicationContext webApplicationContext = ContextLoader.getCurrentWebApplicationContext();ServletContext context = webApplicationContext.getServletContext();return context;}/*** 根据folder获取文件的真实路径* @param folder 要获取文件夹的真实路径* @return folder的真实路径*/public static String getRealPath(String folder) {ServletContext context = getServletContext();String path = context.getRealPath(folder);return path;}
}

以下是文件下载代码：

@RequestMapping("/{filename}")public ResponseEntity<byte[]> download(@PathVariable String filename) throws IOException {ResponseEntity<byte[]> entity = null;try {HttpHeaders headers = new HttpHeaders();String pathname = getFilepath(filename);File file = new File(pathname);headers.setContentType(MediaType.APPLICATION_OCTET_STREAM);entity = new ResponseEntity<byte[]>(FileUtils.readFileToByteArray(file), headers, HttpStatus.CREATED);return entity;} catch (IOException e) {logger.error(e.getMessage());throw e;}}private String getFilepath(String filename) {String pathname = ServletContextUtils.getRealPath("/file") + "\\" + filename + ".txt";return pathname;}

springmvc4 以上版本已经实现与servlet的低耦合，不知道为什么很多人写代码用的也是springMVC4或者5，仍然在使用httprequest。