spring MVC 获取servletContext,实现文件下载功能

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。