简单的把文件转成流保存的上传下载方法：

常量定义：

	private static final String filePath = "D:/a_photo/";//本地测试
//	private static final String filePath = "/var/";//服务器测试

　注意：对应的 controller 类，注解不能用：@RestController ，而是使用 @Controller

 上传方法：

/**
	 * 上传文件
	 * @author Mongo
	 * @param file
	 * @param request
	 * @param response
	 */
	@RequestMapping(value = "/fileUpload", method = RequestMethod.POST, produces = "text/html; charset=UTF-8")
	public void fileUpload(MultipartFile file, HttpServletRequest request,HttpServletResponse response) {
		
		Map<String, Object> data = new HashMap<String, Object>();
        data.put("msg", "fail");
        data.put("data", null);
        try {
			if (file.isEmpty()) {
				logger.info("==== 上传的文件为空 ====");
				data.put("msg", "上传的文件为空");
				response.setContentType("text/html; charset=UTF-8");
				JsonUtils.writeValue(response.getWriter(), data);
				return;
			}
			String fileName = file.getOriginalFilename(); // 文件名
			String suffixName = fileName.substring(fileName.lastIndexOf(".")); // 后缀名
			String uuid = UUID.randomUUID().toString().replace("-", "");
			fileName = uuid + suffixName; // 新文件名
			File nameAndPath = new File(filePath + fileName);
　　　　　　　　　　　　　　dest.setWritable(true,false);//linux下需要赋予权限才能上传成功
			if (!nameAndPath.getParentFile().exists()) {
				nameAndPath.getParentFile().mkdirs();
			}
			file.transferTo(nameAndPath);
			logger.info("==== 上传成功 ====");
			data.put("msg", "success");
			data.put("data", fileName);
			//往浏览器输出成功与否结果
			response.setContentType("text/html; charset=UTF-8");
			JsonUtils.writeValue(response.getWriter(), data);
        } catch (IOException e) {
			e.printStackTrace();
			logger.error("==== 上传失败异常 ====",e);
		}
		return;
	}

　　下载方法：

/**
	 * 下载文件url
	 * @author Mongo
	 * @param request
	 * @param response
	 * @param filename
	 */
	@RequestMapping(value = "/fileDownland", method = RequestMethod.GET, produces = "text/html; charset=UTF-8")
	public void fileDownland(HttpServletRequest request, HttpServletResponse response) {
		
		String fileName = request.getParameter("fileName");
		String path = filePath + fileName;
		logger.info("== 下载链接为： == "+path);
		File file = new File(path);
		
		OutputStream out = null;
		FileInputStream in = null;
		try {
			// 文件存在才下载
			if (file.exists()) {
				// 1.读取要下载的内容
				in = new FileInputStream(file);
				// 2. 告诉浏览器下载的方式以及一些设置
				// 解决文件名乱码问题，获取浏览器类型，转换对应文件名编码格式，IE要求文件名必须是utf-8, firefo要求是iso-8859-1编码
				String agent = request.getHeader("user-agent");
				if (agent.contains("FireFox")) {
					fileName = new String(fileName.getBytes("UTF-8"), "iso-8859-1");
				} else {
					fileName = URLEncoder.encode(fileName, "UTF-8");
				}
				// 设置下载文件的mineType，告诉浏览器下载文件类型（下面这两句可以不要）
				//String mineType = request.getServletContext().getMimeType(fileName);
				//response.setContentType(mineType);
				// 设置一个响应头，无论是否被浏览器解析，都下载
				response.setHeader("Content-disposition", "attachment; filename=" + fileName);
				// 将要下载的文件内容通过输出流写到浏览器
				out = response.getOutputStream();
				int len = 0;
				byte[] buffer = new byte[1024];
				while ((len = in.read(buffer)) > 0) {
					out.write(buffer, 0, len);
				}
			}
		} catch (Exception e) {
			e.printStackTrace();
		} finally {
			try {
				if (out != null) {
					out.close();
				}
				if (in != null) {
					in.close();
				}
			} catch (Exception e2) {
				// TODO: handle exception
			}
		}
	}

　　对应的工具类：

　　　　private static ObjectMapper mapper = new ObjectMapper();
/**
	 * 将对象转换为JSON流
	 * 
	 * @param writer
	 *            writer
	 * @param value
	 *            对象
	 */
	public static void writeValue(Writer writer, Object value) {
		try {
			mapper.writeValue(writer, value);
		} catch (JsonGenerationException e) {
			e.printStackTrace();
		} catch (JsonMappingException e) {
			e.printStackTrace();
		} catch (IOException e) {
			e.printStackTrace();
		}
	}

　　相应的 jar 包引入：

import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.OutputStream;
import java.net.URLEncoder;
import java.util.HashMap;
import java.util.Map;
import java.util.UUID;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.multipart.MultipartFile;