单例模式和文件上传

单例模式

　　

//读取配置文件的工具类-单例模式
public class ConfigManager {
    private static Properties properties;
    private static ConfigManager configManager;

    // 私有构造器-读取数据库配置文件
    private ConfigManager() {
        properties = new Properties();
        String configFile = "database.properties";
        InputStream is = ConfigManager.class.getClassLoader()
                .getResourceAsStream(configFile);
        try {
            properties.load(is);
            is.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    // 全局访问点
    public static ConfigManager getInstance() {
        if (configManager == null) {
            configManager = new ConfigManager();
        }
        return configManager;
    }

    public String getValue(String key) {
        return properties.getProperty(key);
    }

}

　懒汉模式

　　

　饿汉模式

　　

　　

Spring MVC-Controller的单例管理

　　

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文件上传

　单文件上传

　　

　　

　　

　　

    @RequestMapping(value = "/useradd.do")
    public String addUser(
            User user,
            @RequestParam(value = "a_idPicPath", required = false) MultipartFile file,
            HttpSession session, HttpServletRequest request) {
        String idPicPath = null;
        // 判断文件是否为空
        if (!file.isEmpty()) {
            // 定义目标上传路径
            String path = request.getSession().getServletContext()
                    .getRealPath("statics" + File.separator + "uploadfiles");
            String oldFileName = file.getOriginalFilename();
            String suffix = FilenameUtils.getExtension(oldFileName);
            int filesize = 500000;
            if (file.getSize() > filesize) {
                request.setAttribute("uploadFileError", "* 上传大小不得超过500K");
                return "useradd";
            } else if (suffix.equalsIgnoreCase("jpg")
                    || suffix.equalsIgnoreCase("jpeg")
                    || suffix.equalsIgnoreCase("png")
                    || suffix.equalsIgnoreCase("pneg")) {
                // 当前系统时间+随机数+"_Personal.jpg"
                String fileName = System.currentTimeMillis()
                        + RandomUtils.nextInt(1000000) + "_Personal.jpg";
                File targetFile = new File(path, fileName);
                if (!targetFile.exists()) {
                    targetFile.mkdirs();
                }
                try {
                    file.transferTo(targetFile);
                } catch (Exception e) {
                    e.printStackTrace();
                    request.setAttribute("uploadFileError", "* 上传失败");
                    return "useradd";
                }
                idPicPath = path + File.separator + fileName;
            } else {
                request.setAttribute("uploadFileError", "* 上传图片格式不正确");
                return "useradd";
            }
        }

        user.setCreatedBy(((User) session.getAttribute(Constants.USER_SESSION))
                .getId());
        user.setCreationDate(new Date());
        user.setIdPicPath(idPicPath);
        if (userService.add(user)) {
            return "redirect:/user/userlist.do";
        }
        return "useradd";
    }

　多文件上传