java常用单例

public class TerminalServiceHelper {
    // 静态日志对象
    private static final Logger logger = Logger.getLogger(TerminalServiceHelper.class);
    
    private TerminalServiceHelper() {
　　　　　// 私有构造器
　　　　　　initTerminalService();
    }

    // 私有静态实列对象
    private static TerminalServiceHelper instance;

    // 获取实例对象
    public static TerminalServiceHelper getInstance() {
        // 不存在就创建，存在就返回; 如果多线程调用如何保证唯一单例
        if (instance != null) {
            return instance;
        }
        instance = new TerminalServiceHelper();
        return instance;
    }

    private Map<String, String> serviceMap = new HashMap<String, String>();

    public void add(String requestCode, String serviceName) {
        serviceMap.put(requestCode, serviceName);
    }

　　　　　

　　　　private void initTerminalService() {
　　　　　　// 初始化bean名称到集合对象中

　　　　　　add("1001", "cardSignedService");

　　　　}

public IBaseWebserviceService getService(String requestCode, ServletContext ctx) throws ParamException {
        WebApplicationContext springContext = WebApplicationContextUtils.getWebApplicationContext(ctx);
        IBaseWebserviceService geposAppService = null;
        try {
            geposAppService = (IBaseWebserviceService) springContext.getBean(serviceMap.get(requestCode));
        } catch (Exception e) {
            logger.error(e.getMessage(),e);
            throw new ParamException("请求类型不正常，请确认后重试:"+e.getMessage());
        }
        return geposAppService;
    }

}