应用市场中Java拦截器和切面的使用实例详解

时间:2021-09-21 09:35:18

相信大家对拦截器切面的概念已经不陌生了,本文我们就看一些在应用市场中,拦截器和切面的使用是怎样的。

拦截器的使用:每次接收到某个请求之前,都会调用此拦截器中的方法,其中preHandle方法如果return true,表示继续调用对应的controller,如果return false,

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public class CheckLoginInterceptor implements HandlerInterceptor {
    private Logger logger = Logger.getLogger(CheckLoginInterceptor.class);
    private static String TOKEN_VALID_MSG ;
    static
      {
        TOKEN_VALID_MSG=JsonUtil.writeObject2JSON(new AMSResultVO(CodeNum.TOKEN_VALID, CodeMessage.TOKEN_VALID));
    }
    public Boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
        //request.getMethod获取请求是get,post等
        if ("OPTIONS".equals(request.getMethod()))
             {
            // 指定允许其他域名访问
            response.setHeader("Access-Control-Allow-Origin", "*");
            // 响应类型
            response.setHeader("Access-Control-Allow-Methods", "POST, GET, OPTIONS, DELETE");
            // 响应头设置
            response.setHeader("Access-Control-Allow-Headers", "Content-Type, x-requested-with, X-Custom-Header");
            response.setStatus(204);
            return true;
        }
        // 获取从header中得到的数据
        String userName = request.getHeader(CommonConsts.PARAM_USER_NAME);
        String userToken = request.getHeader(CommonConsts.PARAM_USER_TOKEN);
        Boolean result = true;
        String method = request.getRequestURI();
        if(method.equals("/ams/fileUpload"))
            {
            return true;
        }
        if(StringUtil.isEmpty(userName) || StringUtil.isEmpty(userToken))
            {
            result = false;
        } else
            {
            result = TokenUtil.validToken(userName, userToken);
        }
        // token校验失败
        if(!result)
            {
            response.setContentType("text/html;charset=UTF-8");
            response.getWriter().print(TOKEN_VALID_MSG);
            response.getWriter().flush();
            response.getWriter().close();
        }
        return result;
    }
    public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {
    }
    public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {
    }
}

切面的使用:

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//坏绕通知:需要携带ProceedingJoinPoint类型的参数
//环绕通知类似于动态代理的全过程:ProceedingJoinPoint类型的参数可以决定是否执行目标方法
//且环绕通知必须有返回值,返回值即目标方法的返回值。
@Around("execution(* com.sowell.controller.*Controller.*(..))")
  public Object aroundMethod(ProceedingJoinPoint pjd) {
    Object result = null;
    String methodName = pjd.getSignature().getName();
    Object args = Arrays.asList(pjd.getArgs());
    //执行目标方法
    try {
        logger.info("request channels begin, param{pageNum:" + methodName + ", pageSize:" + args);
        //前置通知,表示在此之前的代码会在调用controller之前调用
        result = pjd.proceed();
        recordOprationLog(result, methodName, result);
        //后置通知
        logger.info("Arround:The method "+ methodName+" ends");
    }
    catch (Throwable e) {
        e.printStackTrace();
        //异常通知
        logger.error("Arround:The method "+ methodName+"occurs exception:"+e);
        //throw new RuntimeException(e);
        //不抛出异常的话,异常就被上面抓住,执行下去,返回result,result值为null,转换为int
    }
    //返回通知
    logger.info("Arround:The method "+ methodName+" ends with the Result "+ result);
    return result;
}

总结

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原文链接:http://blog.csdn.net/qq_28893679/article/details/72841958