Spring MVC学习-day06

Spring MVC 拦截器

拦截器的执行流程图

代码清单

在Spring MVC的配置文件中配置拦截器(这里配置了两个拦截器)

<!-- 配置拦截器 -->
    <mvc:interceptors>
        <mvc:interceptor>
            <!-- 配置要拦截的请求 -->
            <mvc:mapping path="/*"/>
            <!-- 配置自定义的拦截器 -->
            <bean class="com.zgz.springmvc.interceptors.FirstInterceptor"></bean>
        </mvc:interceptor>
        <mvc:interceptor>
            <!-- 配置多个拦截器 -->            
            <mvc:mapping path="/*"/>
            <bean class="com.zgz.springmvc.interceptors.SecondInterceptor"></bean>
        </mvc:interceptor>
    </mvc:interceptors>

拦截器必须实现HandlerInterceptor接口，该接口定义了三个方法，掌握这三个方法的作用和有多个拦截器时的执行过程即可
多个拦截器时的执行流程图

两个拦截器

public class FirstInterceptor implements HandlerInterceptor {

    /**
     * 该方法在目标方法之前调用
     * 若该方法返回值为true，则继续调用后续的拦截器和目标方法
     * 若返回值为false，则不会调用后续的拦截器和目标方法
     * 
     * 可以考虑做权限，日志，事务等
     * @return
     * @throws Exception
     */
    @Override
    public boolean preHandle(HttpServletRequest arg0, HttpServletResponse arg1, Object arg2) throws Exception {
        System.out.println("preHandle: ");
        return true;
    }

    /**
     * 调用目标方法之后，但在渲染视图之前
     * 可以对请求域中的属性或视图做出修改
     * @throws Exception
     */
    @Override
    public void postHandle(HttpServletRequest arg0, HttpServletResponse arg1, Object arg2, ModelAndView arg3)
            throws Exception {
        System.out.println("postHandle: ");
    }

    /***
     * 渲染试图之后被调用
     * 可以释放资源
     * @throws Exception
     */
    @Override
    public void afterCompletion(HttpServletRequest arg0, HttpServletResponse arg1, Object arg2, Exception arg3)
            throws Exception {
        System.out.println("afterCompletion: ");
    }

}

public class SecondInterceptor implements HandlerInterceptor {

    @Override
    public boolean preHandle(HttpServletRequest arg0, HttpServletResponse arg1, Object arg2) throws Exception {
        System.out.println("preHandle2: ");
        return true;
    }

    @Override
    public void postHandle(HttpServletRequest arg0, HttpServletResponse arg1, Object arg2, ModelAndView arg3)
            throws Exception {
        System.out.println("postHandle2: ");
    }

    @Override
    public void afterCompletion(HttpServletRequest arg0, HttpServletResponse arg1, Object arg2, Exception arg3)
            throws Exception {
        System.out.println("afterCompletion2: ");
    }

}

执行结果