SpringMVC：拦截器

一般我们会做一些统一的操作这个时候我们需要使用springmvc提供的拦截器，例如token的验证，字段必填的操作，接口超时判断，签名验证，字段加密等操作，所以我们需要了解执行先后顺序。 我们来简单介绍下实现过程及对应代码，执行结果：

1、定义自己的spring mvc拦截器需要实现HandlerInterceptor 接口或者继承HandlerInterceptorAdapter

2、boolean preHandle()方法在controller被调用之前调用；

3、void postHandle()方法在controller被调用之后调用，可在modelandview中加入数据，比如当前时间；

4、void afterCompletion()在呈现视图之后调用，可用于清理资源等；

5、当设置多个拦截器时，先按顺序调用preHandle方法，然后逆序调用每个拦截器的postHandle和afterCompletion方法

public class MyInterceptor1 extends HandlerInterceptorAdapter {

	@Override
	public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
		System.out.println("-------preHandle1-------");
        // 如果返回false，则不再调用之后的方法  
		return true;
	}

	@Override
	public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {
		System.out.println("-------postHandle1-------");
		if (modelAndView != null) { 
            // 当前时间  
			modelAndView.addObject("now", new Date());
		}
	}

	@Override
	public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {
		System.out.println("-------afterCompletion1-------");
	}


}

 public class MyInterceptor2 extends HandlerInterceptorAdapter {

	@Override
	public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
		System.out.println("-------preHandle2-------");
        // 如果返回false，则不再调用之后的方法  
		return true;
	}

	@Override
	public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {
		System.out.println("-------postHandle2-------");
		if (modelAndView != null) { 
            // 加入当前时间  
			modelAndView.addObject("now", new Date());
		}
	}

	@Override
	public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {
		System.out.println("-------afterCompletion2-------");
	}


}

<mvc:interceptors>
	<mvc:interceptor>
		<mvc:mapping path="/**"/>
		<bean class="com.kingbal.web.interceptor.MyInterceptor1" />
	</mvc:interceptor>
	<mvc:interceptor>
		<mvc:mapping path="/**"/>
		<bean class="com.kingbal.web.interceptor.MyInterceptor2" />
	</mvc:interceptor>
</mvc:interceptors>  

会根据配置先后顺序往下执行，执行结果如下图 >>