SpringMVC——拦截器

拦截器

拦截器是SpringMVC 框架提供的一个组件，作用于过滤器相似。处理请求的大致流程如下。

1.拦截器的使用

首先需要实现HandlerInterceptor接口

public class CityInterceptor implements HandlerInterceptor {

    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
        System.out.println("拦截成功");
        // 此处返回true，是允许放行。
        return true;
    }

    @Override
    public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {
        System.out.println("post 拦截成功");
    }

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

配置一下xml

<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xmlns:context="http://www.springframework.org/schema/context"
       xmlns:mvc="http://www.springframework.org/schema/mvc"
       xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
		http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-4.3.xsd http://www.springframework.org/schema/mvc https://www.springframework.org/schema/mvc/spring-mvc.xsd">
    <context:component-scan base-package="cn.zl"/>
    <mvc:annotation-driven />
	    <!-- 此处是视图解析器的配置 -->
    <bean class="org.springframework.web.servlet.view.InternalResourceViewResolver">
        <property name="prefix" value="/WEB-INF/views/"/>
        <property name="suffix" value=".jsp"/>
    </bean>

    <!-- 拦截器的配置 -->
    <mvc:interceptors>
        <mvc:interceptor>
            <!-- ** 表示当前目录及其子目录路径 -->
            <mvc:mapping path="/**"/>
            <bean class="cn.zl.Interceptor.CityInterceptor"></bean>
        </mvc:interceptor>
    </mvc:interceptors>
</beans>

2.拦截器方法说明

查看一下HandlerInterceptor接口，看一下都有哪些方法

public interface HandlerInterceptor {

	// 此方法在处理器之前进行调用
	default boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler)
			throws Exception {

		return true;
	}
	// 此方法在处理器之后进行调用
	default void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler,
			@Nullable ModelAndView modelAndView) throws Exception {
	}
	// 当处理器调用中出现异常，此方法被调用
	default void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler,
			@Nullable Exception ex) throws Exception {
	}
}