SpringMVC-拦截器快速入门

1.创建拦截器类实现HandlerInterceptor

//该拦截器类必须实现HandlerInterceptor接口，手动覆盖其中的方法
public class MyInterceptor1 implements HandlerInterceptor {
    //目标方法执行之前执行
    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
        System.out.println("preHandle");
        return true;//这一步如果返回false，则下面所有的东西都不会被执行
    }
    //目标方法执行之后，视图返回之前执行
    @Override
    public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {
        System.out.println("postHandle");
    }
    //在整个流程都执行完毕之后执行
    @Override
    public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {
        System.out.println("afterCompletion");
    }
}

2.创建目标类

@Controller
public class TargetController {

    @RequestMapping("/target")
    public ModelAndView show(){
        System.out.println("目标资源执行....");
        ModelAndView modelAndView = new ModelAndView();
        modelAndView.addObject("name","zsh");
        modelAndView.setViewName("index");
        return modelAndView;
    }
}

3.在spring-mvc配置文件中指明拦截器类

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xmlns:mvc="http://www.springframework.org/schema/mvc"
       xmlns:context="http://www.springframework.org/schema/context"
       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.xsd
       http://www.springframework.org/schema/mvc  http://www.springframework.org/schema/mvc/spring-mvc.xsd">

    <!--注解驱动-->
    <mvc:annotation-driven/>

<!--    扫描controller包下的类-->
    <context:component-scan base-package="com.hao.controller"/>

<!--    配置内部资源视图解析器-->
    <bean id="viewResolver" class="org.springframework.web.servlet.view.InternalResourceViewResolver">
        <property name="prefix" value="/"></property>
        <property name="suffix" value=".jsp"></property>
    </bean>

<!--开放静态资源访问权限-->
    <mvc:default-servlet-handler/>
<!--    <mvc:resources mapping="/js/**" location="/js/"/>-->

<!--    配置拦截器-->
    <mvc:interceptors>
        <mvc:interceptor>
<!--            对哪些资源执行拦截操作-->
            <mvc:mapping path="/**"/>
            <!-- 可以添加多个拦截器-->
            <bean class="com.hao.interceptor.MyInterceptor1"/>
        </mvc:interceptor>
    </mvc:interceptors>
</beans>

4.web.xml配置前端控制器

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xmlns="http://java.sun.com/xml/ns/javaee"
         xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd"
         id="WebApp_ID" version="3.0">

<!--    配置springMVC的核心配置控制器DispatcherServlet-->
    <servlet>
        <servlet-name>DispatcherServlet</servlet-name>
        <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
        <init-param>
            <param-name>contextConfigLocation</param-name>
            <param-value>classpath:spring-mvc.xml</param-value>
        </init-param>
        <load-on-startup>1</load-on-startup>
    </servlet>
    <servlet-mapping>
        <servlet-name>DispatcherServlet</servlet-name>
        <url-pattern>/</url-pattern>
    </servlet-mapping>
    
<!--    配置监听器-->
    <listener>
        <listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
    </listener>
    <!--    全局初始化参数,告诉配置文件路径-->

    <context-param>
        <param-name>contextConfigLocation</param-name>
        <param-value>classpath:applicationContext.xml</param-value>
    </context-param>

<!--    配置编码过滤器-->
    <filter>
        <filter-name>CharacterEncoding</filter-name>
        <filter-class>org.springframework.web.filter.CharacterEncodingFilter</filter-class>
        <init-param>
            <param-name>encoding</param-name>
            <param-value>utf-8</param-value>
        </init-param>
    </filter>
    <filter-mapping>
        <filter-name>CharacterEncoding</filter-name>
        <url-pattern>/*</url-pattern>
    </filter-mapping>
</web-app>

5.启动tomcat进行测试,访问http://localhost:8080/target
控制台结果：

---

拦截器方法说明：
1.preHandler：返回false，表示请求结束；后面的Interceptor和controller都不会再执行

2.postHandler：目标方法执行之后，视图返回之前执行，所以可以对这个方法中的Controller处理之后的ModelAndView进行修改

3.afterCompletion：当前端控制器渲染了视图之后执行