SpringBoot中过滤器、监听器以及拦截器

时间：2024-11-27 20:07:20
属于javax.servlet所提供的Api

拦截器原理

简单来讲是通过动态代理实现，被访问的目标方法通过代理类（方法）来执行，这样我们就可以在真正要执行的方法执行前、后做一些处理；

通过拦截器这种方式，使得代码可以进行更高度的抽象。

过滤器初始化、销毁

package com.example.demo.filter;

import javax.servlet.*;

import javax.servlet.annotation.WebFilter;

import java.io.IOException;

/**

 * Created by flyme

 * on 2017/11/6 19:30

 */

@WebFilter(filterName = "myfilter", urlPatterns = "/*")

public class MyFilter implements Filter {

    @Override

    public void init(FilterConfig filterConfig) {

        System.out.println("过滤器初始化");

    }

    @Override

    public void destroy() {

        System.out.println("过滤器销毁");

    }

    @Override

    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {

        System.out.println("执行过滤操作");

        filterChain.doFilter(servletRequest, servletResponse);

    }

}

监听器 ServletContex初始化、ServletContex销毁

package com.example.demo.listener;

import javax.servlet.ServletContextEvent;

import javax.servlet.ServletContextListener;

import javax.servlet.annotation.WebListener;

/**

 * Created by flyme

 * on 2017/11/6 19:37

 * //

 */

@WebListener

public class MyServletContextListener implements ServletContextListener {

    @Override

    public void contextInitialized(ServletContextEvent servletContextEvent) {

        System.out.println("ServletContex初始化");

        System.out.println(servletContextEvent.getServletContext().getServerInfo());

    }

    @Override

    public void contextDestroyed(ServletContextEvent servletContextEvent) {

        System.out.println("ServletContex销毁");

    }

}

监听器 ServletContex初始化、Session被创建

package com.example.demo.listener;

import javax.servlet.annotation.WebListener;

import javax.servlet.http.HttpSessionEvent;

import javax.servlet.http.HttpSessionListener;

/**

 * Created by flyme

 * on 2017/11/6 19:39

 */

@WebListener

public class MyHttpSessionLister implements HttpSessionListener {

    @Override

    public void sessionCreated(HttpSessionEvent httpSessionEvent) {

        System.out.println("Session被创建");

    }

    @Override

    public void sessionDestroyed(HttpSessionEvent httpSessionEvent) {

        System.out.println("ServletContex初始化");

    }

}

拦截器

实现自定义拦截器只需要3步：

1、创建我们自己的拦截器类并实现 HandlerInterceptor接口。
2、创建一个Java类继承WebMvcConfigurerAdapter，并重写 addInterceptors 方法。
2、实例化我们自定义的拦截器，然后将对像手动添加到拦截器链中（在addInterceptors方法中添加）

第一个拦截器

package com.example.demo.interceptor;

import org.springframework.web.servlet.HandlerInterceptor;

import org.springframework.web.servlet.ModelAndView;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

/**

 * Created by flyme

 * on 2017/11/6 20:04

 *

 */

public class MyInterceptor1 implements HandlerInterceptor {

    @Override

    public boolean preHandle(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, Object o) throws Exception {

        System.out.println(">>>MyInterceptor1>>>>>>>在请求处理之前进行调用（Controller方法调用之前）");

        return true;

    }

    @Override

    public void postHandle(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, Object o, ModelAndView modelAndView) throws Exception {

        System.out.println(">>>MyInterceptor1>>>>>>>请求处理之后进行调用，但是在视图被渲染之前（Controller方法调用之后）");

    }

    @Override

    public void afterCompletion(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, Object o, Exception e) throws Exception {

        System.out.println(">>>MyInterceptor1>>>>>>>在整个请求结束之后被调用，也就是在DispatcherServlet 渲染了对应的视图之后执行（主要是用于进行资源清理工作）");

    }

}

第二个拦截器

package com.example.demo.interceptor;

import org.springframework.web.servlet.HandlerInterceptor;

import org.springframework.web.servlet.ModelAndView;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

/**

 * Created by flyme

 * on 2017/11/6 20:27

 */

public class MyInterceptor2 implements HandlerInterceptor {

    @Override

    public boolean preHandle(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, Object o) throws Exception {

        System.out.println(">>>MyInterceptor2>>>>>>>在请求处理之前进行调用（Controller方法调用之前）");

        return true;

    }

    @Override

    public void postHandle(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, Object o, ModelAndView modelAndView) throws Exception {

        System.out.println(">>>MyInterceptor2>>>>>>>请求处理之后进行调用，但是在视图被渲染之前（Controller方法调用之后）");

    }

    @Override

    public void afterCompletion(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, Object o, Exception e) throws Exception {

        System.out.println(">>>MyInterceptor2>>>>>>>在整个请求结束之后被调用，也就是在DispatcherServlet 渲染了对应的视图之后执行（主要是用于进行资源清理工作）");

    }

}

将自定义的拦截器手动添加到拦截器链

package com.example.demo;

import com.example.demo.interceptor.MyInterceptor1;

import com.example.demo.interceptor.MyInterceptor2;

import org.springframework.context.annotation.Configuration;

import org.springframework.web.servlet.config.annotation.InterceptorRegistry;

import org.springframework.web.servlet.config.annotation.WebMvcConfigurerAdapter;

/**

 * Created by flyme

 * on 2017/11/6 20:28

 */

@Configuration

public class MyWebAppConfigurer extends WebMvcConfigurerAdapter {

    public void addInterceptors(InterceptorRegistry registry){

        // 多个拦截器组成一个拦截器链

        // addPathPatterns 用于添加拦截规则

        // excludePathPatterns 用户排除拦截

        registry.addInterceptor(new MyInterceptor1()).addPathPatterns("/**");

        registry.addInterceptor(new MyInterceptor2()).addPathPatterns("/**");

        super.addInterceptors(registry);

    }

}

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