springboot自动以filter,interceptor,listener实现自定义过滤、拦截、监听

1:自定义拦截器

（1）实现Filter接口

（2）添加注解WebFilter，指定要过滤的路径、指定filer的名字、指定初始化参数

 （3）添加@ServletComponentScan注解开启扫描servlet组件

package top.lrshuai.fli.filter;

import java.io.IOException;

import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.annotation.WebFilter;


/**
 * 
 * 使用注解标注过滤器
 * @WebFilter将一个实现了javax.servlet.Filter接口的类定义为过滤器
 * 属性filterName 声明过滤器的名称,可选
 * 属性urlPatterns指定要过滤 的URL模式,这是一个数组参数，可以指定多个。也可使用属性value来声明.(指定要过滤的URL模式是必选属性)
 */
@WebFilter(filterName="myFilter",urlPatterns={"/*"})
public class MyFilter implements Filter{

	@Override
	public void destroy() {
		System.out.println("myfilter 的 销毁方法");
	}

	@Override
	public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain)
			throws IOException, ServletException {
		System.out.println("myfilter 的 过滤方法。这里可以执行过滤操作");
		//继续下一个拦截器
		chain.doFilter(request, response);
	}

	@Override
	public void init(FilterConfig arg0) throws ServletException {
		System.out.println("myfilter 的 初始化方法");
	}

}

过滤器最先执行所有请求路径是/*的请求。

2:自定义实现拦截器

（1）实现InterceptorHandler接口

  (2)  拦截器preHandler（controller之前执行）和postHandler(controller执行之后，视图被渲染之前执行)方法和

afterCompletion(请求结束之后调用,也就是视图渲染完成之后调用。主要用于资源清理工作)

package top.lrshuai.fli.interceptor;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.springframework.web.servlet.HandlerInterceptor;
import org.springframework.web.servlet.ModelAndView;
/**
 * 可以验证用户是否登录来拦截，没登陆返回false
 * @author tyro
 *
 */
public class LoginInterceptor implements HandlerInterceptor{

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

	@Override
	public void postHandle(HttpServletRequest arg0, HttpServletResponse arg1, Object arg2, ModelAndView arg3)
			throws Exception {
		System.out.println("LoginInterceptor  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 boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object arg2) throws Exception {
		System.out.println("LoginInterceptor 在请求处理之前进行调用（Controller方法调用之前） 这里是拦截的操作");
		String user = (String) request.getSession().getAttribute("user");
		System.out.println("user="+user);
		if(null == user || "".equals(user)){
			response.setContentType("text/html;charset=utf-8");
			response.getWriter().println("你没登陆，请去登录页面：<a href='http://localhost:8080/login'>登录</a>。");
			return false;
		}
		return true;
	}

}

package top.lrshuai.fli.interceptor;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.springframework.web.servlet.HandlerInterceptor;
import org.springframework.web.servlet.ModelAndView;

public class MyInterceptor implements HandlerInterceptor{

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

	@Override
	public void postHandle(HttpServletRequest arg0, HttpServletResponse arg1, Object arg2, ModelAndView arg3)
			throws Exception {
		System.out.println("MyInterceptor  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 boolean preHandle(HttpServletRequest arg0, HttpServletResponse arg1, Object arg2) throws Exception {
		System.out.println("MyInterceptor 在请求处理之前进行调用（Controller方法调用之前）这里是拦截的操作");
		return true;
	}

}

定义完拦截器之后。要对拦截器进行注册，才能使拦截器起到作用。实现

WebMvcConfigurerAdapter.重写addInterceptors方法即可代码如下:指定拦截器拦截的请求和排除拦截的请求

package top.lrshuai.fli.interceptor;

import org.springframework.context.annotation.Configuration;
import org.springframework.web.servlet.config.annotation.InterceptorRegistry;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurerAdapter;

@Configuration
public class WebConfigurer extends WebMvcConfigurerAdapter {

	@Override
	public void addInterceptors(InterceptorRegistry registry) {
		 // addPathPatterns 用于添加拦截规则
		// excludePathPatterns 排除拦截
		registry.addInterceptor(new LoginInterceptor()).addPathPatterns("/**").excludePathPatterns("/login");
		registry.addInterceptor(new MyInterceptor()).addPathPatterns("/**");
		super.addInterceptors(registry);
	}
}

(3)自定义监听器：ServletContextListerner    HttpSessionListener。实现这两个接口。并且添加@weblinstener注解指定其

为自定义web监听器

package top.lrshuai.fli.listener;

import javax.servlet.ServletContextEvent;
import javax.servlet.ServletContextListener;
import javax.servlet.annotation.WebListener;

@WebListener
public class ServletListener implements ServletContextListener{

	@Override
	public void contextDestroyed(ServletContextEvent arg0) {
		System.out.println("servlet 销毁时调用");
	}

	@Override
	public void contextInitialized(ServletContextEvent arg0) {
		System.out.println("servlet 初始化时调用");
	}

}

@RequestMapping("/logout")
	public String logout(){
		System.out.println("这是在logout方法里销毁session试试");
		((ServletRequestAttributes) RequestContextHolder.getRequestAttributes())
		.getRequest().getSession().removeAttribute("user");
		((ServletRequestAttributes) RequestContextHolder.getRequestAttributes())
		.getRequest().getSession().invalidate();
		
		return "logout success";
	}

package top.lrshuai.fli.listener;

import javax.servlet.annotation.WebListener;
import javax.servlet.http.HttpSessionEvent;
import javax.servlet.http.HttpSessionListener;

@WebListener
public class SessionListener implements HttpSessionListener{

	@Override
	public void sessionCreated(HttpSessionEvent arg0) {
		System.out.println("监听 创建session");
	}

	@Override
	public void sessionDestroyed(HttpSessionEvent arg0) {
		System.out.println("监听 销毁session");
	}

}

session销毁后执行的对应监听器的方法