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SpringBoot中过滤器、监听器以及拦截器


 

 
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;
 
/**
 */
@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;
 
 
/**
 
 *
 */
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;
 
/**
 
 */
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;
 
/**
 
 */
@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);
    }
}