Filter01.java

package com.aistart.filter;import javax.servlet.*;
import javax.servlet.annotation.WebFilter;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
import java.io.IOException;/*
2.制定过滤规则你想对哪个接口,哪个映射,进行拦截/过滤* */
@WebFilter("/product/*")/*
* 常见的过滤规则
* /product/*   某映射下都被过滤/*      所有的映射都被过滤
*  *.jsp  对于某资源文件,应该是禁止直接访问的(前面不带/)
*
*
* *//*1.实现Filter 接口,注意不要导错类 */
public class Filter01 implements Filter {@Overridepublic void init(FilterConfig filterConfig) throws ServletException {System.out.println("我初始化了1");}@Overridepublic void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {System.out.println("普通的过滤");//2.5放行之前,应该先将请求和相应转为http格式HttpServletRequest request = (HttpServletRequest) servletRequest;HttpServletResponse response = (HttpServletResponse) servletResponse;/*过滤之前*/System.out.println("过滤前");HttpSession session = request.getSession();Object user = session.getAttribute("user");if (user == null) {response.getWriter().println("还未登录,请登录");filterChain.doFilter(request,response);//放行}else{//3.如果满足放行条件,应当放行filterChain.doFilter(request,response);//放行}/*返回之前*/System.out.println("过滤后");}@Overridepublic void destroy() {System.out.println("我死了,遗言是....");}
}

Filter02.java

package com.aistart.filter;import javax.servlet.*;
import javax.servlet.annotation.WebFilter;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;@WebFilter("*.jsp")
public class Filter02 implements Filter {@Overridepublic void init(FilterConfig filterConfig) throws ServletException {}@Overridepublic void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {System.out.println("jsp的过滤生效了");HttpServletResponse response = (HttpServletResponse) servletResponse;HttpServletRequest request = (HttpServletRequest) servletRequest;filterChain.doFilter(request,response);//        response.sendError(404,"当前页面不存在");}@Overridepublic void destroy() {}
}

Filter03.java

package com.aistart.filter;import javax.servlet.*;
import javax.servlet.annotation.WebFilter;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;@WebFilter("/*")/*
*
* 对于相同的,都符合的规则,优先执行,文件排名靠上的
*
* */
public class Filter03 implements Filter {@Overridepublic void init(FilterConfig filterConfig) throws ServletException {}@Overridepublic void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {System.out.println("所有的过滤前1");filterChain.doFilter((HttpServletRequest)servletRequest,(HttpServletResponse)servletResponse);System.out.println("所有的过滤1后");}@Overridepublic void destroy() {}
}

Filter04.java

package com.aistart.filter;import javax.servlet.*;
import javax.servlet.annotation.WebFilter;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;@WebFilter("/*")/*
*
* 对于相同的,都符合的规则,优先执行,文件排名靠上的
*
* */
public class Filter04 implements Filter {@Overridepublic void init(FilterConfig filterConfig) throws ServletException {}@Overridepublic void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {System.out.println("过滤前2");filterChain.doFilter((HttpServletRequest)servletRequest,(HttpServletResponse)servletResponse);System.out.println("过滤后2");}@Overridepublic void destroy() {}
}