JAVA-EE引入Filter实现对Servlet的过滤处理------计算机网络经典

女爷i 2024-02-21 10:37 15阅读 0赞

>     Filter过滤器
>     每一个Servlet都需要解决自己业务的问题,但是它们都需要判断用户是否已经登陆,
>     如果登陆了,才可以执行后续操作,如果没有则需要登录
>     这部分我们可以使用Filter过滤器来将这部分从Servlet中抽离,达到复用效果
>     我们可以把Servlet程序看作是需要执行的目标,我们可以使用过滤器Filter来添加过滤代码
>     Filter可以添加到Servlet执行之前也可以是执行之后
>     过滤器也是根据请求路径来执行的
>     Servlet对象默认情况下,服务器启动,不会创建对象
>     Filter对象默认在服务器启动创建对象
> 
>     Filter过滤器
>     每一个Servlet都需要解决自己业务的问题,但是它们都需要判断用户是否已经登陆,
>     如果登陆了,才可以执行后续操作,如果没有则需要登录
>     这部分我们可以使用Filter过滤器来将这部分从Servlet中抽离,达到复用效果
>     我们可以把Servlet程序看作是需要执行的目标,我们可以使用过滤器Filter来添加过滤代码
>     Filter可以添加到Servlet执行之前也可以是执行之后
>     过滤器也是根据请求路径来执行的
>     Servlet对象默认情况下,服务器启动,不会创建对象
>     Filter对象默认在服务器启动创建对象

>     <?xml version="1.0" encoding="UTF-8"?>
>     <web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee"
>              xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
>              xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_4_0.xsd"
>              version="4.0">
>         <session-config>
>     
>             <session-timeout>30</session-timeout>
>         </session-config>
>     
>         <welcome-file-list>
>             <welcome-file>Welcome</welcome-file>
>         </welcome-file-list>
>         <filter>
>             <filter-name>filter1</filter-name>
>             <filter-class>com.bjpowernode.oa.web.Servlet.Filter1</filter-class>
>         </filter>
>         <filter-mapping>
>             <filter-name>filter1</filter-name>
>             <url-pattern>/Test/A</url-pattern>
>         </filter-mapping>
>     </web-app>
> 
>     <?xml version="1.0" encoding="UTF-8"?>
>     <web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee"
>              xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
>              xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_4_0.xsd"
>              version="4.0">
>         <session-config>
>     
>             <session-timeout>30</session-timeout>
>         </session-config>
>     
>         <welcome-file-list>
>             <welcome-file>Welcome</welcome-file>
>         </welcome-file-list>
>         <filter>
>             <filter-name>filter1</filter-name>
>             <filter-class>com.bjpowernode.oa.web.Servlet.Filter1</filter-class>
>         </filter>
>         <filter-mapping>
>             <filter-name>filter1</filter-name>
>             <url-pattern>/Test/A</url-pattern>
>         </filter-mapping>
>     </web-app>

>     package com.bjpowernode.oa.web.Servlet;
>     
>     import jakarta.servlet.*;
>     import jakarta.servlet.annotation.WebFilter;
>     
>     import java.io.IOException;
>     
>     @WebFilter({"/Test/A","/Test/B"})
>     public class Filter1 implements Filter
>     {
>         public Filter1()
>         {
>             System.out.println("构造方法");
>         }
>         @Override
>         public void init(FilterConfig filterConfig) throws ServletException
>         {
>             System.out.println("init方法执行");
>         }
>     
>         @Override
>         public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException
>         {
>             //请求发送的时候添加过滤规则
>             System.out.println("doFilter方法执行");
>             //往下走,下一个是过滤器,就继续过滤,不是就走Servlet
>             //放行,但是该过滤器方法执行未结束,servlet结束才结束
>             chain.doFilter(request,response);
>             //响应的时候添加过滤规则
>             System.out.println("doFilter方法结束");
>         }
>     
>         @Override
>         public void destroy()
>         {
>             System.out.println("destroy方法执行");
>         }
>     }
> 
>     package com.bjpowernode.oa.web.Servlet;
>     
>     import jakarta.servlet.*;
>     import jakarta.servlet.annotation.WebFilter;
>     
>     import java.io.IOException;
>     
>     @WebFilter({"/Test/A","/Test/B"})
>     public class Filter1 implements Filter
>     {
>         public Filter1()
>         {
>             System.out.println("构造方法");
>         }
>         @Override
>         public void init(FilterConfig filterConfig) throws ServletException
>         {
>             System.out.println("init方法执行");
>         }
>     
>         @Override
>         public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException
>         {
>             //请求发送的时候添加过滤规则
>             System.out.println("doFilter方法执行");
>             //往下走,下一个是过滤器,就继续过滤,不是就走Servlet
>             //放行,但是该过滤器方法执行未结束,servlet结束才结束
>             chain.doFilter(request,response);
>             //响应的时候添加过滤规则
>             System.out.println("doFilter方法结束");
>         }
>     
>         @Override
>         public void destroy()
>         {
>             System.out.println("destroy方法执行");
>         }
>     }

>     package com.bjpowernode.oa.web.Servlet;
>     
>     import jakarta.servlet.ServletException;
>     import jakarta.servlet.annotation.WebServlet;
>     import jakarta.servlet.http.HttpServlet;
>     import jakarta.servlet.http.HttpServletRequest;
>     import jakarta.servlet.http.HttpServletResponse;
>     
>     import java.io.IOException;
>     
>     @WebServlet("/Test/A")
>     public class AServlet extends HttpServlet
>     {
>         @Override
>         protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException
>         {
>             System.out.println("AServlet执行了");
>         }
>     }
> 
>     package com.bjpowernode.oa.web.Servlet;
>     
>     import jakarta.servlet.ServletException;
>     import jakarta.servlet.annotation.WebServlet;
>     import jakarta.servlet.http.HttpServlet;
>     import jakarta.servlet.http.HttpServletRequest;
>     import jakarta.servlet.http.HttpServletResponse;
>     
>     import java.io.IOException;
>     
>     @WebServlet("/Test/A")
>     public class AServlet extends HttpServlet
>     {
>         @Override
>         protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException
>         {
>             System.out.println("AServlet执行了");
>         }
>     }

>     package com.bjpowernode.oa.web.Servlet;
>     
>     import jakarta.servlet.ServletException;
>     import jakarta.servlet.annotation.WebServlet;
>     import jakarta.servlet.http.HttpServlet;
>     import jakarta.servlet.http.HttpServletRequest;
>     import jakarta.servlet.http.HttpServletResponse;
>     
>     import java.io.IOException;
>     
>     @WebServlet("/Test/B")
>     public class BServlet extends HttpServlet
>     {
>         @Override
>         protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException
>         {
>             System.out.println("BServlet执行了");
>         }
>     }
> 
>     package com.bjpowernode.oa.web.Servlet;
>     
>     import jakarta.servlet.ServletException;
>     import jakarta.servlet.annotation.WebServlet;
>     import jakarta.servlet.http.HttpServlet;
>     import jakarta.servlet.http.HttpServletRequest;
>     import jakarta.servlet.http.HttpServletResponse;
>     
>     import java.io.IOException;
>     
>     @WebServlet("/Test/B")
>     public class BServlet extends HttpServlet
>     {
>         @Override
>         protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException
>         {
>             System.out.println("BServlet执行了");
>         }
>     }