Servlet中web.xml的配置

引言：这是一个采用原生Servlet开发的项目的一个简要配置，在这里记录一下，以便以后用到了

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<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" version="2.5">
  <display-name>netctoss</display-name>
  <welcome-file-list>
    <welcome-file>index.html</welcome-file>
    <welcome-file>index.htm</welcome-file>
    <welcome-file>index.jsp</welcome-file>
    <welcome-file>default.html</welcome-file>
    <welcome-file>default.htm</welcome-file>
    <welcome-file>default.jsp</welcome-file>
  </welcome-file-list>
  
  <servlet>
    <servlet-name>main</servlet-name>
    <servlet-class>web.MainServlet</servlet-class>
  </servlet>
  <servlet-mapping>
    <servlet-name>main</servlet-name>
    <url-pattern>*.do</url-pattern>
  </servlet-mapping>
  
   <!-- 声明发生哪种异常时转发到哪个错误的页面 -->
  <!--  注意，此处错误的页面的路径应该写绝对路径，而tomcat会主动帮我们加上项目名，
          所以此处的绝对就不要再写项目名，避免重复 -->
  <!-- 1.按照异常类型声明 -->
 <!--  <error-page>
              <exception-type>java.lang.Exception</exception-type>
              <location>/WEB-INF/error.jsp</location>
         </error-page> -->
  
  <!-- 2.按照异常的编号声明 -->
  <error-page>
    <error-code>404</error-code>
    <location>/WEB-INF/error.jsp</location>
  </error-page>
  <error-page>
    <error-code>405</error-code>
    <location>/WEB-INF/error.jsp</location>
  </error-page>
  <error-page>
    <error-code>500</error-code>
    <location>/WEB-INF/error.jsp</location>
  </error-page>
  
  <!-- 登录检查过滤器 -->
  <filter>
    <filter-name>login</filter-name>
    <filter-class>web.LoginFilter</filter-class>
  </filter>
  <filter-mapping>
    <filter-name>login</filter-name>
    <url-pattern>*.do</url-pattern>
  </filter-mapping>
</web-app>

以下是一个过滤器：

package web;

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

public class LoginFilter implements Filter {

    public void destroy() {

    }

    public void doFilter(ServletRequest req, ServletResponse res, FilterChain chain)
            throws IOException, ServletException {
        /*
         * 1.Filter由tomcat自动调用，tomcat会在接收到请求后，调用Servlet前调用Filter。
         * 2.tomcat在调用Filter前就会创建好request和response。
         * 3.tomcat实例化的是接口的实现类：
         *   RequestFacade implements HttpServletRequest
         *   HttpServletRequest extends ServletRequest
         */
        HttpServletRequest request=(HttpServletRequest) req;
        HttpServletResponse response=(HttpServletResponse) res;
        //排除掉3个不需要检查的路径，即发现是这3个路径，直接让请求继续执行
        String[] paths=new String[]{"/toLogin.do","/login.do","/createImg.do"};
        String p=request.getServletPath();//获取当前路径
        for(String path : paths){
            if(p.equals(path)){
                chain.doFilter(request, response);
                return;
            }
        }
        //从session获取账号
        HttpSession session=request.getSession();
        String adminCode=(String)session.getAttribute("adminCode");
        //根据账号判断用户是否登录
        if(adminCode ==null){
            //没登录，重定向到登录页
            response.sendRedirect("/netctoss/toLogin.do");
        }else{
            //已登录，请求继续执行
            chain.doFilter(request, response);
        }
    }

    public void init(FilterConfig cfg) throws ServletException {

    }

}