使用filter过滤器实现登陆权限验证

1.首先写一个权限过滤filter类,实现Filter接口

import javax.servlet.Filter;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.FilterChain;
import java.io.IOException;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpSession;
import javax.servlet.http.HttpServletResponse;

public class RightFilter
    implements Filter ...{
  public void init(FilterConfig filterConfig) throws ServletException ...{
  }

  public void doFilter(ServletRequest request, ServletResponse response,
                       FilterChain chain) throws IOException, ServletException ...{
    HttpServletRequest req = (HttpServletRequest) request;
    HttpServletResponse res = (HttpServletResponse) response;
    
    HttpSession session = req.getSession(true);

    //从session里取的用户名信息
    String username = (String) session.getAttribute("username");
    
    //判断如果没有取到用户信息,就跳转到登陆页面
    if (username == null || "".equals(username)) ...{
      //跳转到登陆页面
      res.sendRedirect("http://"+req.getHeader("Host")+"/login.jsp");
    }
    else ...{
      //已经登陆,继续此次请求
      chain.doFilter(request,response);
    }
  }

  public void destroy() ...{
  }
} 

 

2.然后在web.xml里配置需要登陆权限验证的JSP文件:

     a.如果是某个具体的JSP文件(如a.jsp)需要登陆验证

<web-app>
  ...
  <filter>
    <filter-name>right</filter-name>
    <filter-class>com.taihuatalk.taihua.common.RightFilter</filter-class>
  </filter>

  <filter-mapping>
    <filter-name>right</filter-name>
    <url-pattern>/a.jsp</url-pattern>
  </filter-mapping>
  ...
</web-app>

    b.如果是某一个目录(如a/目录)整个目录下的文件都需要登陆验证:

<web-app>
  ...
  <filter>
    <filter-name>right</filter-name>
    <filter-class>com.taihuatalk.taihua.common.RightFilter</filter-class>
  </filter>

  <filter-mapping>
    <filter-name>right</filter-name>
    <url-pattern>/a/*</url-pattern>
  </filter-mapping>
  ...
</web-app>