过滤器的使用

系统需要Check session是否失效,添加了一个过滤器来check,如果发现没有session,令其页面跳转到登陆页面

 java 代码

import java.io.IOException;
import java.io.PrintWriter;
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 SessionFilter implements Filter {

    private FilterConfig filterConfig = null;

    // 初始化过滤器

    public void init(FilterConfig filterConfig) throws ServletException {

        this.filterConfig = filterConfig;

    }

    // 执行过滤器功能

    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain)

    throws IOException, ServletException {

        HttpServletRequest hreq = (HttpServletRequest) request;
        HttpServletResponse hres = (HttpServletResponse) response;
        HttpSession session = hreq.getSession();

        if (session.getAttribute("UserID") != null) // 检查是否失效
        {
            chain.doFilter(request, response);
            return;
        } else {

            // 屏蔽掉login页面,以免在login页面过滤器会去check session
            if ("/login.jsp".equals(hreq.getServletPath())
                    || "/login.do".equals(hreq.getServletPath())
                    || "/loginInternet.jsp".equals(hreq.getServletPath())) {
                chain.doFilter(request, response);
                return;
            } else {
                PrintWriter out = response.getWriter();
                // 利用JS跳转页面
                out.println("");
                // hres.sendRedirect(hreq.getContextPath());//如果失效了，把视图派发到登录页面
            }
        }
    }

    // 销毁过滤器

    public void destroy() {
        this.filterConfig = null;
    }

}

同时web.xml需要配置

xml 代码

<filter>
  <filter-name>sessionCheck</filter-name>
  <filter-class>xxxx</filter-class>
</filter>
<filter-mapping>
  <filter-name>sessionCheck</filter-name>
  <url-pattern>*.jsp</url-pattern>
</filter-mapping>

 

         网上很多地方据说可以在web.xml上直接可以配置mapping,直接让login页面绕过过滤器,自己试了几次不知道怎么弄,最后只好在fliter里面用逻辑判断了