有这样一个需求,用户密码登录网站,在session中保留了用户的信息,但是用户很长时间没有再操作该界面,用户的session则被浏览器清除,而一些业务逻辑则是需要用到用户的信息,那么用户再执行操作后,则会引起业务代码报错,这时我们就需要在用户访问的时候判断一下用户的信息是否存在,如何实现这个功能,我们这里用到了过滤器这个功能,在用户访问特定界面或者特定接口的时候,先进行过滤,复合条件再执行下一步操作,具体代码如下:
package com.demo.filter;
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;
import com.demo.entity.User;
/**
* 全站判断用户是否登录过滤器
* @author zhangdi
*
*/
public class AuthFilter implements Filter{
@Override
public void destroy() {
}
@Override
public void doFilter(ServletRequest request, ServletResponse response,
FilterChain chain) throws IOException, ServletException {
HttpServletResponse resp = (HttpServletResponse)response;
HttpServletRequest req = (HttpServletRequest)request;
HttpSession session = req.getSession();
User user = (User)session.getAttribute("user");
String uri = req.getRequestURI();
//简单判断缓存中是否有用户
if(user==null){//没有用户
//判断用户是否是选择跳到登录界面
if(uri.endsWith("login.jsp")||uri.endsWith("login.do")){
chain.doFilter(request, response);
}else{
resp.sendRedirect(req.getContextPath()+"/login.jsp");
}
}else{//有用户
chain.doFilter(request, response);
}
chain.doFilter(request, response);
}
@Override
public void init(FilterConfig filterConfig) throws ServletException {
}
}
注意,这个过滤器需要在web.xml中声明,不然不会被项目调用,代码如下:
<!-- 登录认证过滤器 -->
<filter>
<filter-name>auth</filter-name>
<filter-class>com.demo.filter.AuthFilter</filter-class>
</filter>
<filter-mapping>
<filter-name>auth</filter-name>
<url-pattern>*.jsp</url-pattern>
</filter-mapping>
<filter-mapping>
<filter-name>auth</filter-name>
<url-pattern>*.do</url-pattern>
</filter-mapping>
这里配置过滤的范围是所有的jsp界面以及所有以.do结尾的接口