Filter实现web未登录跳转到登录页面

import javax.servlet.*;

import javax.servlet.http.*;

import javax.servlet.annotation.*;

import java.io.*;

@WebFilter(filterName="authority"

, urlPatterns={"/*"}

, initParams={

@WebInitParam(name="encoding", value="GBK"),

@WebInitParam(name="loginPage", value="/login.jsp"),

@WebInitParam(name="proLogin", value="/proLogin.jsp")})

public class AuthorityFilter implements Filter 

{

//FilterConfig可用于访问Filter的配置信息

private FilterConfig config;

//实现初始化方法

public void init(FilterConfig config)

{

this.config = config; 

}

//实现销毁方法

public void destroy()

{

this.config = null; 

}

//执行过滤的核心方法

public void doFilter(ServletRequest request,

ServletResponse response, FilterChain chain)

throws IOException,ServletException

{

//获取该Filter的配置参数

String encoding = config.getInitParameter("encoding");

String loginPage = config.getInitParameter("loginPage");

String proLogin = config.getInitParameter("proLogin");

//设置request编码用的字符集

request.setCharacterEncoding(encoding); //①

HttpServletRequest requ = (HttpServletRequest)request;

HttpSession session = requ.getSession(true);

//获取客户请求的页面

String requestPath = requ.getServletPath();

//如果session范围的user为null，即表明没有登录

//且用户请求的既不是登录页面，也不是处理登录的页面

if( session.getAttribute("user") == null

&& !requestPath.endsWith(loginPage)

&& !requestPath.endsWith(proLogin))

{

//forward到登录页面

request.setAttribute("tip" , "对不起，您还没有登录！");

request.getRequestDispatcher(loginPage)

.forward(request, response);

}

//"放行"请求

else

{

chain.doFilter(request, response);

}

} 

}