SSM项目使用过滤器实现登录监听

SSM项目中配置过滤器实现登录监听，未登录不能访问某些页面

1. 编写一个过滤器的类实现Filter接口，在实现方法中添加具体操作

import javax.servlet.*;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
import java.io.IOException;

public class LoginFilter implements Filter {
    
	//初始化：web服务器启动时就会初始化
    @Override
    public void init(FilterConfig filterConfig) throws ServletException {
    

    }

    @Override
    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
    
        HttpServletRequest request = (HttpServletRequest)servletRequest;
        HttpServletResponse response =(HttpServletResponse)servletResponse;
        HttpSession session = request.getSession();
        if (session.getAttribute("loginuser")==null){
    
            response.sendRedirect(request.getContextPath()+"/login/adminLogin.jsp");
        }else {
    
        	//让请求继续往下走，如果不写，到这里请求就会被拦截
            filterChain.doFilter(servletRequest,servletResponse);
        }
    }
	
	//销毁，web服务器关闭的时候会销毁
    @Override
    public void destroy() {
    

    }

2. 在web.xml中配置过滤器

<filter>
        <filter-name>LoginFilter</filter-name>
        <!-- 实现filter接口的类 -->
        <filter-class>edu.gnnu.newcomer.aop.LoginFilter</filter-class>
</filter>
<filter-mapping>
        <filter-name>LoginFilter</filter-name>
        <!-- 要过滤的页面 -->
        <url-pattern>/manager/*</url-pattern>
</filter-mapping>

配置过后这些页面都会先经过过滤器，如果不满足过滤器中的条件则执行过滤器中定义的操作