ssm框架实现用户登录的拦截器和过滤器[通俗易懂]

public class LoginInterceptor implements HandlerInterceptor {

	@Override
	public void afterCompletion(HttpServletRequest arg0, HttpServletResponse arg1, Object arg2, Exception arg3)
			throws Exception {
		// 执行完毕，返回前拦截		
	}

	@Override
	public void postHandle(HttpServletRequest arg0, HttpServletResponse arg1, Object arg2, ModelAndView arg3)
			throws Exception {
		// 在处理过程中，执行拦截		
	}

	@Override
	public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object arg2) throws Exception {
		// 在拦截点执行前拦截，如果返回true则不执行拦截点后的操作（拦截成功）
		// 返回false则不执行拦截
		HttpSession session = request.getSession();
		//String uri = request.getRequestURI(); // 获取登录的uri，这个是不进行拦截的
		//if(session.getAttribute("LOGIN_USER")!=null || uri.indexOf("system/login")!=-1) {// 说明登录成功 或者 执行登录功能			
		if(session.getAttribute("LOGIN_USER")!=null) {
			// 登录成功不拦截
			return true;
		}else {
			// 拦截后进入登录页面
			response.sendRedirect(request.getContextPath()+"/system/login");
			return false;
		}
	}
}

        <!-- 配置拦截器 -->
	<mvc:interceptors>
		<mvc:interceptor>
			<!-- 拦截所有mvc控制器 -->
			<mvc:mapping path="/**"/>
			<!-- mvc:exclude-mapping是另外一种拦截，它可以在你后来的测试中对某个页面进行不拦截，这样就不用在
				LoginInterceptor的preHandler方法里面获取不拦截的请求uri地址了(优选) -->
			<mvc:exclude-mapping path="/system/login" />
			<bean class="com.lingshi.bookstore.interceptor.LoginInterceptor"></bean>			
		</mvc:interceptor>
	</mvc:interceptors>

<mvc:mapping path="/**"/> 是已经拦截了所有请求，包括登录，如果后来想不拦截某个页面，就在拦截配置里面配置 

<mvc:exclude-mapping path="/system/login" />

//String uri = request.getRequestURI(); // 获取登录的uri，这个是不进行拦截的
		//if(session.getAttribute("LOGIN_USER")!=null || uri.indexOf("system/login")!=-1)

<div align="center">
		<br><br><br>
		<!-- 作业：post方法与get方法的区别 -->
		<form action="${pageContext.request.contextPath}/system/login" method="post">
			<p>用户登录</p>
			账号：<input name="account" type="text" />
			<br><br>
			密码：<input name="password" type="password" />
			<br><br>
			<input type="reset" value="撤 销" />
			<input type="submit" value="提 交" />
		</form>
	</div>

public class LoginFilter implements Filter {

	@Override
	public void destroy() {
		// TODO Auto-generated method stub
		
	}

	@Override
	public void doFilter(ServletRequest arg0, ServletResponse arg1, FilterChain arg2)
			throws IOException, ServletException {
		// TODO Auto-generated method stub
		HttpServletRequest request = (HttpServletRequest)arg0;
		HttpServletResponse response = (HttpServletResponse)arg1;
		HttpSession session = request.getSession();
		
		if(session.getAttribute("LOGIN_USER")==null
				&& request.getRequestURI().indexOf("/system/login") == -1){
			// 没有登录
			response.sendRedirect(request.getContextPath()+"/system/login");
		}else{
			// 已经登录，继续请求下一级资源（继续访问）
			arg2.doFilter(arg0, arg1);
		}
		
	}

	@Override
	public void init(FilterConfig arg0) throws ServletException {
		// TODO Auto-generated method stub
		
	}
	
}

	<!-- 使用filter实现登录控制 -->
	<filter>
		<filter-name>SessionFilter</filter-name>
		<filter-class>com.lingshi.bookstore.filter.LoginFilter</filter-class>
	</filter>
	<filter-mapping>
		<filter-name>SessionFilter</filter-name>
		<!-- 所有的管理页面需要登录后才能访问 -->
		<url-pattern>/views/*</url-pattern>
	</filter-mapping>