对用户登陆后才能访问指定的页面

例如：main.jsp是用户登陆后才可以访问，如果用户没有登陆，则无法访问
问题：拦截器不能拦截jsp
解决：在WEB-INF下新建文件夹page,把main.jsp放入。
解释：进入jsp前需要走控制器，否则无法进入main.jsp

用springmvc进行写入——控制器层

@Controller
public class DemoController {
	@RequestMapping("{page}")
	public String main(@PathVariable String page){
		System.out.println("restful");
		return page;
	}
	@RequestMapping("login")
	public String login(Users users,HttpSession session){
		if(users.getUsername().equals("admin")&&users.getPassword().equals("123")){
			session.setAttribute("users", users);
			return "main";
		}else{
			return "redirect:/login.jsp";
		}
	}
}

用视图解析器

在springmvc.xml中

 <!-- 扫描注解 -->
	<context:component-scan base-package="com.youdian.controller"></context:component-scan>
	<!-- 注解驱动 -->
	<!-- org.springframework.web.servlet.mvc.annotation.DefaultAnnotationHandlerMapping -->
	<!-- org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter -->
	<mvc:annotation-driven></mvc:annotation-driven>
	<!-- 静态资源 -->
	<mvc:resources location="/js/" mapping="/js/**"></mvc:resources>
	<mvc:resources location="/css/" mapping="/css/**"></mvc:resources>
	<mvc:resources location="/images/" mapping="/images/**"></mvc:resources>
	<mvc:resources location="/files/" mapping="/files/**"></mvc:resources>
	
	<!-- 视图解析器 -->
	<bean id="viewResolver" class="org.springframework.web.servlet.view.InternalResourceViewResolver">
		<property name="prefix" value="/WEB-INF/page/"></property>
		<property name="suffix" value=".jsp"></property>
	</bean>
	
	<!-- 配置拦截器 -->
	<mvc:interceptors>
		<bean class="com.youdian.interceptor.LoginInterceptor"></bean>
	</mvc:interceptors>
</beans>

1.建立拦截器

在com.youdian.interceptor下建立类LoginInterceptor，并在springmvc中配置拦截器

public class LoginInterceptor implements HandlerInterceptor {

	@Override
	public void afterCompletion(HttpServletRequest arg0, HttpServletResponse arg1, Object arg2, Exception arg3)
			throws Exception {
		// TODO Auto-generated method stub
		
	}

	@Override
	public void postHandle(HttpServletRequest arg0, HttpServletResponse arg1, Object arg2, ModelAndView arg3)
			throws Exception {
		// TODO Auto-generated method stub
		
	}

	@Override
	public boolean preHandle(HttpServletRequest req, HttpServletResponse res, Object arg2) throws Exception {
		String uri = req.getRequestURI();
		if(uri.equals("/springmvc03/login")){
			return true;
		}else{
			Object obj = req.getSession().getAttribute("users");
			if(obj!=null){
				return true;
			}
			//全路径
			res.sendRedirect("/springmvc03/login.jsp");
			return false;
		}
	}

}