JavaWeb springmvc 拦截器

具体的使用方法：
创建interceptor类，有两种方法：
1.一种是实现接口org.springframework.web.servlet.HandlerInterceptor，并重写preHandle、postHandle、afterCompletion三个方法，如下：
public class MyInterceptor implements HandlerInterceptor {
@Override
public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {
System.out.println("zxs- 最后执行！！！一般用于释放资源！！ ");
}
@Override
public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {
System.out.println("zxs-Action 执行之后，生成视图之前执行！！ ");
}
@Override
public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
System.out.println("zxs-action 之前执行！！！ ");
return true; //  继续执行 action
}
}
2.另一种是继承适配器org.springframework.web.servlet.handler.HandlerInterceptorAdapter 
public class MyInterceptor2 extends HandlerInterceptorAdapter {
@Override
public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
System.out.println("MyInterceptor2.preHandle()");
return true; //  继续执行 action
}
}
拦截器的基本配置：
<!-- 拦截器配置 -->  
<mvc:interceptors>  
 <!-- session超时 -->  
 <mvc:interceptor>  
<mvc:mapping path="/*/*"/>  
<bean class="com.demo.conf.interceptor.MyInterceptor">  
 <property name="allowUrls">  
<list>  
 <!-- 如果请求中包含以下路径，则不进行拦截 -->  
 <value>/login</value>  
 <value>/js</value>  
 <value>/css</value>  
 <value>/image</value>  
 <value>/images</value>  
</list>  
 </property>  
</bean>  
 </mvc:interceptor>  
</mvc:interceptors>  

实际的拦截器：
/**
* 处理session超时的拦截器
*/
public class SessionTimeoutInterceptor  implements HandlerInterceptor{

public String[] allowUrls;//还没发现可以直接配置不拦截的资源，所以在代码里面来排除

public void setAllowUrls(String[] allowUrls) {
this.allowUrls = allowUrls;
}


@Override
public boolean preHandle(HttpServletRequest request, HttpServletResponse response,
Object arg2) throws Exception {
String requestUrl = request.getRequestURI().replace(request.getContextPath(), "");  
System.out.println(requestUrl);
if(null != allowUrls && allowUrls.length>=1)
for(String url : allowUrls) {  
if(requestUrl.contains(url)) {  
return true;  
}  
}

User user = (User) request.getSession().getAttribute("user");
if(user != null) {  
return true;  //返回true，则这个方面调用后会接着调用postHandle(),  afterCompletion()
}else{
// 未登录  跳转到登录页面
throw new SessionTimeoutException();//返回到配置文件中定义的路径
}
}

@Override
public void afterCompletion(HttpServletRequest arg0,
HttpServletResponse arg1, Object arg2, Exception arg3)
throws Exception {
}


@Override
public void postHandle(HttpServletRequest arg0, HttpServletResponse arg1,
Object arg2, ModelAndView arg3) throws Exception {
}


}

除此之外，在登录成功后，要设置一个session的超时时间，和拦截器中药检查的参数：
request.getSession().setMaxInactiveInterval(20);//20秒  
request.getSession().setAttribute("user", user);