前言
spring拦截器能帮我们实现验证是否登陆、验签校验请求是否合法、预先设置数据等功能，那么该如何设置拦截器以及它的原理如何呢，下面将进行简单的介绍
1.设置
HandlerInterceptor接口
```
public interface HandlerInterceptor {
/**
* Intercept the execution of a handler. Called after HandlerMapping determined
* an appropriate handler object, but before HandlerAdapter invokes the handler.
* <p>DispatcherServlet processes a handler in an execution chain, consisting
* of any number of interceptors, with the handler itself at the end.
* With this method, each interceptor can decide to abort the execution chain,
* typically sending a HTTP error or writing a custom response.
* </p><p><strong>Note:</strong> special considerations apply for asynchronous
* request processing. For more details see