springboot web开发登录拦截器

在SpringBoot中我们可以使用HandlerInterceptorAdapter这个适配器来实现自己的拦截器。这样就可以拦截所有的请求并做相应的处理。

应用场景

日志记录，可以记录请求信息的日志，以便进行信息监控、信息统计等。
权限检查：如登陆检测，进入处理器检测是否登陆，如果没有直接返回到登陆页面。
性能监控：典型的是慢日志。

在HandlerInterceptorAdapter中主要提供了以下的方法：

preHandle：在方法被调用前执行。在该方法中可以做类似校验的功能。如果返回true，则继续调用下一个拦截器。如果返回false，则中断执行，也就是说我们想调用的方法不会被执行，但是你可以修改response为你想要的响应。
postHandle：在方法执行后调用。
afterCompletion：在整个请求处理完毕后进行回调，也就是说视图渲染完毕或者调用方已经拿到响应。

HandlerInterceptor

public interface HandlerInterceptor {default boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {return true;}default void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, @Nullable ModelAndView modelAndView) throws Exception {}default void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, @Nullable Exception ex) throws Exception {}
}

AsyncHandlerInterceptor

public interface AsyncHandlerInterceptor extends HandlerInterceptor {default void afterConcurrentHandlingStarted(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {}
}

abstract class HandlerInterceptorAdapter

public abstract class HandlerInterceptorAdapter implements AsyncHandlerInterceptor {public HandlerInterceptorAdapter() {}public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {return true;}public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, @Nullable ModelAndView modelAndView) throws Exception {}public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, @Nullable Exception ex) throws Exception {}public void afterConcurrentHandlingStarted(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {}
}

看到这3个类和接口关系我们就明白了集成 HandlerInterceptorAdapter 只是为了能让我们只重写自己需要的方法即可,如果我们需要全部重写,也可以直接实现接口

运行流程总结如下：

拦截器执行顺序是按照Spring配置文件中定义的顺序而定的。
会先按照顺序执行所有拦截器的preHandle方法，一直遇到return false为止，比如第二个preHandle方法是return false，则第三个以及以后所有拦截器都不会执行。若都是return true，则按顺序加载完preHandle方法。
然后执行主方法（自己的controller接口），若中间抛出异常，则跟return false效果一致，不会继续执行postHandle，只会倒序执行afterCompletion方法。
在主方法执行完业务逻辑（页面还未渲染数据）时，按倒序执行postHandle方法。若第三个拦截器的preHandle方法return false，则会执行第二个和第一个的postHandle方法和afterCompletion（postHandle都执行完才会执行这个，也就是页面渲染完数据后，执行after进行清理工作）方法。（postHandle和afterCompletion都是倒序执行）

编写拦截器

public class LoginInterceptor extends HandlerInterceptorAdapter {Logger logger = LoggerFactory.getLogger(getClass());@Overridepublic boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {System.out.println("==============LoginInterceptor========preHandle==========");return true;}@Overridepublic void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, @Nullable ModelAndView modelAndView) throws Exception {System.out.println("==============LoginInterceptor======postHandle============");}@Overridepublic void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, @Nullable Exception ex) throws Exception {System.out.println("==============LoginInterceptor=======afterCompletion===========");}@Overridepublic void afterConcurrentHandlingStarted(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {System.out.println("==============LoginInterceptor========afterConcurrentHandlingStarted==========");}}

public class LoginInterceptor2 extends HandlerInterceptorAdapter {Logger logger = LoggerFactory.getLogger(getClass());@Overridepublic boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {System.out.println("==============LoginInterceptor2========preHandle==========");return true;}@Overridepublic void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, @Nullable ModelAndView modelAndView) throws Exception {System.out.println("==============LoginInterceptor2======postHandle============");}@Overridepublic void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, @Nullable Exception ex) throws Exception {System.out.println("==============LoginInterceptor2=======afterCompletion===========");}@Overridepublic void afterConcurrentHandlingStarted(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {System.out.println("==============LoginInterceptor2========afterConcurrentHandlingStarted==========");}}

WebMvcConfigurerAdapter 抽象类是对WebMvcConfigurer接口的简单抽象（增加了一些默认实现），但在在SpringBoot2.0及Spring5.0中WebMvcConfigurerAdapter已被废弃。官方推荐直接实现WebMvcConfigurer或者直接继承WebMvcConfigurationSupport

实现WebMvcConfigurer配置拦截器

@Configuration
public class SpringMVCConfig implements WebMvcConfigurer {@Overridepublic void addInterceptors(InterceptorRegistry registry) {registry.addInterceptor(new LoginInterceptor());registry.addInterceptor(new LoginInterceptor2());}
}