背景
这里介绍一下本文的背景(废话,可跳过)。上周有个我们服务的调用方反馈某个接口调用失败率很高,排查了一下,发现是因为这个接口被我之前写的一个限流器给拦截了,随着我们的服务接入了 Sentinel,这个 限流器也可以下线了。于是今天又看了一下当初了实现,发现实现的很粗糙,核心还是基于 Spring AOP 实现的。
又突然想起前段时间由于某些原因想过下掉我们服务中使用的 Shiro,因为只是因为要使用 Shiro 的鉴权( @RequiresPermissions
)就要单独引入一个框架,有点重。感觉这种鉴权完全可以自己实现,那怎么实现呢,脑子第一印象又是 Spring AOP。
这里就陷入了一种误区,啥事都用 Spring AOP。Spring AOP 的实现会依赖动态代理,无论是使用 JDK 动态代理还是 CGLIB 动态代理,都会有一定的性能开销。但其实在 Web 端很多功能,都是可以避免使用 Spring AOP 减少无意义的性能损耗,比如上面提到的限流和鉴权。
抽象实现
其实原理很简单,就是基于 HandlerInterceptor
来做。但由于类似的功能会很多,比如限流、鉴权、日志打印等,可以将相关功能进行抽象,便于后续类似功能快速实现。
核心抽象类:
package blog.dongguabai.spring.web.mvc.handlerinterceptor.core;import org.springframework.web.method.HandlerMethod;
import org.springframework.web.servlet.HandlerInterceptor;
import org.springframework.web.servlet.ModelAndView;import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.lang.annotation.Annotation;
import java.lang.reflect.ParameterizedType;
import java.util.Objects;/*** @author dongguabai* @date 2023-11-19 23:43*/
public abstract class CustomizedHandlerMethodInterceptor<A extends Annotation> implements HandlerInterceptor {private final Class<A> annotationType;protected CustomizedHandlerMethodInterceptor() {ParameterizedType superclass = (ParameterizedType) getClass().getGenericSuperclass();this.annotationType = (Class<A>) superclass.getActualTypeArguments()[0];}protected abstract boolean preHandle(HttpServletRequest request, HttpServletResponse response, HandlerMethod handlerMethod, A annotation) throws Exception;protected abstract void afterCompletion(HttpServletRequest request, HttpServletResponse response, HandlerMethod handlerMethod, A annotation, Exception ex) throws Exception;protected abstract void postHandle(HttpServletRequest request, HttpServletResponse response, HandlerMethod handlerMethod, ModelAndView modelAndView, A annotation) throws Exception;@Overridepublic final boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {if (handler instanceof HandlerMethod) {A annotation = getAnnotation((HandlerMethod) handler);if (match(annotation)) {return preHandle(request, response, (HandlerMethod) handler, annotation);}}return true;}@Overridepublic final void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {if (handler instanceof HandlerMethod) {A annotation = getAnnotation((HandlerMethod) handler);if (match(annotation)) {postHandle(request, response, (HandlerMethod) handler, modelAndView, annotation);}}}@Overridepublic final void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {if (handler instanceof HandlerMethod) {A annotation = getAnnotation((HandlerMethod) handler);if (match(annotation)) {afterCompletion(request, response, (HandlerMethod) handler, annotation, ex);}}}protected A getAnnotation(HandlerMethod handlerMethod) {return handlerMethod.getMethodAnnotation(annotationType);}protected boolean match(A annotation) {return Objects.nonNull(annotation);}}
接下来其他的业务功能只需要定义注解后,编写拦截器继承 CustomizedHandlerMethodInterceptor
即可。
业务快速实现:鉴权
定义注解:
package blog.dongguabai.spring.web.mvc.handlerinterceptor.require;import java.lang.annotation.Documented;
import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;/*** @author Dongguabai* @description* @date 2023-11-19 23:31*/
@Retention(RetentionPolicy.RUNTIME)
@Target({ElementType.METHOD})
@Documented
public @interface RequiresPermissions {// PermissionsString[] value();
}
拦截器实现:
package blog.dongguabai.spring.web.mvc.handlerinterceptor.require;import blog.dongguabai.spring.web.mvc.handlerinterceptor.RequestContext;
import blog.dongguabai.spring.web.mvc.handlerinterceptor.core.CustomizedHandlerMethodInterceptor;
import org.springframework.stereotype.Component;
import org.springframework.web.method.HandlerMethod;
import org.springframework.web.servlet.ModelAndView;import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.util.Arrays;
import java.util.List;/*** @author dongguabai* @date 2023-11-19 23:34*/
@Component
public class RequiresPermissionsHandlerMethodInterceptor extends CustomizedHandlerMethodInterceptor<RequiresPermissions> {@Overrideprotected boolean preHandle(HttpServletRequest request, HttpServletResponse response, HandlerMethod handlerMethod, RequiresPermissions annotation) throws Exception {List<String> permissons = Arrays.asList(annotation.value());if (RequestContext.getCurrentUser().getPermissions().stream().anyMatch(permissons::contains)){return true;}System.out.println("无权限.....");return false;}@Overrideprotected void afterCompletion(HttpServletRequest request, HttpServletResponse response, HandlerMethod handlerMethod, RequiresPermissions annotation, Exception ex) throws Exception {}@Overrideprotected void postHandle(HttpServletRequest request, HttpServletResponse response, HandlerMethod handlerMethod, ModelAndView modelAndView, RequiresPermissions annotation) throws Exception {}
}
也就是说标注了 RequiresPermissions
注解的接口都会进行鉴权。
验证一下:
package blog.dongguabai.spring.web.mvc.handlerinterceptor;import blog.dongguabai.spring.web.mvc.handlerinterceptor.require.RequiresPermissions;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;/*** @author dongguabai* @date 2023-11-20 00:17*/
@RestController
public class TestController {//只有拥有 BOSS 权限的用户才能调用@GetMapping("/get-reports")@RequiresPermissions("BOSS")public String getReports() {return "ALL...";}
}
模拟当前登陆用户(无 BOSS
权限):
package blog.dongguabai.spring.web.mvc.handlerinterceptor;import java.util.Arrays;/*** @author dongguabai* @date 2023-11-20 01:21*/
public final class RequestContext {public static User getCurrentUser() {User user = new User();user.setUsername("tom");user.setPermissions(Arrays.asList("ADMIN", "STUDENT"));return user;}
}
调用:
➜ github curl http://localhost:8080/get-reports
{"message":"无权限..."}%
即拦截成功。
业务快速实现:限流
定义注解:
package blog.dongguabai.spring.web.mvc.handlerinterceptor.canyon;import java.lang.annotation.Documented;
import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
import java.util.concurrent.TimeUnit;/*** @author dongguabai* @date 2023-11-20 01:56*/
@Retention(RetentionPolicy.RUNTIME)
@Target({ElementType.METHOD})
@Documented
public @interface Canyon {double value();long timeout() default 0;TimeUnit timeunit() default TimeUnit.SECONDS;String message() default "系统繁忙,请稍后再试.";
}
实现拦截器:
package blog.dongguabai.spring.web.mvc.handlerinterceptor.canyon;import blog.dongguabai.spring.web.mvc.handlerinterceptor.RequestContext;
import blog.dongguabai.spring.web.mvc.handlerinterceptor.core.CustomizedHandlerMethodInterceptor;
import blog.dongguabai.spring.web.mvc.handlerinterceptor.require.RequiresPermissions;
import org.springframework.stereotype.Component;
import org.springframework.web.method.HandlerMethod;
import org.springframework.web.servlet.ModelAndView;import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.lang.reflect.Method;
import java.util.Arrays;
import java.util.List;
import java.util.Map;/*** @author dongguabai* @date 2023-11-19 23:34*/
@Component
public class CanyonHandlerMethodInterceptor extends CustomizedHandlerMethodInterceptor<Canyon> {@Overrideprotected boolean preHandle(HttpServletRequest request, HttpServletResponse response, HandlerMethod handlerMethod, Canyon annotation) throws Exception {if (tryAcquire()) {return true;}response.setContentType("application/json");response.setCharacterEncoding("UTF-8");response.getWriter().write(String.format("{\"message\":\"%s\"}", annotation.message()));return false;}@Overrideprotected void afterCompletion(HttpServletRequest request, HttpServletResponse response, HandlerMethod handlerMethod, Canyon annotation, Exception ex) throws Exception {}@Overrideprotected void postHandle(HttpServletRequest request, HttpServletResponse response, HandlerMethod handlerMethod, ModelAndView modelAndView, Canyon annotation) throws Exception {}/*** todo:流量控制逻辑*/private boolean tryAcquire() {return false;}
}
验证一下:
package blog.dongguabai.spring.web.mvc.handlerinterceptor;import blog.dongguabai.spring.web.mvc.handlerinterceptor.canyon.Canyon;
import blog.dongguabai.spring.web.mvc.handlerinterceptor.require.RequiresPermissions;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;/*** @author dongguabai* @date 2023-11-20 00:17*/
@RestController
public class TestController {@GetMapping("/get-reports")@RequiresPermissions("BOSS")public String getReports() {return "ALL...";}@GetMapping("/search")@RequiresPermissions("ADMIN")@Canyon(1)public String search() {return "search...";}
}
调用:
➜ github curl http://localhost:8080/search
{"message":"系统繁忙,请稍后再试."}%
即限流成功。
总结
本文首先阐述了虽然 Spring AOP 可以实现限流、鉴权等需要代理的功能,但由于依赖动态代理,会带来一定的性能损耗。然后通过对 HandlerInterceptor
的抽象,我们实现了一套在 Spring Web MVC 层面的静态代理机制,从而方便快速地在 Web 端实现代理功能。
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