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Springboot-自定义注解

网友: 文章列表 2024-03-21 15:48:58

Springboot-自定义注解

业务上我们使用注解实现限流和幂等性校验，下面已限流为例介绍

一、注解的定义

元注解

有一些注解可以修饰其他注解，这些注解就称为元注解（meta annotation）

@Inherited

使用@Inherited定义子类是否可继承父类定义的Annotation。@Inherited仅针对@Target(ElementType.TYPE)类型的annotation有效，并且仅针对class的继承，对interface的继承无效。

@Documented 注解

指明修饰的注解，可以被例如javadoc此类的工具文档化，只负责标记，没有成员取值。

@Target

指明了修饰的这个注解的使用范围，即被描述的注解可以用在哪里：

  • 类或接口：ElementType.TYPE

  • 字段：ElementType.FIELD

  • 方法：ElementType.METHOD

  • 构造方法：ElementType.CONSTRUCTOR

  • 方法参数：ElementType.PARAMETER

@Retention

指明修饰的注解的生存周期，即会保留到哪个阶段：

  • 仅编译期：RetentionPolicy.SOURCE

  • 仅class文件：RetentionPolicy.CLASS

  • 运行期：RetentionPolicy.RUNTIME

二、限流注解

Java语言使用@interface语法来定义注解（Annotation），它的格式如下：

import java.lang.annotation.*;
import java.util.concurrent.TimeUnit;/* 限流注解* @author meng* @date 2021/11/17 9:38*/
@Inherited
@Documented
@Target({ElementType.TYPE,ElementType.METHOD})
@Retention(RetentionPolicy.RUNTIME)
public @interface RequestRateLimiter {/* 这里指吞吐率每秒多少许可数（通常是指QPS，每秒多少查询）* @return*/double QPS() default 100D;/* 获取令牌超时时间* @return*/long acquireTokenTimeout() default 100;/* 获取令牌超时时间单位：默认为 毫秒* @return*/TimeUnit timeunit() default TimeUnit.MILLISECONDS;}

三、限流拦截器

import com.google.common.util.concurrent.RateLimiter;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.core.annotation.AnnotatedElementUtils;
import org.springframework.core.annotation.AnnotationUtils;
import org.springframework.stereotype.Component;
import org.springframework.web.method.HandlerMethod;
import org.springframework.web.servlet.HandlerInterceptor;import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.lang.reflect.Method;
import java.util.Enumeration;
import java.util.Map;
import java.util.Objects;
import java.util.concurrent.ConcurrentHashMap;/* @author meng* @date 2021/11/17 9:35*/
@Component
public class RateLimiterInterceptor implements HandlerInterceptor {private static final Logger logger = LoggerFactory.getLogger(RateLimiterInterceptor.class);/* 根据请求地址保存不同的令牌桶*/private static final Map<String, RateLimiter> rateLimiterMap = new ConcurrentHashMap<String, RateLimiter>(16);@Overridepublic boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) {if (handler instanceof HandlerMethod) {HandlerMethod handlerMethod = (HandlerMethod) handler;Method method = ((HandlerMethod) handler).getMethod();//没有标注注解，放行if (AnnotatedElementUtils.isAnnotated(method, RequestRateLimiter.class)) {//首先获取方法上的注解RequestRateLimiter requestRateLimiter = AnnotationUtils.findAnnotation(method, RequestRateLimiter.class);//方法上没有标注该注解，尝试获取类上的注解if (Objects.isNull(requestRateLimiter)) {//获取类上的注解requestRateLimiter = AnnotationUtils.findAnnotation(handlerMethod.getBean().getClass(), RequestRateLimiter.class);}// 获取请求 urlString url = request.getRequestURI();// 定义令牌桶RateLimiter rateLimiter = null;if (!rateLimiterMap.containsKey(url)) {// 为当前请求创建令牌桶rateLimiter = RateLimiter.create(requestRateLimiter.QPS());rateLimiterMap.put(url, rateLimiter);} else {// 根据请求 url 获取令牌桶rateLimiter = rateLimiterMap.get(url);}// 获取令牌boolean acquire = rateLimiter.tryAcquire(requestRateLimiter.acquireTokenTimeout(), requestRateLimiter.timeunit());logger.info("IP:{},url:{},acquire:{}", getIpAddr(request), url, acquire);if (!acquire) {throw new RateLimiterValidatorException();}}}return true;}@Overridepublic void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) {}public static String getIpAddr(HttpServletRequest request) {String ipAddress = null;try {ipAddress = request.getHeader("x-forwarded-for");if (ipAddress == null || ipAddress.length() == 0 || "unknown".equalsIgnoreCase(ipAddress)) {ipAddress = request.getHeader("Proxy-Client-IP");}if (ipAddress == null || ipAddress.length() == 0 || "unknown".equalsIgnoreCase(ipAddress)) {ipAddress = request.getHeader("WL-Proxy-Client-IP");}if (ipAddress == null || ipAddress.length() == 0 || "unknown".equalsIgnoreCase(ipAddress)) {ipAddress = request.getRemoteAddr();if (ipAddress.equals("127.0.0.1")) {// 根据网卡取本机配置的IPInetAddress inet = null;try {inet = InetAddress.getLocalHost();} catch (UnknownHostException e) {e.printStackTrace();}ipAddress = inet.getHostAddress();}}// 对于通过多个代理的情况，第一个IP为客户端真实IP，多个IP按照','分割if (ipAddress != null && ipAddress.length() > 15) { // "*.*.*.*".length()if (ipAddress.indexOf(",") > 0) {ipAddress = ipAddress.substring(0, ipAddress.indexOf(","));}}} catch (Exception e) {ipAddress = "";}return ipAddress;}}

PS：

  1. 使用Guava RateLimiter实现限流

  1. RateLimiterValidatorException自定义异常，详见博客：Springboot - 统一异常处理

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