介绍
幂等性的概念是,任意多次执行所产生的影响都与一次执行产生的影响相同,按照这个含义,最终的解释是对数据库的影响只能是一次性的,不能重复处理。手段如下
数据库建立唯一索引token机制悲观锁或者是乐观锁先查询后判断
小小主要带你们介绍Redis实现自动幂等性。其原理如下图所示。
实现过程
引入 maven 依赖
<dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-data-redis</artifactId></dependency>
spring 配置文件写入
server.port=8080core.datasource.druid.enabled=truecore.datasource.druid.url=jdbc:mysql://192.168.1.225:3306/?useUnicode=true&characterEncoding=UTF-8core.datasource.druid.username=rootcore.datasource.druid.password=core.redis.enabled=truespring.redis.host=192.168.1.225 #本机的redis地址spring.redis.port=16379spring.redis.database=3spring.redis.jedis.pool.max-active=10spring.redis.jedis.pool.max-idle=10spring.redis.jedis.pool.max-wait=5sspring.redis.jedis.pool.min-idle=10
引入 Redis
引入 Spring boot 中的redis相关的stater,后面需要用到 Spring Boot 封装好的 RedisTemplate
package cn.smallmartial.demo.utils;import org.springframework.beans.factory.annotation.Autowired;import org.springframework.data.redis.core.RedisTemplate;import org.springframework.data.redis.core.ValueOperations;import org.ponent;import java.io.Serializable;import java.util.Objects;import java.util.concurrent.TimeUnit;/*** @Author smallmartial* @Date /4/16* @Email smallmarital@*/@Componentpublic class RedisUtil {@Autowiredprivate RedisTemplate redisTemplate;/*** 写入缓存** @param key* @param value* @return*/public boolean set(final String key, Object value) {boolean result = false;try {ValueOperations<Serializable, Object> operations = redisTemplate.opsForValue();operations.set(key, value);result = true;} catch (Exception e) {e.printStackTrace();}return result;}/*** 写入缓存设置时间** @param key* @param value* @param expireTime* @return*/public boolean setEx(final String key, Object value, long expireTime) {boolean result = false;try {ValueOperations<Serializable, Object> operations = redisTemplate.opsForValue();operations.set(key, value);redisTemplate.expire(key, expireTime, TimeUnit.SECONDS);result = true;} catch (Exception e) {e.printStackTrace();}return result;}/*** 读取缓存** @param key* @return*/public Object get(final String key) {Object result = null;ValueOperations<Serializable, Object> operations = redisTemplate.opsForValue();result = operations.get(key);return result;}/*** 删除对应的value** @param key*/public boolean remove(final String key) {if (exists(key)) {Boolean delete = redisTemplate.delete(key);return delete;}return false;}/*** 判断key是否存在** @param key* @return*/public boolean exists(final String key) {boolean result = false;ValueOperations<Serializable, Object> operations = redisTemplate.opsForValue();if (Objects.nonNull(operations.get(key))) {result = true;}return result;}}
自定义注解
自定义一个注解,定义此注解的目的是把它添加到需要实现幂等的方法上,只要某个方法注解了其,都会自动实现幂等操作。其代码如下
@Target({ElementType.METHOD})@Retention(RetentionPolicy.RUNTIME)public @interface AutoIdempotent {}
token 的创建和实现
token 服务接口,我们新建一个接口,创建token服务,里面主要是有两个方法,一个用来创建 token,一个用来验证token
public interface TokenService {/*** 创建token* @return*/public String createToken();/*** 检验token* @param request* @return*/public boolean checkToken(HttpServletRequest request) throws Exception;}
token 的实现类,token中引用了服务的实现类,token引用了 redis 服务,创建token采用随机算法工具类生成随机 uuid 字符串,然后放入 redis 中,如果放入成功,返回token,校验方法就是从 header 中获取 token 的值,如果不存在,直接跑出异常,这个异常信息可以被直接拦截到,返回给前端。
package cn.smallmartial.demo.service.impl;import cn.smallmartial.demo.bean.RedisKeyPrefix;import cn.smallmartial.demo.bean.ResponseCode;import cn.smallmartial.demo.exception.ApiResult;import cn.smallmartial.demo.exception.BusinessException;import cn.smallmartial.demo.service.TokenService;import cn.smallmartial.demo.utils.RedisUtil;import ty.util.internal.StringUtil;import org.springframework.beans.factory.annotation.Autowired;import org.springframework.stereotype.Service;import org.springframework.util.StringUtils;import javax.servlet.http.HttpServletRequest;import java.util.Random;import java.util.UUID;/*** @Author smallmartial* @Date /4/16* @Email smallmarital@*/@Servicepublic class TokenServiceImpl implements TokenService {@Autowiredprivate RedisUtil redisService;/*** 创建token** @return*/@Overridepublic String createToken() {String str = UUID.randomUUID().toString().replace("-", "");StringBuilder token = new StringBuilder();try {token.append(RedisKeyPrefix.TOKEN_PREFIX).append(str);redisService.setEx(token.toString(), token.toString(), 10000L);boolean empty = StringUtils.isEmpty(token.toString());if (!empty) {return token.toString();}} catch (Exception ex) {ex.printStackTrace();}return null;}/*** 检验token** @param request* @return*/@Overridepublic boolean checkToken(HttpServletRequest request) throws Exception {String token = request.getHeader(RedisKeyPrefix.TOKEN_NAME);if (StringUtils.isEmpty(token)) {// header中不存在tokentoken = request.getParameter(RedisKeyPrefix.TOKEN_NAME);if (StringUtils.isEmpty(token)) {// parameter中也不存在tokenthrow new BusinessException(ApiResult.BADARGUMENT);}}if (!redisService.exists(token)) {throw new BusinessException(ApiResult.REPETITIVE_OPERATION);}boolean remove = redisService.remove(token);if (!remove) {throw new BusinessException(ApiResult.REPETITIVE_OPERATION);}return true;}}
拦截器的配置
用于拦截前端的 token,判断前端的 token 是否有效
@Configurationpublic class WebMvcConfiguration extends WebMvcConfigurationSupport {@Beanpublic AuthInterceptor authInterceptor() {return new AuthInterceptor();}/*** 拦截器配置** @param registry*/@Overridepublic void addInterceptors(InterceptorRegistry registry) {registry.addInterceptor(authInterceptor());//.addPathPatterns("/ksb/**")//.excludePathPatterns("/ksb/auth/**", "/api/common/**", "/error", "/api/*");super.addInterceptors(registry);}@Overridepublic void addResourceHandlers(ResourceHandlerRegistry registry) {registry.addResourceHandler("/**").addResourceLocations("classpath:/static/");registry.addResourceHandler("swagger-ui.html").addResourceLocations("classpath:/META-INF/resources/");registry.addResourceHandler("/webjars/**").addResourceLocations("classpath:/META-INF/resources/webjars/");super.addResourceHandlers(registry);}}
拦截处理器:主要用于拦截扫描到 Autoldempotent 到注解方法,然后调用 tokenService 的 checkToken 方法校验 token 是否正确,如果捕捉到异常就把异常信息渲染成 json 返回给前端。这部分代码主要和自定义注解部分挂钩。其主要代码如下所示
@Slf4jpublic class AuthInterceptor extends HandlerInterceptorAdapter {@Autowiredprivate TokenService tokenService;@Overridepublic boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {if (!(handler instanceof HandlerMethod)) {return true;}HandlerMethod handlerMethod = (HandlerMethod) handler;Method method = handlerMethod.getMethod();//被ApiIdempotment标记的扫描AutoIdempotent methodAnnotation = method.getAnnotation(AutoIdempotent.class);if (methodAnnotation != null) {try {return tokenService.checkToken(request);// 幂等性校验, 校验通过则放行, 校验失败则抛出异常, 并通过统一异常处理返回友好提示} catch (Exception ex) {throw new BusinessException(ApiResult.REPETITIVE_OPERATION);}}return true;}}
测试用例
这里进行相关的测试用例 模拟业务请求类,通过相关的路径获得相关的token,然后调用 testidempotence 方法,这个方法注解了 @Autoldempotent,拦截器会拦截所有的请求,当判断到处理的方法上面有该注解的时候,就会调用 TokenService 中的 checkToken() 方法,如果有异常会跑出,代码如下所示
/*** @Author smallmartial* @Date /4/16* @Email smallmarital@*/@RestControllerpublic class BusinessController {@Autowiredprivate TokenService tokenService;@GetMapping("/get/token")public Object getToken(){String token = tokenService.createToken();return ResponseUtil.ok(token) ;}@AutoIdempotent@GetMapping("/test/Idempotence")public Object testIdempotence() {String token = "接口幂等性测试";return ResponseUtil.ok(token) ;}}
用浏览器进行访问
用获取到的token第一次访问
用获取到的token再次访问
可以看到,第二次访问失败,即,幂等性验证通过。
作者:___mySoul原文链接:/melovemingming/article/details/109665270