Spring Boot实现接口幂等

1、pom依赖

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd"><modelVersion>4.0.0</modelVersion><parent><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-parent</artifactId><version>2.5.6</version><relativePath/></parent><groupId>com.example</groupId><artifactId>idempotent_demo</artifactId><version>0.0.1-SNAPSHOT</version><name>idempotent_demo</name><description>idempotent_demo</description><properties><java.version>1.8</java.version></properties><dependencies><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-web</artifactId></dependency><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-test</artifactId><scope>test</scope></dependency><!--springboot data redis--><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-data-redis</artifactId></dependency><dependency><groupId>org.projectlombok</groupId><artifactId>lombok</artifactId></dependency><!-- StringUtils工具类 --><dependency><groupId>commons-lang</groupId><artifactId>commons-lang</artifactId><version>2.5</version></dependency><dependency><groupId>org.apache.commons</groupId><artifactId>commons-pool2</artifactId></dependency><!--fastjson--><dependency><groupId>com.alibaba</groupId><artifactId>fastjson</artifactId><version>2.0.25</version></dependency></dependencies><build><plugins><plugin><groupId>org.springframework.boot</groupId><artifactId>spring-boot-maven-plugin</artifactId></plugin></plugins></build></project>

2、Redis工具类

package com.example.idempotent_demo.util;import lombok.extern.slf4j.Slf4j;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.data.redis.core.StringRedisTemplate;
import org.springframework.data.redis.core.script.DefaultRedisScript;
import org.springframework.data.redis.core.script.RedisScript;
import org.springframework.stereotype.Component;import java.util.Arrays;
import java.util.concurrent.TimeUnit;/*** @author tom* Redis工具类*/
@Slf4j
@Component
public class RedisUtil {private StringRedisTemplate stringRedisTemplate;@Autowiredpublic void setRedisTemplate(StringRedisTemplate stringRedisTemplate) {this.stringRedisTemplate = stringRedisTemplate;}/*** 将key和value存入redis** @param key        redis的key* @param value      redis的value* @param expireTime key过期时间* @return 保存进redis是否成功*/public boolean save(String key, String value, Long expireTime) {try {// 存储Token到Redis,且设置过期时间为5分钟stringRedisTemplate.opsForValue().set(key, value, expireTime, TimeUnit.MINUTES);} catch (Exception e) {e.printStackTrace();return false;}return true;}/*** 验证key和value并删除key** @param key   redis的key* @param value redis的value* @return 验证是否成功*/public boolean valid(String key, String value) {// 设置Lua脚本,其中KEYS[1]是key,KEYS[2]是valueString script = "if redis.call('get', KEYS[1]) == KEYS[2] then return redis.call('del', KEYS[1]) else return 0 end";RedisScript<Long> redisScript = new DefaultRedisScript<>(script, Long.class);// 执行Lua脚本Long result = stringRedisTemplate.execute(redisScript, Arrays.asList(key, value));// 根据返回结果判断是否成功成功匹配并删除Redis键值对,若果结果不为空和0,则验证通过if (null != result && result != 0L) {log.info("验证 key={},value={} 成功", key, value);return true;}log.error("验证 key={},value={} 失败", key, value);return false;}
}

3、Token服务类

token 服务，里面主要是两个方法，一个用来创建 token，一个用来验证 token。

package com.example.idempotent_demo.service;import javax.servlet.http.HttpServletRequest;/*** @author tom*/
public interface TokenService {/*** 创建token** @return*/String generateToken();/*** 检验token** @param request* @return*/boolean validToken(HttpServletRequest request);}

package com.example.idempotent_demo.service.impl;import com.example.idempotent_demo.constant.Constant;
import com.example.idempotent_demo.exception.NoTokenException;
import com.example.idempotent_demo.exception.ValidTokenException;
import com.example.idempotent_demo.service.TokenService;
import com.example.idempotent_demo.util.RedisUtil;
import lombok.extern.slf4j.Slf4j;
import org.apache.commons.lang.StringUtils;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;import javax.servlet.http.HttpServletRequest;
import java.util.UUID;/*** @author tom*/
@Service
@Slf4j
public class TokenServiceImpl implements TokenService {private RedisUtil redisUtil;@Autowiredpublic void setRedisUtil(RedisUtil redisUtil) {this.redisUtil = redisUtil;}/*** 创建token** @return*/@Overridepublic String generateToken() {// 实例化生成ID工具对象String uuid = UUID.randomUUID().toString();String token = Constant.IDEMPOTENT_TOKEN_PREFIX + uuid;boolean success = redisUtil.save(token, token, 5L);if (success) {log.info("save token {} to redis success", token);return token;}log.error("save token {} to redis fail", token);return null;}/*** 检验token** @param request* @return*/@Overridepublic boolean validToken(HttpServletRequest request) {String token = request.getHeader(Constant.IDEMPOTENT_TOKEN_HEADER);// header中不存在tokenif (StringUtils.isBlank(token)) {log.error("用户未携带token!");throw new NoTokenException();}// 验证token失败if (!redisUtil.valid(token, token)) {log.error("重复提交!");throw new ValidTokenException();}return true;}
}

redis.get(token) 、token.equals 、redis.del(token) 如果这几个操作不是原子，可能导致，高并发下，都get到同

样的数据，判断都成功，继续业务并发执行。这里 redis 使用 lua 脚本完成这个操作：

if redis.call('get', KEYS[1]) == ARGV[1] then return redis.call('del', KEYS[1]) else return 0 end

package com.example.idempotent_demo.exception;/*** 用户为携带token* @author tom*/
public class NoTokenException extends RuntimeException {public NoTokenException() {super();}
}

package com.example.idempotent_demo.exception;/*** @author* 验证token失败*/
public class ValidTokenException extends RuntimeException{public ValidTokenException(){super();}
}

package com.example.idempotent_demo.util;/*** @author 结果集返回封装*/
public class ResponseResult {/*** 响应业务状态*/private Integer code;/*** 响应消息*/private String msg;/*** 响应中的数据*/private Object data;public Integer getCode() {return code;}public void setCode(Integer code) {this.code = code;}public String getMsg() {return msg;}public void setMsg(String msg) {this.msg = msg;}public Object getData() {return data;}public void setData(Object data) {this.data = data;}/*** 无参构造方法*/public ResponseResult() {}/*** 全参构造方法** @param code* @param msg* @param data*/public ResponseResult(Integer code, String msg, Object data) {this.code = code;this.msg = msg;this.data = data;}}

package com.example.idempotent_demo.constant;/*** @author tom*/
public class Constant {/*** 存入Redis的Token键的前缀*/public static final String IDEMPOTENT_TOKEN_PREFIX = "idempotent_token:";/*** 请求头的token名称*/public static final String IDEMPOTENT_TOKEN_HEADER = "idempotent_token";
}

4、Redis配置

spring:redis:ssl: falsehost: 127.0.0.1port: 6379database: 0timeout: 1000password:lettuce:pool:max-active: 100max-wait: -1min-idle: 0max-idle: 20
server:servlet:encoding:charset: UTF-8

5、自定义注解

自定义一个注解，定义此注解的主要目的是把它添加在需要实现幂等的方法上，凡是某个方法注解了它，都会实现

自动幂等。

后台利用反射如果扫描到这个注解，就会处理这个方法实现自动幂等，使用元注解 ElementType.METHOD 表示它

只能放在方法上，EetentionPolicy.RUNTIME 表示它在运行时。

package com.example.idempotent_demo.annotation;import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;/*** @author tom*/
@Target({ElementType.METHOD})
@Retention(RetentionPolicy.RUNTIME)
public @interface AutoIdempotent {
}

6、拦截器配置

主要的功能是拦截扫描到 AutoIdempotent 注解的方法，然后调用 TokenService 的 validToken方法校验 token

是否正确，如果捕捉到异常就将异常信息渲染成json返回给前端。

package com.example.idempotent_demo.config;import com.alibaba.fastjson.JSON;
import com.alibaba.fastjson.serializer.SerializerFeature;
import com.example.idempotent_demo.annotation.AutoIdempotent;
import com.example.idempotent_demo.exception.NoTokenException;
import com.example.idempotent_demo.exception.ValidTokenException;
import com.example.idempotent_demo.service.TokenService;
import com.example.idempotent_demo.util.ResponseResult;
import lombok.extern.slf4j.Slf4j;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Component;
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.io.IOException;
import java.io.PrintWriter;
import java.lang.reflect.Method;/*** @author tom*/
@Slf4j
@Component
public class AutoIdempotentInterceptor implements HandlerInterceptor {private TokenService tokenService;@Autowiredpublic void setTokenService(TokenService tokenService) {this.tokenService = tokenService;}/*** 预处理** @param request* @param response* @param handler* @return* @throws Exception*/@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AutoIdempotent注解标记的方法AutoIdempotent methodAnnotation = method.getAnnotation(AutoIdempotent.class);if (methodAnnotation != null) {try {// 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return tokenService.validToken(request);} catch (NoTokenException ex) {log.error("用户未携带token!");returnJson(response, JSON.toJSONString(new ResponseResult(10001, "用户未携带token!", null), SerializerFeature.WriteMapNullValue));return false;} catch (ValidTokenException ex) {log.error("重复提交!");returnJson(response, JSON.toJSONString(new ResponseResult(10002, "重复提交!", null), SerializerFeature.WriteMapNullValue));return false;}}//必须返回true,否则会被拦截一切请求return true;}@Overridepublic void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {}@Overridepublic void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {}private void returnJson(HttpServletResponse response, String json) {PrintWriter writer = null;response.setCharacterEncoding("UTF-8");response.setContentType("application/json; charset=utf-8");try {writer = response.getWriter();writer.print(json);} catch (IOException e) {e.printStackTrace();} finally {if (writer != null) {writer.close();}}}
}

7、注册拦截器

添加autoIdempotentInterceptor到配置类中，这样我们到拦截器才能生效，注意使用@Configuration注解，

这样在容器启动是时候就可以添加进入context中。

package com.example.idempotent_demo.config;import org.springframework.context.annotation.Configuration;
import org.springframework.web.servlet.config.annotation.InterceptorRegistry;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurer;import javax.annotation.Resource;/*** @author*/
@Configuration
public class WebConfiguration implements WebMvcConfigurer {@Resourceprivate AutoIdempotentInterceptor autoIdempotentInterceptor;/*** 添加拦截器** @param registry*/@Overridepublic void addInterceptors(InterceptorRegistry registry) {registry.addInterceptor(autoIdempotentInterceptor);}
}

8、启动类

package com.example.idempotent_demo;import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;/*** @author tom*/
@SpringBootApplication
public class IdempotentDemoApplication {public static void main(String[] args) {SpringApplication.run(IdempotentDemoApplication.class, args);}}