Java注解方式之防止重复请求
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自定义注解方式防止前端同一时间多次重复提交
一、 前情提要
有这样一个业务，上课的时候老师给表现好的学生送小花花，
每节课都能统计出某个学生收到的花的总数。
按照产品需求，前端点击送花按钮后30秒内是不能再次送花的(信任的基础)
(上课老师送花行为都进行统计了，可见互联网是多么可怕)
二、技术设计
2.1 库表设计
CREATE TABLE `t_student_flower` (
`id` bigint(20) NOT NULL AUTO_INCREMENT COMMENT '主键（自增）',
`classroom_id` bigint(20) NOT NULL COMMENT '每堂课的唯一标识',
`student_id` bigint(20) NOT NULL COMMENT '学生唯一标识',
`flower_num` bigint(20) NOT NULL DEFAULT '0' COMMENT '学生收到的花数量',
PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8
2.2 业务逻辑
业务逻辑很简单，针对某一堂课的某一个学生，老师第一次送花就新增一条记录，之后老师给这个学生送花就在原有的记录基础上增加送花数量即可。
如果前端能保证一堂课，一个学生，30秒内只能送一次花，这样设计能99.9999%的保证业务没问题
2.3 代码编写
至于创建SpringBoot项目，连接Mybatis 准备在Mybatis篇章写，这里主要点不是这些。
重要是业务逻辑
pom.xml
<?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>2.5.4</version>
<relativePath/> <!-- lookup parent from repository -->
</parent>
<groupId>com.example</groupId>
<artifactId>student_flower</artifactId>
<version>0.0.1-SNAPSHOT</version>
<name>student_flower</name>
<description>Demo project for Spring Boot</description>
<properties>
<java.version>1.8</java.version>
</properties>
<dependencies>
<!--web-->
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>
<!--mybatis-->
<dependency>
<groupId>org.mybatis.spring.boot</groupId>
<artifactId>mybatis-spring-boot-starter</artifactId>
<version>1.3.2</version>
</dependency>
<!--mysql驱动-->
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<scope>runtime</scope>
</dependency>
<!--lombok 一款还不错的副主编程工具-->
<dependency>
<groupId>org.projectlombok</groupId>
<artifactId>lombok</artifactId>
<version>1.16.18</version>
<scope>provided</scope>
</dependency>
<!--测试使用-->
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-test</artifactId>
<scope>test</scope>
</dependency>
</dependencies>
<build>
<plugins>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
</plugin>
</plugins>
</build>
</project>
application.yml
server:
# 服务端口配置
port: 8888
spring:
# 数据源配置
datasource:
driver-class-name: com.mysql.cj.jdbc.Driver
url: jdbc:mysql://127.0.0.1:3306/test?characterEncoding=utf-8&useSSL=false
username: root
password: 123456
mybatis:
# mapper扫描路径
mapper-locations: classpath:mapper
@RestController
public class StudentFlowerController {
@Autowired
StudentFlowerService studentFlowerService;
@GetMapping(value = "/test/sendflower/{classroomId}/{studentId}")
public void sendFlower(@NotNull @PathVariable("classroomId") Long classroomId , @NotNull @PathVariable("studentId") Long studentId){
studentFlowerService.SendFlower(classroomId,studentId);
}
}
StudentFlowerService
package com.example.student_flower.service;
import com.example.student_flower.dao.TStudentFlowerMapper;
import com.example.student_flower.entity.TStudentFlower;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
@Service
public class StudentFlowerService {
@Autowired
TStudentFlowerMapper mapper;
public void SendFlower(Long classroomId, Long studentId){
TStudentFlower tStudentFlower = mapper.selectByClassroomIdAndStudentId(classroomId, studentId);
// 第一次送花 没有记录 新增
if (tStudentFlower == null) {
TStudentFlower tsf = new TStudentFlower();
tsf.setClassroomId(classroomId);
tsf.setStudentId(studentId);
tsf.setFlowerNum(1);
mapper.insert(tsf);
} else {
// 已经送过花了 原来数量上+1
tStudentFlower.setFlowerNum(tStudentFlower.getFlowerNum() + 1);
mapper.update(tStudentFlower);
}
}
}
TStudentFlowerMapper
package com.example.student_flower.dao;
import com.example.student_flower.entity.TStudentFlower;
import org.apache.ibatis.annotations.Mapper;
import org.apache.ibatis.annotations.Param;
@Mapper
public interface TStudentFlowerMapper {
// 插入
void insert(TStudentFlower tStudentFlower);
// 更新
void update(TStudentFlower tStudentFlower);
// 查询
TStudentFlower selectByClassroomIdAndStudentId(
@Param("classroomId") Long classroomId,
@Param("studentId") Long studentId);
}
TStudentFlowerMapper.xml
<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd" >
<mapper namespace="com.example.student_flower.dao.TStudentFlowerMapper">
<!--新增-->
<insert id="insert" parameterType="TStudentFlower">
INSERT INTO t_student_flower (classroom_id,student_id,flower_num)
VALUES (#{classroomId},#{studentId},#{flowerNum})
</insert>
<!--更新-->
<update id="update" parameterType="TStudentFlower">
UPDATE t_student_flower
SET flower_num = #{flowerNum}
WHERE id=#{id};
</update>
<select id="selectByClassroomIdAndStudentId"
resultType="TStudentFlower">
select * from t_student_flower
where classroom_id = #{classroomId} and student_id = #{studentId}
</select>
</mapper>
2.4 测试
浏览器直接访问：
http://127.0.0.1:8888/test/sendflower/1/1
就会给classroomId = 1 ,studentId = 1 的学生送一朵花
2.5 问题所在
一切看似没有问题，因为请求频率还没有达到可以出错的速度。
我们写一个测试用了来模拟前端不可信任的时候（由于某种原因他们送花事件绑定了多次没有解绑，也就是同一时间发送多次送花请求）
package com.example.student_flower;
import com.example.student_flower.service.StudentFlowerService;
import org.junit.jupiter.api.Test;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;
import java.util.concurrent.TimeUnit;
@SpringBootTest
class StudentFlowerApplicationTests {
@Autowired
StudentFlowerService service;
@Test
void sendFlower() throws InterruptedException {
final Long classroomId = 2L;
final Long studengId = 102L;
Thread thread1 = new Thread(() -> {
service.SendFlower(classroomId, studengId);
System.out.println("thread1执行完了");
});
Thread thread2 = new Thread(() -> {
service.SendFlower(classroomId, studengId);
System.out.println("thread2执行完了");
});
Thread thread3 = new Thread(() -> {
service.SendFlower(classroomId, studengId);
System.out.println("thread3执行完了");
});
thread1.start();
thread2.start();
thread3.start();
// 睡会儿 等三个线程跑完 很low? 做测试凑活用吧
Thread.sleep(TimeUnit.SECONDS.toMillis(20));
}
}
执行完看一下数据库结果：
这肯定是有问题的 多三条要出问题的，要扣钱绩效的
三、解决方案
解决方案有很多，我今天介绍一种自定义注解的方式（其实就是用了分布redis锁）
方案看似很简单：
自定义注解MyAnotation
package com.example.student_flower.common.anotation;
import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
@Target({ElementType.METHOD}) // 方法上使用的注解
@Retention(RetentionPolicy.RUNTIME) // 运行时通过反射访问
public @interface MyAnotation {
int waitTime() default 3;
int expireTime() default 20;
String redisKey() default "";
String[] params() default {};
}
自定义切面处理逻辑，进行放重复提交校验MyAspect
package com.example.student_flower.common.aspect;
import com.example.student_flower.common.anotation.MyAnotation;
import com.example.student_flower.util.HttpContextUtils;
import com.example.student_flower.util.SpelUtil;
import io.micrometer.core.instrument.util.StringUtils;
import lombok.extern.slf4j.Slf4j;
import org.aspectj.lang.ProceedingJoinPoint;
import org.aspectj.lang.annotation.Around;
import org.aspectj.lang.annotation.Aspect;
import org.aspectj.lang.annotation.Pointcut;
import org.aspectj.lang.reflect.MethodSignature;
import org.redisson.api.RLock;
import org.redisson.api.RedissonClient;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Component;
import javax.servlet.http.HttpServletRequest;
import java.lang.reflect.Method;
import java.util.concurrent.TimeUnit;
@Slf4j
@Aspect
@Component
public class MyAspect {
@Autowired
RedissonClient redissonClient;
// 这个是那些方法需要被切 -- 被标记注解MyAnotation的方法要被切
@Pointcut("@annotation(com.example.student_flower.common.anotation.MyAnotation)")
public void whichMethodAspect() {
}
@Around("whichMethodAspect()")
public Object around(ProceedingJoinPoint joinPoint) throws Throwable {
// 1. 获取注解
MethodSignature signature = (MethodSignature) joinPoint.getSignature();
Method method = signature.getMethod();
MyAnotation myAnotation = method.getAnnotation(MyAnotation.class);
// 2. 锁等待时间
int waitTime = myAnotation.waitTime();
// 2. 锁超时时间 怕万一finally没有被执行到的时候 多长时间自动释放锁（基本不会不执行finnaly 除非那个点机器down了）
final int lockSeconds = myAnotation.expireTime();
// 3. 特殊业务自定义key
String key = myAnotation.redisKey();
// 自定义redisKey是否使用参数
String[] params = myAnotation.params();
// 4.获取HttpServletRequest
HttpServletRequest request = HttpContextUtils.getRequest();
if (request == null) {
throw new Exception("错误的请求 request为null");
}
assert request != null;
// 5. 组合redis锁key
// 5.1 如果没有自定义 用默认的 url+token
if (StringUtils.isBlank(key) && (params == null || params.length == 0)) {
// 这里怎么获取token 主要看自己项目用的什么框架 token在哪个位置存储着
String token = request.getHeader("Authorization");
String requestURI = request.getRequestURI();
key = requestURI+token;
} else {
// 5.2 自定义key
key = SpelUtil.generateKeyBySpEL(key, params, joinPoint);
}
// 6. 获取key
// 获取锁 获取不到最多等waitTime秒 lockSeconds秒后自动释放锁
// 每个项目组应该会有自己的redisUtil的封装 我这里就用最简单的方式
// 怎么使用锁不是重点 重点是这个思想
RLock lock = redissonClient.getLock(key);
log.info("tryLock key = {}", key);
boolean b = lock.tryLock(waitTime, lockSeconds, TimeUnit.SECONDS);
// 获取锁成功
if (b) {
try {
log.info("tryLock success, key = {}", key);
// 7. 执行业务代码 返回结果
return joinPoint.proceed();
} finally {
lock.unlock();
}
} else {
// 获取锁失败
log.info("tryLock fail, key = {}", key);
throw new Exception("请求频繁，请稍后重试");
}
}
}
Redisson配置RedissonConfig
package com.example.student_flower;
import org.redisson.Redisson;
import org.redisson.api.RedissonClient;
import org.redisson.config.Config;
import org.springframework.context.annotation.Bean;
public class RedissonConfig {
// 这里就简单设置 真实项目中会做到配置文件或配置中心
@Bean
public RedissonClient getRedisson() {
Config config = new Config();
config.useSingleServer().setAddress("redis://127.0.0.1:6379");
return Redisson.create(config);
}
}
获取request对象HttpContextUtils
package com.example.student_flower.util;
import org.springframework.web.context.request.RequestContextHolder;
import org.springframework.web.context.request.ServletRequestAttributes;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public class HttpContextUtils {
// 获取request
public static HttpServletRequest getRequest(){
ServletRequestAttributes servletRequestAttributes = (ServletRequestAttributes) RequestContextHolder.getRequestAttributes();
HttpServletRequest request = servletRequestAttributes.getRequest();
return request;
}
// 获取response
public static HttpServletResponse getResponse(){
ServletRequestAttributes servletRequestAttributes = (ServletRequestAttributes) RequestContextHolder.getRequestAttributes();
HttpServletResponse response = servletRequestAttributes.getResponse();
return response;
}
}
El表达式解析 SpelUtil
package com.example.student_flower.util;
import java.lang.reflect.Method;
import org.aspectj.lang.ProceedingJoinPoint;
import org.aspectj.lang.reflect.MethodSignature;
import org.springframework.core.DefaultParameterNameDiscoverer;
import org.springframework.expression.EvaluationContext;
import org.springframework.expression.Expression;
import org.springframework.expression.spel.standard.SpelExpressionParser;
import org.springframework.expression.spel.support.StandardEvaluationContext;
public class SpelUtil {
private static SpelExpressionParser parser = new SpelExpressionParser();
private static DefaultParameterNameDiscoverer nameDiscoverer = new DefaultParameterNameDiscoverer();
public static String generateKeyBySpEL(String key, String[] params, ProceedingJoinPoint joinPoint) {
StringBuilder spELString = new StringBuilder();
if (params != null && params.length > 0) {
spELString.append("'" + key + "'");
for (int i = 0; i < params.length; i++) {
spELString.append("+#" + params[i]);
}
} else {
return key;
}
// 通过joinPoint获取被注解方法
MethodSignature methodSignature = (MethodSignature) joinPoint.getSignature();
Method method = methodSignature.getMethod();
// 使用spring的DefaultParameterNameDiscoverer获取方法形参名数组
String[] paramNames = nameDiscoverer.getParameterNames(method);
// 解析过后的Spring表达式对象
Expression expression = parser.parseExpression(spELString.toString());
// spring的表达式上下文对象
EvaluationContext context = new StandardEvaluationContext();
// 通过joinPoint获取被注解方法的形参
Object[] args = joinPoint.getArgs();
// 给上下文赋值
for (int i = 0; i < args.length; i++) {
context.setVariable(paramNames[i], args[i]);
}
return expression.getValue(context).toString();
}
}
controller使用注解：
package com.example.student_flower.controller;
import com.example.student_flower.common.anotation.MyAnotation;
import com.example.student_flower.service.StudentFlowerService;
import com.sun.istack.internal.NotNull;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RestController;
@RestController
public class StudentFlowerController {
@Autowired
StudentFlowerService studentFlowerService;
@MyAnotation(redisKey = "/test/sendflower", params = {"classroomId", "studentId"})
@GetMapping(value = "/test/sendflower/{classroomId}/{studentId}")
public void sendFlower(@NotNull @PathVariable("classroomId") Long classroomId , @NotNull @PathVariable("studentId") Long studentId){
studentFlowerService.SendFlower(classroomId,studentId);
}
}
测试类（这里用了MockMvc直接测试controller）
package com.example.student_flower;
import org.junit.jupiter.api.Test;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.autoconfigure.web.servlet.AutoConfigureMockMvc;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.http.MediaType;
import org.springframework.test.web.servlet.MockMvc;
import org.springframework.test.web.servlet.request.MockMvcRequestBuilders;
import org.springframework.test.web.servlet.result.MockMvcResultHandlers;
import org.springframework.test.web.servlet.result.MockMvcResultMatchers;
import java.util.concurrent.TimeUnit;
@SpringBootTest
@AutoConfigureMockMvc
class StudentFlowerTests {
@Autowired
protected MockMvc mockMvc;
@Test
void sendFlower() throws Exception {
final Long classroomId = 7L;
final Long studengId = 102L;
Thread thread1 = new Thread(() -> {
try {
mockMvc.perform(MockMvcRequestBuilders
.get("/test/sendflower/" + classroomId + "/"
+ studengId).accept(MediaType.APPLICATION_JSON))
.andExpect(MockMvcResultMatchers.status().isOk())
.andDo(MockMvcResultHandlers.print())
.andReturn();
} catch (Exception e) {
e.printStackTrace();
}
});
Thread thread2 = new Thread(() -> {
try {
mockMvc.perform(MockMvcRequestBuilders
.get("/test/sendflower/" + classroomId + "/"
+ studengId).accept(MediaType.APPLICATION_JSON))
.andExpect(MockMvcResultMatchers.status().isOk())
.andDo(MockMvcResultHandlers.print())
.andReturn();
} catch (Exception e) {
e.printStackTrace();
}
});
Thread thread3 = new Thread(() -> {
try {
mockMvc.perform(MockMvcRequestBuilders
.get("/test/sendflower/" + classroomId + "/"
+ studengId).accept(MediaType.APPLICATION_JSON))
.andExpect(MockMvcResultMatchers.status().isOk())
.andDo(MockMvcResultHandlers.print())
.andReturn();
} catch (Exception e) {
e.printStackTrace();
}
});
thread1.start();
thread2.start();
thread3.start();
// 睡会儿 等三个线程跑完 很low? 做测试凑活用吧
Thread.sleep(TimeUnit.SECONDS.toMillis(20));
}
}
去掉controller注解测试 会插入多条，加上MyAnotation注解只会生成一条
四 、唠唠
4.1 项目
主要用到了自定义注解、RedissonClient的redis锁、AOP等知识
可能么有写过这种场景代码的人会觉得比较乱：木有关系全部代码已经提交到github上了，
地址：https://github.com/githubforliming/student_flower
4.2 redis服务
贴心的我把redis的windows免安装包都放到项目里了
test/java/soft 解压 双击redis-server.exe 即可运行
默认没密码
4.3 其他问题
支持参数是对象的自定义key
@MyAnotation(redisKey = "/test/sendflower", params = {"p.id"})
@PostMapping(value = "/test/sendflower02")
public void sendFlower(@RequestBody Person p){
// xxx
}
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