Java注解方式之防止重复请求-编程学习网

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

在这里插入图片描述

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：

在这里插入图片描述

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：

在这里插入图片描述

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

在这里插入图片描述

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

在这里插入图片描述

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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文章详情

Java注解方式之防止重复请求

目录

一、前情提要

二、技术设计

2.1 库表设计

2.2 业务逻辑

2.3 代码编写

2.4 测试

2.5 问题所在

三、解决方案

四、唠唠

4.1 项目

4.2 redis服务

4.3 其他问题

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