基于SSM实现高并发秒杀API(DAO层)

略

首先

1. SSM的整合
2. 秒杀类系统需求的理解和实现
3. 常用技术解决高并发问题

Spring MVC + Spring + MyBatis

• 框架容易使用,轻量级
• 侵入性比较低
• 成熟的社区和用户群

为什么用秒杀类系统

• 秒杀有典型的事务特性
• 秒杀/红包类需求很常见
• 面试常问的问题(如何设计优化秒杀系统)

内容概括

1. 秒杀列表
2. 详情页内秒杀按钮或者等待时间或者秒杀结束
3. 秒杀后库存会减少
4. 秒杀需要输入电话号码存到cookie中.

开始

MySQL

• 表设计
• SQL技巧
• 事务和行级锁

MyBatis合理使用

• DAO层设计与开发
• MyBatis合理使用
• MyBatis与Spring整合

Spring

• Spring IOC整合Service
• 声明式事务的运用

Spring MVC

• Restful接口的设计和使用
• 框架运作流程
• Controller开发技巧

前端

• 交互设计
• BootStrap
• JQuery

高并发

• 高并发点和高并发分析
• 优化思路并实现

基于Maven创建项目

建议从官网中获取文档

mvn archetype:generate -DgroupId=com.yuda.test -DartifactId=seckill -DarchetypeArtifactId=maven-archetype-webapp

<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 http://maven.apache.org/maven-v4_0_0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <groupId>com.yuda.test</groupId>
    <artifactId>seckill</artifactId>
    <packaging>war</packaging>
    <version>1.0-SNAPSHOT</version>
    <name>seckill Maven Webapp</name>
    <url>http://maven.apache.org</url>
    <dependencies>
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.11</version>
            <scope>test</scope>
        </dependency>
        <!--
            日志相关
            slf4j: 是规范/接口
            日志实现: log4j,logback,common-logging
            这里使用: slf4j + logback
        -->
        <dependency>
            <groupId>org.slf4j</groupId>
            <artifactId>slf4j-log4j12</artifactId>
            <version>1.7.12</version>
        </dependency>
        <dependency>
            <groupId>ch.qos.logback</groupId>
            <artifactId>logback-core</artifactId>
            <version>1.1.1</version>
        </dependency>
        <!--  整合slf4j  -->
        <dependency>
            <groupId>ch.qos.logback</groupId>
            <artifactId>logback-classic</artifactId>
            <version>1.1.1</version>
        </dependency>
        <!--数据库相关依赖-->
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>5.1.35</version>
            <scope>runtime</scope>
        </dependency>
        <dependency>
            <groupId>c3p0</groupId>
            <artifactId>c3p0</artifactId>
            <version>0.9.1.2</version>
        </dependency>
        <!-- DAO相关 -->
        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis</artifactId>
            <version>3.3.0</version>
        </dependency>
        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis-spring</artifactId>
            <version>1.2.3</version>
        </dependency>
        <!-- Servlet相关依赖 -->
        <dependency>
            <groupId>taglibs</groupId>
            <artifactId>standard</artifactId>
            <version>1.1.2</version>
        </dependency>
        <dependency>
            <groupId>javax.servlet</groupId>
            <artifactId>jstl</artifactId>
            <version>1.2</version>
        </dependency>
        <dependency>
            <groupId>com.fasterxml.jackson.core</groupId>
            <artifactId>jackson-databind</artifactId>
            <version>2.5.4</version>
        </dependency>
        <dependency>
            <groupId>javax.servlet</groupId>
            <artifactId>javax.servlet-api</artifactId>
            <version>3.1.0</version>
        </dependency>
        <!-- Spring依赖 -->
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-core</artifactId>
            <version>4.1.7.RELEASE</version>
        </dependency>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-beans</artifactId>
            <version>4.1.7.RELEASE</version>
        </dependency>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-context</artifactId>
            <version>4.1.7.RELEASE</version>
        </dependency>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-context-support</artifactId>
            <version>4.1.7.RELEASE</version>
        </dependency>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-jdbc</artifactId>
            <version>4.1.7.RELEASE</version>
        </dependency>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-tx</artifactId>
            <version>4.1.7.RELEASE</version>
        </dependency>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-web</artifactId>
            <version>4.1.7.RELEASE</version>
        </dependency>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-webmvc</artifactId>
            <version>4.1.7.RELEASE</version>
        </dependency>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-test</artifactId>
            <version>4.1.7.RELEASE</version>
        </dependency>
    </dependencies>
    <build>
        <finalName>seckill</finalName>
    </build>
</project>

秒杀系统业务流程

1. 角色有: 商家, 库存, 用户;
2. 库存是核心;
3. 用户针对库存的业务:
   1. 减库存+记录购买明细 = 完整事务
   2. 完整事务需要准确的事务落地
4. 购买行为: 记录用户谁购买成功,成功时间有效期,付款/发货信息

如果…

1. 减库存没有记录购买明细;
2. 记了明细没有库存减少;
3. 出现了超卖/少卖;

数据落地(两种)

MySQL vs NoSQL

MySQL 用事务实现准确且最可靠的落地方案
NoSQL 性能,高可用,分布式

难点分析

1. 竞争问题:大量用户
   MySQL: 事务+行级锁

   Strat Transaction
   Update 减库存
   Insert 记录购买明细
   Commit

   当一个用户update时,其他用户处于等待状态

   难点是如何高效处理竞争???

2. 秒杀相关的功能有:

   • 秒杀接口暴露;
   • 执行秒杀;
   • 相关查询

代码开发阶段

编写数据库

-- 创建数据库
CREATE DATABASE seckill;

USE seckill;

-- 库存表

CREATE TABLE t_seckill (
  `seckill_id`  BIGINT       NOT NULL AUTO_INCREMENT
  COMMENT '商品库存ID',
  `name`        VARCHAR(120) NOT NULL
  COMMENT '商品名称',
  `number`      INT          NOT NULL
  COMMENT '库存数量',
  `start_time`  TIMESTAMP    NOT NULL
  COMMENT '秒杀开始时间',
  `end_time`    TIMESTAMP    NOT NULL
  COMMENT '秒杀结束时间',
  `create_time` TIMESTAMP    NOT NULL DEFAULT current_timestamp
  COMMENT '创建时间',
  PRIMARY KEY (seckill_id),
  KEY idx_start_time(start_time),
  KEY idx_end_time(end_time),
  KEY idx_create_time(create_time)
)
  ENGINE = InnoDB
  AUTO_INCREMENT = 1000
  DEFAULT CHARSET = utf8
  COMMENT ='秒杀库存表';

-- 初始化数据省略

-- 用户登录认证相关
CREATE TABLE success_killed (
  `seckill_id`  BIGINT    NOT NULL
  COMMENT '秒杀商品ID',
  `user_phone`  BIGINT    NOT NULL
  COMMENT '用户手机号',
  `state`       TINYINT   NOT NULL DEFAULT -1
  COMMENT '状态标示:-1无效,0成功,1已付款,2发货',
  `create_time` TIMESTAMP NOT NULL
  COMMENT '创建时间',
  PRIMARY KEY (seckill_id, user_phone), /*联合主键*/
  KEY idx_create_time(create_time)
)
  ENGINE = InnoDB
  DEFAULT CHARSET = utf8
  COMMENT ='秒杀成功明细表';

-- 修改
ALTER TABLE seckill.t_seckill
  DROP INDEX idx_create_time,
  ADD INDEX idx_c_s(start_time, create_time)

> **注意**:购买记录表中的主键使用了联合主键(商品和用户唯一表示),防止了用户购买多个同种商品,

mybatis-config.xml

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE configuration
        PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration>
    <!--全局属性-->
    <settings>
        <!--使用jdbc的getGeneratedKeys 获取数据库的自增加主键-->
        <setting name="useGeneratedKeys" value="true"/>
        <!--使用列别名替换列名 默认:true-->
        <setting name="useColumnLabel" value="true"/>
        <!--开启驼峰命名转换-->
        <setting name="mapUnderscoreToCamelCase" value="true"/>
    </settings>
    <!--下面的配置交给Spring(为Spring打Call)-->
</configuration>

实体类mapper.xml

<!DOCTYPE mapper
    PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
    "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<!--映射接口-->
<mapper namespace="com.yuda.dao.SeckillDao">
    <!--具体的sql语句-->
    <update id="reduceNumber">
        UPDATE seckill.t_seckill
        SET number = number - 1
        WHERE seckill_id = #{seckillId}
              AND start_time <![CDATA[ <= ]]> #{killTime}
              AND end_time >= #{killTime}
              AND number > 0;
    </update>
    <select id="queryById" parameterType="long" resultType="com.yuda.entity.Seckill">
        SELECT
            seckill_id,
            name,
            number,
            start_time,
            end_time,
            create_time
        FROM seckill.t_seckill
        WHERE seckill_id = #{seckillId};
    </select>
    <select id="queryAll" resultType="com.yuda.entity.Seckill">
        SELECT
            seckill_id,
            name,
            number,
            start_time,
            end_time,
            create_time
        FROM seckill.t_seckill
        ORDER BY create_time DESC
        LIMIT #{offset}, #{limit};
    </select>
</mapper>

<!DOCTYPE mapper
    PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
    "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<!--映射接口-->
<mapper namespace="com.yuda.dao.SuccessKilledDao">
    <!-- 如果出现重复插入问题(主键冲突),不报错,返回0 -->
    <insert id="insertSucceccKilled">
        INSERT IGNORE INTO seckill.success_killed (seckill_id, user_phone, state)
        VALUES (#{seckillId}, #{userPhone}, 0);
    </insert>
    <!--设置别名用于级联操作-->
    <select id="queryByIdWithSeckill" resultType="com.yuda.entity.SuccessKilled">
        SELECT
            sk.seckill_id,
            sk.user_phone,
            sk.create_time,
            sk.state,
            s.seckill_id  "seckill.seckill_id",
            s.name        "seckill.name",
            s.number      "seckill.number",
            s.start_time  "seckill.start_time",
            s.end_time    "seckill.end_time",
            s.create_time "seckill.create_time"
        FROM seckill.success_killed sk
            INNER JOIN seckill.t_seckill s
                ON sk.seckill_id = s.seckill_id
        WHERE sk.seckill_id = #{seckillId} AND sk.user_phone = #{userPhone};
    </select>
</mapper>

spring-dao.xml

> 整合Spring后:
> 1. 更少的编码 (只写接口)
> 2. 更少的配置 (包扫描)
> 3. 足够的灵活性 (SQL自己定义,还可以动态拼接)
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xmlns:context="http://www.springframework.org/schema/context"
       xsi:schemaLocation="http://www.springframework.org/schema/beans
       http://www.springframework.org/schema/beans/spring-beans.xsd
       http://www.springframework.org/schema/context
       http://www.springframework.org/schema/context/spring-context.xsd">
    <context:component-scan base-package="com.yuda"/>
    <context:property-placeholder location="classpath*:jdbc.properties"/>
    <!--DataSource-->
    <bean id="dataSource" class="com.mchange.v2.c3p0.ComboPooledDataSource">
        <property name="driverClass" value="${mysql.driver}"/>
        <property name="jdbcUrl" value="${mysql.url}"/>
        <property name="user" value="${mysql.username}"/>
        <property name="password" value="${mysql.password}"/>
        <!--配置连接池属性-->
        <property name="maxPoolSize" value="30"/>
        <property name="minPoolSize" value="10"/>
        <!--关闭连接后不自动commit-->
        <property name="autoCommitOnClose" value="false"/>
        <!--获取连接超时时间-->
        <property name="checkoutTimeout" value="1000"/>
        <!--重试次数-->
        <property name="acquireRetryAttempts" value="2"/>
    </bean>
    <!-- 用spring来创建sqlsessionfactory-->
    <bean id="sessionFactory" class="org.mybatis.spring.SqlSessionFactoryBean">
        <property name="dataSource" ref="dataSource"/>
        <!--管理MyBatis-->
        <!--主配文件-->
        <property name="configLocation" value="classpath:mybatis-config.xml"/>
        <!-- 扫描entity,生成别名 -->
        <property name="typeAliasesPackage" value="com.yuda.entity"/>
        <!--扫描实体类配置文件-->
        <property name="mapperLocations" value="classpath:com/yuda/mapper/*.xml"/>
    </bean>
    <!--扫描,配置DAO接口包,注入到容器-->
    <bean class="org.mybatis.spring.mapper.MapperScannerConfigurer">
        <!-- 扫描Mapper -->
        <property name="basePackage" value="com.yuda.dao"/>
        <!--注入sessionFactory-->
        <property name="sqlSessionFactoryBeanName" value="sessionFactory"/>
    </bean>
</beans>

Entity

Table -> 对应 -> Entity
import lombok.Data;
@Data
public class Seckill {
    private long seckillId;
    private String name;
    private int number;
    private Date startTime;
    private Date endTime;
    private Date createTime;
}
@Data
public class SuccessKilled {
    private long seckillId;
    private long userPhone;
    private short state;
    private Date createTime;
    //多对一
    private Seckill seckill;
}

Mapper

public interface SuccessKilledDao {

    int insertSucceccKilled(@Param("seckillId") long seckillId, @Param("userPhone") long userPhone);

    SuccessKilled queryByIdWithSeckill(@Param("seckillId") long seckillId, @Param("userPhone") long userPhone);
}
public interface SeckillDao {

    int reduceNumber(@Param("seckillId") long seckillId,@Param("killTime") Date killTime);

    Seckill queryById(long seckillId);

    List<Seckill> queryAll(@Param("offset") int offset, @Param("limit") int limit);
}

测试功能

@RunWith(value = SpringJUnit4ClassRunner.class)
@ContextConfiguration(locations = "classpath*:spring-dao.xml")
public class MainTest {

    //Autowired和Resource作用一样不过A是根据类型注入,R是根据名字注入
    @Autowired
    private SeckillDao seckillDao;
    @Resource
    private SuccessKilledDao successKilledDao;

    @Test
    public void demo1() {
        Seckill seckill = seckillDao.queryById(1000);
        System.out.println("灿宇达" + seckill);
    }

    @Test
    public void demo2() throws Exception {
        List<Seckill> seckills = seckillDao.queryAll(0, 5);
        for (Seckill seckill : seckills) {
            System.out.println(seckill);
        }
    }

    @Test
    public void demo3() throws Exception {
        Date killTime = new Date();
        int i = seckillDao.reduceNumber(1000, killTime);
        System.out.println("状态码::" + i);
    }

    @Test
    public void insertSucceccKilled() throws Exception {
        int i = successKilledDao.insertSucceccKilled(1001L, 13972218121L);
        System.out.println("状态码::" + i);
    }

    @Test
    public void queryByIdWithSeckill() throws Exception {
        SuccessKilled successKilled = successKilledDao.queryByIdWithSeckill(1001L, 13972218121L);
        System.out.println(successKilled);
        System.out.println(successKilled.getSeckill());
    }
}

总结

I am a slow walker,but I never walk backwards.