SSM实战——秒杀系统之Service层接口设计与实现、Spring托管、声明式事务

一：Service层接口设计

准备工作：新建三个包：service包、exception包、dto包，分别用来存放业务接口、自定义异常类、dto类。

1：定义接口

package org.myseckill.service;

import java.util.List;

import org.myseckill.dto.Exposer;
import org.myseckill.dto.SeckillExecution;
import org.myseckill.entity.Seckill;
import org.myseckill.exception.RepeatKillException;
import org.myseckill.exception.SeckillClosedException;
import org.myseckill.exception.SeckillException;

public interface SeckillService {

    //查询所有
    List<Seckill> getSeckillList();
    //根据ID查询
    Seckill getById(long seckillId);
    //暴露秒杀网页地址
    Exposer exportSeckillUrl(long seckillId);

    //md5用于与内部md5做比较，防止用于篡改url进行秒杀
    SeckillExecution executeSeckill(long seckillId,long userPhone,String md5) throws SeckillException,RepeatKillException,SeckillClosedException;

}

2：定义接口中用到的相关dto：

package org.myseckill.dto;

//封装暴露信息
public class Exposer {
    //是否开启秒杀
    private boolean exposed;

    private String md5;

    private long seckillId;

    private long now;

    private long start;

    private long end;

    public Exposer(boolean exposed, String md5, long seckillId) {
        super();
        this.exposed = exposed;
        this.md5 = md5;
        this.seckillId = seckillId;
    }

    public Exposer(long now, long start, long end) {
        super();
        this.now = now;
        this.start = start;
        this.end = end;
    }

    public Exposer(boolean exposed, long seckillId) {
        super();
        this.exposed = exposed;
        this.seckillId = seckillId;
    }

    public boolean isExposed() {
        return exposed;
    }

    public void setExposed(boolean exposed) {
        this.exposed = exposed;
    }

    public String getMd5() {
        return md5;
    }

    public void setMd5(String md5) {
        this.md5 = md5;
    }

    public long getSeckillId() {
        return seckillId;
    }

    public void setSeckillId(long seckillId) {
        this.seckillId = seckillId;
    }

    public long getNow() {
        return now;
    }

    public void setNow(long now) {
        this.now = now;
    }

    public long getStart() {
        return start;
    }

    public void setStart(long start) {
        this.start = start;
    }

    public long getEnd() {
        return end;
    }

    public void setEnd(long end) {
        this.end = end;
    }

}

package org.myseckill.dto;

import org.myseckill.entity.SuccessKilled;

//封装秒杀后信息
public class SeckillExecution {

    private long seckillId;
    private int state;
    private String stateInfo;
    private SuccessKilled successKilled;
    public long getSeckillId() {
        return seckillId;
    }
    public void setSeckillId(long seckillId) {
        this.seckillId = seckillId;
    }
    public int getState() {
        return state;
    }
    public void setState(int state) {
        this.state = state;
    }
    public String getStateInfo() {
        return stateInfo;
    }
    public void setStateInfo(String stateInfo) {
        this.stateInfo = stateInfo;
    }
    public SuccessKilled getSuccessKilled() {
        return successKilled;
    }
    public void setSuccessKilled(SuccessKilled successKilled) {
        this.successKilled = successKilled;
    }
    //秒杀成功的构造函数
    public SeckillExecution(long seckillId, int state, String stateInfo,
            SuccessKilled successKilled) {
        super();
        this.seckillId = seckillId;
        this.state = state;
        this.stateInfo = stateInfo;
        this.successKilled = successKilled;
    }
    //秒杀失败的构造函数
    public SeckillExecution(long seckillId, int state, String stateInfo) {
        super();
        this.seckillId = seckillId;
        this.state = state;
        this.stateInfo = stateInfo;
    }

}

3：定义接口中用到的自定义异常

package org.myseckill.exception;

//秒杀相关通用异常
public class SeckillException extends RuntimeException {

    public SeckillException() {
        super();
        // TODO Auto-generated constructor stub
    }

    public SeckillException(String message, Throwable cause) {
        super(message, cause);
        // TODO Auto-generated constructor stub
    }

    public SeckillException(String message) {
        super(message);
        // TODO Auto-generated constructor stub
    }

    public SeckillException(Throwable cause) {
        super(cause);
        // TODO Auto-generated constructor stub
    }

}

package org.myseckill.exception;

//重复秒杀异常
public class RepeatKillException extends SeckillException {

    public RepeatKillException(String message, Throwable cause) {
        super(message, cause);
    }

    public RepeatKillException(String message) {
        super(message);
    }

    public RepeatKillException(Throwable cause) {
        super(cause);
    }

}

package org.myseckill.exception;

//秒杀已关闭异常
public class SeckillClosedException extends SeckillException {

    public SeckillClosedException() {
        super();

    }

    public SeckillClosedException(String message, Throwable cause) {
        super(message, cause);

    }

    public SeckillClosedException(String message) {
        super(message);

    }

    public SeckillClosedException(Throwable cause) {
        super(cause);

    }

}

二：Service层接口实现

1：在Service包下，新建一个Impl包，用于存放接口的实现类。

2：定义接口实现类SeckillServiceImpl

package org.myseckill.service.Impl;

import java.util.Date;
import java.util.List;

import org.myseckill.dao.SeckillDao;
import org.myseckill.dao.SuccessKilledDao;
import org.myseckill.dto.Exposer;
import org.myseckill.dto.SeckillExecution;
import org.myseckill.entity.Seckill;
import org.myseckill.entity.SuccessKilled;
import org.myseckill.exception.RepeatKillException;
import org.myseckill.exception.SeckillClosedException;
import org.myseckill.exception.SeckillException;
import org.myseckill.service.SeckillService;
import org.myseckill.enums.SeckillStateEnum;
import org.myseckill.exception.RepeatKillException;
import org.myseckill.exception.SeckillClosedException;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.util.DigestUtils;

public class SeckillServiceImpl implements SeckillService {

    //使用slf4j日志
    private Logger logger=LoggerFactory.getLogger(this.getClass());

    private SeckillDao seckillDao;

    private SuccessKilledDao successKilledDao;

    //用于加密的混淆字符串，随机串
   private final String slat="asfdfadsf45qa@$E#iudkgj15=sdf=daf5";

    //本例只用了4跳记录，实际项目中可以再定义一个selectall的SQL语句查询所有
    public List<Seckill> getSeckillList() {
        return seckillDao.queryAll(0, 4);
    }

    @Override
    public Seckill getById(long seckillId) {

        return seckillDao.queryById(seckillId);
    }

    @Override
    public Exposer exportSeckillUrl(long seckillId) {
        Seckill seckill=seckillDao.queryById(seckillId);
        if(seckill==null){//没有这个产品的秒杀记录，不进行暴露
            return new Exposer(false, seckillId);
        }

        Date now=new Date();
        Date start=seckill.getStartTime();
        Date end=seckill.getEndTime();
        //若时间非法，不秒杀
        if(now.getTime()<start.getTime() || now.getTime()>end.getTime()){
            return new Exposer(false, seckillId, now.getTime(), start.getTime(), end.getTime());
        }
        //否则，进行秒杀网址暴露
        String md5=getMD5(seckillId);
        return new Exposer(true, md5, seckillId);
    }

    //用md5加密
    private String getMD5(long seckillId){
        String base=seckillId+"/"+slat;
        String md5=DigestUtils.md5DigestAsHex(base.getBytes());
        return md5;
    }
    @Override
    public SeckillExecution executeSeckill(long seckillId, long userPhone, String md5)
            throws SeckillException, RepeatKillException, SeckillException {
        if(md5==null||!md5.equals(getMD5(seckillId))){
            throw new SeckillException("seckill data rewrite");
        }
        //执行秒杀逻辑：减库存+记录购买行为
        try {
            //记录购买行为
            int insertCount = successKilledDao.insertSuccessKilled(seckillId, userPhone);
            if(insertCount <= 0 ){
                //重复秒杀
                throw new RepeatKillException("seckill repeated");
            }else{
                //减库存,热点商品竞争（高并发点）
                int updateCount = seckillDao.reduceNumber(seckillId, new Date());
                if(updateCount<=0){
                    //没有更新到记录,秒杀结束，rollback
                    throw new SeckillClosedException("seckill is closed");
                }else{
                    //秒杀成功,commit
                    SuccessKilled successKilled = successKilledDao.queryByIdWithSeckill(seckillId, userPhone);
                    return new SeckillExecution(seckillId,SeckillStateEnum.SUCCESS,successKilled);
                }
            }

        } catch(SeckillClosedException e1){
            throw e1;
        } catch(RepeatKillException e2){
            throw e2;
        }catch (Exception e) {
            logger.error(e.getMessage(),e);
            //所有异常转化为运行期异常
            throw new SeckillException("seckill inner error:"+e.getMessage());
        }
    }

}

3：把状态与状态信息常量，封装成枚举常量

在org.myseckill包下新建enums包，包中新建一个枚举类SeckillStateEnum:

package org.myseckill.enums;

//在实际开发中，全局常用的常量们用枚举常量存储
public enum SeckillStateEnum {
    //定义一系列枚举常量
    SUCCESS(1,"秒杀成功"),
    END(0,"秒杀结束"),
    REPEAT_KILL(-1,"重复秒杀"),
    INNER_ERROR(-2,"系统异常"),
    DATA_REWRITE(-3,"数据篡改");

    private int state;

    private String stateInfo;

    SeckillStateEnum(int state, String stateInfo) {
        this.state = state;
        this.stateInfo = stateInfo;
    }

    public int getState() {
        return state;
    }

    public void setState(int state) {
        this.state = state;
    }

    public String getStateInfo() {
        return stateInfo;
    }

    public void setStateInfo(String stateInfo) {
        this.stateInfo = stateInfo;
    }

    public static SeckillStateEnum stateOf(int index) {
        //迭代枚举常量，返回state值等于index的常量
        for (SeckillStateEnum stateEnum : values()) {
            if (stateEnum.getState() == index) {
                return stateEnum;
            }
        }
        return null;
    }

}

4：修改SeckillExecution类的构造函数:

//秒杀成功的构造函数
    public SeckillExecution(long seckillId, SeckillStateEnum success,SuccessKilled successKilled) {
        super();
        this.seckillId = seckillId;
        this.state = success.getState();
        this.stateInfo = success.getStateInfo();
        this.successKilled = successKilled;
    }
    //秒杀失败的构造函数
    public SeckillExecution(long seckillId, SeckillStateEnum success) {
        super();
        this.seckillId = seckillId;
        this.state = success.getState();
        this.stateInfo = success.getStateInfo();
    }

三：Spring托管Service层的类

SpringIOC中，注入主要分为两种场景：

1：第三方类库提供的类，如：datasource等。使用XML中ref来注入；

2：自己定义的类，则在代码中，使用注解来注入；

1：在resource.spring包下，新建一个spring-service.xml，用于负责托管service层bean以及进行事务管理。

2：托管bean：

如果 Web 应用程序采用了经典的三层分层结构的话，最好在持久层、业务层和控制层分别采用上述注解对分层中的类进行注释。

@Service用于标注业务层组件

@Controller用于标注控制层组件（如struts中的action）

@Repository用于标注数据访问组件，即DAO组件

@Component泛指组件，当组件不好归类的时候，我们可以使用这个注解进行标注。

component-scan标签默认情况下自动扫描指定路径下的包（含所有子包），将带有@Component、@Repository、@Service、@Controller标签的类自动注册到spring容器。

托管bean分两步：

首先在配置文件开启包扫描：

<?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">
   <!-- 包扫描，找到包下使用注解来依赖注入的属性，进行托管 -->
   <context:component-scan base-package="org.myseckill.service"/>

</beans>

然后，在bean类加注解：为类加组件注解，类中需要注入属性的加注入注解：

@Service
public class SeckillServiceImpl implements SeckillService {

    @Autowired
    private SeckillDao seckillDao;
    @Autowired
    private SuccessKilledDao successKilledDao;

        ......
}

3：声明式事务管理

事务管理主要有两种：

1：XML配置，使用tx:advice标签配置aop进行事务管理。好处是一次配置处处生效（可以自己配置切入点），坏处是，阅读代码时不知道哪个方法是被事务管理的，需要频繁查阅xml。

2：@Transactional注解：使用该注解注释的方法，表示把该方法交给spring进行事务管理。推荐使用这个方法，一是简便，二是在阅读代码时清晰地看到该方法被事务托管。

事务托管：

首先，在xml中配置事务管理器，并开启事务注解：

<?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"
    xmlns:tx="http://www.springframework.org/schema/tx"
    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-4.1.xsd
        http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-4.1.xsd">
    <!-- 扫描service包下所有的类型 -->
    <context:component-scan base-package="org.myseckill.service"></context:component-scan>

    <!-- 配置事务管理器 -->
    <bean id="transactionManager" class="org.springframework.jdbc.datasource.DataSourceTransactionManager">
        <!-- 注入数据库连接池 -->
        <property name="dataSource" ref="dataSource"/>
    </bean>

    <!-- 配置基于注解的声明式事务
        默认使用注解来管理事务行为-->
    <tx:annotation-driven transaction-manager="transactionManager"/>

</beans>

然后，在bean中，需要事务托管的方法前面，加@Transactional注解：

 @Transactional
 public SeckillExecution executeSeckill(long seckillId, long userPhone, String md5)
            throws SeckillException, RepeatKillExeception, SeckillException{}