经过之前的学习积累，今天将各部分知识结合了下，做了个Demo，参考《深入浅出SpringBoot2.x》的抢购商品Demo做了个升级，书中是使用jsp来做视图，我将它改变为使用thymeleaf模板引擎，因为这样将前后端分离，也可以减少一些配置，方便了编写与查看；书中在配置Mapper是使用的xml，我将其修改为注解，我感觉这样更直观，xml写法的信噪比太低了（ps:学通信的嘛：)），好多无效信息，看的比较烦。下面是整个Demo的介绍：
1、数据库表设计
分为两张表，一张为产品表（t_product），一张为购买信息表（t_purchase_record）:
产品表（t_product）
t_purchase_record
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CREATE TABLE `t_product` (
`id` int(12) NOT NULL AUTO_INCREMENT,
`product_name` varchar(60) NOT NULL,
`stock` int(10) NOT NULL,
`price` decimal(16,2) NOT NULL,
`version` int(10) NOT NULL DEFAULT '0',
`note` varchar(256) DEFAULT NULL,
PRIMARY KEY (`id`)
);
CREATE TABLE `t_purchase_record` (
`id` int(12) NOT NULL AUTO_INCREMENT,
`user_id` int(12) NOT NULL,
`product_id` int(12) NOT NULL,
`price` decimal(16,2) NOT NULL,
`quantity` int(12) NOT NULL,
`sum` decimal(16,2) NOT NULL,
`purchase_date` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP,
`note` varchar(512) DEFAULT NULL,
PRIMARY KEY (`id`)
);
2、创建POJO，实体类对象
@Alias("product")
public class ProductPo implements Serializable{
private Long id;
private String productName;
private int stock;
private double price;
private int version;
private String note;
/*Getter and Setter*/
}
@Alias("purchaseRecord")
public class PurchaseRecordPo implements Serializable {
private Long id;
private Long userId;
private Long productId;
private double price;
private int quantity;
private double sum;
private Timestamp purchaseTime;
private String note;
/*Getter and Setter*/
}
3、持久层，Mybatis接口定义，使用注解方法生成Mapper映射
@Mapper
public interface ProductMapper {
@Select("SELECT id, product_name as productName, stock, price, version, note FROM t_product where id=#{id}")
ProductPo getProduct(Long id);
@Update("UPDATE t_product SET stock = stock - #{quantity} WHERE id = #{id} ")
int decreaseProduct(@Param("id") Long id, @Param("quantity") int quantity);
}
这里之前@Param没写，导致请求/test时无法获取到quantity的值，调试了好久，最后锁定在初始化购买记录时quantity的值无法传给SQL语句，便去查看Mapper文件中的SQL有没有写正确，一看也没写错啊，后来看到书上他使用了@Param来标注参数，一查才发现，当需要传递多个参数给MyBatis时，需要用@Param来标注。
@Mapper
public interface PurchaseRecordMapper {
@Insert("insert into t_purchase_record(\n" +
" user_id,product_id,price,quantity,sum,purchase_date,note)\n" +
" values(#{userId},#{productId},#{price},#{quantity},#{sum},now(),#{note})")
int insertPurchaseRecord(PurchaseRecordPo pr);
}
4、使用Spring开发业务层
public interface PurchaseService {
/*
* 处理购买业务
* @param userId: 用户编号
* @param productId: 产品编号
* @param quantity: 购买数量
* @return 成功 or 失败
* */
public boolean purchase(Long userId, Long productId, int quantity);
}
@Service
public class PurchaseServiceImpl implements PurchaseService {
@Autowired
private ProductMapper productMapper = null;
@Autowired
private PurchaseRecordMapper purchaseRecordMapper = null;
@Override
// 启动Spring数据库事务机制
@Transactional
public boolean purchase(Long userId, Long productId, int quantity) {
// 获取产品
ProductPo product = productMapper.getProduct(productId);
// 比较库存和购买数量
if (product.getStock() < quantity) {
// 库存不足
return false;
}
// 扣减库存
productMapper.decreaseProduct(productId, quantity);
// 初始化购买记录
PurchaseRecordPo pr = this.initPurchaseRecord(userId, product, quantity);
// 插入购买记录
purchaseRecordMapper.insertPurchaseRecord(pr);
return true;
}
private PurchaseRecordPo initPurchaseRecord(Long userId, ProductPo product, int quantity) {
PurchaseRecordPo pr = new PurchaseRecordPo();
pr.setNote("购买日志，时间：" + System.currentTimeMillis());
pr.setPrice(product.getPrice());
pr.setProductId(product.getId());
pr.setQuantity(quantity);
double sum = product.getPrice() * quantity;
pr.setSum(sum);
pr.setUserId(userId);
return pr;
}
}
5、控制层以及HTML页面
@RestController
public class PurchaseController {
@Autowired
PurchaseService purchaseService = null;
@GetMapping("/test")
public ModelAndView testPage(){
ModelAndView mv = new ModelAndView("test");
return mv;
}
@PostMapping("/purchase")
public Result purchase(Long userId, Long productId, Integer quantity){
boolean success = purchaseService.purchase(userId, productId, quantity);
String message = success?"抢购成功":"抢购失败";
Result result = new Result(success, message);
return result;
}
class Result {
private boolean success = false;
private String message;
public Result(){};
public Result(Boolean success, String message){
this.success = success;
this.message = message;
}
public boolean isSuccess() {
return success;
}
public void setSuccess(boolean success) {
this.success = success;
}
public String getMessage() {
return message;
}
public void setMessage(String message) {
this.message = message;
}
}
}
Title
抢购产品测试
6、pom.xml以及application.properties设置
在pom.xml中添加web, Mybatis, MySQL, thymeleaf的相关依赖
org.springframework.boot
spring-boot-starter-jdbc
org.springframework.boot
spring-boot-starter-web
org.mybatis.spring.boot
mybatis-spring-boot-starter
2.0.1
org.springframework.boot
spring-boot-starter-thymeleaf
mysql
mysql-connector-java
runtime
org.springframework.boot
spring-boot-starter-test
test
# 数据库配置
spring.datasource.url= jdbc:mysql://localhost:3306/shopping?serverTimezone=UCT
spring.datasource.username=root
spring.datasource.password=root
spring.datasource.tomcat.max-idle=10
spring.datasource.tomcat.max-active=50
spring.datasource.tomcat.max-wait=10000
spring.datasource.tomcat.initial-size=5
# 事务的隔离级别设置为 读写提交
spring.datasource.tomcat.default-transaction-isolation=2
mybatis.type-aliases-package=com.wayne.springboot.pojo
7、运行测试
启动项目后在在浏览器输入localhost:8080/test，便可以执行一次购买，在数据库的t_product表中会将产品库存减去所购数量，如果数量不够的话，就购买失败，如果数量足够的话就购买成功，并向t_purchase_record表中插入一条购买记录。
抢购成功
购买记录
下一篇来介绍如何应对高并发：使用悲观锁，乐观锁，以及Redis来提高高并发能力。