經(jīng)過(guò)之前的學(xué)習(xí)積累准给，今天將各部分知識(shí)結(jié)合了下，做了個(gè)Demo，參考《深入淺出SpringBoot2.x》的搶購(gòu)商品Demo做了個(gè)升級(jí)供搀，書中是使用jsp來(lái)做視圖，我將它改變?yōu)槭褂胻hymeleaf模板引擎钠至，因?yàn)檫@樣將前后端分離葛虐，也可以減少一些配置，方便了編寫與查看棉钧；書中在配置Mapper是使用的xml屿脐，我將其修改為注解，我感覺這樣更直觀宪卿，xml寫法的信噪比太低了（ps:學(xué)通信的嘛：)）的诵，好多無(wú)效信息，看的比較煩佑钾。下面是整個(gè)Demo的介紹：

1西疤、數(shù)據(jù)庫(kù)表設(shè)計(jì)

分為兩張表，一張為產(chǎn)品表（t_product）休溶，一張為購(gòu)買信息表（t_purchase_record）:

產(chǎn)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代赁、創(chuàng)建POJO扰她，實(shí)體類對(duì)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、持久層芭碍，Mybatis接口定義徒役，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);
}

這里之前@Param沒寫，導(dǎo)致請(qǐng)求/test時(shí)無(wú)法獲取到quantity的值窖壕，調(diào)試了好久忧勿，最后鎖定在初始化購(gòu)買記錄時(shí)quantity的值無(wú)法傳給SQL語(yǔ)句，便去查看Mapper文件中的SQL有沒有寫正確瞻讽，一看也沒寫錯(cuò)啊鸳吸，后來(lái)看到書上他使用了@Param來(lái)標(biāo)注參數(shù)，一查才發(fā)現(xiàn)卸夕，當(dāng)需要傳遞多個(gè)參數(shù)給MyBatis時(shí)层释，需要用@Param來(lái)標(biāo)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快集、使用Spring開發(fā)業(yè)務(wù)層

public interface PurchaseService {
    /*
    * 處理購(gòu)買業(yè)務(wù)
    * @param userId: 用戶編號(hào)
    * @param productId: 產(chǎn)品編號(hào)
    * @param quantity: 購(gòu)買數(shù)量
    * @return 成功 or 失敗
    * */
    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
     // 啟動(dòng)Spring數(shù)據(jù)庫(kù)事務(wù)機(jī)制
     @Transactional
     public boolean purchase(Long userId, Long productId, int quantity) {
         // 獲取產(chǎn)品
         ProductPo product = productMapper.getProduct(productId);
         // 比較庫(kù)存和購(gòu)買數(shù)量
         if (product.getStock() < quantity) {
         // 庫(kù)存不足
         return false;
         }
         // 扣減庫(kù)存
         productMapper.decreaseProduct(productId, quantity);
         // 初始化購(gòu)買記錄
         PurchaseRecordPo pr = this.initPurchaseRecord(userId, product, quantity);
         // 插入購(gòu)買記錄
         purchaseRecordMapper.insertPurchaseRecord(pr);
         return true;
     }

    private PurchaseRecordPo initPurchaseRecord(Long userId, ProductPo product, int quantity) {
        PurchaseRecordPo pr = new PurchaseRecordPo();
        pr.setNote("購(gòu)買日志贡羔，時(shí)間：" + 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、控制層以及HTML頁(yè)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?"搶購(gòu)成功":"搶購(gòu)失敗";
        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;
        }
    }
}

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <script type="text/javascript"
            src="https://code.jquery.com/jquery-3.2.1.min.js"></script>

    <script type="text/javascript">
            var params = {
                userId : 1,
                productId : 1,
                quantity : 2
            };
            // 通過(guò)POST請(qǐng)求后端
            $.post("./purchase", params, function(result) {
                alert(result.message);
            });
    </script>

</head>
<body>
<h1>搶購(gòu)產(chǎn)品測(cè)試</h1>
</body>
</html>

6个初、pom.xml以及application.properties設(shè)置

在pom.xml中添加web, Mybatis, MySQL, thymeleaf的相關(guān)依賴

<dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-jdbc</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <!-- Mybatis 依賴 -->
        <dependency>
            <groupId>org.mybatis.spring.boot</groupId>
            <artifactId>mybatis-spring-boot-starter</artifactId>
            <version>2.0.1</version>
        </dependency>

        <!-- ThymeLeaf 依賴 -->
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-thymeleaf</artifactId>
        </dependency>
        <!-- mysql 依賴 -->
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <scope>runtime</scope>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>

# 數(shù)據(jù)庫(kù)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

# 事務(wù)的隔離級(jí)別設(shè)置為 讀寫提交
spring.datasource.tomcat.default-transaction-isolation=2

mybatis.type-aliases-package=com.wayne.springboot.pojo

7乖寒、運(yùn)行測(cè)試

啟動(dòng)項(xiàng)目后在在瀏覽器輸入localhost:8080/test，便可以執(zhí)行一次購(gòu)買院溺，在數(shù)據(jù)庫(kù)的t_product表中會(huì)將產(chǎn)品庫(kù)存減去所購(gòu)數(shù)量楣嘁，如果數(shù)量不夠的話，就購(gòu)買失敗珍逸，如果數(shù)量足夠的話就購(gòu)買成功逐虚，并向t_purchase_record表中插入一條購(gòu)買記錄。

搶購(gòu)成功

購(gòu)買記錄

下一篇來(lái)介紹如何應(yīng)對(duì)高并發(fā)：使用悲觀鎖谆膳，樂觀鎖叭爱，以及Redis來(lái)提高高并發(fā)能力。