在库存服务中实现缓存与数据库双写一致性保障方案（二）

封装请求接口，第一个实现类，data数据更新的操作，比如一个商品发生了交易，就要修改商品对应的库存了，此时就
data update request，数据更新请求
1.删除缓存
2.更新数据库

实体类:

package com.roncoo.eshop.entity;

/**
 * 库存数量model
 * @author Administrator
 *
 */
public class ProductInventory {

	/**
	 * 商品id
	 */
	private Integer productId;
	/**
	 * 库存数量
	 */
	private Long inventoryCnt;

	public ProductInventory() {

	}

	public ProductInventory(Integer productId, Long inventoryCnt) {
		this.productId = productId;
		this.inventoryCnt = inventoryCnt;
	}

	public Integer getProductId() {
		return productId;
	}
	public void setProductId(Integer productId) {
		this.productId = productId;
	}
	public Long getInventoryCnt() {
		return inventoryCnt;
	}
	public void setInventoryCnt(Long inventoryCnt) {
		this.inventoryCnt = inventoryCnt;
	}

}

　　mapper:

package com.roncoo.eshop.dao;

import com.roncoo.eshop.entity.ProductInventory;
import org.apache.ibatis.annotations.Param;

public interface ProductInventoryMapper {

    /**
     * 更新库存数量
     * @param productInventory 商品库存
     */
    void updateProductInventory(ProductInventory productInventory);

    /**
     * 根据商品id查询商品库存信息
     * @param productId 商品id
     * @return 商品库存信息
     */
    ProductInventory findProductInventory(@Param("productId") Integer productId);
}

　　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.roncoo.eshop.dao.ProductInventoryMapper">

  	<update id="updateProductInventory" parameterType="com.roncoo.eshop.entity.ProductInventory">
		update product_inventory set inventory_cnt=#{inventoryCnt} where product_id=#{productId}
  	</update>

  	<select id="findProductInventory" resultType="com.roncoo.eshop.entity.ProductInventory">
  		select product_id as "productId",inventory_cnt as "inventoryCnt" from
  		 product_inventory where product_id=#{productId}
  	</select>

</mapper>

　　sql:

create table product_inventory
(
    product_id    int auto_increment
        primary key,
    inventory_cnt bigint(255) null
);

　　

public interface RedisDAO {
    void set(String key, String value);

    String get(String key);

    void delete(String key);
}

　　

@Repository("redisDAO")
public class RedisDAOImpl implements RedisDAO {
    @Resource
    private JedisCluster jedisCluster;

    @Override
    public void set(String key, String value) {
        jedisCluster.set(key, value);
    }

    @Override
    public String get(String key) {
        return jedisCluster.get(key);
    }

    @Override
    public void delete(String key) {
        jedisCluster.del(key);
    }

}

　　

/**
 * 商品库存Service
 */
public interface ProductInventoryService {
    /**
     * 查询商品库存
     * @param productId 商品id
     * @return
     */
    ProductInventory findProductInventory(Integer productId);

    /**
     * 更新商品库存到缓存中
     * @param productInventory
     */
    void setProductInventoryCache(ProductInventory productInventory);

    /**
     * 删除缓存
     * @param productInventory
     */
    void removeProductInventoryCache(ProductInventory productInventory);

    /**
     * 更新数据库的库存
     * @param productInventory
     */
    void updateProductInventory(ProductInventory productInventory);
}

　　

@Service
public class ProductInventoryServiceImpl implements ProductInventoryService {

    @Resource
    private ProductInventoryMapper productInventoryMapper;

    @Resource
    private RedisDAO redisDAO;

    /***
     *
     * @param productId 商品id
     * @return
     */
    @Override
    public ProductInventory findProductInventory(Integer productId) {
        return productInventoryMapper.findProductInventory(productId);
    }

    @Override
    public void setProductInventoryCache(ProductInventory productInventory) {
        String key = "product:inventory:" + productInventory.getProductId();
        redisDAO.set(key, String.valueOf(productInventory.getInventoryCnt()));
    }

    @Override
    public void removeProductInventoryCache(ProductInventory productInventory) {
        String key = "product:inventory:" + productInventory.getProductId();
        redisDAO.delete(key);
    }

    @Override
    public void updateProductInventory(ProductInventory productInventory) {
        productInventoryMapper.updateProductInventory(productInventory);
    }
}

　　

package com.roncoo.eshop.req;

import com.roncoo.eshop.entity.ProductInventory;
import com.roncoo.eshop.service.ProductInventoryService;

/**
 * 删除缓存修改数据库
 */
public class DataUpdateRequest implements Request{


    private ProductInventory productInventory;
    /**
     * 商品库存Service
     */
    private ProductInventoryService productInventoryService;

    public DataUpdateRequest(ProductInventory productInventory, ProductInventoryService productInventoryService) {
        this.productInventory = productInventory;
        this.productInventoryService = productInventoryService;
    }

    /**
     * 删除redis中的缓存
     * 修改数据库中的库存
     */
    @Override
    public void process(){
        productInventoryService.removeProductInventoryCache(productInventory);
        productInventoryService.updateProductInventory(productInventory);
    }
}

　　

package com.roncoo.eshop.req;

import com.roncoo.eshop.entity.ProductInventory;
import com.roncoo.eshop.service.ProductInventoryService;

/**
 * 重新加载商品库存的缓存
 * 读缓存读空，需要发送一个更新缓存的请求
 * @author Administrator
 *
 */
public class ProductInventoryCacheRefreshRequest implements Request {
    /**
     * 商品id
     */
    private Integer productId;
    /**
     * 商品库存Service
     */
    private ProductInventoryService productInventoryService;
    public ProductInventoryCacheRefreshRequest(Integer productId,
                                               ProductInventoryService productInventoryService) {
        this.productId = productId;
        this.productInventoryService = productInventoryService;
    }

    /**
     *  从数据库中查询最新的商品库存数量
     * 将最新的商品库存数量，刷新到redis缓存中去
     */
    @Override
    public void process() {
        ProductInventory productInventory = productInventoryService.findProductInventory(productId);

        productInventoryService.setProductInventoryCache(productInventory);
    }
}