MyBatisSystemException異常產生原因及解決方案

01 異常發生場景

• 當我使用mybatis對數據庫操作時報的錯誤

<resultMap id="shoppingCartProduct" type="shoppingCartProductVo">
        <id property="shoppingCartId" column="shopping_cart_id"></id>
        <result property="productId" column="product_id"></result>
        <result property="num" column="num"></result>
        <result property="productName" column="product_name"></result>
        <result property="productTitle" column="product_title"></result>
        <result property="productIntro" column="product_intro"></result>
        <result property="productPicture" column="product_picture"></result>
        <result property="productPrice" column="product_price"></result>
        <result property="productSellingPrice" column="product_selling_price"></result>
    </resultMap>
    <select id="selectShoppingCartByIds" resultMap="shoppingCartProduct">
        select
            s.shopping_cart_id,
            s.num,
            s.product_id,
            p.product_name,
            p.product_title,
            p.product_intro,
            p.product_picture,
            p.product_price,
            p.product_selling_price
            FROM
            shopping_cart AS s
            left JOIN
            product AS p
            ON s.product_id = p.product_id
            WHERE
            s.shopping_cart_id 
            in (<foreach collection="list" index="id" separator=",">
                #{id}
            </foreach>)
    </select>

02 嘗試解決問題的過程

1.事務問題

• 一開始，我以為是事務問題，于是在service層加上了@Transactional開啟事務

@Override
@Transactional
public GetData postOrders(List<Long> shoppingCartIds, Long userId) {
    //1.判斷用戶是否存在
    if (msUserMapper.FindUser(userId) == null) {
        GetData getData=new GetData(500,"無此賬號",null);
        return getData;
    }
    //2.生成訂單
    Orders orders=new Orders();
    orders.setOrderNum(UUID.randomUUID().toString());
    orders.setUserId(userId);
    orders.setOrderTime(new Date());
    orderProductMapper.addOrders(orders);
    System.out.println(orders.getOrderId());
    System.out.println(orders.getOrderId().getClass().getTypeName());
    System.out.println(shoppingCartIds);

    //3.查詢購物車商品數據
    List<ShoppingCartProductVo> shoppingCartProductVos = productMapper.selectShoppingCartByIds(shoppingCartIds);
    System.out.println(shoppingCartProductVos.size());
    System.out.println(shoppingCartProductVos);
    List<OrdersDtl> ordersDtls = new ArrayList<>();
    for (ShoppingCartProductVo vo : shoppingCartProductVos) {
        OrdersDtl ordersDtl = new OrdersDtl();
        ordersDtl.setOrderId(orders.getOrderId());
        ordersDtl.setProductId(vo.getProductId());
        ordersDtl.setProductIntro(vo.getProductIntro());
        ordersDtl.setProductName(vo.getProductName());
        ordersDtl.setProductPicture(vo.getProductPicture());
        ordersDtl.setProductPrice(vo.getProductPrice());
        ordersDtl.setProductSellingPrice(vo.getProductSellingPrice());
        ordersDtl.setProductTitle(vo.getProductTitle());
        ordersDtl.setNum(vo.getNum());
        ordersDtls.add(ordersDtl);
    }
    System.out.println(ordersDtls);
    orderProductMapper.addBatchOrderDtlsInt(ordersDtls);
    System.out.println(1);
    int rs =shoppingCartMapper.deleteShoppingCarts(shoppingCartIds);

    if (rs>0){
        GetData getData=new GetData(200,"操作成功",null);
        return getData;
    }else {
        GetData getData=new GetData(500,"操作成功",rs);
        return getData;
    }

}

• 現在想想，真是沒抓住重點，看錯了代碼的報錯信息

2.MyBatis一級緩存問題

• 接著排查發現發現查詢出的數據與同樣的代碼在數據庫里不一樣，人當場傻了
• 面向百度編程后認為是出現了MyBatis一級緩存問題
• 于是在yml文件中關閉關閉了MyBatis一級緩存

# 配置mybatis
mybatis:
  # mapper配置文件
  mapper-locations: classpath:mapper/*.xml
  # resultType別名，沒有這個配置resultType包名要寫全，配置后只要寫類名
  type-aliases-package: com.example.demo.com.mashang.dao
  configuration:
    log-impl: org.apache.ibatis.logging.stdout.StdOutImpl
    map-underscore-to-camel-case: true
    local-cache-scope: statement # 設置一級緩存關閉，mybatis默認開啟

• 當然還是不對，無可奈何之下，我只能回歸最初的報錯信息，意思大概是文件映射有問題

03 問題的產生及其原因

• 沒辦法，如果真是映射出了錯，那就只能一個一個排查過去了
• 終于在結合了springboot的報錯日志
• log-impl: org.apache.ibatis.logging.stdout.StdOutImpl

select 
s.num, s.product_id, p.product_name, p.product_title, p.product_intro, p.product_picture, p.product_price, p.product_selling_price 
FROM shopping_cart AS s 
INNER JOIN product AS p 
ON s.product_id = p.product_id 
WHERE s.shopping_cart_id 
in ( ? , ? , ? )

• 終于，我發現mybatis執行的語句中，三個問號插入的值是固定的0,1,2
• 也就是循環插入出了問題
• 果然，我錯誤的使用了標簽index

04 解決方式

• 只要認真檢查mybatis的映射文件，我的話是把標簽換成即可，以下是修改后的mybatis映射文件

<resultMap id="shoppingCartProduct" type="shoppingCartProductVo">
    <id property="shoppingCartId" column="shopping_cart_id"></id>
    <result property="productId" column="product_id"></result>
    <result property="num" column="num"></result>
    <result property="productName" column="product_name"></result>
    <result property="productTitle" column="product_title"></result>
    <result property="productIntro" column="product_intro"></result>
    <result property="productPicture" column="product_picture"></result>
    <result property="productPrice" column="product_price"></result>
    <result property="productSellingPrice" column="product_selling_price"></result>
</resultMap>
<select id="selectShoppingCartByIds" resultMap="shoppingCartProduct">
    select
        s.shopping_cart_id,
        s.num,
        s.product_id,
        p.product_name,
        p.product_title,
        p.product_intro,
        p.product_picture,
        p.product_price,
        p.product_selling_price
        FROM
        shopping_cart AS s
        left JOIN
        product AS p
        ON s.product_id = p.product_id
        WHERE
        s.shopping_cart_id 
        in (<foreach collection="list" item="id" separator=",">
            #{id}
        </foreach>)
</select>