上程式碼

//簡單訂單實體
public class Order {
    private String orderid;
    private String price;
    private List<OrderGoods> goods;
}
//簡單訂單包含商品實體
public class OrderGoods{
    private String orderid;
    private String goodsCode;
    private Integer buyNUM;
    private String goodsNAME;
}

//mybatis.xml檔案
 

<select id="searchOrdersAll" parameterType="com.entity.vo.OrderSearch" resultMap="orderMap">
        SELECT * FROM
        Order  
        LEFT JOIN Order_Goods 
        ON Order.orderid=Order_Goods.orderid 
        LIMIT 0,20
</select>

<resultMap type="com.entity.Order" id="orderMap">
 

     <result column="ORDER_ID" property="orderid"/>
     <result column="PRICE" property="price"/>
    <collection property="goods" ofType="com.entity.OrderGoods"        resultMap="ordergoodsMap" />  
</resultMap>
<resultMap type="com.entity.OrderGoods" id="ordergoodsMap">
 

     <result column="ORDER_ID" property="orderid"/>
     <result column="ORDER_ID" property="goodsCode"/>
     <result column="BUY_NUM" property="buyNUM"/>
     <result column="GOODS_NAME" property="goodsNAME"/> 
</resultMap>

返回結果為List<Order>

今天做訂單優化發現程式碼先返回訂單，在根據訂單ID去查詢訂單包含商品，這樣在查詢大數量時明顯變慢，處理方法一就是上邊方法，方法二就是把先查詢訂單並返返回頁面顯示，檢視訂單詳情時在查詢選中訂單詳情，累死懶載入。因專案頁面要直接顯示所有訂單及詳情，所以我用的方法一。