Mybatis查询返回异常(返回代理对象)

使用嵌套子查询分页查询时,错误的返回了代理对象没有返回实际的bean

在collection 指定fetchType = “lazy”导致 ,修改为 fetchType=”eager” 解决

在使用**ListPage分页工具类进行分页操作时，如果使用一对多查询，会造成查询出来每一页数据数量不等于实际规定的每一个数据数量。原因在于，一对多查询的结果是包含了与子表链接的数据，例如在查询10个订单(order_header)数据时，假如有两个订单均包含2条订单条目(order_detail)数据，那么最终查询的10条数据只有8条order_header表的数据。

通常，我们为了解决这种问题，首先会先获取到10条order_header数据，然后在遍历订单数据分别获取每一条订单数据的订单条目数据，这样会浪费数据库的执行时间，下面使用collection进行查询的方法，可以避开普通collection查询造成的问题，也能达到其效果。

Mapper：

<?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="OrderHeaderMapper">
    <resultMap id="OrderView_M" type="OrderView_M">
        <id column="order_id" property="orderID" jdbcType="INTEGER"/>
        <result column="order_number" property="orderNumber" jdbcType="VARCHAR"/>
        <result column="total_amount" property="totalAmount" jdbcType="DECIMAL"/>
	<result column="pay_status_id" property="payStatusID"/>
        <result column="order_status_id" property="orderStatusID"/>
        <collection property="orderDetail" column="order_id" ofType="OrderDetailView_M" javaType="ArrayList" select="getOrderDetailByOrderID">
 
        </collection>
    </resultMap>

<resultMap id="OrderDetailView_M" type="OrderDetailView_M">
    <id column="order_detail_id" property="orderDetailID" jdbcType="INTEGER"/>
    <result column="product_name" property="productName" jdbcType="VARCHAR"/>
    <result column="photo_path" property="photoPath" jdbcType="VARCHAR"/>
</resultMap>
<!-- page为一个自定义分页类，其中包括一个pd的map -->
<select id="getOrderByCustomerListPage" parameterType="page" resultMap="OrderView_M">
        SELECT
        oh.order_id,
        oh.order_number,
        oh.total_amount,
        oh.pay_status_id,
                oh.order_status_id
    FROM
        order_header oh
    WHERE oh.pay_status_id = #{pd.orderStatusID}
    ORDER BY oh.order_date DESC
    </select>

<select id="getOrderDetailByOrderID" parameterType="java.lang.Integer" resultMap="OrderDetailView_M">
    SELECT
    od.order_detail_id,
    od.product_name,
    od.photo_path,
    od.order_id
    FROM
    order_detail od
    LEFT JOIN product p ON p.product_id = od.product_id
    WHERE od.order_id = #{order_id}
    ORDER BY p.sku
</select>

public class OrderView_M {
     private Integer orderID;
     private String orderNumber;
     private BigDecimal totalAmount;
     private Integer payStatusID;
     private Integer orderStatusID;
     private List orderDetail;
public Integer getPayStatusID() {
    return payStatusID;
}

public Integer getOrderStatusID() {
    return orderStatusID;
}

public void setOrderStatusID(Integer orderStatusID) {
    this.orderStatusID = orderStatusID;
}

public void setPayStatusID(Integer payStatusID) {
    this.payStatusID = payStatusID;
}

public Integer getOrderID() {
    return orderID;
}

public void setOrderID(Integer orderID) {
    this.orderID = orderID;
}

public String getOrderNumber() {
    return orderNumber;
}

public void setOrderNumber(String orderNumber) {
    this.orderNumber = orderNumber;
}

public BigDecimal getTotalAmount() {
    return totalAmount;
}

public void setTotalAmount(BigDecimal totalAmount) {
    this.totalAmount = totalAmount;
}

public List<OrderDetailView_M> getOrderDetail() {
    return orderDetail;
}

public void setOrderDetail(List<OrderDetailView_M> orderDetail) {
    this.orderDetail = orderDetail;
}
}




public class OrderDetailView_M {
     private Integer orderDetailID;
     private String productName;
     private String photoPath;
public String getProductName() {
    return productName;
}

public void setProductName(String productName) {
    this.productName = productName;
}

public String getPhotoPath() {
    return photoPath;
}

public void setPhotoPath(String photoPath) {
    this.photoPath = photoPath;
}

public Integer getOrderDetailID() {
    return orderDetailID;
}

public void setOrderDetailID(Integer orderDetailID) {
    this.orderDetailID = orderDetailID;
}
}