【报错】两个稀奇古怪的问题

第一个问题

不明白为什么标记处只能填item才能获取到值，之前我的属性名是type

public class ExpenseReportItem {
    private Integer id;
    private String type;
    private Double amount;
    private String comment;

<mapper namespace="com.oa.dao.ExpenseReportItemDao">

    <resultMap id="expenseReportItem" type="ExpenseReportItem">
        <id property="id" column="id" javaType="Integer"/>
        <result property="expenseReportId" column="expense_report_id" javaType="Integer"/>
        <result property="type" column="type" javaType="String"/>
        <result property="amount" column="amount" javaType="Double"/>
        <result property="comment" column="comment" javaType="String"/>
    resultMap>

    <insert id="insert" parameterType="ExpenseReportItem">
        insert into expense_report_item(expense_report_id,type,amount,comment) values(#{expenseReportId},#{type},#{amount},#{comment})
    insert>

    <update id="update" parameterType="ExpenseReportItem">
        update expense_report_item set expense_report_id=#{expenseReportId},type=#{type},amount=#{amount},comment=#{comment} where id=#{id}
    update>

items是ExpenseReportItem集合

public class ExpenseReportInfo {
    private ExpenseReport expenseReport;
    private List items;

将所有type属性改为item后才取到值，至于为什么，一脸懵逼。

第二个问题

标记的地方命名要一致才能在下面取到值。