iBatis自动生成的主键 (Oracle,MS Sql Server,MySQL)

iBatis的sqlMap配置文件的 selectKey元素有个 type属性，可以指定 pre或者 post表示前生成( pre)还是后生成( post)。

Oracle设置

<!-- Oracle SEQUENCE -->
<insertid="insertProduct-ORACLE"parameterClass="com.domain.Product">
    <selectKeyresultClass="int"keyProperty="id"type="pre">
        <![CDATA[SELECT STOCKIDSEQUENCE.NEXTVAL AS ID FROM DUAL]]>
    </selectKey>
    <![CDATA[insert into PRODUCT (PRD_ID,PRD_DESCRIPTION) values(#id#,#description#)]]>
</insert>

MS SQL Server配置

<!-- Microsoft SQL Server IDENTITY Column -->
<insertid="insertProduct-MS-SQL"parameterClass="com.domain.Product">
    <![CDATA[insert into PRODUCT (PRD_DESCRIPTION) values(#description#) ]]>
    <selectKeyresultClass="int"keyProperty="id"type="post">
        <![CDATA[SELECT @@IDENTITY AS ID ]]>
        <!-- 该方法不安全 应当用SCOPE_IDENTITY() 但这个函数属于域函数，需要在一个语句块中执行。 -->
    </selectKey>
</insert>

上述MS SQL Server配置随是官网提供的配置，但实际上却恰恰隐患重重！按下述配置，确保获得有效主键。

<!-- Microsoft SQL Server IDENTITY Column 改进-->
<insertid="insertProduct-MS-SQL"parameterClass="com.domain.Product">
    <selectKeyresultClass="int"keyProperty="id">
        <![CDATA[insert into PRODUCT (PRD_DESCRIPTION) values(#description#)
         SELECT SCOPE_IDENTITY() AS ID ]]>
    </selectKey>
</insert>

MySQL配置

<!-- MySQL Last Insert Id -->
<insertid="insertProduct-Mysql"parameterClass="com.domain.Product">
    <![CDATA[insert into PRODUCT(PRD_DESCRIPTION) values(#description#)]]>
    <selectKeyresultClass="int"keyProperty="id">
        <![CDATA[SELECT LAST_INSERT_ID() AS ID ]]>
        <!-- 该方法LAST_INSERT_ID()与数据库连接绑定，同属统一会话级别，不会发生上述MS SQL Server的函数问题。 -->
    </selectKey>
</insert>

通过以上方式，可以最大程度上确保插入数据的时候获得当前自增主键

<!-- Oracle SEQUENCE Example using .NET 1.1 System.Data.OracleClient -->
<insert id="insertProduct-ORACLE" parameterClass="product">
    <selectKey resultClass="int" type="pre"keyProperty="id">
        SELECT STOCKIDSEQUENCE.NEXTVAL AS VALUE FROM DUAL
    </selectKey>
    insert into PRODUCT (PRD_ID,PRD_DESCRIPTION) values (#id#,#description#)
</insert>

<!-- Microsoft SQL Server IDENTITY Column Example -->
<insert id="insertProduct-MS-SQL" parameterClass="product">
    insert into PRODUCT (PRD_DESCRIPTION)
    values (#description#)
    <selectKey resultClass="int" type="post"keyProperty="id">
        select @@IDENTITY as value
    </selectKey>
</insert>

<!-- MySQL Example -->
<insert id="insertProduct-MYSQL" parameterClass="product">
    insert into PRODUCT (PRD_DESCRIPTION)
    values (#description#)
    <selectKey resultClass="int" type="post"keyProperty="id" >
        select LAST_INSERT_ID() as value
    </selectKey>
</insert>