MyBatis之主键自增——useGeneratedKeys

如果你的数据库支持主键自增，例如MySQL和SQL Server，那么你可以简单的设置 useGeneratedKeys="true" ，用keyProperty 去指定主键名称, if the Authortable above had used an auto-generated column type for the id, the statement would be modified as follows:

<insert id="insertAuthor" useGeneratedKeys="true"    keyProperty="id">  insert into Author (username,password,email,bio)  values (#{username},#{password},#{email},#{bio})</insert>

If your database also supports multi-row insert, you can pass a list or an array of Authors and retrieve the auto-generated keys.

<insert id="insertAuthor" useGeneratedKeys="true"    keyProperty="id">  insert into Author (username, password, email, bio) values  <foreach item="item" collection="list" separator=",">    (#{item.username}, #{item.password}, #{item.email}, #{item.bio})  </foreach></insert>

MyBatis has another way to deal with key generation for databases that don't support auto-generated column types, or perhaps don't yet support the JDBC driver support for auto-generated keys.

Here's a simple (silly) example that would generate a random ID (something you'd likely never do, but this demonstrates the flexibility and how MyBatis really doesn't mind):

<insert id="insertAuthor">  <selectKey keyProperty="id" resultType="int" order="BEFORE">    select CAST(RANDOM()*1000000 as INTEGER) a from SYSIBM.SYSDUMMY1  </selectKey>  insert into Author    (id, username, password, email,bio, favourite_section)  values    (#{id}, #{username}, #{password}, #{email}, #{bio}, #{favouriteSection,jdbcType=VARCHAR})</insert>