关于mybatis:Mybatis中的标签

官网文档：mybatis官网

mapper中的几个顶级元素：

• cache
• cache-ref
• resultMap
• parameterMap
• sql
• insert
• delete
• update
• select

SELECT

<select  id="selectPerson"  parameterType="int"  parameterMap="deprecated"  resultType="hashmap"  resultMap="personResultMap"  flushCache="false"  useCache="true"  timeout="10"  fetchSize="256"  statementType="PREPARED"  resultSetType="FORWARD_ONLY">

注：resultType与resultMap中只能二选一。

resultType能够是任意包装类型/实体类；而resultMap更加弱小。

能够先看一篇文章先理解一下：[ResultType与ResultMap区别]
(https://blog.csdn.net/weixin_...

flushCache：调用sql后，清空本地缓存和二级缓存，默认值为false。
useCache：调用后二级缓存存下来，对select默认为true。
statementType: PREPARED|STATEMENT|CALLABLE,别离对应相应的statement类型。

INSERT/DELETE/UPDATE

<insert  id="insertAuthor"  parameterType="domain.blog.Author"  flushCache="true"  statementType="PREPARED"  keyColumn=""  useGeneratedKeys=""  keyProperty=""  timeout="20"><update  id="updateAuthor"  parameterType="domain.blog.Author"  flushCache="true"  statementType="PREPARED"  timeout="20"><delete  id="deleteAuthor"  parameterType="domain.blog.Author"  flushCache="true"  statementType="PREPARED"  timeout="20">

次级元素(顶级标签下的标签)

• foreach

<foreach item="item" collection="list" separator=",">    (#{item.username}, #{item.password}, #{item.email}, #{item.bio})</foreach>

• selectKey

<selectKey keyProperty="id" resultType="int" order="BEFORE">    select CAST(RANDOM()*1000000 as INTEGER) a from SYSIBM.SYSDUMMY1  </selectKey>

• sql 定义可重用的代码片段

定义

<sql id="userColumns"> ${alias}.id,${alias}.username,${alias}.password </sql>

应用

<select id="selectUsers" resultType="map">  select    <include refid="userColumns"><property name="alias" value="t1"/></include>,    <include refid="userColumns"><property name="alias" value="t2"/></include>  from some_table t1    cross join some_table t2</select>

• 动静sql（if,choose/when/otherwise,trim,where,set,bind）