Mybatis 连接池，事务，动态sql

1、连接池
pooled 用连接池
unpooled 不用连接池

<dataSource type="POOLED">
<property name="driver" value="${jdbc.driver}"/>
<property name="url" value="${jdbc.url}"/>
<property name="username" value="${jdbc.username}"/>
<property name="password" value="${jdbc.password}"/>
</dataSource>

2、事务

当autocommit为true时会自动提交
3、动态sql
if标签

<select id="findByUser" resultType="user" parameterType="user">
    select * from user where 1=1

    <if test="username!=null and username != '' ">
        and username like #{username}
    </if>
    <if test="address != null">
        and address like #{address}
    </if>
</select>

where标签

<sql id="defaultSql">
    select * from user
</sql>

<select id="findByUser" resultType="user" parameterType="user">
    <include refid="defaultSql"></include>
    <where>
        <if test="username!=null and username != '' ">
        and username like #{username}
        </if>
        <if test="address != null">
        and address like #{address}
        </if>
    </where>
</select>

foreach标签

<!-- 查询所有用户在 id 的集合之中 -->
<select id="findInIds" resultType="user" parameterType="queryvo">
    <!-- select * from user where id in (1,2,3,4,5); -->
    <include refid="defaultSql"></include>
    <where>
        <if test="ids != null and ids.size() > 0">
            <foreach collection="ids" open="id in ( " close=")" item="uid" separator=",">
                #{uid}
            </foreach>
        </if>
    </where>
</select>
SQL 语句：
select 字段 from user where id in (?)

<foreach>标签用于遍历集合，它的属性：
collection:代表要遍历的集合元素，注意编写时不要写#{}
open:代表语句的开始部分
close:代表结束部分
item:代表遍历集合的每个元素，生成的变量名
sperator:代表分隔符