3.9.11. MyBatis 集成

MyBatis 框架，与 ORM 本地查询或QueryRunner相比，提供了更广泛的执行 SQL 和将查询结果映射到对象的功能。

按照下面的步骤在 CUBA 项目中集成 MyBatis。

1. 在 core 模块的根 java 包创建处理 UUID 类型的类。

   import com.haulmont.cuba.core.global.UuidProvider;
   import org.apache.ibatis.type.JdbcType;
   import org.apache.ibatis.type.TypeHandler;
   import java.sql.*;
   public class UUIDTypeHandler implements TypeHandler {
       @Override
       public void setParameter(PreparedStatement ps, int i, Object parameter, JdbcType jdbcType) throws SQLException {
           ps.setObject(i, parameter, Types.OTHER);
       }
       @Override
       public Object getResult(ResultSet rs, String columnName) throws SQLException {
           String val = rs.getString(columnName);
           if (val != null) {
               return UuidProvider.fromString(val);
           } else {
               return null;
           }
       }
       @Override
       public Object getResult(ResultSet rs, int columnIndex) throws SQLException {
           String val = rs.getString(columnIndex);
           if (val != null) {
               return UuidProvider.fromString(val);
           } else {
               return null;
           }
       }
       @Override
       public Object getResult(CallableStatement cs, int columnIndex) throws SQLException {
           String val = cs.getString(columnIndex);
           if (val != null) {
               return UuidProvider.fromString(val);
           } else {
               return null;
           }
       }
   }

2. 在 core 模块的 spring.xml 文件所在目录创建 mybatis.xml 配置文件，在文件内正确引用 UUIDTypeHandler：

   <!DOCTYPE configuration PUBLIC "-//mybatis.org//DTD Config 3.0//EN" "http://mybatis.org/dtd/mybatis-3-config.dtd">
   <configuration>
       <settings>
           <setting name="lazyLoadingEnabled" value="false"/>
       </settings>
       <typeHandlers>
           <typeHandler javaType="java.util.UUID"
                        handler="com.company.demo.core.UUIDTypeHandler"/>
       </typeHandlers>
   </configuration>

3. 将下面的 bean 都添加到 spring.xml 文件以便在项目中使用 MyBatis：

   <bean id="sqlSessionFactory" class="org.mybatis.spring.SqlSessionFactoryBean">
       <property name="dataSource" ref="cubaDataSource"/>
       <property name="configLocation" value="com/company/demo/mybatis.xml"/>
       <property name="mapperLocations" value="com/company/demo/core/sqlmap/*.xml"/>
   </bean>
   <bean class="org.mybatis.spring.mapper.MapperScannerConfigurer">
       <property name="basePackage" value="com/company/demo.core.dao"/>
       <property name="sqlSessionFactory" ref="sqlSessionFactory"/>
   </bean>
   <bean id="sqlSession" class="org.mybatis.spring.SqlSessionTemplate">
       <constructor-arg index="0" ref="sqlSessionFactory" />
   </bean>

   sqlSessionFactory bean 包含了指向 mybatis.xml 的引用。

   MapperLocations 参数定义了 mapperLocations 映射文件的路径（根据 Spring 中 ResourceLoader 接口的资源解析规则）。

4. 最后，在 build.gradle 中的 core 模块添加 MyBatis 的依赖：

   compile('org.mybatis:mybatis:3.2.8')
   compile('org.mybatis:mybatis-spring:1.2.5')

下面是一个映射文件的示例，用于加载 订单(Order) 的实例以及相关的 客户(Customer) 和 订单商品(order item) 集合：

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.sample.sales">
    <select id="selectOrder" resultMap="orderResultMap">
        select
        o.ID as order_id,
        o.DATE as order_date,
        o.AMOUNT as order_amount,
        c.ID as customer_id,
        c.NAME as customer_name,
        c.EMAIL as customer_email,
        i.ID as item_id,
        i.QUANTITY as item_quantity,
        p.ID as product_id,
        p.NAME as product_name
        from
        SALES_ORDER o
        left join SALES_CUSTOMER c on c.ID = o.CUSTOMER_ID
        left join SALES_ITEM i on i.ORDER_ID = o.id and i.DELETE_TS is null
        left join SALES_PRODUCT p on p.ID = i.PRODUCT_ID
        where
        c.id = #{id}
    </select>
    <resultMap id="orderResultMap" type="com.sample.sales.entity.Order">
        <id property="id" column="order_id"/>
        <result property="date" column="order_date"/>
        <result property="amount" column="order_amount"/>
        <association property="customer" column="customer_id" javaType="com.sample.sales.entity.Customer">
            <id property="id" column="customer_id"/>
            <result property="name" column="customer_name"/>
            <result property="email" column="customer_email"/>
        </association>
        <collection property="items" ofType="com.sample.sales.entity.Item">
            <id property="id" column="item_id"/>
            <result property="quantity" column="item_quantity"/>
            <association property="product" column="product_id" javaType="com.sample.sales.entity.Product">
                <id property="id" column="product_id"/>
                <result property="name" column="product_name"/>
            </association>
        </collection>
    </resultMap>
</mapper>

以下代码可用于获取上面示例中的查询结果：

try (Transaction tx = persistence.createTransaction()) {
    SqlSession sqlSession = AppBeans.get("sqlSession");
    Order order = (Order) sqlSession.selectOne("com.sample.sales.selectOrder", orderId);
    tx.commit();