ibatis如何支持clob 和blob

这几天仔细看了一下ibatis的文档，发现2.2后，ibatis的改变还是挺大的。对于自定义类型支持的也不错，这样对于blob和clob数据的处理也就简单多了。
    不过在spring 中已经提供了很好的实现，所以这又省去了很多的功夫，接下来看看ibatis是如何支持clob和blob的。

    ibatis提供了TypeHandler接口，用于处理数据类型，基本的实现类为BaseTypeHandler
    在spring 中，提供了AbstractLobTypeHandler作为基础类，并且提供了相应的模版方法，所有的工作由LobHandler处理。
    BlobByteArrayTypeHandler 主要用于处理blob类型数据，使用byte[]来映射相应的blob
    ClobStringTypeHandler 用于处理clob类型数据，使用字符串来映射Clob
    有一点需要注意的是，AbstractLobTypeHandler中实现了事务支持，需要用来释放相应的资源，所以一定需要在事务环境中进行。

下面是一个简单的例子：

public class Food {
    private String content;

    private String id;

    private byte[] image;

    private String name;   
        ...
}

xml如下：说明一下，在resultMap中可以通过typeHandler来指定具体的handler.在inline变量中，可以通过handler来定义相应的typeHandler

<sqlMap namespace="Food">
   
    <typeAlias alias="Food" type="org.esoft.hdb.bo.Food"/>
    <resultMap id="foodResult" class="Food">
        <result property="id" column="C_ID"/>
        <result property="name" column="C_NAME"/>
        <result property="content" column="C_content"
            typeHandler="org.springframework.orm.ibatis.support.ClobStringTypeHandler"/>
        <result property="image" column="C_image"
            typeHandler="org.springframework.orm.ibatis.support.BlobByteArrayTypeHandler"/>
    </resultMap>
    <sql id="foodFragment">select C_ID,C_NAME,C_CONTENT,C_IMAGE from T_FOOD</sql>
        <select id="getAll" resultMap="foodResult">
        <include refid="foodFragment"/>
    </select>
    <select id="selectById" parameterClass="string" resultMap="foodResult">
        <include refid="foodFragment"/> where C_ID=#id#</select>
   
    <insert id="insert" parameterClass="Food"> insert into T_FOOD ( C_ID,
        C_NAME,C_CONTENT, C_IMAGE) values ( #id#,
        #name#,#content,handler=org.springframework.orm.ibatis.support.ClobStringTypeHandler#,
        #image,handler=org.springframework.orm.ibatis.support.BlobByteArrayTypeHandler#)
        </insert>
   
    <update id="update" parameterClass="Food"> update T_FOOD set C_NAME = #name#,
        C_CONTENT =
        #content,handler=org.springframework.orm.ibatis.support.ClobStringTypeHandler#,
        C_IMAGE =
        #image,handler=org.springframework.orm.ibatis.support.BlobByteArrayTypeHandler#
        where C_ID = #id# </update>
   
    <delete id="deleteById" parameterClass="string"> delete from T_FOOD where C_ID = #id#
        </delete>
   
</sqlMap>


public interface FoodService {

   
    void save(Food food);
    Food get(String id);
    /**
     * @param food
     */
    void update(Food food);
}

public class FoodServiceImpl implements FoodService {
     private FoodDAO foodDAO;

    private DaoCreator creator;

    public void setCreator(DaoCreator creator) {
        this.creator = creator;
    }

    protected FoodDAO getFoodDAO() {
        if (foodDAO == null) {
            foodDAO = (FoodDAO) creator.createDao(FoodDAO.class, Food.class);
        }
        return foodDAO;
    }

    public Food get(String id) {
        return getFoodDAO().get(id);
    }
    public void save(Food food) {
        getFoodDAO().save(food);
    }
    public void update(Food food) {
        getFoodDAO().update(food);
    }

}

spring xml 配置：
。。。
          <bean id="lobHandler"
        class="org.springframework.jdbc.support.lob.DefaultLobHandler"/>
   
    <bean id="transactionManager"
        class="org.springframework.jdbc.datasource.DataSourceTransactionManager">
        <property name="dataSource" ref="dataSource"/>
    </bean>
   
    <bean id="sqlMapClient"
        class="org.springframework.orm.ibatis.SqlMapClientFactoryBean">
        <property name="dataSource" ref="dataSource"/>
        <property name="configLocation">
            <value>SqlMapConfig.xml</value>
        </property>
        <property name="lobHandler" ref="lobHandler"/>
    </bean>
   
    <bean id="daoCreate" class="org.esoft.hdb.ibatis.IbatisDaoCreator">
        <property name="sqlMapClient" ref="sqlMapClient"/>
    </bean>
   
    <bean id="foodService" class="org.esoft.hdb.service.FoodServiceImpl">
        <property name="creator" ref="daoCreate"/>
    </bean>
   
   
    <aop:config>
        <aop:pointcut id="foodServiceMethods"
            expression="execution(* org.esoft.hdb.service.FoodService.*(..))"/>
        <aop:advisor advice-ref="txAdvice" pointcut-ref="foodServiceMethods"/>
    </aop:config>
    <tx:advice id="txAdvice" transaction-manager="transactionManager">
        <tx:attributes>
            <tx:method name="*" propagation="REQUIRED"/>
        </tx:attributes>
    </tx:advice>

简单的测试：
save :
        Food food = new Food();
        food.setPk("1");
        food.setName("food1");
        BufferedInputStream in = new BufferedInputStream(getClass()
                .getResourceAsStream("/1.gif"));
        byte[] b = FileCopyUtils.copyToByteArray(in);
        food.setImage(b);
                in = new BufferedInputStream(getClass().getResourceAsStream(
                "/hibernate.cfg.xml"));
        b = FileCopyUtils.copyToByteArray(in);
        food.setContent(new String(b));
        foodService.save(food);
update:
              Food food = foodService.get("1");
        BufferedInputStream in = new BufferedInputStream(getClass()
                .getResourceAsStream("/jdbc.properties"));
        byte[] b = FileCopyUtils.copyToByteArray(in);
        food.setContent(new String(b));
        foodService.update(food);
        food = foodService.get("1");
        assertNotNull(food.getImage());