使用Spring JdbcTemplate处理Blob和Clob字段

spring定义了一个以统一的方式操作各种数据库的Lob类型数据的LobCreator(保存的时候用),同时提供了一个LobHandler为操作二进制字段和大文本字段提供统一接口访问。?
举例，例子里面的t_post表中post_text字段是CLOB类型,而post_attach是BLOG类型：

public class PostJdbcDao extends JdbcDaoSupport implements PostDao {
private?LobHandler?lobHandler;
private DataFieldMaxValueIncrementer incre;
public?LobHandler?getLobHandler() {
?? return?lobHandler;
}
public void setLobHandler(LobHandler?lobHandler) {
?? this.lobHandler?=?lobHandler;
}
public void addPost(final Post post) {??
?? String sql = " INSERT INTO t_post(post_id,user_id,post_text,post_attach)"
???? + " VALUES(?,?,?,?)";
?? getJdbcTemplate().execute(
???? sql,
???? new AbstractLobCreatingPreparedStatementCallback(
?????? this.lobHandler) {
????? protected void setValues(PreparedStatement ps,
??????? LobCreator lobCreator) throws SQLException {
?????? ps.setInt(1, incre.nextIntValue());?
?????? ps.setInt(2, post.getUserId());?
?????? lobCreator.setClobAsString(ps, 3, post.getPostText());
?????? lobCreator.setBlobAsBytes(ps, 4, post.getPostAttach());
????? }
???? });
}
}

设置相对应的配置文件(Oracle 9i版本),Oracle的数据库最喜欢搞搞特别的东西啦：

<bean id="nativeJdbcExtractor"
?? />
<bean id="oracleLobHandler"
?? ref="nativeJdbcExtractor" />
</bean>
<bean id="dao" abstract="true">
?? <property name="jdbcTemplate" ref="jdbcTemplate" />
</bean>
<bean id="postDao" parent="dao"
?? ref="oracleLobHandler" />
</bean>

Oracle 10g或其他数据库如下设置：

<bean id="defaultLobHandler"
?? />
<bean id="dao" abstract="true">
?? <property name="jdbcTemplate" ref="jdbcTemplate" />
</bean>
<bean id="postDao" parent="dao"
?? ref="defaultLobHandler" />
</bean>

读取BLOB/CLOB块,举例：

public List getAttachs(final int userId){
?? String sql = "SELECT post_id,post_attach FROM t_post where user_id =? and post_attach is not null";
?? return getJdbcTemplate().query(
?????? sql,new Object[] {userId},
?????? new RowMapper() {
??????? public Object mapRow(ResultSet rs, int rowNum) throws SQLException {
??????? Post post = new Post();
??????? int postId = rs.getInt(1);
???????? byte[] attach =?lobHandler.getBlobAsBytes(rs, 2);
???????? post.setPostId(postId);
???????? post.setPostAttach(attach);
???????? return post;
??????? }
?????? });
}