DB2\Oracle数据库对clob的处理
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：
//db2数据库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; } });}