编程.读书.思考

1、利用spring的jdbcTemplate调用存储过程
假如我们有P_GET_TOPIC_NUM这一个存储过程,有两个参数,第一个参数userId是传进去的,第二个参数是传出来的,举例如下:

	public int getUserTopicNum(final int userId) {
		String sql = "{call P_GET_TOPIC_NUM(?,?)}";
		//使用	Object execute(String callString, CallableStatementCallback action)接口
		Object obj = getJdbcTemplate().execute(sql,new CallableStatementCallback(){
			public Object doInCallableStatement(CallableStatement cs) throws SQLException, DataAccessException {
				cs.setInt(1,userId);
				cs.registerOutParameter(2, Types.INTEGER);
				cs.execute();
				return new Integer(cs.getInt(2));
			}	
		});
	    return ((Integer)obj).intValue();
	}

2、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"
		class="org.springframework.jdbc.support.nativejdbc.CommonsDbcpNativeJdbcExtractor"
		lazy-init="true" />
	<bean id="oracleLobHandler"
		class="org.springframework.jdbc.support.lob.OracleLobHandler"
		lazy-init="true">
		<property name="nativeJdbcExtractor" ref="nativeJdbcExtractor" />
	</bean>
	<bean id="dao" abstract="true">
		<property name="jdbcTemplate" ref="jdbcTemplate" />
	</bean>
	<bean id="postDao" parent="dao"
		class="com.baobaotao.dao.jdbc.PostJdbcDao">
		<property name="lobHandler" ref="oracleLobHandler" />
	</bean>

Oracle 10g或其他数据库如下设置：

	<bean id="defaultLobHandler"
		class="org.springframework.jdbc.support.lob.DefaultLobHandler"
		lazy-init="true" />
	<bean id="dao" abstract="true">
		<property name="jdbcTemplate" ref="jdbcTemplate" />
	</bean>
	<bean id="postDao" parent="dao"
		class="com.baobaotao.dao.jdbc.PostJdbcDao">
		<property name="lobHandler" 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;
				    }
			    });
	}

注：代码均来自<<精通spring2.x企业应用开发详解>>