JAVA读取、写入、更新CLOB字段_JAVA_编程开发_程序员俱乐部

class="java">
	/*
	--建表语句如下：
	create table t_clob(
			id varchar2(32) primary key,
			clobfield CLOB
			);
	 */

	/**
	 * 读取CLOB字段的代码示例
	 * 
	 * 作者：wallimn<br/>
	 * 时间：2015-1-16<br/>
	 * 联系：wallimn@sohu.com<br/>
	 */
	public void readClob() {
		Connection conn = DbManager.getInstance().getConnection();
		try {
			PreparedStatement stat = conn
					.prepareStatement("select clobfield from t_clob where id='1'");
			ResultSet rs = stat.executeQuery();
			if (rs.next()) {
				oracle.sql.CLOB clob = (oracle.sql.CLOB) rs
						.getClob("clobfield");
				String value = clob.getSubString(1, (int) clob.length());
				System.out.println("CLOB字段的值：" + value);
			}
			conn.commit();
		} catch (SQLException e) {
			e.printStackTrace();
		}

		DbManager.getInstance().closeConnection(conn);
	}

	/**
	 * 写入、更新CLOB字段的代码示例
	 * 
	 * 作者：wallimn<br/>
	 * 时间：2015-1-16<br/>
	 * 联系：wallimn@sohu.com<br/>
	 */
	public void writeClob() {
		Connection conn = DbManager.getInstance().getConnection();
		try {
			conn.setAutoCommit(false);
			// 1.这种方法写入CLOB字段可以。
			PreparedStatement stat = conn
					.prepareStatement("insert into t_clob (id,clobfield) values(sys_guid(),?)");
			String clobContent = "This is clob string";
			StringReader reader = new StringReader(clobContent);
			stat.setCharacterStream(1, reader, clobContent.length());
			stat.executeUpdate();

			// 2.使用类似的方法进行更新CLOB字段，则不能成功　
			// stat.close();
			// stat =null;
			// stat =
			// conn.prepareStatement("update t_clob set clobfield=? where id=1");
			// stat.setCharacterStream(1, reader, clobContent.length());
			// stat.executeUpdate();

			// 3.需要使用for update方法来进行更新，
			// 但是，特别需要注意，如果原来CLOB字段有值，需要使用empty_clob()将其清空。
			stat = conn
					.prepareStatement("select clobfield from t_clob where id='1' for update");
			ResultSet rs = stat.executeQuery();
			if (rs.next()) {
				oracle.sql.CLOB clob = (oracle.sql.CLOB) rs
						.getClob("clobfield");
				Writer outStream = clob.getCharacterOutputStream();
				char[] c = clobContent.toCharArray();
				outStream.write(c, 0, c.length);
				outStream.flush();
				outStream.close();
			}
			conn.commit();
		} catch (SQLException | IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}

		DbManager.getInstance().closeConnection(conn);

	}