JDBC读取CLOB

    CLOB用于存储大量的字符数据，读取CLOB的JDBC代码如下所示

import java.sql.*;
import java.io.*;

public class ReadClob {
	public static void main(String[] args) {
		PreparedStatement pstmt = null;
		ResultSet rset = null;
		BufferedReader reader = null;
		Connection conn = null;
		String driver = "oracle.jdbc.driver.OracleDriver";
		String strUrl = "jdbc:oracle:thin@127.0.0.1:1521:ORCL";
		try {
			Class.forName(driver);
			conn = DriverManager.getConnection(strUrl, "scott", "tiger");
			pstmt = conn
					.prepareStatement("select v_clob form ord where ORD_id =?");
			pstmt.setInt(1, 1);
			rset = pstmt.executeQuery();
			while (rset.next()) {
				Clob clob = rset.getClob(1);// java.sql.Clob类型
				reader = new BufferedReader(new InputStreamReader(clob
						.getAsciiStream()));
				String line = null;
				while ((line = reader.readLine()) != null) {
					System.out.println(line);
				}
			}
		} catch (ClassNotFoundException e) {
			e.printStackTrace();
		} catch (SQLException e) {
			e.printStackTrace();
		} catch (IOException e) {
			e.printStackTrace();
		}
	}
}

    程序代码从结果集中获取CLOB字段，再将其转化为IO流进行读取。那么，JDBC将大量自读数据写入CLOB字段的操作需要首先用“for update”字句查找CLOB字段，然后从结果集中获取CLOB字段并转化为oracle.sql.CLOB类型进行写入操作。

 	//写入操作
			String stmtString = "select v_clob form ord  where ord_id =? for update";
			pstmt = conn.prepareStatement(stmtString);
			pstmt.setInt(1, 2);
			rset = pstmt.executeQuery();
			while(rset.next()){
				//造型为oracle.sql.CLOB
				CLOB clob = (CLOB)rset.getClob(1);
				String newClobDate = new String("NEW CLOOB DATE");
				Writer writer = clob.getCharacterOutputStream();
				//OutStream writer = clob.getAsciiOutputStream();
				writer.write(newClobDate);
			}