解析jdbc处理oracle的clob字段的详解

public class ClobUtil {

 /**
  * 
  * @param insertSQL 插入sql语句 有clob字段时，值必须设置成empty_clob()函数 例:insert into ba valus(1,empty_clob())
  * @param updateSQL 带有修改的查询语句,并应增加条件判断.例：select * from BA where ba_id = '"+ba.getBA_id()+"' for update
  * @param con 数据库链接
  * @param bigString 要插入的clob值
  * @param updateColumn 要插入的表字段名
  * @return
  * @throws SQLException
  */
 public static Boolean clobInsert(String insertSQL,String updateSQL,Connection con,String bigString,String updateColumn ) throws SQLException{ 
      // 结果集
      ResultSet rs = null;
      // 插入数据库的sql
      String query = insertSQL;
      // 设置不自动提交
      con.setAutoCommit(false);
      // 定义预处理
      java.sql.PreparedStatement pstmt = con.prepareStatement( query);
      // 执行插入语句
      pstmt.executeUpdate();
      //清空
      pstmt = null;
      // 执行更改
      query = updateSQL; 
         //显示执行带有修改方式的select
      pstmt = con.prepareStatement(query); 
      rs = pstmt.executeQuery(); 
      // 采用流的方式处理结果集
      if(rs.next())  
      { 
        // 得到指定的clob字段 
        oracle.sql.CLOB singnaturedateClob = (oracle.sql.CLOB)rs.getClob(updateColumn);  
        // 把clob字段放到输出流当中
        BufferedOutputStream out = new BufferedOutputStream(singnaturedateClob.getAsciiOutputStream());
        // 判断传入的数据是否为空
        if(bigString!=null){
        try{
         // 把要保存的数据转换成输入流
         InputStream  is = (InputStream)(new   ByteArrayInputStream(bigString.getBytes()));  
      copyStream( is, out );
      out.close();
    } catch (IOException e) {
     // TODO Auto-generated catch block
     e.printStackTrace();
    }
        }
      } 
      rs.close();
      con.commit();

   return true;
 }

 /**
  * 将输入流写入到输出流当中
  * @param is 输入流
  * @param os 输出流
  * @throws IOException
  */ 
 public static void copyStream( InputStream is, OutputStream os )
 throws IOException
 {
  byte[] data             = new byte[4096];
  int readed              = is.read(data);
  while (readed != -1)
  {
   os.write(data,0,readed);
   readed = is.read(data);
  }
 }

 /**
  * 通过Clob对象返回字符串
  * @param c
  * @return
  */
 public static String getClobString(Clob c) {  
        try { 

            Reader reader=c.getCharacterStream();
            if (reader == null) { 
                return null; 
            } 
            StringBuffer sb = new StringBuffer(); 
            char[] charbuf = new char[4096]; 
            for (int i = reader.read(charbuf); i > 0; i = reader.read(charbuf)) { 
                sb.append(charbuf, 0, i); 
            } 
            return sb.toString(); 
        } catch (Exception e) { 
            return ""; 
        } 
    }

}