oracle中CLOB类型的存取 博客分类： 数据库 cloboracleEMPTY_CLOB()for update

当oracle数据库中某个字段的长度不较大的时候，用clob类型。
在向带有Lob类型的字段加入数据时,使用EMPTY_CLOB()初始化CLOB字段,然后再使用输出流向字段中写数据(这些数据往往都是字节流量相对较大的). 如果是直接在oracle客户端向表中写数据,就不用这么麻烦了.

好了,具体的操作:

CREATE TABLE article(  
    subject VARCHAR2(50 char),  
    content CLOB ,  
    tstamp TIMESTAMP DEFAULT SYSDATE   
);  
 
--使用EMPTY_CLOB()来初始化CLOB字段  
String strSql = "INSERT INTO article(subject,content) VALUES('文章标题:Empty_clob()的使用方法',EMPTY_CLOB())";  
Connection conn = db.getConnection();  
conn.setAutoCommit(false);  
 
PreparedStatement ptmt = conn.prepareStatement(sqlBuffer.toString());  
ptmt.executeUpdate();  
strSql = "select content from article where subject = "+subject+" for update ";  
ResultSet rs = ptmt.executeQuery(strSql);  
if (rs.next()) {  
        /**//* 取出此CLOB对象 */ 
        oracle.sql.CLOB clob = null;  
        clob = (oracle.sql.CLOB) rs.getClob("content");  
        /**//* 向CLOB对象中写入数据 */ 
        BufferedWriter out = new BufferedWriter(clob.getCharacterOutputStream());  
        out.write(content);  
        out.close();  
        out = null;  
        conn.commit();  
} 
CREATE TABLE article(
    subject VARCHAR2(50 char),
    content CLOB ,
    tstamp TIMESTAMP DEFAULT SYSDATE
);

--使用EMPTY_CLOB()来初始化CLOB字段
String strSql = "INSERT INTO article(subject,content) VALUES('文章标题:Empty_clob()的使用方法',EMPTY_CLOB())";
Connection conn = db.getConnection();
conn.setAutoCommit(false);

PreparedStatement ptmt = conn.prepareStatement(sqlBuffer.toString());
ptmt.executeUpdate();
strSql = "select content from article where subject = "+subject+" for update ";
ResultSet rs = ptmt.executeQuery(strSql);
if (rs.next()) {
        /**//* 取出此CLOB对象 */
        oracle.sql.CLOB clob = null;
        clob = (oracle.sql.CLOB) rs.getClob("content");
        /**//* 向CLOB对象中写入数据 */
        BufferedWriter out = new BufferedWriter(clob.getCharacterOutputStream());
        out.write(content);
        out.close();
        out = null;
        conn.commit();
}