在oracle中更新BLOB字段出现问题.

[ls176]

如果数据表中有数据的话,并且数据的长度大于更新的数据的长度,那么更新后,数据长度还是为原有数据的长度.
我是使用下面的语句更新的,要怎么改才能清空原有的数据?
BLOB b = ( BLOB )dr.getItem( 0 );
OutputStream outs = b.getBinaryOutputStream();
ByteArrayInputStream bais = new ByteArrayInputStream( com.system.util.util.BASE64Decoder( dm.getParams().get( paramName ).getValue() ) );
byte[] buf = new byte[ b.getChunkSize() ];
int len;
{
outs.write( buf , 0 , len );
}
outs.flush();
outs.close();
bais.close();

[ls176]

不好意思,int len;下有个while
BLOB b = ( BLOB )dr.getItem( 0 );
OutputStream outs = b.getBinaryOutputStream();
ByteArrayInputStream bais = new ByteArrayInputStream( com.system.util.util.BASE64Decoder( dm.getParams().get( paramName ).getValue() ) );
byte[] buf = new byte[ b.getChunkSize() ];
int len;
while( ( len = bais.read( buf ) ) != -1 )
{
outs.write( buf , 0 , len );
}
outs.flush();
outs.close();
bais.close();

[hbzyduwu]

up

[ls176]

顶

[bafver]

ftherwktg

[ls176]

再顶

[wayto]

我也想知道啊，也顶一下！

[stonegump]

有问题吧？len都没有初始化：
int len;
{
outs.write( buf , 0 , len );
}

[ls176]

顶一顶

[wayto]

顶到望月湖去吃鱼

[ls176]

没人知道吗?

[ls176]

晕啊,两天了,还没有人回答我呀.

[bafver]

我用过Clob大字段，不过也只是读里面的数据，没写过

[rambostar]

替换CLOB对象（将原CLOB对象清除，换成一个全新的CLOB对象），详细信息请参考：

http://www.s8s8.net/ipb/lofiversion/index.php/t20319.html

[huanlw]

我在写入BLOB字段是也遇到了同样的问题，更主要的是，在存入的数据大于2K时，无法正常读出

[追求自由]

这种情况我碰到过，如果文件太长，哪么就用循环来处理，一次写一定长度的字节

[liuchuntao]

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

public class WriteBlob {

public static void main(String[] args) {

try {
DriverManager.registerDriver(new oracle.jdbc.driver.OracleDriver());
Connection conn = DriverManager.getConnection(
"jdbc:oracle:thin:@192.168.0.204:1521:main", "lct", "lct");
conn.setAutoCommit(false);
BLOB blob = null;
//清空
PreparedStatement pstmt = conn.prepareStatement(
"update javatest set content=empty_blob() where name=?");
pstmt.setString(1, "liuchuntao");
pstmt.executeUpdate();

pstmt = conn.prepareStatement(
"select content from javatest where name= ? for update");
pstmt.setString(1, "liuchuntao");
ResultSet rset = pstmt.executeQuery();
if (rset.next()) {
blob = (BLOB) rset.getBlob(1);

}
String fileName = "e:\\pic\\1.jpg";
File f = new File(fileName);
FileInputStream fin = new FileInputStream(f);
System.out.println("file size = " + fin.available());

pstmt = conn.prepareStatement(
"update javatest set content=? where name=?");

OutputStream out = blob.getBinaryOutputStream();

int count = -1, total = 0;
byte[] data = new byte[ (int) fin.available()];
fin.read(data);
out.write(data);

fin.close();
out.close();

pstmt.setBlob(1, blob);
pstmt.setString(2, "fankai");

pstmt.executeUpdate();
pstmt.close();

conn.commit();
rset.close();
conn.close();
}
catch (SQLException e) {
System.err.println(e.getMessage());
System.out.println(e.getErrorCode());
e.printStackTrace();
}
catch (IOException e) {
System.err.println(e.getMessage());
}
}

}