How to convert Blob to String and String to Blob i

问题:

I'm trying to get string from BLOB datatype by using

Blob blob = rs.getBlob(cloumnName[i]);
byte[] bdata = blob.getBytes(1, (int) blob.length());
String s = new String(bdata);

It is working fine but when I'm going to convert String to Blob and trying to insert into database then nothing inserting into database. I've used below code for converting String to Blob:

String value = (s);
byte[] buff = value.getBytes();
Blob blob = new SerialBlob(buff);

Can anyone help me about to converting of Blob to String and String to Blob in Java?

回答1:

try this (a2 is BLOB col)

PreparedStatement ps1 = conn.prepareStatement("update t1 set a2=? where id=1");
Blob blob = conn.createBlob();
blob.setBytes(1, str.getBytes());
ps1.setBlob(1, blob);
ps1.executeUpdate();

it may work even without BLOB, driver will transform types automatically:

   ps1.setBytes(1, str.getBytes);
   ps1.setString(1, str);

Besides if you work with text CLOB seems to be a more natural col type

回答2:

Use this to convert String to Blob. Where connection is the connection to db object.

    String strContent = s;
    byte[] byteConent = strContent.getBytes();
    Blob blob = connection.createBlob();//Where connection is the connection to db object. 
    blob.setBytes(1, byteContent);

回答3:

How are you setting blob to DB? You should do:

 //imagine u have a a prepared statement like:
 PreparedStatement ps = conn.prepareStatement("INSERT INTO table VALUES (?)");
 String blobString= "This is the string u want to convert to Blob";
oracle.sql.BLOB myBlob = oracle.sql.BLOB.createTemporary(conn, false,oracle.sql.BLOB.DURATION_SESSION);
 byte[] buff = blobString.getBytes();
 myBlob.putBytes(1,buff);
 ps.setBlob(1, myBlob);
 ps.executeUpdate();