code: public void truncate(final long len) throws SQLException {
          this.blobContent = Utils.copyWithLength(this.blobContent, (int) len);
          this.actualSize = (int) len;
      }
docs: Truncates the <code>BLOB</code> value that this <code>Blob</code> object represents to be <code>len</code> bytes
  in length.
  <p/>
  <b>Note:</b> If the value specified for <code>pos</code> is greater then the length+1 of the <code>BLOB</code>
  value then the behavior is undefined. Some JDBC drivers may throw a <code>SQLException</code> while other drivers
  may support this operation.
  
  @param len the length, in bytes, to which the <code>BLOB</code> value that this <code>Blob</code> object
  represents should be truncated
  @throws java.sql.SQLException if there is an error accessing the <code>BLOB</code> value or if len is less than
  0