Question

I have a CLOB field in a derby table. After a simple SQL SELECT I try to convert CLOBs into Strings.

• DBConnection autocommit is off
• DBConnection is open
• This code fails although I never call the free() method:

dbCon.connect;

  dbSourceDataList = dbCon.executeQuery(getSql());

   // convert all CLOBs to Strings      
  for (int i = 0; i < dbSourceDataList.size(); i++) {
    Object[] arr = dbSourceDataList.get(i);
    for (int j = 0; j < arr.length; j++) {
      if (arr[j] instanceof Clob) {
        Clob clob = (Clob) arr[j]; 
        arr[j] = clob.getSubString(1, (int) clob.length());
      }
    }
  }

No java.sql.Clob/java.sql.Blob methods can be called after free() method has been called or a blob/clob transactions has been commited or rollbacked.

Answer 1

Convert CLOBs to Strings using directly the getClob() method of the java.sql.ResultSet:

if (rs.getObject(i) instanceof java.sql.Clob) {
   // Convert CLOBs to Strings
   Clob clob = rs.getClob(i);
   stringValue = clob.getSubString(1, (int) clob.length());
}