How to create a ContainerHandle from a given LogRecord

[Miguel Matos]

Hello!

to an arbitrary stream to do some post-processing latter on.

I will try to explain better with a small code snippet:

//<java>
void parseLog(){
       StreamLogScan redoScan;
           try {
           LogInstant a = ...
          LogInstant b = ...
          //go from LogInstant 'a' to 'b'
               redoScan = (StreamLogScan) logFactory.openForwardsScan(a,b);
               LogRecord record;

               }
               return ;
}





           ArrayInputStream logIn = new ArrayInputStream();
           LogRecord logRecord = new LogRecord();
           logRecord.setValue(transactionId, operation);

           //ERROR here when logrecord group is Loggable.RAWSTORE

           //do something with the data ...
   }
//</java>


Thanks for you time.

Miguel

I've been studying derby's logging system. I want to parse the log files on disk extract its LogRecord(s) and write those I am using LogFactory.openForwardsScan() to traverse the log between the desired LogInstant(s). This works well except for the log records on the group Loggable.RAWSTORE (and ContainerOperation instances in particular). The problem is that when I try to invoke writeExternal on LogRecords of that group I get an NPE because some fields of the Loggable are null (due to being transient and hence not saved to disk). while ((record = redoScan.getNextRecord(logIn, null, 0)) != null) { writeLog(record.getTransactionId(),record.getLoggable(),redoScan.getInstant()); //write the LogRecord to a stream ... void writeLog(TransactionId transactionId,Loggable operation, long instant) throws IOException, StandardException { DynamicByteArrayOutputStream logOutputBuffer = new DynamicByteArrayOutputStream(1024); FormatIdOutputStream logicalOut = new FormatIdOutputStream(logOutputBuffer); logicalOut.writeObject(logRecord); byte[] data = logOutputBuffer.getByteArray(); Let's focus on the particular case that the LogRecord's Loggable is a ContainerOperation. The line "logicalOut.writeObject(logRecord)" eventually invokes ContainerOperation.writeExternal() and because that object is not correctly instantiated it throws an NPE when trying to access the RawContainerHandle containerHdl. I think that I must create a ContainerOperation object with an adequate RawContainerHandle but I am unable to do it from the information contained _only_ in the LogRecord. I have been playing around with RawStoreFactory and TransactionFactory but without any success. What am I missing ? Is my reasoning correct ? And if so how can I solve this problem?

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