db4o 2.0

com.db4o.types
Interface Blob

All Superinterfaces:
Db4oType

public interface Blob
extends Db4oType

the db4o Blob type to store blobs independant of the main database file and to perform asynchronous upload and download operations.

Usage:
- Define Blob fields on your user classes.
- As soon as an object of your class is stored, db4o automatically takes care that the Blob field is set.
- Call readFrom to read a blob file into the db4o system.
- Call writeTo to write a blob file from within the db4o system.
- getStatus may help you to determine, whether data has been previously stored. It may also help you to track the completion of the current process.

db4o client/server carries out all blob operations in a seperate thread on a specially dedicated socket. One socket is used for all blob operations and operations are queued. Your application may continue to access db4o while a blob is transferred in the background.


Field Summary
static double STATUS_AVAILABLE
          available data was previously stored to the Blob field.
static double STATUS_COMPLETED
          the last operation on this field was completed successfully
static double STATUS_ERROR
          the last operation on this field failed
static double STATUS_QUEUED
          an operation was triggered and is waiting for it's turn in the Blob queue.
static double STATUS_UNUSED
          no data was ever stored to the Blob field.
 
Method Summary
 double getStatus()
          returns the status after the last read- or write-operation.
 void readFrom(java.io.File file)
          reads a file into the db4o system and stores it as a blob.
 void writeTo(java.io.File file)
          writes stored blob data to a file.
 

Field Detail

STATUS_UNUSED

public static final double STATUS_UNUSED
no data was ever stored to the Blob field.

STATUS_AVAILABLE

public static final double STATUS_AVAILABLE
available data was previously stored to the Blob field.

STATUS_QUEUED

public static final double STATUS_QUEUED
an operation was triggered and is waiting for it's turn in the Blob queue.

STATUS_COMPLETED

public static final double STATUS_COMPLETED
the last operation on this field was completed successfully

STATUS_ERROR

public static final double STATUS_ERROR
the last operation on this field failed
Method Detail

getStatus

public double getStatus()
returns the status after the last read- or write-operation.

The status may be any of the five STATUS constants defined in this interface or a double between 0 and 1 that signifies the completion of the currently running operation.

Returns:
status - the current status
See Also:
STATUS constants

writeTo

public void writeTo(java.io.File file)
             throws java.io.IOException
writes stored blob data to a file.

In Client/Server mode db4o will open an additional socket and process writing data in an additional thread.

Parameters:
File - the file the blob is to be written to.
Throws:
java.io.IOException - in case of errors and in case no blob data was stored

readFrom

public void readFrom(java.io.File file)
              throws java.io.IOException
reads a file into the db4o system and stores it as a blob.

In Client/Server mode db4o will open an additional socket and process writing data in an additional thread.

Parameters:
File - the file the blob is to be read from.
Throws:
java.io.IOException - in case of errors

db4o 2.0