com.db4o.types

Interface Blob

All Superinterfaces:

Db4oType

All Known Implementing Classes:

BlobImpl

public interface Blob
extends Db4oType

the db4o Blob type to store blobs independent of the main database file and allows 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 separate 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.

Method Summary

Methods

Modifier and Type	Method and Description
void	deleteFile() Deletes the current file stored in this BLOB.
java.lang.String	getFileName() returns the name of the file the blob was stored to.
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	readLocal(java.io.File file) reads a file into the db4o system and stores it as a blob.
void	writeLocal(java.io.File file) writes stored blob data to a file.
void	writeTo(java.io.File file) writes stored blob data to a file.

Method Detail

getFileName

java.lang.String getFileName()

returns the name of the file the blob was stored to.

The method may return null, if the file was never stored.

Returns:

String the name of the file.

getStatus

double getStatus()

returns the status after the last read- or write-operation.

The status value returned may be any of the following:
Status.UNUSED no data was ever stored to the Blob field.
Status.AVAILABLE available data was previously stored to the Blob field.
Status.QUEUED an operation was triggered and is waiting for it's turn in the Blob queue.
Status.COMPLETED the last operation on this field was completed successfully.
Status.PROCESSING for internal use only.
Status.ERROR the last operation failed.
or a double between 0 and 1 that signifies the current completion percentage of the currently running operation.

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:

constants

readFrom

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

readLocal

void readLocal(java.io.File file)
               throws java.io.IOException

reads a file into the db4o system and stores it as a blob.

db4o will use the local file system in Client/Server mode also.

Parameters:

file - the file the blob is to be read from.

Throws:

java.io.IOException - in case of errors

writeLocal

void writeLocal(java.io.File file)
                throws java.io.IOException

writes stored blob data to a file.

db4o will use the local file system in Client/Server mode also.

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

writeTo

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

deleteFile

void deleteFile()
                throws java.io.IOException

Deletes the current file stored in this BLOB.

Throws:

java.io.IOException - in case of errors and in case no data was stored