Module org.firebirdsql.jaybird
Package org.firebirdsql.gds.ng

Interface FbBlob

All Superinterfaces:
AutoCloseable, ExceptionListenable
All Known Subinterfaces:
FbWireBlob
All Known Implementing Classes:
AbstractFbBlob, AbstractFbWireBlob, AbstractFbWireInputBlob, AbstractFbWireOutputBlob, V10InputBlob, V10OutputBlob, V11InputBlob, V11OutputBlob
public interface FbBlob extends ExceptionListenable, AutoCloseable
Interface for blob operations.

All methods defined in this interface are required to notify all SQLException thrown from the methods defined in this interface.

Implementations may defer the open or create the blob (meaning it's only open client-side), so the actual open or create is done when server-side access to the blob is needed. As a result getBlobId() and getHandle() may report invalid or unexpected values, see those methods for details.

Since:
3.0
Author:
Mark Rotteveel

  • Field Details

  • Method Details

    • getBlobId

      long getBlobId()
      Returns the blob id.

      For output blobs, this will return NO_BLOB_ID (0L) if the blob wasn't opened yet, or if the blob is deferred opened (client-side only). The value NO_BLOB_ID is technically invalid, but Firebird will handle it as an empty blob (both for input and output).

      Returns:
      The Firebird blob id

    • getHandle

      int getHandle()
      Returns the blob handle identifier.

      If the blob wasn't opened yet, this will return 0. If the blob was deferred opened (client-side only), this will return an invalid blob handle value (e.g. 0xFFFF, though this value is potentially protocol/implementation specific).

      Returns:
      The Firebird blob handle identifier

    • getDatabase

      FbDatabase getDatabase()
      Returns:
      The database connection that created this blob

    • open

      void open() throws SQLException
      Opens an existing input blob, or creates an output blob.
      Throws:
      SQLException - If the blob is already open, this is a (closed) output blob and it already has a blobId, the transaction is not active, or a database connection error occurred

    • isOpen

      boolean isOpen()
      Returns:
      true if this blob is currently open.

    • isEof

      boolean isEof()
      Returns:
      true if this blob has reached the end or has been closed, always true for an open output blob.

    • close

      void close() throws SQLException
      Closes the blob.

      Closing an already closed blob is a no-op.

      Specified by:
      close in interface AutoCloseable
      Throws:
      SQLException - If the transaction is not active, or a database connection error occurred

    • cancel

      void cancel() throws SQLException
      Cancels an output blob (which means its contents will be thrown away).

      Calling cancel on an input blob will close it. Contrary to close(), calling cancel on an already closed (or cancelled) blob will throw an SQLException.

      Throws:
      SQLException - If the blob has already been closed, the transaction is not active, or a database connection error occurred.

    • isOutput

      boolean isOutput()
      Returns:
      true if this is an output blob (write only), false if this is an input blob (read only)

    • getSegment

      byte[] getSegment(int sizeRequested) throws SQLException
      Gets a segment of blob data.

      When sizeRequested exceeds getMaximumSegmentSize() it is silently reduced to the maximum segment size.

      Parameters:
      sizeRequested - Requested segment size (> 0).
      Returns:
      Retrieved segment (size may be less than requested)
      Throws:
      SQLException - If this is an output blob, the blob is closed, the transaction is not active, or a database connection error occurred.
      See Also:

    • get

      int get(byte[] b, int off, int len) throws SQLException
      Reads content from the blob into b starting at off for len bytes.

      Implementations must read the requested number of bytes (len), unless end-of-blob is reached before the requested number of bytes were read. The return value of this method is the actual number of bytes read.

      If the implementation cannot perform reads without additional allocation, it should use at most DatabaseConnectionProperties.getBlobBufferSize() as an internal buffer. If the implementation can perform reads without additional allocation, it is recommended it performs reads using (at most) getMaximumSegmentSize().

      Contrary to similar methods like InputStream.read(byte[], int, int), this method returns 0 when no bytes were read if end-of-blob is reached without reading any bytes, not -1.

      Given this method attempts to fulfill the entire request for len bytes, it may not always be efficient. For example, requests near multiples of the maximum segment size (or blob buffer size) may result in a final request for just a few bytes. This is not a problem if the entire blob is requested at once, but for intermediate buffering it might be better not to do that final request, and instead work with a smaller number of bytes than requested. For those cases, use get(byte[], int, int, float).

      Parameters:
      b - target byte array
      off - offset to start
      len - number of bytes
      Returns:
      actual number of bytes read; this will only be less than len when end-of-blob was reached
      Throws:
      SQLException - for database access errors, if off < 0, len < 0, or if off + len > b.length
      Since:
      6

    • get

      int get(byte[] b, int off, int len, float minFillFactor) throws SQLException
      Variant of get(byte[], int, int) to exert some control over the number of requests performed.

      This method will request segments until at least (int) (minFillFactor * len) bytes have been retrieved, or end-of-blob is reached. This method is intended as an alternative to get(byte[], int, int) where avoiding the potential inefficiencies of that method are preferred over getting all the requested len bytes.

      If the implementation cannot perform reads without additional allocation, it should use at most DatabaseConnectionProperties.getBlobBufferSize() as an internal buffer. If the implementation can perform reads without additional allocation, it is recommended it performs reads using (at most) getMaximumSegmentSize().

      Contrary to similar methods like InputStream.read(byte[], int, int), this method returns 0 when no bytes were read if end-of-blob is reached without reading any bytes, not -1.

      Parameters:
      b - target byte array
      off - offset to start
      len - number of bytes
      minFillFactor - minimum fill factor (0 < minFillFactor <= 1)
      Returns:
      actual number of bytes read, this method returns at least (int) (minFillFactor * len) bytes, unless end-of-blob is reached
      Throws:
      SQLException - for database access errors, if off < 0, len < 0, or if off + len > b.length, minFillFactor <= 0, or minFillFactor > 1 or minFillFactor is NaN
      Since:
      6

    • putSegment

      void putSegment(byte[] segment) throws SQLException
      Writes a segment of blob data.

      Implementations must handle segment lengths exceeding getMaximumSegmentSize() by batching. This method should either call put(segment, 0, segment.length), or produce the same effects as that call.

      Passing a section that is length 0 will throw an SQLException.

      Parameters:
      segment - segment to write
      Throws:
      SQLException - if this is an input blob, the blob is closed, the transaction is not active, the segment is length 0, or a database connection error occurred
      See Also:

    • put

      void put(byte[] b, int off, int len) throws SQLException
      Writes content of b starting at off for length bytes to the blob.

      Implementations must write all bytes to the blob, using multiple round-trips if necessary.

      If the implementation cannot perform writes without additional allocation, it should use at most DatabaseConnectionProperties.getBlobBufferSize() as an internal buffer. If the implementation can perform writes without additional allocation, it is recommended it performs reads using (at most) getMaximumSegmentSize().

      Parameters:
      b - source byte array
      off - offset to start
      len - number of bytes
      Throws:
      SQLException - for database access errors, if off < 0, len < 0, or if off + len > b.length
      Since:
      6

    • seek

      void seek(int offset, FbBlob.SeekMode seekMode) throws SQLException
      Performs a seek on a blob with the specified seekMode and offset.

      Firebird only supports seek on stream blobs.

      Parameters:
      offset - Offset of the seek, effect depends on value of seekMode
      seekMode - Value of FbBlob.SeekMode
      Throws:
      SQLException - If the blob is closed, the transaction is not active, or a database error occurred.

    • getMaximumSegmentSize

      int getMaximumSegmentSize()
      The maximum segment size allowed by the protocol for getSegment(int) and putSegment(byte[]).

      This value is not the segment size (optionally) defined for the column.

      Returns:
      The maximum segment size allowed for get or put.

    • getBlobInfo

      <T> T getBlobInfo(byte[] requestItems, int bufferLength, InfoProcessor<T> infoProcessor) throws SQLException
      Request blob info.
      Parameters:
      requestItems - Array of info items to request
      bufferLength - Response buffer length to use
      infoProcessor - Implementation of InfoProcessor to transform the info response
      Returns:
      Transformed info response of type T
      Throws:
      SQLException - For errors retrieving or transforming the response.

    • length

      long length() throws SQLException
      Requests the blob length from the server.
      Returns:
      Length of the blob.
      Throws:
      SQLException - For Errors retrieving the length, or if the blob is not associated with a blob id, or the database is not attached.

    • getBlobInfo

      byte[] getBlobInfo(byte[] requestItems, int bufferLength) throws SQLException
      Request blob info.
      Parameters:
      requestItems - Array of info items to request
      bufferLength - Response buffer length to use
      Returns:
      Response buffer
      Throws:
      SQLException