Package org.apache.derby.impl.jdbc

Class EmbedBlob

  • All Implemented Interfaces:
    java.sql.Blob, EngineLOB
    final class EmbedBlob
extends ConnectionChild
implements java.sql.Blob, EngineLOB
    Implements java.sql.Blob (see the JDBC 2.0 spec). A blob sits on top of a BINARY, VARBINARY or LONG VARBINARY column. If its data is small (less than 1 page) it is a byte array taken from the SQLBit class. If it is large (more than 1 page) it is a long column in the database. The long column is accessed as a stream, and is implemented in store as an OverflowInputStream. The Resetable interface allows sending messages to that stream to initialize itself (reopen its container and lock the corresponding row) and to reset itself to the beginning. NOTE: In the case that the data is large, it is represented as a stream. This stream is returned to the user in the getBinaryStream() method. This means that we have limited control over the state of the stream, since the user can read bytes from it at any time. Thus all methods here reset the stream to the beginning before doing any work. CAVEAT: The methods may not behave correctly if a user sets up multiple threads and sucks data from the stream (returned from getBinaryStream()) at the same time as calling the Blob methods.

    Supports

    • JSR169 - no subsetting for java.sql.Blob
    • JDBC 2.0
    • JDBC 3.0 - no new dependencies on new JDBC 3.0 or JDK 1.4 classes, new update methods can safely be added into implementation.

    • Method Summary

      All Methods Instance Methods Concrete Methods 
      Modifier and Type Method Description
      private boolean checkMatch​(byte[] pattern, long pos)
      Checks if the pattern (starting from the second byte) appears inside the Blob content.
      private boolean checkMatch​(java.sql.Blob pattern, long pos)
      Checks if the pattern (starting from the second byte) appears inside the Blob content.
      private void checkValidity()  
      protected void finalize()  
      void free()
      This method frees the Blob object and releases the resources that it holds.
      java.io.InputStream getBinaryStream()
      Retrieves the BLOB designated by this Blob instance as a stream.
      java.io.InputStream getBinaryStream​(long pos, long length)
      Returns an InputStream object that contains a partial Blob value, starting with the byte specified by pos, which is length bytes in length.
      byte[] getBytes​(long startPos, int length)
      Returns as an array of bytes part or all of the BLOB value that this Blob object designates.
      int getLocator()
      Return locator for this lob.
      private java.sql.SQLException handleMyExceptions​(java.lang.Throwable t)  
      private int handleStreamValue​(java.io.InputStream dvdStream, EmbedConnection con)
      Constructs a Blob object on top of a stream.
      (package private) boolean isMaterialized()
      Returns if blob data is stored locally (using LOBStreamControl).
      long length()
      Returns the number of bytes in the BLOB value designated by this Blob object.
      long position​(byte[] pattern, long start)
      Determines the byte position at which the specified byte pattern begins within the BLOB value that this Blob object represents.
      long position​(java.sql.Blob pattern, long start)
      Determines the byte position in the BLOB value designated by this Blob object at which pattern begins.
      private int read​(long pos)
      Reads one byte from the Blob at the specified position.
      java.io.OutputStream setBinaryStream​(long pos)
      JDBC 3.0 Retrieves a stream that can be used to write to the BLOB value that this Blob object represents.
      private long setBlobPosition​(long logicalPos)
      Sets the position of the Blob to logicalPos, where position 0 is the beginning of the Blob content.
      int setBytes​(long pos, byte[] bytes)
      Writes the given array of bytes to the BLOB value that this Blob object represents, starting at position pos, and returns the number of bytes written.
      int setBytes​(long pos, byte[] bytes, int offset, int len)
      Writes all or part of the given array of byte array to the BLOB value that this Blob object represents and returns the number of bytes written.
      void truncate​(long len)
      JDBC 3.0 Truncates the BLOB value that this Blob object represents to be len bytes in length.

      • Methods inherited from class java.lang.Object

        clone, equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

    • Field Detail

      • materialized

        private boolean materialized
        Tells whether the Blob has been materialized or not.

        Materialization happens when the Blob is updated by the user. A materialized Blob is represented either in memory or in a temporary file on disk, depending on size.

        A Blob that has not been materialized is represented by a stream into the Derby store, and is read-only.

      • locator

        private int locator
        Locator value for this Blob, used as a handle by the client driver to map operations to the correct Blob on the server side.
        See Also:
        getLocator()

      • streamLength

        private long streamLength
        Length of the stream representing the Blob.

        Set to -1 when the stream has been materialized or the length of the stream is not currently known.

      • streamPositionOffset

        private final int streamPositionOffset
        Position offset for the stream representing the Blob, if any.

        This offset accounts for the bytes encoding the stream length at the head of the stream. Data byte pos is at pos + streamPositionOffset in the underlying stream. Set to Integer.MIN_VALUE if the Blob isn't represented by a store stream.

      • isValid

        private boolean isValid

    • Constructor Detail

      • EmbedBlob

        EmbedBlob​(byte[] blobBytes,
          EmbedConnection con)
   throws java.sql.SQLException
        This constructor is used to create a empty Blob object. It is used by the Connection interface method createBlob().
        Parameters:
        blobBytes - A byte array containing the data to be stores in the Blob.
        con - The EmbedConnection object associated with this Blob object.
        Throws:
        java.sql.SQLException

    • Method Detail

      • handleStreamValue

        private int handleStreamValue​(java.io.InputStream dvdStream,
                              EmbedConnection con)
                       throws StandardException,
                              java.sql.SQLException
        Constructs a Blob object on top of a stream.
        Parameters:
        dvdStream - the source stream
        con - the connection owning the Blob
        Returns:
        The offset into the stream where the user data begins (used if resetting the stream).
        Throws:
        StandardException - if accessing the stream fails, or if writing data to temporary storage fails
        java.sql.SQLException

      • setBlobPosition

        private long setBlobPosition​(long logicalPos)
                      throws StandardException,
                             java.io.IOException
        Sets the position of the Blob to logicalPos, where position 0 is the beginning of the Blob content.

        The position is only guaranteed to be valid from the time this method is invoked until the synchronization monitor is released, or until the next invokation of this method.

        The position is logical in the sense that it specifies the requested position in the Blob content. This position might be at a different position in the underlying representation, for instance the Derby store stream prepends the Blob content with a length field.

        Parameters:
        logicalPos - requested Blob position, 0-based
        Returns:
        The new position, which will be equal to the requested position.
        Throws:
        java.io.IOException - if reading/accessing the Blob fails
        StandardException - throws BLOB_POSITION_TOO_LARGE if the requested position is larger than the Blob length, throws other SQL states if resetting the stream fails

      • read

        private int read​(long pos)
          throws java.io.IOException,
                 StandardException
        Reads one byte from the Blob at the specified position.

        Depending on the representation, this might result in a read from a byte array, a temporary file on disk or from a Derby store stream.

        Returns:
        the byte at the current position, or -1 if end of file has been reached
        Throws:
        java.io.IOException - if reading from the underlying data representation fails
        StandardException

      • length

        public long length()
            throws java.sql.SQLException
        Returns the number of bytes in the BLOB value designated by this Blob object.
        Specified by:
        length in interface java.sql.Blob
        Returns:
        length of the BLOB in bytes
        Throws:
        java.sql.SQLException - if there is an error accessing the length of the BLOB

      • getBytes

        public byte[] getBytes​(long startPos,
                       int length)
                throws java.sql.SQLException
        Returns as an array of bytes part or all of the BLOB value that this Blob object designates. The byte array contains up to length consecutive bytes starting at position startPos. The starting position must be between 1 and the length of the BLOB plus 1. This allows for zero-length BLOB values, from which only zero-length byte arrays can be returned. If a larger length is requested than there are bytes available, characters from the start position to the end of the BLOB are returned.
        Specified by:
        getBytes in interface java.sql.Blob
        Parameters:
        startPos - the ordinal position of the first byte in the BLOB value to be extracted; the first byte is at position 1
        length - is the number of consecutive bytes to be copied
        Returns:
        a byte array containing up to length consecutive bytes from the BLOB value designated by this Blob object, starting with the byte at position startPos.
        Throws:
        java.sql.SQLException - if there is an error accessing the BLOB NOTE: If the starting position is the length of the BLOB plus 1, zero bytess are returned regardless of the length requested.

      • getBinaryStream

        public java.io.InputStream getBinaryStream()
                                    throws java.sql.SQLException
        Retrieves the BLOB designated by this Blob instance as a stream.
        Specified by:
        getBinaryStream in interface java.sql.Blob
        Returns:
        a stream containing the BLOB data
        Throws:
        java.sql.SQLException - if there is an error accessing the BLOB

      • position

        public long position​(byte[] pattern,
                     long start)
              throws java.sql.SQLException
        Determines the byte position at which the specified byte pattern begins within the BLOB value that this Blob object represents. The search for pattern. begins at position start
        Specified by:
        position in interface java.sql.Blob
        Parameters:
        pattern - the byte array for which to search
        start - the position at which to begin searching; the first position is 1
        Returns:
        the position at which the pattern appears, else -1.
        Throws:
        java.sql.SQLException - if there is an error accessing the BLOB

      • checkMatch

        private boolean checkMatch​(byte[] pattern,
                           long pos)
                    throws java.io.IOException,
                           StandardException
        Checks if the pattern (starting from the second byte) appears inside the Blob content.

        At this point, the first byte of the pattern must already have been matched, and pos must be pointing at the second byte to compare.

        Parameters:
        pattern - the byte array to search for, passed in by the user
        pos - the position in the Blob content to start searching from
        Returns:
        true if a match is found, false if not.
        Throws:
        java.io.IOException
        StandardException

      • position

        public long position​(java.sql.Blob pattern,
                     long start)
              throws java.sql.SQLException
        Determines the byte position in the BLOB value designated by this Blob object at which pattern begins. The search begins at position start.
        Specified by:
        position in interface java.sql.Blob
        Parameters:
        pattern - the Blob object designating the BLOB value for which to search
        start - the position in the BLOB value at which to begin searching; the first position is 1
        Returns:
        the position at which the pattern begins, else -1
        Throws:
        java.sql.SQLException - if there is an error accessing the BLOB

      • checkMatch

        private boolean checkMatch​(java.sql.Blob pattern,
                           long pos)
                    throws java.io.IOException,
                           StandardException
        Checks if the pattern (starting from the second byte) appears inside the Blob content.
        Parameters:
        pattern - the Blob to search for, passed in by the user
        pos - the position in the Blob (this) content to start searching
        Returns:
        true if a match is found, false if not.
        Throws:
        java.io.IOException
        StandardException

      • handleMyExceptions

        private java.sql.SQLException handleMyExceptions​(java.lang.Throwable t)
                                          throws java.sql.SQLException
        Throws:
        java.sql.SQLException

      • finalize

        protected void finalize()
        Overrides:
        finalize in class java.lang.Object

      • setBytes

        public int setBytes​(long pos,
                    byte[] bytes)
             throws java.sql.SQLException
        Writes the given array of bytes to the BLOB value that this Blob object represents, starting at position pos, and returns the number of bytes written.
        Specified by:
        setBytes in interface java.sql.Blob
        Parameters:
        pos - the position in the BLOB object at which to start writing
        bytes - the array of bytes to be written to the BLOB value that this Blob object represents
        Returns:
        The number of bytes written to the BLOB.
        Throws:
        java.sql.SQLException - if writing the bytes to the BLOB fails
        Since:
        1.4

      • setBytes

        public int setBytes​(long pos,
                    byte[] bytes,
                    int offset,
                    int len)
             throws java.sql.SQLException
        Writes all or part of the given array of byte array to the BLOB value that this Blob object represents and returns the number of bytes written. Writing starts at position pos in the BLOB value; len bytes from the given byte array are written.
        Specified by:
        setBytes in interface java.sql.Blob
        Parameters:
        pos - the position in the BLOB object at which to start writing
        bytes - the array of bytes to be written to the BLOB value that this Blob object represents
        offset - the offset into the byte array at which to start reading the bytes to be written
        len - the number of bytes to be written to the BLOB value from the array of bytes bytes
        Returns:
        The number of bytes written to the BLOB.
        Throws:
        java.sql.SQLException - if writing the bytes to the BLOB fails
        java.lang.IndexOutOfBoundsException - if len is larger than bytes.length - offset
        Since:
        1.4

      • setBinaryStream

        public java.io.OutputStream setBinaryStream​(long pos)
                                     throws java.sql.SQLException
        JDBC 3.0 Retrieves a stream that can be used to write to the BLOB value that this Blob object represents. The stream begins at position pos.
        Specified by:
        setBinaryStream in interface java.sql.Blob
        Parameters:
        pos - - the position in the BLOB object at which to start writing
        Returns:
        a java.io.OutputStream object to which data can be written
        Throws:
        java.sql.SQLException - Feature not implemented for now.

      • truncate

        public void truncate​(long len)
              throws java.sql.SQLException
        JDBC 3.0 Truncates the BLOB value that this Blob object represents to be len bytes in length.
        Specified by:
        truncate in interface java.sql.Blob
        Parameters:
        len - - the length, in bytes, to which the BLOB value that this Blob object represents should be truncated
        Throws:
        java.sql.SQLException - Feature not implemented for now.

      • free

        public void free()
          throws java.sql.SQLException
        This method frees the Blob object and releases the resources that it holds. The object is invalid once the free method is called. If free is called multiple times, the subsequent calls to free are treated as a no-op.
        Specified by:
        free in interface java.sql.Blob
        Specified by:
        free in interface EngineLOB
        Throws:
        java.sql.SQLException - if an error occurs releasing the Blob's resources

      • getBinaryStream

        public java.io.InputStream getBinaryStream​(long pos,
                                           long length)
                                    throws java.sql.SQLException
        Returns an InputStream object that contains a partial Blob value, starting with the byte specified by pos, which is length bytes in length.
        Specified by:
        getBinaryStream in interface java.sql.Blob
        Parameters:
        pos - the offset to the first byte of the partial value to be retrieved. The first byte in the Blob is at position 1
        length - the length in bytes of the partial value to be retrieved
        Returns:
        through which the partial Blob value can be read.
        Throws:
        java.sql.SQLException - if pos is less than 1 or if pos is greater than the number of bytes in the Blob or if pos + length is greater than Blob.length() +1

      • checkValidity

        private void checkValidity()
                    throws java.sql.SQLException
        Throws:
        java.sql.SQLException

      • isMaterialized

        boolean isMaterialized()
        Returns if blob data is stored locally (using LOBStreamControl).
        Returns:
        true if materialized else false

      • getLocator

        public int getLocator()
        Return locator for this lob.
        Specified by:
        getLocator in interface EngineLOB
        Returns:
        The locator identifying this lob.