Package org.apache.derby.client.am

Class Lob

    • Field Detail

      • agent_

        protected Agent agent_

      • dataType_

        protected int dataType_

      • locator_

        protected int locator_

      • sqlLength_

        private long sqlLength_

      • lengthObtained_

        private boolean lengthObtained_

      • isValid_

        protected boolean isValid_
        This boolean variable indicates whether the Lob object has been invalidated by calling free() on it

      • willBeLayerBStreamed_

        private final boolean willBeLayerBStreamed_

      • updateCount

        private long updateCount

      • transactionID_

        private int transactionID_
        This integer identifies which transaction the Lob is associated with

      • LOB_OBJECT_LENGTH_UNKNOWN_YET

        private static final ClientMessageId LOB_OBJECT_LENGTH_UNKNOWN_YET

    • Constructor Detail

      • Lob

        protected Lob​(Agent agent,
              boolean willBeLayerBStreamed)

    • Method Detail

      • sqlLength

        long sqlLength()
        throws SqlException
        Return the length of the Lob value represented by this Lob object. If length is not already known, and Lob is locator based, length will be retrieved from the server. If not, locator based, Lob will first be materialized. NOTE: The caller needs to deal with synchronization.
        Returns:
        length of Lob value
        Throws:
        SqlException - on execution errors while materializing the stream, or if Layer B streaming is used and length not yet obtained.

      • setSqlLength

        void setSqlLength​(long length)
        Update the registered length of the Lob value. To be called by methods that make changes to the length of the Lob. NOTE: The caller needs to deal with synchronization.
        Parameters:
        length - the new length of the Lob value

      • getLocatorLength

        long getLocatorLength()
               throws SqlException
        Get the length of locator based Lob from the server. This is a dummy implementation that is supposed to be overridden by subclasses. A stored procedure call will be made to get the length from the server.
        Returns:
        length of Lob
        Throws:
        SqlException

      • getAgent

        public Agent getAgent()

      • materializeStream

        protected abstract void materializeStream()
                                   throws SqlException
        Method to be implemented by subclasses, so that #materializedStream(InputStream, String) can be called with subclass specific parameters and the result assigned to the right stream.
        Throws:
        SqlException

      • materializeStream

        protected java.io.InputStream materializeStream​(java.io.InputStream is,
                                                java.lang.String typeDesc)
                                         throws SqlException
        Materialize the given stream into memory and update the internal length variable.
        Parameters:
        is - stream to use for input
        typeDesc - description of the data type we are inserting, for instance java.sql.Clob
        Returns:
        a stream whose source is the materialized data
        Throws:
        SqlException - if the stream exceeds 2 GB, or an error happens while reading from the stream

      • length

        public abstract long length()
                     throws java.sql.SQLException
        Throws:
        java.sql.SQLException

      • isLayerBStreamingPossible

        protected static boolean isLayerBStreamingPossible​(Agent agent)

      • willBeLayerBStreamed

        public boolean willBeLayerBStreamed()

      • isLocator

        public boolean isLocator()
        Check whether this Lob is based on a locator
        Returns:
        true if Lob is based on locator, false otherwise

      • getLocator

        public int getLocator()
        Get locator for this Lob
        Returns:
        locator for this Lob, INVALID_LOCATOR if Lob is not based on locator

      • checkPosAndLength

        protected void checkPosAndLength​(long pos,
                                 long length)
                          throws java.sql.SQLException
        Checks the pos and length.
        Parameters:
        pos - a long that contains the position that needs to be checked
        length - a long that contains the length that needs to be checked
        Throws:
        java.sql.SQLException - if a) pos <= 0 b) pos > (length of LOB) c) length < 0 d) (pos -1) + length > (length of LOB)

      • incrementUpdateCount

        protected void incrementUpdateCount()
        Increments and returns the new updateCount of this Lob. The method needs to be synchronized since multiple updates can happen on this Lob simultaneously. It will be called from the 1) Locator Writers 2) Locator OutputStreams 3) From the update methods within the Lobs like setString, truncate. since all of the above acesses are inside the am package, this method will have default access. We do not need to worry about the non-locator streams since non-locator InputStreams would not depend on updateCount for invalidation

      • getUpdateCount

        long getUpdateCount()
        Returns the current updateCount of the Clob.

      • checkForLocatorValidity

        void checkForLocatorValidity()
                      throws SqlException
        Calls SqlLength() to check if the Locator associated with the underlying Lob is valid. If it is not it throws an exception.
        Throws:
        SqlException

      • checkValidity

        protected void checkValidity()
                      throws java.sql.SQLException
        Checks if isValid is true and whether the transaction that created the Lob is still active. If any of which is not true throws a SQLException stating that a method has been called on an invalid LOB object.
        Throws:
        java.sql.SQLException - if isValid is not true or the transaction that created the Lob is not active