Package org.apache.derby.client.am

Class ClobLocatorReader

  • All Implemented Interfaces:
    java.io.Closeable, java.lang.AutoCloseable, java.lang.Readable
    class ClobLocatorReader
extends java.io.Reader
    An Reader that will use an locator to fetch the Clob value from the server.

    This Reader implementation is pretty basic. No buffering of data is done. Hence, for efficiency #read(char[]) should be used instead of #read(). Marks are not supported, but it should be pretty simple to extend the implementation to support this. A more efficient skip implementation should also be straight-forward.

    • Field Summary

      Fields 
      Modifier and Type Field Description
      private ClientClob clob
      The Clob to be accessed.
      private ClientConnection connection
      Connection used to read Clob from server.
      private long currentPos
      Current position in the underlying Clob.
      private boolean isClosed
      Stores the information to whether this Reader has been closed or not.
      private long maxPos
      Position in Clob where to stop reading.

      • Fields inherited from class java.io.Reader

        lock

    • Method Summary

      All Methods Instance Methods Concrete Methods 
      Modifier and Type Method Description
      private void checkClosed()
      Check to see if this Reader is closed.
      void close()  
      int read()  
      int read​(char[] c, int off, int len)  
      private char[] readCharacters​(int len)
      Read the next len characters of the Clob value from the server.

      • Methods inherited from class java.io.Reader

        mark, markSupported, nullReader, read, read, ready, reset, skip, transferTo

      • Methods inherited from class java.lang.Object

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

    • Field Detail

      • connection

        private final ClientConnection connection
        Connection used to read Clob from server.

      • clob

        private final ClientClob clob
        The Clob to be accessed.

      • currentPos

        private long currentPos
        Current position in the underlying Clob. Clobs are indexed from 1

      • maxPos

        private final long maxPos
        Position in Clob where to stop reading. maxPos starts counting from 1.

      • isClosed

        private boolean isClosed
        Stores the information to whether this Reader has been closed or not. Is set to true if close() has been called. Is false otherwise.

    • Constructor Detail

      • ClobLocatorReader

        ClobLocatorReader​(ClientConnection connection,
                  ClientClob clob)
           throws SqlException
        Create an Reader for reading the Clob value represented by the given locator based Clob object.
        Parameters:
        connection - connection to be used to read the Clob value from the server
        clob - Clob object that contains locator for the Clob value on the server.
        Throws:
        SqlException

      • ClobLocatorReader

        ClobLocatorReader​(ClientConnection connection,
                  ClientClob clob,
                  long pos,
                  long len)
           throws SqlException
        Create an Reader for reading the Clob value represented by the given locator based Clob object.
        Parameters:
        connection - connection to be used to read the Clob value from the server
        clob - Clob object that contains locator for the Clob value on the server.
        pos - The offset to the first character of the partial value to be retrieved.
        len - The length in characters of the partial value to be retrieved.
        Throws:
        SqlException

    • Method Detail

      • read

        public int read()
         throws java.io.IOException
        Overrides:
        read in class java.io.Reader
        Throws:
        java.io.IOException
        See Also:
        This method fetches one character at a time from the server. For more efficient retrieval, use #read(char[]).

      • read

        public int read​(char[] c,
                int off,
                int len)
         throws java.io.IOException
        Specified by:
        read in class java.io.Reader
        Throws:
        java.io.IOException
        See Also:
        Reader.read(char[], int, int)

      • close

        public void close()
           throws java.io.IOException
        Specified by:
        close in interface java.lang.AutoCloseable
        Specified by:
        close in interface java.io.Closeable
        Specified by:
        close in class java.io.Reader
        Throws:
        java.io.IOException
        See Also:
        Reader.close()

      • checkClosed

        private void checkClosed()
                  throws java.io.IOException
        Check to see if this Reader is closed. If it is closed throw an IOException that states that the stream is closed.
        Throws:
        java.io.IOException - if isClosed = true.

      • readCharacters

        private char[] readCharacters​(int len)
                       throws java.io.IOException
        Read the next len characters of the Clob value from the server.
        Parameters:
        len - number of characters to read.
        Returns:
        char[] containing the read characters.
        Throws:
        java.io.IOException - Wrapped SqlException if reading from server fails.