org.apache.derby.impl.jdbc
Interface InternalClob

All Known Implementing Classes:
StoreStreamClob, TemporaryClob

interface InternalClob

A set of operations available on internal Clob content representations.

The methods defined by Clob must be implemented on top of this interface. In addition, there are some methods to aid internal tasks and organization, like transferring one internal Clob representation to another one.


Method Summary
 long getCharLength()
          Gets the number of characters in the Clob.
 long getCharLengthIfKnown()
          Gets the number of characters in the Clob if it is already known.
 java.io.Reader getInternalReader(long characterPosition)
          Returns an internal reader for the Clob content, initialized at the specified character position.
 java.io.InputStream getRawByteStream()
          Returns a stream serving the raw bytes of the Clob.
 java.io.Reader getReader(long characterPosition)
          Returns a reader for the Clob content, initialized at the specified character position.
 long getUpdateCount()
          Returns the update count of the Clob.
 java.io.Writer getWriter(long charPos)
          Returns a writer to write data into the Clob.
 long insertString(java.lang.String str, long pos)
          Inserts the given string at the specified character position.
 boolean isReleased()
          Tells if the the Clob has been released.
 boolean isWritable()
          Tells if the Clob representation is intended to be writable.
 void release()
          Frees the resources held by the internal Clob representation.
 void truncate(long newLength)
           
 

Method Detail

getCharLength

long getCharLength()
                   throws java.io.IOException,
                          java.sql.SQLException
Gets the number of characters in the Clob.

Returns:
Number of characters in the Clob.
Throws:
java.io.IOException - if accessing underlying I/O resources fail
java.sql.SQLException - if accessing underlying resources fail

getCharLengthIfKnown

long getCharLengthIfKnown()
Gets the number of characters in the Clob if it is already known.

This method will not do any work to obtain the length if it isn't already known. Due to special handling of zero in the code, this method will return -1 if a length of zero is cached internally.

If a positive value is returned, it is expected to be equal to the actual length of the Clob (i.e., no stale values must be returned).

Returns:
Number of characters in the Clob, or -1 if the length is currently unknown (not cached).

getRawByteStream

java.io.InputStream getRawByteStream()
                                     throws java.io.IOException,
                                            java.sql.SQLException
Returns a stream serving the raw bytes of the Clob.

Note that it is up to the caller of this method to handle the issue of encoding. There is no predetermined encoding associated with this byte stream, it is up to the Clob representation which one it uses.

This stream may be an internal store stream, and should not be directly published to the end user (returned through the JDBC API). There are three reasons for this:

The primary use of this method is to clone the Clob contents without going via char (or String). Make sure the clone uses the same encoding as the original Clob representation.

Returns:
A stream of bytes representing the content of the Clob, initialized at byte position 0.
Throws:
java.io.IOException - if accessing underlying I/O resources fail
java.sql.SQLException - if accessing underlying resources fail

getReader

java.io.Reader getReader(long characterPosition)
                         throws java.io.IOException,
                                java.sql.SQLException
Returns a reader for the Clob content, initialized at the specified character position.

Parameters:
characterPosition - character position. The first character is at position 1.
Returns:
A Reader serving the content of the Clob.
Throws:
EOFException - if the position is larger then the Clob
java.io.IOException - if accessing underlying I/O resources fail
java.sql.SQLException - if accessing underlying resources fail

getInternalReader

java.io.Reader getInternalReader(long characterPosition)
                                 throws java.io.IOException,
                                        java.sql.SQLException
Returns an internal reader for the Clob content, initialized at the specified character position.

This method can return a shared reader object, avoiding instantiation and repositioning costs for internal operations where the stream itself is not published to the end-user. One such example is Clob.getSubString.

Parameters:
characterPosition - character position. The first character is at position 1.
Returns:
A Reader serving the content of the Clob.
Throws:
EOFException - if the position is larger then the Clob
java.io.IOException - if accessing underlying I/O resources fail
java.sql.SQLException - if accessing underlying resources fail

getUpdateCount

long getUpdateCount()
Returns the update count of the Clob.

The update count is increased each time a modification of the Clob content is made.

Returns:
Update count, starting at zero.

getWriter

java.io.Writer getWriter(long charPos)
                         throws java.io.IOException,
                                java.sql.SQLException
Returns a writer to write data into the Clob.

The semantics of the writer is the same as for insertString(java.lang.String, long).

Parameters:
charPos - the starting character position. The first character is at position 1.
Returns:
A writer initialized at the specified character position.
Throws:
java.io.IOException - if writing to the Clob fails
java.sql.SQLException - if accessing underlying resources fail
java.lang.UnsupportedOperationException - if the Clob representation is read-only

insertString

long insertString(java.lang.String str,
                  long pos)
                  throws java.io.IOException,
                         java.sql.SQLException
Inserts the given string at the specified character position.

The behavior of this method can be defined by the following examples on the Clob clob with value "ABCDEFG";

Parameters:
str - the string to insert
pos - the character position the string will be inserted at. Must be between 1 and clob.length() +1, inclusive.
Returns:
The number of characters inserted.
Throws:
java.io.IOException - if writing to the I/O resources fail
java.sql.SQLException - it the position is invalid
java.lang.IllegalArgumentException - if the string is null
java.lang.UnsupportedOperationException - if the Clob representation is read-only

isReleased

boolean isReleased()
Tells if the the Clob has been released.

Depending on the context, a Clob is released either because the internal representation has been changed, or because the Clob itself has been closed. The former can happen when a user modifies a stream that is currently represented as a store stream. The latter can happen if Clob.free has been called, or if Derby implicitly closes the Clob.

Returns:
true if released, false if not.

isWritable

boolean isWritable()
Tells if the Clob representation is intended to be writable.

Note that even if this method returns true, it might not be possible to write to the Clob. If this happens, it is because the assoicated database is read-only, and the internal Clob representation is unable to obtain the resources it require (could be an area on disk to write temporary data).

Returns:
true if the Clob is intended to be writable, false if modifying the Clob is definitely not possible.

release

void release()
             throws java.io.IOException,
                    java.sql.SQLException
Frees the resources held by the internal Clob representation.

After calling this method, all other operations on the Clob will be invalid and throw an exception.

Throws:
java.io.IOException - if freeing associated I/O resources fails
java.sql.SQLException - if freeing associated resources fails

truncate

void truncate(long newLength)
              throws java.io.IOException,
                     java.sql.SQLException
Parameters:
newLength - the length in characters to truncate to
Throws:
java.io.IOException - if accessing the underlying I/O resources fails
java.sql.SQLException - if accessing underlying resources fail
java.lang.UnsupportedOperationException - if the Clob representation is read-only

Built on Thu 2012-03-29 21:53:33+0000, from revision ???

Apache Derby V10.6 Internals - Copyright © 2004,2007 The Apache Software Foundation. All Rights Reserved.