Interface InternalClob
- All Known Implementing Classes:
StoreStreamClob
,TemporaryClob
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.
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Method Summary
Modifier and TypeMethodDescriptionlong
Gets the number of characters in the Clob.long
Gets the number of characters in the Clob if it is already known.getInternalReader
(long characterPosition) Returns an internal reader for the Clob content, initialized at the specified character position.Returns a stream serving the raw bytes of the Clob.getReader
(long characterPosition) Returns a reader for the Clob content, initialized at the specified character position.long
Returns the update count of the Clob.getWriter
(long charPos) Returns a writer to write data into the Clob.long
insertString
(String str, long pos) Inserts the given string at the specified character position.boolean
Tells if the the Clob has been released.boolean
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)
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Method Details
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getCharLength
Gets the number of characters in the Clob.- Returns:
- Number of characters in the Clob.
- Throws:
IOException
- if accessing underlying I/O resources failSQLException
- if accessing underlying resources fail
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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).
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getRawByteStream
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 stream may be closed by the end user when it is not supposed to
- operations on the stream might throw exceptions we don't want to present to the end user unwrapped
- the stream may contain a Derby specific end-of-stream marker
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:
IOException
- if accessing underlying I/O resources failSQLException
- if accessing underlying resources fail
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getReader
Returns a reader for the Clob content, initialized at the specified character position.- Parameters:
characterPosition
- character position. The first character is at position1
.- Returns:
- A
Reader
serving the content of the Clob.
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getInternalReader
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 position1
.- Returns:
- A
Reader
serving the content of the Clob.
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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.
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getWriter
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 position1
.- Returns:
- A writer initialized at the specified character position.
- Throws:
IOException
- if writing to the Clob failsSQLException
- if accessing underlying resources failUnsupportedOperationException
- if the Clob representation is read-only
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insertString
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"
;clob.setString(2, "XX")
- "AXXDEFG"clob.setString(1, "XX")
- "XXCDEFG"clob.setString(8, "XX")
- "ABCDEFGXX"clob.setString(7, "XX")
- "ABCDEFXX"clob.setString(9, "XX")
- throws exception
- Parameters:
str
- the string to insertpos
- the character position the string will be inserted at. Must be between1
andclob.length() +1
, inclusive.- Returns:
- The number of characters inserted.
- Throws:
IOException
- if writing to the I/O resources failSQLException
- it the position is invalidIllegalArgumentException
- if the string isnull
UnsupportedOperationException
- if the Clob representation is read-only
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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.
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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.
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release
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:
IOException
- if freeing associated I/O resources failsSQLException
- if freeing associated resources fails
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truncate
- Parameters:
newLength
- the length in characters to truncate to- Throws:
IOException
- if accessing the underlying I/O resources failsSQLException
- if accessing underlying resources failUnsupportedOperationException
- if the Clob representation is read-only
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