java.lang.Object
- org.apache.derby.impl.jdbc.StoreStreamClob

All Implemented Interfaces:

InternalClob
```
final class StoreStreamClob
extends java.lang.Object
implements InternalClob
```
A read-only Clob representation operating on streams out of the Derby store module.
Note that the streams from the store are expected to have the following properties:
1. The first few bytes are used for length encoding. Currently the number of bytes is either 2 or 5.
2. A Derby-specific end-of-stream marker at the end of the stream can be present. The marker is expected to be 0xe0 0x00 0x00

Field Summary

Fields
Modifier and Type	Field	Description
`private ConnectionChild`	`conChild`	The connection (child) this Clob belongs to.
`private CharacterStreamDescriptor`	`csd`	The descriptor used to describe the underlying source stream.
`private UTF8Reader`	`internalReader`	Shared internal reader, closed when the Clob is released.
`private PositionedStoreStream`	`positionedStoreStream`	The stream from store, used to read bytes from the database.
`private boolean`	`released`	Tells whether this Clob has been released or not.
`private java.lang.Object`	`synchronizationObject`	Object used for synchronizing access to the store stream.
`private java.io.FilterReader`	`unclosableInternalReader`	The internal reader wrapped so that it cannot be closed.

Constructor Summary

Constructors
Constructor Description

StoreStreamClob(CharacterStreamDescriptor csd, ConnectionChild conChild)
Creates a new Clob based on a stream from store.

Method Summary

All Methods Static Methods Instance Methods Concrete Methods
Modifier and Type	Method	Description
`private void`	`checkIfValid()`	Makes sure the Clob has not been released.
`long`	`getCharLength()`	Returns the number of characters in the Clob.
`long`	`getCharLengthIfKnown()`	Returns the cached character count for the Clob, if any.
`java.io.Reader`	`getInternalReader(long characterPosition)`	Returns an internal reader for the Clob, initialized at the specified character position.
`java.io.InputStream`	`getRawByteStream()`	Returns a stream serving the raw bytes of this Clob.
`java.io.Reader`	`getReader(long pos)`	Returns a reader for the Clob, initialized at the specified character position.
`long`	`getUpdateCount()`	Returns the update count of this Clob.
`java.io.Writer`	`getWriter(long pos)`	Not supported.
`long`	`insertString(java.lang.String str, long pos)`	Not supported.
`boolean`	`isReleased()`	Tells if this Clob has been released.
`boolean`	`isWritable()`	Tells if this Clob can be modified.
`private static java.sql.SQLException`	`noStateChangeLOB(java.lang.Throwable t)`	Wrap real exception in a `SQLException` to avoid changing the state of the connection child by cleaning it up.
`void`	`release()`	Releases resources associated with this Clob.
`void`	`truncate(long newLength)`	Not supported.

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

- Field Detail
  - released
```
private volatile boolean released
```
    Tells whether this Clob has been released or not.
  - positionedStoreStream
```
private final PositionedStoreStream positionedStoreStream
```
    The stream from store, used to read bytes from the database.
    To be able to support the requirements, the stream must implement Resetable.
  - csd
```
private CharacterStreamDescriptor csd
```
    The descriptor used to describe the underlying source stream.
  - conChild
```
private final ConnectionChild conChild
```
    The connection (child) this Clob belongs to.
  - synchronizationObject
```
private final java.lang.Object synchronizationObject
```
    Object used for synchronizing access to the store stream.
  - internalReader
```
private UTF8Reader internalReader
```
    Shared internal reader, closed when the Clob is released. This is a performance optimization, and the stream is shared between "one time" operations, for instance getSubString calls. Often a subset, or the whole, of the Clob is read subsequently and then this optimization avoids repositioning costs (the store does not support random access for LOBs). NOTE: Do not publish this reader to the end-user.
  - unclosableInternalReader
```
private java.io.FilterReader unclosableInternalReader
```
    The internal reader wrapped so that it cannot be closed.
- Constructor Detail
  - StoreStreamClob
```
public StoreStreamClob(CharacterStreamDescriptor csd,
                       ConnectionChild conChild)
                throws StandardException
```
    Creates a new Clob based on a stream from store.
    The stream used as a source for this Clob has to implement the interface Resetable, as the stream interface from store only allows for movement forwards. If the stream has been advanced too far with regards to the user request, the stream must be reset and we start from the beginning.
    
    Parameters:
    
    csd - descriptor for the source stream, including a reference to it
    
    conChild - the connection (child) this Clob belongs to
    
    Throws:
    
    StandardException
- Method Detail
  - release
```
public void release()
```
    Releases resources associated with this Clob.
    
    Specified by:
    
    release in interface InternalClob
  - getCharLength
```
public long getCharLength()
                   throws java.sql.SQLException
```
    Returns the number of characters in the Clob.
    
    Specified by:
    
    getCharLength in interface InternalClob
    
    Returns:
    
    Number of characters in the Clob.
    
    Throws:
    
    java.sql.SQLException - if any kind of error is encountered, be it related to I/O or something else
  - getCharLengthIfKnown
```
public long getCharLengthIfKnown()
```
    Returns the cached character count for the Clob, if any.
    
    Specified by:
    
    getCharLengthIfKnown in interface InternalClob
    
    Returns:
    
    The number of characters in the Clob, or -1 if unknown.
  - getRawByteStream
```
public java.io.InputStream getRawByteStream()
                                     throws java.io.IOException,
                                            java.sql.SQLException
```
    Returns a stream serving the raw bytes of this Clob.
    Note that the stream returned is an internal stream, and it should not be pulished to end users.
    
    Specified by:
    
    getRawByteStream in interface InternalClob
    
    Returns:
    
    A stream serving the bytes of this Clob, initialized at byte 0 of the data. The buffer must be assumed to be unbuffered, but no such guarantee is made.
    
    Throws:
    
    java.io.IOException - if accessing the I/O resources fail
    
    java.sql.SQLException - if accessing the store resources fail
  - getReader
```
public java.io.Reader getReader(long pos)
                         throws java.io.IOException,
                                java.sql.SQLException
```
    Returns a reader for the Clob, initialized at the specified character position.
    
    Specified by:
    
    getReader in interface InternalClob
    
    Parameters:
    
    pos - character position. The first character is at position 1.
    
    Returns:
    
    A reader initialized at the specified position.
    
    Throws:
    
    java.io.EOFException - if the positions is larger than the Clob
    
    java.io.IOException - if accessing the I/O resources fail
    
    java.sql.SQLException - if accessing the store resources fail
  - getInternalReader
```
public java.io.Reader getInternalReader(long characterPosition)
                                 throws java.io.IOException,
                                        java.sql.SQLException
```
    Returns an internal reader for the Clob, initialized at the specified character position.
    
    Specified by:
    
    getInternalReader in interface InternalClob
    
    Parameters:
    
    characterPosition - 1-based character position.
    
    Returns:
    
    A reader initialized at the specified position.
    
    Throws:
    
    java.io.EOFException - if the positions is larger than the Clob
    
    java.io.IOException - if accessing the I/O resources fail
    
    java.sql.SQLException - if accessing the store resources fail
  - getUpdateCount
```
public long getUpdateCount()
```
    Returns the update count of this Clob.
    Always returns zero, as this Clob cannot be updated.
    
    Specified by:
    
    getUpdateCount in interface InternalClob
    
    Returns:
    
    Zero (read-only Clob).
  - getWriter
```
public java.io.Writer getWriter(long pos)
```
    Not supported.
    
    Specified by:
    
    getWriter in interface InternalClob
    
    Parameters:
    
    pos - the starting character position. The first character is at position 1.
    
    Returns:
    
    A writer initialized at the specified character position.
    
    See Also:
    
    InternalClob.getWriter(long)
  - insertString
```
public long insertString(java.lang.String str,
                         long pos)
```
    Not supported.
    
    Specified by:
    
    insertString in interface InternalClob
    
    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.
    
    See Also:
    
    InternalClob.insertString(java.lang.String, long)
  - isReleased
```
public boolean isReleased()
```
    Tells if this Clob has been released.
    
    Specified by:
    
    isReleased in interface InternalClob
    
    Returns:
    
    true if released, false if not.
  - isWritable
```
public boolean isWritable()
```
    Tells if this Clob can be modified.
    
    Specified by:
    
    isWritable in interface InternalClob
    
    Returns:
    
    false, this Clob is read-only.
  - truncate
```
public void truncate(long newLength)
```
    Not supported.
    
    Specified by:
    
    truncate in interface InternalClob
    
    Parameters:
    
    newLength - the length in characters to truncate to
    
    See Also:
    
    InternalClob.truncate(long)
  - noStateChangeLOB
```
private static java.sql.SQLException noStateChangeLOB(java.lang.Throwable t)
```
    Wrap real exception in a SQLException to avoid changing the state of the connection child by cleaning it up.
    
    Parameters:
    
    t - real cause of error that we want to "ignore" with respect to transaction context cleanup
    
    Returns:
    
    A SQLException wrapped around the real cause of the error
  - checkIfValid
```
private void checkIfValid()
```
    Makes sure the Clob has not been released.
    All operations are invalid on a released Clob.
    
    Throws:
    
    java.lang.IllegalStateException - if the Clob has been released

Class StoreStreamClob

Field Summary

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Field Detail

released

positionedStoreStream

csd

conChild

synchronizationObject

internalReader

unclosableInternalReader

Constructor Detail

StoreStreamClob

Method Detail

release

getCharLength

getCharLengthIfKnown

getRawByteStream

getReader

getInternalReader

getUpdateCount

getWriter

insertString

isReleased

isWritable

truncate

noStateChangeLOB

checkIfValid