Package org.apache.derby.client.am
Class ClobLocatorReader
- java.lang.Object
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- java.io.Reader
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- org.apache.derby.client.am.ClobLocatorReader
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- All Implemented Interfaces:
java.io.Closeable
,java.lang.AutoCloseable
,java.lang.Readable
class ClobLocatorReader extends java.io.Reader
AnReader
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.
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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.
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Constructor Summary
Constructors Constructor Description ClobLocatorReader(ClientConnection connection, ClientClob clob)
Create anReader
for reading theClob
value represented by the given locator basedClob
object.ClobLocatorReader(ClientConnection connection, ClientClob clob, long pos, long len)
Create anReader
for reading theClob
value represented by the given locator basedClob
object.
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Method Summary
All Methods Instance Methods Concrete Methods Modifier and Type Method Description private void
checkClosed()
Check to see if thisReader
is closed.void
close()
int
read()
int
read(char[] c, int off, int len)
private char[]
readCharacters(int len)
Read the nextlen
characters of theClob
value from the server.
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Field Detail
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connection
private final ClientConnection connection
Connection used to read Clob from server.
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clob
private final ClientClob clob
The Clob to be accessed.
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currentPos
private long currentPos
Current position in the underlying Clob. Clobs are indexed from 1
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maxPos
private final long maxPos
Position in Clob where to stop reading. maxPos starts counting from 1.
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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.
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Constructor Detail
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ClobLocatorReader
ClobLocatorReader(ClientConnection connection, ClientClob clob) throws SqlException
Create anReader
for reading theClob
value represented by the given locator basedClob
object.- Parameters:
connection
- connection to be used to read theClob
value from the serverclob
-Clob
object that contains locator for theClob
value on the server.- Throws:
SqlException
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ClobLocatorReader
ClobLocatorReader(ClientConnection connection, ClientClob clob, long pos, long len) throws SqlException
Create anReader
for reading theClob
value represented by the given locator basedClob
object.- Parameters:
connection
- connection to be used to read theClob
value from the serverclob
-Clob
object that contains locator for theClob
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
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Method Detail
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read
public int read() throws java.io.IOException
- Overrides:
read
in classjava.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[]).
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read
public int read(char[] c, int off, int len) throws java.io.IOException
- Specified by:
read
in classjava.io.Reader
- Throws:
java.io.IOException
- See Also:
Reader.read(char[], int, int)
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close
public void close() throws java.io.IOException
- Specified by:
close
in interfacejava.lang.AutoCloseable
- Specified by:
close
in interfacejava.io.Closeable
- Specified by:
close
in classjava.io.Reader
- Throws:
java.io.IOException
- See Also:
Reader.close()
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checkClosed
private void checkClosed() throws java.io.IOException
Check to see if thisReader
is closed. If it is closed throw anIOException
that states that the stream is closed.- Throws:
java.io.IOException
- if isClosed = true.
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readCharacters
private char[] readCharacters(int len) throws java.io.IOException
Read the nextlen
characters of theClob
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.
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