public class JDBCClobFile
extends java.lang.Object
implements java.sql.Clob
Starting with 2.1, in addition to HSQLDB driver support for both client-side in-memory and remote SQL CLOB data implementations, this class is provided to expose efficient, relatively high-performance CLOB operations over client accessible files.
Design Notes
Although it is possible to implement a transactional version of this class, the present implementation directly propagates changes to the underlying file such that changes become visible as soon as they are either implicitly or explicitly flushed to disk.
Modifier and Type | Field and Description |
---|---|
static java.lang.String |
TEMP_FILE_PREFIX |
static java.lang.String |
TEMP_FILE_SUFFIX |
Constructor and Description |
---|
JDBCClobFile()
Convenience constructor for
JDBCClobFile((String)null) . |
JDBCClobFile(java.io.File file)
Convenience constructor for
JDBCClobFile(file,null) . |
JDBCClobFile(java.io.File file,
java.lang.String encoding)
Constructs a new JDBCClobFile instance backed by the given File object
using the given encoding to read and write file content.
|
JDBCClobFile(java.lang.String encoding)
Constructs a new JDBCClobFile instance backed by an File object
created by File.createTempFile(TEMP_FILE_PREFIX, TEMP_FILE_SUFFIX),
using the given encoding to read and write file content.
|
Modifier and Type | Method and Description |
---|---|
void |
free()
This method frees the
Clob object and releases the resources the resources
that it holds. |
java.io.InputStream |
getAsciiStream()
Retrieves the
CLOB value designated by this Clob
object as an ASCII stream. |
java.io.Reader |
getCharacterStream()
Retrieves the
CLOB value designated by this Clob
object as a java.io.Reader object (or as a stream of
characters). |
java.io.Reader |
getCharacterStream(long pos,
long length)
Returns a
Reader object that contains a partial Clob value, starting
with the character specified by pos, which is length characters in length. |
java.lang.String |
getEncoding() |
java.io.File |
getFile()
Retrieves the canonical File object denoting the file that
backs this CLOB.
|
java.lang.String |
getSubString(long pos,
int length)
Retrieves a copy of the specified substring
in the
CLOB value
designated by this Clob object. |
boolean |
isDeleteOnFree()
Retrieves whether an attempt to delete the backing file
is made in response to invocation of
free() . |
long |
length()
Retrieves the number of characters
in the
CLOB value
designated by this Clob object. |
long |
position(char[] pattern,
long start)
Retrieves the character position at which the specified char[]
pattern appears in the CLOB value
represented by this Clob object. |
long |
position(java.sql.Clob pattern,
long start)
Retrieves the character position at which the specified
Clob object searchstr appears in this
Clob object. |
long |
position(java.lang.String searchstr,
long start)
Retrieves the character position at which the specified substring
searchstr appears in the SQL CLOB value
represented by this Clob object. |
java.io.OutputStream |
setAsciiStream(long pos)
Retrieves a stream to be used to write Ascii characters to the
CLOB value that this Clob object represents,
starting at position pos . |
java.io.Writer |
setCharacterStream(long pos)
Retrieves a stream to be used to write a stream of Unicode characters
to the
CLOB value that this Clob object
represents, at position pos . |
void |
setDeleteOnFree(boolean deleteOnFree)
Assigns whether an attempt to delete the backing file
is made in response to invocation of
free() . |
int |
setString(long pos,
java.lang.String str)
Writes the given Java
String to the CLOB
value that this Clob object designates at the position
pos . |
int |
setString(long pos,
java.lang.String str,
int offset,
int len)
Writes
len characters of str , starting
at character offset , to the CLOB value
that this Clob represents. |
void |
truncate(long len)
Truncates the
CLOB value that this Clob
designates to have a length of len
characters. |
public static final java.lang.String TEMP_FILE_PREFIX
public static final java.lang.String TEMP_FILE_SUFFIX
public JDBCClobFile() throws java.sql.SQLException
JDBCClobFile((String)null)
. java.sql.SQLException
- if the platform encoding is unsupported,
the temp file cannot be created or some other
error occurs that prevents the construction of a
valid instance of this class.public JDBCClobFile(java.lang.String encoding) throws java.sql.SQLException
encoding
- the name of the character encoding used to read and write
character data in the underlying file, as well as to determine
the character length of and character offsets into the underlying
file. Specify null to denote the platform encoding.java.sql.SQLException
- if the given encoding is unsupported,
the backing temp file could not be created or if a security
manager exists and its SecurityManager.checkWrite(java.lang.String)
method does not allow a file to be created.public JDBCClobFile(java.io.File file) throws java.sql.SQLException
JDBCClobFile(file,null)
.file
- that is to back the new CLOB instance.java.sql.SQLException
- if an I/O error occurs, which is possible because the
construction of the canonical pathname may require
file-system queries; a required system property value
cannot be accessed; a security manager exists and its
SecurityManager.checkRead(java.io.FileDescriptor)
method denies read access to the filepublic JDBCClobFile(java.io.File file, java.lang.String encoding) throws java.sql.SQLException
file
- that is to back the new CLOB instance.encoding
- the name of the character encoding used to read and write
character data in the underlying file, as well as to determine
the character length of and character offsets into the underlying
file. Specify null to denote the platform encoding.java.sql.SQLException
- if the given encoding is unsupported;
an I/O error occurs, which is possible because the
construction of the canonical pathname may require
file-system queries; a required system property value
cannot be accessed; a security manager exists and its
SecurityManager.checkRead(java.io.FileDescriptor)
method denies read access to the filepublic long length() throws java.sql.SQLException
CLOB
value
designated by this Clob
object.length
in interface java.sql.Clob
CLOB
in charactersjava.sql.SQLException
- if there is an error accessing the
length of the CLOB
valuejava.sql.SQLFeatureNotSupportedException
- if the JDBC driver does not support
this methodpublic java.lang.String getSubString(long pos, int length) throws java.sql.SQLException
CLOB
value
designated by this Clob
object.
The substring begins at position
pos
and has up to length
consecutive
characters.getSubString
in interface java.sql.Clob
pos
- the first character of the substring to be extracted.
The first character is at position 1.length
- the number of consecutive characters to be copied;
the value for length must be 0 or greaterString
that is the specified substring in
the CLOB
value designated by this Clob
objectjava.sql.SQLException
- if there is an error accessing the
CLOB
value; if pos is less than 1 or length is
less than 0java.sql.SQLFeatureNotSupportedException
- if the JDBC driver does not support
this methodpublic java.io.Reader getCharacterStream() throws java.sql.SQLException
CLOB
value designated by this Clob
object as a java.io.Reader
object (or as a stream of
characters).getCharacterStream
in interface java.sql.Clob
java.io.Reader
object containing the
CLOB
datajava.sql.SQLException
- if there is an error accessing the
CLOB
valuejava.sql.SQLFeatureNotSupportedException
- if the JDBC driver does not support
this methodsetCharacterStream(long)
public java.io.InputStream getAsciiStream() throws java.sql.SQLException
CLOB
value designated by this Clob
object as an ASCII stream.getAsciiStream
in interface java.sql.Clob
java.io.InputStream
object containing the
CLOB
datajava.sql.SQLException
- if there is an error accessing the
CLOB
valuejava.sql.SQLFeatureNotSupportedException
- if the JDBC driver does not support
this methodsetAsciiStream(long)
public long position(char[] pattern, long start) throws java.sql.SQLException
pattern
appears in the CLOB
value
represented by this Clob
object. The search
begins at position start
.pattern
- the substring for which to searchstart
- the position at which to begin searching; the first position
is 1java.sql.SQLException
- if there is an error accessing the
CLOB
value or if pos is less than 1java.sql.SQLFeatureNotSupportedException
- if the JDBC driver does not support
this methodpublic long position(java.lang.String searchstr, long start) throws java.sql.SQLException
searchstr
appears in the SQL CLOB
value
represented by this Clob
object. The search
begins at position start
.position
in interface java.sql.Clob
searchstr
- the substring for which to searchstart
- the position at which to begin searching; the first position
is 1java.sql.SQLException
- if there is an error accessing the
CLOB
value or if pos is less than 1java.sql.SQLFeatureNotSupportedException
- if the JDBC driver does not support
this methodpublic long position(java.sql.Clob pattern, long start) throws java.sql.SQLException
Clob
object searchstr
appears in this
Clob
object. The search begins at position
start
.position
in interface java.sql.Clob
pattern
- the Clob
object for which to searchstart
- the position at which to begin searching; the first
position is 1Clob
object appears
or -1 if it is not present; the first position is 1java.sql.SQLException
- if there is an error accessing the
CLOB
value or if start is less than 1java.sql.SQLFeatureNotSupportedException
- if the JDBC driver does not support
this methodpublic int setString(long pos, java.lang.String str) throws java.sql.SQLException
String
to the CLOB
value that this Clob
object designates at the position
pos
. The string will overwrite the existing characters
in the Clob
object starting at the position
pos
. If the end of the Clob
value is reached
while writing the given string, then the length of the Clob
value will be increased to accommodate the extra characters.
Note: If the value specified for pos
is greater then the length+1 of the CLOB
value then the
behavior is undefined. Some JDBC drivers may throw a
SQLException
while other drivers may support this
operation.
setString
in interface java.sql.Clob
pos
- the position at which to start writing to the CLOB
value that this Clob
object represents;
The first position is 1str
- the string to be written to the CLOB
value that this Clob
designatesjava.sql.SQLException
- if there is an error accessing the
CLOB
value or if pos is less than 1java.sql.SQLFeatureNotSupportedException
- if the JDBC driver does not support
this methodpublic int setString(long pos, java.lang.String str, int offset, int len) throws java.sql.SQLException
len
characters of str
, starting
at character offset
, to the CLOB
value
that this Clob
represents. The string will overwrite the existing characters
in the Clob
object starting at the position
pos
. If the end of the Clob
value is reached
while writing the given string, then the length of the Clob
value will be increased to accommodate the extra characters.
Note: If the value specified for pos
is greater then the length+1 of the CLOB
value then the
behavior is undefined. Some JDBC drivers may throw a
SQLException
while other drivers may support this
operation.
setString
in interface java.sql.Clob
pos
- the position at which to start writing to this
CLOB
object; The first position is 1str
- the string to be written to the CLOB
value that this Clob
object representsoffset
- the offset into str
to start reading
the characters to be writtenlen
- the number of characters to be writtenjava.sql.SQLException
- if there is an error accessing the
CLOB
value or if pos is less than 1java.sql.SQLFeatureNotSupportedException
- if the JDBC driver does not support
this methodpublic java.io.OutputStream setAsciiStream(long pos) throws java.sql.SQLException
CLOB
value that this Clob
object represents,
starting at position pos
. Characters written to the stream
will overwrite the existing characters
in the Clob
object starting at the position
pos
. If the end of the Clob
value is reached
while writing characters to the stream, then the length of the Clob
value will be increased to accommodate the extra characters.
Note: If the value specified for pos
is greater then the length+1 of the CLOB
value then the
behavior is undefined. Some JDBC drivers may throw a
SQLException
while other drivers may support this
operation.
setAsciiStream
in interface java.sql.Clob
pos
- the position at which to start writing to this
CLOB
object; The first position is 1java.sql.SQLException
- if there is an error accessing the
CLOB
value or if pos is less than 1java.sql.SQLFeatureNotSupportedException
- if the JDBC driver does not support
this methodgetAsciiStream()
public java.io.Writer setCharacterStream(long pos) throws java.sql.SQLException
CLOB
value that this Clob
object
represents, at position pos
. Characters written to the stream
will overwrite the existing characters
in the Clob
object starting at the position
pos
. If the end of the Clob
value is reached
while writing characters to the stream, then the length of the Clob
value will be increased to accommodate the extra characters.
Note: If the value specified for pos
is greater then the length+1 of the CLOB
value then the
behavior is undefined. Some JDBC drivers may throw a
SQLException
while other drivers may support this
operation.
When the value specified for pos
is greater then the
length+1, an SQLException
is thrown.
setCharacterStream
in interface java.sql.Clob
pos
- the position at which to start writing to the
CLOB
value; The first position is 1java.sql.SQLException
- if there is an error accessing the
CLOB
value or if pos is less than 1java.sql.SQLFeatureNotSupportedException
- if the JDBC driver does not support
this methodgetCharacterStream()
public void truncate(long len) throws java.sql.SQLException
CLOB
value that this Clob
designates to have a length of len
characters.
Note: If the value specified for pos
is greater then the length+1 of the CLOB
value then the
behavior is undefined. Some JDBC drivers may throw a
SQLException
while other drivers may support this
operation.
truncate
in interface java.sql.Clob
len
- the length, in characters, to which the CLOB
value
should be truncatedjava.sql.SQLException
- if there is an error accessing the
CLOB
value or if len is less than 0java.sql.SQLFeatureNotSupportedException
- if the JDBC driver does not support
this methodpublic void free() throws java.sql.SQLException
Clob
object and releases the resources the resources
that it holds. The object is invalid once the free
method
is called.
After free
has been called, any attempt to invoke a
method other than free
will result in a SQLException
being thrown. If free
is called multiple times, the subsequent
calls to free
are treated as a no-op.
free
in interface java.sql.Clob
java.sql.SQLException
- if an error occurs releasing
the Clob's resourcesjava.sql.SQLFeatureNotSupportedException
- if the JDBC driver does not support
this methodpublic java.io.Reader getCharacterStream(long pos, long length) throws java.sql.SQLException
Reader
object that contains a partial Clob
value, starting
with the character specified by pos, which is length characters in length.getCharacterStream
in interface java.sql.Clob
pos
- the offset to the first character of the partial value to
be retrieved. The first character in the Clob is at position 1.length
- the length in characters of the partial value to be retrieved.Reader
through which the partial Clob
value can be read.java.sql.SQLException
- if pos is less than 1 or if pos is greater than the number of
characters in the Clob
or if pos + length is greater than the number of
characters in the Clob
java.sql.SQLFeatureNotSupportedException
- if the JDBC driver does not support
this methodpublic java.io.File getFile()
public java.lang.String getEncoding()
public boolean isDeleteOnFree()
free()
.public void setDeleteOnFree(boolean deleteOnFree)
free()
.deleteOnFree
- the new value to assignCopyright © 2001 - 2018 HSQL Development Group.