Class JDBCClobFile

java.lang.Object
org.hsqldb.jdbc.JDBCClobFile
All Implemented Interfaces:
Clob
public class JDBCClobFile extends Object implements Clob
A client-side file-based implementation of Clob.

HSQLDB-Specific Information:

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.

Since:
HSQLDB 2.1
Author:
Campbell Burnet (campbell-burnet@users dot sourceforge.net)

  • Field Summary

    Fields
    Modifier and Type
    Field
    Description
    static final String
    TEMP_FILE_PREFIX
     
    static final String
    TEMP_FILE_SUFFIX
     

  • Constructor Summary

    Constructors
    Constructor
    Description
    JDBCClobFile()
    Convenience constructor for JDBCClobFile((String)null).
    JDBCClobFile(File file)
    Convenience constructor for JDBCClobFile(file,null).
    JDBCClobFile(File file, String encoding)
    Constructs a new JDBCClobFile instance backed by the given File object using the given encoding to read and write file content.
    JDBCClobFile(String encoding)
    Constructs a new JDBCClobFile instance backed by a File object created by File.createTempFile(TEMP_FILE_PREFIX, TEMP_FILE_SUFFIX), using the given encoding to read and write file content.

  • Method Summary

    Modifier and Type
    Method
    Description
    void
    free()
    This method frees the Clob object and releases the resources that it holds.
    InputStream
    getAsciiStream()
    Retrieves the CLOB value designated by this Clob object as an ASCII stream.
    Reader
    getCharacterStream()
    Retrieves the CLOB value designated by this Clob object as a java.io.Reader object (or as a stream of characters).
    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.
    String
    getEncoding()
     
    File
    getFile()
    Retrieves the canonical File object denoting the file that backs this CLOB.
    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(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.
    long
    position(Clob pattern, long start)
    Retrieves the character position at which the specified Clob object searchstr appears in this Clob object.
    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.
    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, String str)
    Writes the given Java String to the CLOB value that this Clob object designates at the position pos.
    int
    setString(long pos, 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.

    Methods inherited from class Object

    equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

  • Field Details

  • Constructor Details

    • JDBCClobFile

      public JDBCClobFile() throws SQLException
      Convenience constructor for JDBCClobFile((String)null).
      Throws:
      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.

    • JDBCClobFile

      public JDBCClobFile(String encoding) throws SQLException
      Constructs a new JDBCClobFile instance backed by a File object created by File.createTempFile(TEMP_FILE_PREFIX, TEMP_FILE_SUFFIX), using the given encoding to read and write file content.
      Parameters:
      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.
      Throws:
      SQLException - if the given encoding is unsupported, the backing temp file could not be created or if a security manager exists and its {@link java.lang.SecurityManager#checkWrite(java.lang.String)} method does not allow a file to be created.

    • JDBCClobFile

      public JDBCClobFile(File file) throws SQLException
      Convenience constructor for JDBCClobFile(file,null).
      Parameters:
      file - that is to back the new CLOB instance.
      Throws:
      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 {@link java.lang.SecurityManager#checkRead} method denies read access to the file

    • JDBCClobFile

      public JDBCClobFile(File file, String encoding) throws SQLException
      Constructs a new JDBCClobFile instance backed by the given File object using the given encoding to read and write file content.
      Parameters:
      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.
      Throws:
      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 {@link java.lang.SecurityManager#checkRead} method denies read access to the file

  • Method Details

    • length

      public long length() throws SQLException
      Retrieves the number of characters in the CLOB value designated by this Clob object.
      Specified by:
      length in interface Clob
      Returns:
      length of the CLOB in characters
      Throws:
      SQLException - if there is an error accessing the length of the CLOB value
      SQLFeatureNotSupportedException - if the JDBC driver does not support this method
      Since:
      JDK 1.2

    • getSubString

      public String getSubString(long pos, int length) throws SQLException
      Retrieves a copy of the specified substring in the CLOB value designated by this Clob object. The substring begins at position pos and has up to length consecutive characters.
      Specified by:
      getSubString in interface Clob
      Parameters:
      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 greater
      Returns:
      a String that is the specified substring in the CLOB value designated by this Clob object
      Throws:
      SQLException - if there is an error accessing the CLOB value; if pos is less than 1 or length is less than 0
      SQLFeatureNotSupportedException - if the JDBC driver does not support this method
      Since:
      JDK 1.2

    • getCharacterStream

      public Reader getCharacterStream() throws SQLException
      Retrieves the CLOB value designated by this Clob object as a java.io.Reader object (or as a stream of characters).
      Specified by:
      getCharacterStream in interface Clob
      Returns:
      a java.io.Reader object containing the CLOB data
      Throws:
      SQLException - if there is an error accessing the CLOB value
      SQLFeatureNotSupportedException - if the JDBC driver does not support this method
      Since:
      JDK 1.2
      See Also:

    • getAsciiStream

      public InputStream getAsciiStream() throws SQLException
      Retrieves the CLOB value designated by this Clob object as an ASCII stream.
      Specified by:
      getAsciiStream in interface Clob
      Returns:
      a java.io.InputStream object containing the CLOB data
      Throws:
      SQLException - if there is an error accessing the CLOB value
      SQLFeatureNotSupportedException - if the JDBC driver does not support this method
      Since:
      JDK 1.2
      See Also:

    • position

      public long position(char[] pattern, long start) throws SQLException
      Retrieves the character position at which the specified char[] pattern appears in the CLOB value represented by this Clob object. The search begins at position start.
      Parameters:
      pattern - the substring for which to search
      start - the position at which to begin searching; the first position is 1
      Returns:
      the position at which the substring appears or -1 if it is not present; the first position is 1
      Throws:
      SQLException - if there is an error accessing the CLOB value or if pos is less than 1
      SQLFeatureNotSupportedException - if the JDBC driver does not support this method

    • position

      public long position(String searchstr, long start) throws SQLException
      Retrieves the character position at which the specified substring searchstr appears in the SQL CLOB value represented by this Clob object. The search begins at position start.
      Specified by:
      position in interface Clob
      Parameters:
      searchstr - the substring for which to search
      start - the position at which to begin searching; the first position is 1
      Returns:
      the position at which the substring appears or -1 if it is not present; the first position is 1
      Throws:
      SQLException - if there is an error accessing the CLOB value or if pos is less than 1
      SQLFeatureNotSupportedException - if the JDBC driver does not support this method
      Since:
      JDK 1.2

    • position

      public long position(Clob pattern, long start) throws SQLException
      Retrieves the character position at which the specified Clob object searchstr appears in this Clob object. The search begins at position start.
      Specified by:
      position in interface Clob
      Parameters:
      pattern - the Clob object for which to search
      start - the position at which to begin searching; the first position is 1
      Returns:
      the position at which the Clob object appears or -1 if it is not present; the first position is 1
      Throws:
      SQLException - if there is an error accessing the CLOB value or if start is less than 1
      SQLFeatureNotSupportedException - if the JDBC driver does not support this method
      Since:
      JDK 1.2

    • setString

      public int setString(long pos, String str) throws SQLException
      Writes the given Java 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 than 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.

      Specified by:
      setString in interface Clob
      Parameters:
      pos - the position at which to start writing to the CLOB value that this Clob object represents; The first position is 1
      str - the string to be written to the CLOB value that this Clob designates
      Returns:
      the number of characters written
      Throws:
      SQLException - if there is an error accessing the CLOB value or if pos is less than 1
      SQLFeatureNotSupportedException - if the JDBC driver does not support this method
      Since:
      JDK 1.4

    • setString

      public int setString(long pos, String str, int offset, int len) throws SQLException
      Writes 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 than 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.

      Specified by:
      setString in interface Clob
      Parameters:
      pos - the position at which to start writing to this CLOB object; The first position is 1
      str - the string to be written to the CLOB value that this Clob object represents
      offset - the offset into str to start reading the characters to be written
      len - the number of characters to be written
      Returns:
      the number of characters written
      Throws:
      SQLException - if there is an error accessing the CLOB value or if pos is less than 1
      SQLFeatureNotSupportedException - if the JDBC driver does not support this method
      Since:
      JDK 1.4

    • setAsciiStream

      public OutputStream setAsciiStream(long pos) throws SQLException
      Retrieves a stream to be used to write Ascii characters to the 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 than 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.

      Specified by:
      setAsciiStream in interface Clob
      Parameters:
      pos - the position at which to start writing to this CLOB object; The first position is 1
      Returns:
      the stream to which ASCII encoded characters can be written
      Throws:
      SQLException - if there is an error accessing the CLOB value or if pos is less than 1
      SQLFeatureNotSupportedException - if the JDBC driver does not support this method
      Since:
      JDK 1.4
      See Also:

    • setCharacterStream

      public Writer setCharacterStream(long pos) throws SQLException
      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. 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 than 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.

      HSQLDB-Specific Information:

      When the value specified for pos is greater then the length+1, an SQLException is thrown.
      Specified by:
      setCharacterStream in interface Clob
      Parameters:
      pos - the position at which to start writing to the CLOB value; The first position is 1
      Returns:
      a stream to which Unicode encoded characters can be written
      Throws:
      SQLException - if there is an error accessing the CLOB value or if pos is less than 1
      SQLFeatureNotSupportedException - if the JDBC driver does not support this method
      Since:
      JDK 1.4
      See Also:

    • truncate

      public void truncate(long len) throws SQLException
      Truncates the CLOB value that this Clob designates to have a length of len characters.

      Note: If the value specified for pos is greater than 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.

      Specified by:
      truncate in interface Clob
      Parameters:
      len - the length, in characters, to which the CLOB value should be truncated
      Throws:
      SQLException - if there is an error accessing the CLOB value or if len is less than 0
      SQLFeatureNotSupportedException - if the JDBC driver does not support this method
      Since:
      JDK 1.4

    • free

      public void free() throws SQLException
      This method frees the Clob object and releases 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.

      Specified by:
      free in interface Clob
      Throws:
      SQLException - if an error occurs releasing the Clob's resources
      SQLFeatureNotSupportedException - if the JDBC driver does not support this method
      Since:
      JDK 1.4

    • getCharacterStream

      public Reader getCharacterStream(long pos, long length) throws SQLException
      Returns a Reader object that contains a partial Clob value, starting with the character specified by pos, which is length characters in length.
      Specified by:
      getCharacterStream in interface Clob
      Parameters:
      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.
      Returns:
      Reader through which the partial Clob value can be read.
      Throws:
      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
      SQLFeatureNotSupportedException - if the JDBC driver does not support this method
      Since:
      1.6

    • getFile

      public File getFile()
      Retrieves the canonical File object denoting the file that backs this CLOB.
      Returns:
      the file that backs this CLOB.

    • getEncoding

      public String getEncoding()
      Returns:
      the name of the character encoding used to read and write character data in the underlying files, as well as to determine the character length and character offsets into the underlying file

    • isDeleteOnFree

      public boolean isDeleteOnFree()
      Retrieves whether an attempt to delete the backing file is made in response to invocation of free().
      Returns:
      true if backing file deletion is attempted; otherwise false.

    • setDeleteOnFree

      public void setDeleteOnFree(boolean deleteOnFree)
      Assigns whether an attempt to delete the backing file is made in response to invocation of free().
      Parameters:
      deleteOnFree - the new value to assign