public class JDBCClob extends Object implements Clob
CLOB type.
 An SQL CLOB is a built-in type
 that stores a Character Large Object as a column value in a row of
 a database table.
 By default drivers implement a Clob object using an SQL
 locator(CLOB), which means that a Clob object
 contains a logical pointer to the SQL CLOB data rather than
 the data itself. A Clob object is valid for the duration
 of the transaction in which it was created.
 The Clob interface provides methods for getting the
 length of an SQL CLOB (Character Large Object) value,
 for materializing a CLOB value on the client, and for
 searching for a substring or CLOB object within a
 CLOB value.
 Methods in the interfaces ResultSet,
 CallableStatement, and PreparedStatement, such as
 getClob and setClob allow a programmer to
 access an SQL CLOB value.  In addition, this interface
 has methods for updating a CLOB value.
 
 All methods on the Clob interface must be fully implemented if the
 JDBC driver supports the data type.
 
 
Previous to 2.0, the HSQLDB driver did not implement Clob using an SQL locator(CLOB). That is, an HSQLDB Clob object did not contain a logical pointer to SQL CLOB data; rather it directly contained a representation of the data (a String). As a result, an HSQLDB Clob object was itself valid beyond the duration of the transaction in which is was created, although it did not necessarily represent a corresponding value on the database. Also, the interface methods for updating a CLOB value were unsupported, with the exception of the truncate method, in that it could be used to truncate the local value.
 Starting with 2.0, the HSQLDB driver fully supports both local and remote
 SQL CLOB data implementations, meaning that an HSQLDB Clob object may
 contain a logical pointer to remote SQL CLOB data (see JDBCClobClient) or it may directly contain a local representation of the
 data (as implemented in this class).  In particular, when the product is built
 under JDK 1.6+ and the Clob instance is constructed as a result of calling
 JDBCConnection.createClob(), then the resulting Clob instance is initially
 disconnected (is not bound to the transaction scope of the vending Connection
 object), the data is contained directly and all interface methods for
 updating the CLOB value are supported for local use until the first
 invocation of free(); otherwise, an HSQLDB Clob's implementation is
 determined at runtime by the driver, it is typically not valid beyond
 the duration of the transaction in which is was created, and there no
 standard way to query whether it represents a local or remote value.
| Constructor and Description | 
|---|
| JDBCClob(String data)Constructs a new, read-only JDBCClob object wrapping the given character
 sequence. | 
| Modifier and Type | Method and Description | 
|---|---|
| void | free()This method frees the  Clobobject and releases the resources the resources
 that it holds. | 
| InputStream | getAsciiStream()Retrieves the  CLOBvalue designated by thisClobobject as an ASCII stream. | 
| Reader | getCharacterStream()Retrieves the  CLOBvalue designated by thisClobobject as ajava.io.Readerobject (or as a stream of
 characters). | 
| Reader | getCharacterStream(long pos,
                  long length)Returns a  Readerobject that contains a partialClobvalue, starting
 with the character specified by pos, which is length characters in length. | 
| String | getSubString(long pos,
            int length)Retrieves a copy of the specified substring
 in the  CLOBvalue
 designated by thisClobobject. | 
| long | length()Retrieves the number of characters
 in the  CLOBvalue
 designated by thisClobobject. | 
| long | position(Clob searchstr,
        long start)Retrieves the character position at which the specified
  Clobobjectsearchstrappears in thisClobobject. | 
| long | position(String searchstr,
        long start)Retrieves the character position at which the specified substring
  searchstrappears in the SQLCLOBvalue
 represented by thisClobobject. | 
| OutputStream | setAsciiStream(long pos)Retrieves a stream to be used to write ASCII characters to the
  CLOBvalue that thisClobobject represents,
 starting at positionpos. | 
| Writer | setCharacterStream(long pos)Retrieves a stream to be used to write a stream of Unicode characters
 to the  CLOBvalue that thisClobobject
 represents, at positionpos. | 
| int | setString(long pos,
         String str)Writes the given Java  Stringto theCLOBvalue that thisClobobject designates at the positionpos. | 
| int | setString(long pos,
         String str,
         int offset,
         int len)Writes  lencharacters ofstr, starting
 at characteroffset, to theCLOBvalue
 that thisClobrepresents. | 
| int | setStringBuffer(long pos,
               StringBuffer sb,
               int offset,
               int len)Behaviour is identical to  setString(long, java.lang.String, int, int). | 
| void | truncate(long len)Truncates the  CLOBvalue that thisClobdesignates to have a length oflencharacters. | 
public JDBCClob(String data) throws SQLException
This constructor is used internally to retrieve result set values as Clob objects, yet it must be public to allow access from other packages. As such (in the interest of efficiency) this object maintains a reference to the given String object rather than making a copy and so it is gently suggested (in the interest of effective memory management) that external clients using this constructor either take pause to consider the implications or at least take care to provide a String object whose internal character buffer is not much larger than required to represent the value.
data - the character sequence representing the Clob valueSQLException - if the argument is nullpublic long length()
            throws SQLException
CLOB value
 designated by this Clob object.length in interface ClobCLOB in charactersSQLException - if there is an error accessing the
            length of the CLOB valueSQLFeatureNotSupportedException - if the JDBC driver does not support
 this methodpublic String getSubString(long pos, int length) throws SQLException
CLOB value
 designated by this Clob object.
 The substring begins at position
 pos and has up to length consecutive
 characters.
 
 
 The official specification above is ambiguous in that it does not
 precisely indicate the policy to be observed when
 pos > this.length() - length.  One policy would be to retrieve
 the characters from pos to this.length().  Another would
 be to throw an exception. This class observes the second policy. 
Note
 This method uses String.substring(int, int).
 
Depending on implementation (typically JDK 6 and earlier releases), the returned value may be sharing the underlying (and possibly much larger) character buffer. Depending on factors such as hardware acceleration for array copies, the average length and number of sub-strings taken, and so on, this may or may not result in faster operation and non-trivial memory savings. On the other hand, Oracle / OpenJDK 7, it was decided that the memory leak implications outweigh the benefits of buffer sharing for most use cases on modern hardware.
It is left up to any client of this method to determine if this is a potential factor relative to the target runtime and to decide how to handle space-time trade-offs (i.e. whether to make an isolated copy of the returned substring or risk that more memory remains allocated than is absolutely required).
getSubString in interface Clobpos - 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;
 JDBC 4.1[ the value for length must be 0 or greater]String that is the specified substring in
         the CLOB value designated by this Clob objectSQLException - if there is an error accessing the
            CLOB value; if pos is less than 1 JDBC 4.1[or length is
 less than 0]SQLFeatureNotSupportedException - if the JDBC driver does not support
 this methodpublic Reader getCharacterStream() throws SQLException
CLOB value designated by this Clob
 object as a java.io.Reader object (or as a stream of
 characters).getCharacterStream in interface Clobjava.io.Reader object containing the
         CLOB dataSQLException - if there is an error accessing the
            CLOB valueSQLFeatureNotSupportedException - if the JDBC driver does not support
 this methodsetCharacterStream(long)public InputStream getAsciiStream() throws SQLException
CLOB value designated by this Clob
 object as an ASCII stream.getAsciiStream in interface Clobjava.io.InputStream object containing the
         CLOB dataSQLException - if there is an error accessing the
            CLOB valueSQLFeatureNotSupportedException - if the JDBC driver does not support
 this methodsetAsciiStream(long)public long position(String searchstr, long start) throws SQLException
searchstr appears in the SQL CLOB value
 represented by this Clob object.  The search
 begins at position start.position in interface Clobsearchstr - the substring for which to searchstart - the position at which to begin searching; the first position
              is 1SQLException - if there is an error accessing the
            CLOB value or if start is less than 1SQLFeatureNotSupportedException - if the JDBC driver does not support
 this methodpublic long position(Clob searchstr, long start) throws SQLException
Clob object searchstr appears in this
 Clob object.  The search begins at position
 start.position in interface Clobsearchstr - 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 1SQLException - if there is an error accessing the
            CLOB value or if start is less than 1SQLFeatureNotSupportedException - if the JDBC driver does not support
 this methodpublic int setString(long pos,
                     String str)
              throws 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.
 
 
Starting with HSQLDB 2.0 this feature is supported.
When built under JDK 1.6+ and the Clob instance is constructed as a result of calling JDBCConnection.createClob(), this operation affects only the client-side value; it has no effect upon a value stored in the database because JDBCConnection.createClob() constructs disconnected, initially empty Clob instances. To propagate the Clob value to a database in this case, it is required to supply the Clob instance to an updating or inserting setXXX method of a Prepared or Callable Statement, or to supply the Clob instance to an updateXXX method of an updateable ResultSet.
Implementation Notes:
No attempt is made to ensure precise thread safety. Instead, volatile member field and local variable snapshot isolation semantics are implemented. This is expected to eliminate most issues related to race conditions, with the possible exception of concurrent invocation of free().
In general, if an application may perform concurrent JDBCClob modifications and the integrity of the application depends on total order Clob modification semantics, then such operations should be synchronized on an appropriate monitor.
 When the value specified for pos is greater then the
 length+1, then the CLOB value is extended in length to accept the
 written characters and the undefined region up to @{code pos} is filled
 with with space (' ') characters.
 
setString in interface Clobpos - 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 designatesSQLException - if there is an error accessing the
            CLOB value or if pos is less than 1SQLFeatureNotSupportedException - if the JDBC driver does not support
 this methodpublic int setString(long pos,
                     String str,
                     int offset,
                     int len)
              throws 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.
 
 
Starting with HSQLDB 2.0 this feature is supported.
When built under JDK 1.6+ and the Clob instance is constructed as a result of calling JDBCConnection.createClob(), this operation affects only the client-side value; it has no effect upon a value stored in a database because JDBCConnection.createClob() constructs disconnected, initially empty Clob instances. To propagate the Clob value to a database in this case, it is required to supply the Clob instance to an updating or inserting setXXX method of a Prepared or Callable Statement, or to supply the Clob instance to an updateXXX method of an updateable ResultSet.
Implementation Notes:
 If the value specified for pos
 is greater than the length of the CLOB value, then
 the CLOB value is extended in length to accept the
 written characters and the undefined region up to pos is
 filled with space (' ') characters.
No attempt is made to ensure precise thread safety. Instead, volatile member field and local variable snapshot isolation semantics are implemented. This is expected to eliminate most issues related to race conditions, with the possible exception of concurrent invocation of free().
In general, if an application may perform concurrent JDBCClob modifications and the integrity of the application depends on total order Clob modification semantics, then such operations should be synchronized on an appropriate monitor.
setString in interface Clobpos - 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 writtenSQLException - if there is an error accessing the
            CLOB value or if pos is less than 1SQLFeatureNotSupportedException - if the JDBC driver does not support
 this methodpublic OutputStream setAsciiStream(long pos) throws 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 than the length of the CLOB value, then the
 behavior is undefined. Some JDBC drivers may throw a
 SQLException while other drivers may support this
 operation.
 
 
Starting with HSQLDB 2.0 this feature is supported.
When built under JDK 1.6+ and the Clob instance is constructed as a result of calling JDBCConnection.createClob(), this operation affects only the client-side value; it has no effect upon a value stored in a database because JDBCConnection.createClob() constructs disconnected, initially empty Clob instances. To propagate the Clob value to a database in this case, it is required to supply the Clob instance to an updating or inserting setXXX method of a Prepared or Callable Statement, or to supply the Clob instance to an updateXXX method of an updatable ResultSet.
Implementation Notes:
The data written to the stream does not appear in this Clob until the stream is closed.
 When the stream is closed, if the value specified for pos
 is greater than the length of the CLOB value, then
 the CLOB value is extended in length to accept the
 written characters and the undefined region up to pos is
 filled with space (' ') characters. 
Also, no attempt is made to ensure precise thread safety. Instead, volatile member field and local variable snapshot isolation semantics are implemented. This is expected to eliminate most issues related to race conditions, with the possible exception of concurrent invocation of free().
In general, if an application may perform concurrent JDBCClob modifications and the integrity of the application depends on total order Clob modification semantics, then such operations should be synchronized on an appropriate monitor.
setAsciiStream in interface Clobpos - the position at which to start writing to this
        CLOB object; The first position is 1SQLException - if there is an error accessing the
            CLOB value or if pos is less than 1SQLFeatureNotSupportedException - if the JDBC driver does not support
 this methodgetAsciiStream()public Writer setCharacterStream(long pos) throws 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.
 
 
Starting with HSQLDB 2.0 this feature is supported.
When built under JDK 1.6+ and the Clob instance is constructed as a result of calling JDBCConnection.createClob(), this operation affects only the client-side value; it has no effect upon a value stored in a database because JDBCConnection.createClob() constructs disconnected, initially empty Clob instances. To propagate the Clob value to a database in this case, it is required to supply the Clob instance to an updating or inserting setXXX method of a Prepared or Callable Statement, or to supply the Clob instance to an updateXXX method of an updateable ResultSet.
Implementation Notes:
The data written to the stream does not appear in this Clob until the stream is closed.
 When the stream is closed, if the value specified for pos
 is greater than the length of the CLOB value, then
 the CLOB value is extended in length to accept the
 written characters and the undefined region up to pos is
 filled with space (' ') characters. 
Also, no attempt is made to ensure precise thread safety. Instead, volatile member field and local variable snapshot isolation semantics are implemented. This is expected to eliminate most issues related to race conditions, with the possible exception of concurrent invocation of free().
In general, if an application may perform concurrent JDBCClob modifications and the integrity of the application depends on total order Clob modification semantics, then such operations should be synchronized on an appropriate monitor.
setCharacterStream in interface Clobpos - the position at which to start writing to the
        CLOB value; The first position is 1SQLException - if there is an error accessing the
            CLOB value or if pos is less than 1SQLFeatureNotSupportedException - if the JDBC driver does not support
 this methodgetCharacterStream()public void truncate(long len)
              throws SQLException
CLOB value that this Clob
 designates to have a length of len
 characters.
 
 Note: If the value specified for len
 is greater than the length of the CLOB value, then the
 behavior is undefined. Some JDBC drivers may throw a
 SQLException while other drivers may support this
 operation.
 
 
Starting with HSQLDB 2.0 this feature is fully supported.
When built under JDK 1.6+ and the Clob instance is constructed as a result of calling JDBCConnection.createClob(), this operation affects only the client-side value; it has no effect upon a value stored in a database because JDBCConnection.createClob() constructs disconnected, initially empty Blob instances. To propagate the truncated Clob value to a database in this case, it is required to supply the Clob instance to an updating or inserting setXXX method of a Prepared or Callable Statement, or to supply the Blob instance to an updateXXX method of an updateable ResultSet.
Implementation Notes:
 HSQLDB throws an SQLException if the specified len is greater
 than the value returned by length. 
truncate in interface Cloblen - the length, in characters, to which the CLOB value
        should be truncatedSQLException - if there is an error accessing the
            CLOB value or if len is less than 0SQLFeatureNotSupportedException - if the JDBC driver does not support
 this methodpublic void free()
          throws 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 ClobSQLException - if an error occurs releasing
 the Clob's resourcesSQLFeatureNotSupportedException - if the JDBC driver does not support
 this methodpublic Reader getCharacterStream(long pos, long length) throws 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 Clobpos - 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.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 ClobSQLFeatureNotSupportedException - if the JDBC driver does not support
 this methodpublic int setStringBuffer(long pos,
                           StringBuffer sb,
                           int offset,
                           int len)
                    throws SQLException
setString(long, java.lang.String, int, int).pos - the position at which to start writing to this
        CLOB object; The first position  is 1sb - the buffer to be written to the CLOB
        value that this Clob object representsoffset - the offset into sb to start reading
        the characters to be writtenlen - the number of characters to be writtenSQLException - if there is an error accessing the
            CLOB value or if pos is less than 1Copyright © 2001 - 2017 HSQL Development Group.