org.springframework.jdbc.support.lob

## Interface LobHandler

- All Known Implementing Classes:
    AbstractLobHandler, DefaultLobHandler

      public interface LobHandler

  Abstraction for handling large binary fields and large text fields in specific databases, no matter if represented as simple types or Large OBjects.

  Provides accessor methods for BLOBs and CLOBs, and acts as factory for LobCreator instances, to be used as sessions for creating BLOBs or CLOBs. LobCreators are typically instantiated for each statement execution or for each transaction; they are not thread-safe because they might track allocated database resources in order to free them after execution.

  Most databases/drivers should be able to work with `DefaultLobHandler`, which by default delegates to JDBC's direct accessor methods, avoiding the `java.sql.Blob` and `java.sql.Clob` API completely. `DefaultLobHandler` can also be configured to access LOBs using `PreparedStatement.setBlob/setClob` (e.g. for PostgreSQL), through setting the `"wrapAsLob"` property.

  Of course, you need to declare different field types for each database. In Oracle, any binary content needs to go into a BLOB, and all character content beyond 4000 bytes needs to go into a CLOB. In MySQL, there is no notion of a CLOB type but rather a LONGTEXT type that behaves like a VARCHAR. For complete portability, use a LobHandler for fields that might typically require LOBs on some database because of the field size (take Oracle's numbers as a guideline).

  Summarizing the recommended options (for actual LOB fields):

  - JDBC 4.0 driver (including Oracle 11g driver): Use `DefaultLobHandler`, potentially with `streamAsLob=true` if your database driver requires that hint when populating a LOB field. Fall back to `createTemporaryLob=true` if you happen to run into LOB size limitations with your (Oracle) database setup.
  - Oracle 10g driver: Use `DefaultLobHandler` with standard setup. On Oracle 10.1, set the "SetBigStringTryClob" connection property; as of Oracle 10.2, DefaultLobHandler should work with standard setup out of the box.
  - PostgreSQL: Configure `DefaultLobHandler` with `wrapAsLob=true`, and use that LobHandler to access OID columns (but not BYTEA) in your database tables.
  - For all other database drivers (and for non-LOB fields that might potentially turn into LOBs on some databases): Simply use a plain `DefaultLobHandler`.
  Since:
    23.12.2003
  Author:
    Juergen Hoeller
  See Also:
    `DefaultLobHandler`, `ResultSet.getBlob(int)`, `ResultSet.getClob(int)`, `ResultSet.getBytes(int)`, `ResultSet.getBinaryStream(int)`, `ResultSet.getString(int)`, `ResultSet.getAsciiStream(int)`, `ResultSet.getCharacterStream(int)`

- - ### Method Summary

    All Methods Instance Methods Abstract Methods
    Modifier and Type | Method and Description
    --- | ---
    `InputStream` | `getBlobAsBinaryStream(ResultSet rs, int columnIndex)` Retrieve the given column as binary stream from the given ResultSet.
    `InputStream` | `getBlobAsBinaryStream(ResultSet rs, String columnName)` Retrieve the given column as binary stream from the given ResultSet.
    `byte[]` | `getBlobAsBytes(ResultSet rs, int columnIndex)` Retrieve the given column as bytes from the given ResultSet.
    `byte[]` | `getBlobAsBytes(ResultSet rs, String columnName)` Retrieve the given column as bytes from the given ResultSet.
    `InputStream` | `getClobAsAsciiStream(ResultSet rs, int columnIndex)` Retrieve the given column as ASCII stream from the given ResultSet.
    `InputStream` | `getClobAsAsciiStream(ResultSet rs, String columnName)` Retrieve the given column as ASCII stream from the given ResultSet.
    `Reader` | `getClobAsCharacterStream(ResultSet rs, int columnIndex)` Retrieve the given column as character stream from the given ResultSet.
    `Reader` | `getClobAsCharacterStream(ResultSet rs, String columnName)` Retrieve the given column as character stream from the given ResultSet.
    `String` | `getClobAsString(ResultSet rs, int columnIndex)` Retrieve the given column as String from the given ResultSet.
    `String` | `getClobAsString(ResultSet rs, String columnName)` Retrieve the given column as String from the given ResultSet.
    `LobCreator` | `getLobCreator()` Create a new `LobCreator` instance, i.e.

- - ### Method Detail

    - #### getBlobAsBytes

          @Nullable
          byte[] getBlobAsBytes(ResultSet rs,
                                          String columnName)
                                   throws SQLException

      Retrieve the given column as bytes from the given ResultSet. Might simply invoke `ResultSet.getBytes` or work with `ResultSet.getBlob`, depending on the database and driver.
      Parameters:
        `rs` - the ResultSet to retrieve the content from
        `columnName` - the column name to use
      Returns:
        the content as byte array, or `null` in case of SQL NULL
      Throws:
        `SQLException` - if thrown by JDBC methods
      See Also:
        `ResultSet.getBytes(int)`

    - #### getBlobAsBytes

          @Nullable
          byte[] getBlobAsBytes(ResultSet rs,
                                          int columnIndex)
                                   throws SQLException

      Retrieve the given column as bytes from the given ResultSet. Might simply invoke `ResultSet.getBytes` or work with `ResultSet.getBlob`, depending on the database and driver.
      Parameters:
        `rs` - the ResultSet to retrieve the content from
        `columnIndex` - the column index to use
      Returns:
        the content as byte array, or `null` in case of SQL NULL
      Throws:
        `SQLException` - if thrown by JDBC methods
      See Also:
        `ResultSet.getBytes(int)`

    - #### getBlobAsBinaryStream

          @Nullable
          InputStream getBlobAsBinaryStream(ResultSet rs,
                                                      String columnName)
                                               throws SQLException

      Retrieve the given column as binary stream from the given ResultSet. Might simply invoke `ResultSet.getBinaryStream` or work with `ResultSet.getBlob`, depending on the database and driver.
      Parameters:
        `rs` - the ResultSet to retrieve the content from
        `columnName` - the column name to use
      Returns:
        the content as binary stream, or `null` in case of SQL NULL
      Throws:
        `SQLException` - if thrown by JDBC methods
      See Also:
        `ResultSet.getBinaryStream(int)`

    - #### getBlobAsBinaryStream

          @Nullable
          InputStream getBlobAsBinaryStream(ResultSet rs,
                                                      int columnIndex)
                                               throws SQLException

      Retrieve the given column as binary stream from the given ResultSet. Might simply invoke `ResultSet.getBinaryStream` or work with `ResultSet.getBlob`, depending on the database and driver.
      Parameters:
        `rs` - the ResultSet to retrieve the content from
        `columnIndex` - the column index to use
      Returns:
        the content as binary stream, or `null` in case of SQL NULL
      Throws:
        `SQLException` - if thrown by JDBC methods
      See Also:
        `ResultSet.getBinaryStream(int)`

    - #### getClobAsString

          @Nullable
          String getClobAsString(ResultSet rs,
                                           String columnName)
                                    throws SQLException

      Retrieve the given column as String from the given ResultSet. Might simply invoke `ResultSet.getString` or work with `ResultSet.getClob`, depending on the database and driver.
      Parameters:
        `rs` - the ResultSet to retrieve the content from
        `columnName` - the column name to use
      Returns:
        the content as String, or `null` in case of SQL NULL
      Throws:
        `SQLException` - if thrown by JDBC methods
      See Also:
        `ResultSet.getString(int)`

    - #### getClobAsString

          @Nullable
          String getClobAsString(ResultSet rs,
                                           int columnIndex)
                                    throws SQLException

      Retrieve the given column as String from the given ResultSet. Might simply invoke `ResultSet.getString` or work with `ResultSet.getClob`, depending on the database and driver.
      Parameters:
        `rs` - the ResultSet to retrieve the content from
        `columnIndex` - the column index to use
      Returns:
        the content as String, or `null` in case of SQL NULL
      Throws:
        `SQLException` - if thrown by JDBC methods
      See Also:
        `ResultSet.getString(int)`

    - #### getClobAsAsciiStream

          @Nullable
          InputStream getClobAsAsciiStream(ResultSet rs,
                                                     String columnName)
                                              throws SQLException

      Retrieve the given column as ASCII stream from the given ResultSet. Might simply invoke `ResultSet.getAsciiStream` or work with `ResultSet.getClob`, depending on the database and driver.
      Parameters:
        `rs` - the ResultSet to retrieve the content from
        `columnName` - the column name to use
      Returns:
        the content as ASCII stream, or `null` in case of SQL NULL
      Throws:
        `SQLException` - if thrown by JDBC methods
      See Also:
        `ResultSet.getAsciiStream(int)`

    - #### getClobAsAsciiStream

          @Nullable
          InputStream getClobAsAsciiStream(ResultSet rs,
                                                     int columnIndex)
                                              throws SQLException

      Retrieve the given column as ASCII stream from the given ResultSet. Might simply invoke `ResultSet.getAsciiStream` or work with `ResultSet.getClob`, depending on the database and driver.
      Parameters:
        `rs` - the ResultSet to retrieve the content from
        `columnIndex` - the column index to use
      Returns:
        the content as ASCII stream, or `null` in case of SQL NULL
      Throws:
        `SQLException` - if thrown by JDBC methods
      See Also:
        `ResultSet.getAsciiStream(int)`

    - #### getClobAsCharacterStream

          Reader getClobAsCharacterStream(ResultSet rs,
                                          String columnName)
                                   throws SQLException

      Retrieve the given column as character stream from the given ResultSet. Might simply invoke `ResultSet.getCharacterStream` or work with `ResultSet.getClob`, depending on the database and driver.
      Parameters:
        `rs` - the ResultSet to retrieve the content from
        `columnName` - the column name to use
      Returns:
        the content as character stream
      Throws:
        `SQLException` - if thrown by JDBC methods
      See Also:
        `ResultSet.getCharacterStream(int)`

    - #### getClobAsCharacterStream

          Reader getClobAsCharacterStream(ResultSet rs,
                                          int columnIndex)
                                   throws SQLException

      Retrieve the given column as character stream from the given ResultSet. Might simply invoke `ResultSet.getCharacterStream` or work with `ResultSet.getClob`, depending on the database and driver.
      Parameters:
        `rs` - the ResultSet to retrieve the content from
        `columnIndex` - the column index to use
      Returns:
        the content as character stream
      Throws:
        `SQLException` - if thrown by JDBC methods
      See Also:
        `ResultSet.getCharacterStream(int)`

    - #### getLobCreator

          LobCreator getLobCreator()

      Create a new `LobCreator` instance, i.e. a session for creating BLOBs and CLOBs. Needs to be closed after the created LOBs are not needed anymore - typically after statement execution or transaction completion.
      Returns:
        the new LobCreator instance
      See Also:
        `LobCreator.close()`