# Prepared statements and streaming columns

setXXXStream requests stream data between the application and the database.

JDBC allows an IN parameter to be set to a Java input stream for passing in large amounts of data in smaller chunks. When the statement is run, the JDBC driver makes repeated calls to this input stream. Derby supports the following JDBC stream methods for PreparedStatement objects:

- setBinaryStream

  Use for streams that contain uninterpreted bytes

- setAsciiStream

  Use for streams that contain ASCII characters

- setCharacterStream

  Use for streams that contain characters

Note: Derby does not support the setNCharacterStream method or the deprecated setUnicodeStream method.

JDBC 3.0 requires that you specify the length of the stream, and Derby enforces this requirement if your application runs on JDK 5 or earlier. If your application runs on JDK 6, Derby exposes a JDBC 4.0 implementation, which lets you use the streaming interfaces without having to specify the stream length. The stream object passed to setBinaryStream and setAsciiStream can be either a standard Java stream object or the user's own subclass that implements the standard java.io.InputStream interface. The object passed to setCharacterStream must be a subclass of the abstract java.io.Reader class.

According to the JDBC standard, streams can be stored only in columns with the data types shown in the following table.

Table 1. Streamable JDBC Data Types
Column Data Type | Corresponding Java Type | AsciiStream | CharacterStream | BinaryStream
--- | --- | --- | --- | ---
CLOB | java.sql.Clob | x | x |
CHAR |  | x | x |
VARCHAR |  | x | x |
LONGVARCHAR |  | X | X |
BINARY |  | x | x | x
BLOB | java.sql.Blob | x | x | x
VARBINARY |  | x | x | x
LONGVARBINARY |  | x | x | X

Note:

- A large X indicates the preferred target data type for the type of stream. See Mapping of java.sql.Types to SQL Types.
- For applications using the client driver, if the stream is stored in a column of a type other than LONG VARCHAR or LONG VARCHAR FOR BIT DATA, the entire stream must be able to fit into memory at one time. Streams stored in LONG VARCHAR and LONG VARCHAR FOR BIT DATA columns do not have this limitation.
- Streams cannot be stored in columns of the other built-in data types or columns of user-defined data types.

#### Example

The following code fragment shows how a user can store a streamed, ASCII-encoded java.io.File in a LONG VARCHAR column:

        Statement s = conn.createStatement();
        s.executeUpdate("CREATE TABLE atable (a INT, b LONG VARCHAR)");
        conn.commit();

        java.io.File file = new java.io.File("derby.txt");
        int fileLength = (int) file.length();

        // create an input stream
        java.io.InputStream fin = new java.io.FileInputStream(file);
        PreparedStatement ps = conn.prepareStatement(
            "INSERT INTO atable VALUES (?, ?)");
        ps.setInt(1, 1);

        // set the value of the input parameter to the input stream
        ps.setAsciiStream(2, fin, fileLength);
        ps.execute();
        conn.commit();

Parent topic: java.sql.PreparedStatement interface