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package javax.sql.rowset;

import java.sql.SQLException;

/**

 * The <code>Joinable</code> interface provides the methods for getting and

 * setting a match column, which is the basis for forming the SQL <code>JOIN</code>

 * formed by adding <code>RowSet</code> objects to a <code>JoinRowSet</code>

 * object.

 * <P>

 * Any standard <code>RowSet</code> implementation <b>may</b> implement

 * the <code>Joinable</code> interface in order to be

 * added to a <code>JoinRowSet</code> object. Implementing this interface gives

 * a <code>RowSet</code> object the ability to use <code>Joinable</code> methods,

 * which set, retrieve, and get information about match columns.  An

 * application may add a

 * <code>RowSet</code> object that has not implemented the <code>Joinable</code>

 * interface to a <code>JoinRowSet</code> object, but to do so it must use one

 * of the <code>JoinRowSet.addRowSet</code> methods that takes both a

 * <code>RowSet</code> object and a match column or an array of <code>RowSet</code>

 * objects and an array of match columns.

 * <P>

 * To get access to the methods in the <code>Joinable</code> interface, a

 * <code>RowSet</code> object implements at least one of the

 * five standard <code>RowSet</code> interfaces and also implements the

 * <code>Joinable</code> interface.  In addition, most <code>RowSet</code>

 * objects extend the <code>BaseRowSet</code> class.  For example:

 * <pre>

 *     class MyRowSetImpl extends BaseRowSet implements CachedRowSet, Joinable {

 *         :

 *         :

 *     }

 * </pre>

 *

 * <P>

 * The methods in the <code>Joinable</code> interface allow a <code>RowSet</code> object

 * to set a match column, retrieve a match column, or unset a match column, which is

 * the column upon which an SQL <code>JOIN</code> can be based.

 * An instance of a class that implements these methods can be added to a

 * <code>JoinRowSet</code> object to allow an SQL <code>JOIN</code> relationship to

 *  be established.

 *

 * <pre>

 *     CachedRowSet crs = new MyRowSetImpl();

 *     crs.populate((ResultSet)rs);

 *     (Joinable)crs.setMatchColumnIndex(1);

 *

 *     JoinRowSet jrs = new JoinRowSetImpl();

 *     jrs.addRowSet(crs);

 * </pre>

 * In the previous example, <i>crs</i> is a <code>CachedRowSet</code> object that

 * has implemented the <code>Joinable</code> interface.  In the following example,

 * <i>crs2</i> has not, so it must supply the match column as an argument to the

 * <code>addRowSet</code> method. This example assumes that column 1 is the match

 * column.

 * <PRE>

 *     CachedRowSet crs2 = new MyRowSetImpl();

 *     crs2.populate((ResultSet)rs);

 *

 *     JoinRowSet jrs2 = new JoinRowSetImpl();

 *     jrs2.addRowSet(crs2, 1);

 * </PRE>

 * <p>

 * The <code>JoinRowSet</code> interface makes it possible to get data from one or

 * more <code>RowSet</code> objects consolidated into one table without having to incur

 * the expense of creating a connection to a database. It is therefore ideally suited

 * for use by disconnected <code>RowSet</code> objects. Nevertheless, any

 * <code>RowSet</code> object <b>may</b> implement this interface

 * regardless of whether it is connected or disconnected. Note that a

 * <code>JdbcRowSet</code> object, being always connected to its data source, can

 * become part of an SQL <code>JOIN</code> directly without having to become part

 * of a <code>JoinRowSet</code> object.

 *

 * The index array passed into the <code>setMatchColumn</code> methods indicates

 * how many match columns are being set (the length of the array) in addition to

 * which columns will be used for the match. For example:

 * <pre>

 *     int[] i = {1, 2, 4, 7}; // indicates four match columns, with column

 *                             // indexes 1, 2, 4, 7 participating in the JOIN.

 *     Joinable.setMatchColumn(i);

 * </pre>

 * Subsequent match columns may be added as follows to a different <code>Joinable</code>

 * object (a <code>RowSet</code> object that has implemented the <code>Joinable</code>

 * interface).

 * <pre>

 *     int[] w = {3, 2, 5, 3};

 *     Joinable2.setMatchColumn(w);

 * </pre>

 * When an application adds two or more <code>RowSet</code> objects to a

 * <code>JoinRowSet</code> object, the order of the indexes in the array is

 * particularly important. Each index of

 * the array maps directly to the corresponding index of the previously added

 * <code>RowSet</code> object. If overlap or underlap occurs, the match column

 * data is maintained in the event an additional <code>Joinable</code> RowSet is

 * added and needs to relate to the match column data. Therefore, applications

 * can set multiple match columns in any order, but

 * this order has a direct effect on the outcome of the <code>SQL</code> JOIN.

 * <p>

 * This assertion applies in exactly the same manner when column names are used

 * rather than column indexes to indicate match columns.

 *

 * @see JoinRowSet

 * @author  Jonathan Bruce

 * @since 1.5

 */

public interface Joinable {

    /**

     * Sets the designated column as the match column for this <code>RowSet</code>

     * object. A <code>JoinRowSet</code> object can now add this <code>RowSet</code>

     * object based on the match column.

     * <p>

     * Sub-interfaces such as the <code>CachedRowSet</code>&trade;

     * interface define the method <code>CachedRowSet.setKeyColumns</code>, which allows

     * primary key semantics to be enforced on specific columns.

     * Implementations of the <code>setMatchColumn(int columnIdx)</code> method

     * should ensure that the constraints on the key columns are maintained when

     * a <code>CachedRowSet</code> object sets a primary key column as a match column.

     *

     * @param columnIdx an <code>int</code> identifying the index of the column to be

     *        set as the match column

     * @throws SQLException if an invalid column index is set

     * @see #setMatchColumn(int[])

     * @see #unsetMatchColumn(int)

     *

     */

    public void setMatchColumn(int columnIdx) throws SQLException;

    /**

     * Sets the designated columns as the match column for this <code>RowSet</code>

     * object. A <code>JoinRowSet</code> object can now add this <code>RowSet</code>

     * object based on the match column.

     *

     * @param columnIdxes an array of <code>int</code> identifying the indexes of the

     *      columns to be set as the match columns

     * @throws SQLException if an invalid column index is set

     * @see #setMatchColumn(int[])

     * @see #unsetMatchColumn(int[])

     */

    public void setMatchColumn(int[] columnIdxes) throws SQLException;

    /**

     * Sets the designated column as the match column for this <code>RowSet</code>

     * object. A <code>JoinRowSet</code> object can now add this <code>RowSet</code>

     * object based on the match column.

     * <p>

     * Subinterfaces such as the <code>CachedRowSet</code> interface define

     * the method <code>CachedRowSet.setKeyColumns</code>, which allows

     * primary key semantics to be enforced on specific columns.

     * Implementations of the <code>setMatchColumn(String columnIdx)</code> method

     * should ensure that the constraints on the key columns are maintained when

     * a <code>CachedRowSet</code> object sets a primary key column as a match column.

     *

     * @param columnName a <code>String</code> object giving the name of the column

     *      to be set as the match column

     * @throws SQLException if an invalid column name is set, the column name

     *      is a null, or the column name is an empty string

     * @see #unsetMatchColumn

     * @see #setMatchColumn(int[])

     */

    public void setMatchColumn(String columnName) throws SQLException;

    /**

     * Sets the designated columns as the match column for this <code>RowSet</code>

     * object. A <code>JoinRowSet</code> object can now add this <code>RowSet</code>

     * object based on the match column.

     *

     * @param columnNames an array of <code>String</code> objects giving the names

     *     of the column to be set as the match columns

     * @throws SQLException if an invalid column name is set, the column name

     *      is a null, or the column name is an empty string

     * @see #unsetMatchColumn

     * @see #setMatchColumn(int[])

     */

    public void setMatchColumn(String[] columnNames) throws SQLException;

    /**

     * Retrieves the indexes of the match columns that were set for this

     * <code>RowSet</code> object with the method

     * <code>setMatchColumn(int[] columnIdxes)</code>.

     *

     * @return an <code>int</code> array identifying the indexes of the columns

     *         that were set as the match columns for this <code>RowSet</code> object

     * @throws SQLException if no match column has been set

     * @see #setMatchColumn

     * @see #unsetMatchColumn

     */

    public int[] getMatchColumnIndexes() throws SQLException;

    /**

     * Retrieves the names of the match columns that were set for this

     * <code>RowSet</code> object with the method

     * <code>setMatchColumn(String [] columnNames)</code>.

     *

     * @return an array of <code>String</code> objects giving the names of the columns

     *         set as the match columns for this <code>RowSet</code> object

     * @throws SQLException if no match column has been set

     * @see #setMatchColumn

     * @see #unsetMatchColumn

     *

     */

    public String[] getMatchColumnNames() throws SQLException;

    /**

     * Unsets the designated column as the match column for this <code>RowSet</code>

     * object.

     * <P>

     * <code>RowSet</code> objects that implement the <code>Joinable</code> interface

     * must ensure that a key-like constraint continues to be enforced until the

     * method <code>CachedRowSet.unsetKeyColumns</code> has been called on the

     * designated column.

     *

     * @param columnIdx an <code>int</code> that identifies the index of the column

     *          that is to be unset as a match column

     * @throws SQLException if an invalid column index is designated or if

     *          the designated column was not previously set as a match

     *          column

     * @see #setMatchColumn

     */

    public void unsetMatchColumn(int columnIdx) throws SQLException;

    /**

     * Unsets the designated columns as the match column for this <code>RowSet</code>

     * object.

     *

     * @param columnIdxes an array of <code>int</code> that identifies the indexes

     *     of the columns that are to be unset as match columns

     * @throws SQLException if an invalid column index is designated or if

     *          the designated column was not previously set as a match

     *          column

     * @see #setMatchColumn

     */

    public void unsetMatchColumn(int[] columnIdxes) throws SQLException;

    /**

     * Unsets the designated column as the match column for this <code>RowSet</code>

     * object.

     * <P>

     * <code>RowSet</code> objects that implement the <code>Joinable</code> interface

     * must ensure that a key-like constraint continues to be enforced until the

     * method <code>CachedRowSet.unsetKeyColumns</code> has been called on the

     * designated column.

     *

     * @param columnName a <code>String</code> object giving the name of the column

     *          that is to be unset as a match column

     * @throws SQLException if an invalid column name is designated or

     *          the designated column was not previously set as a match

     *          column

     * @see #setMatchColumn

     */

    public void unsetMatchColumn(String columnName) throws SQLException;

    /**

     * Unsets the designated columns as the match columns for this <code>RowSet</code>

     * object.

     *

     * @param columnName an array of <code>String</code> objects giving the names of

     *     the columns that are to be unset as the match columns

     * @throws SQLException if an invalid column name is designated or the

     *     designated column was not previously set as a match column

     * @see #setMatchColumn

     */

    public void unsetMatchColumn(String[] columnName) throws SQLException;

}