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package javax.sql.rowset;

import java.sql.SQLException;

/**
 * <h3>1.0 Background</h3>
 * 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>
 *
 * <h3>2.0 Usage Guidelines</h3>
 * <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.
 *
 * <h3>3.0 Managing Multiple Match Columns</h3>
 * 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
 */
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;
}