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/* * @(#)Joinable.java 1.6 05/11/17 * * Copyright 2006 Sun Microsystems, Inc. All rights reserved. * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms. */ 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> * <P> * <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. * <p> * <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 emplemented 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. * <P> * <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><sup><font size=-2>TM</font></sup> * 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 arrary 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; }