1. /*

  2.  * @(#)Joinable.java	1.5 04/05/29

  3.  *

  4.  * Copyright 2004 Sun Microsystems, Inc. All rights reserved.

  5.  * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.

  6.  */

  7. 

  8. package javax.sql.rowset;

  9. 

  10. import java.sql.SQLException;

  11. 

  12. /**

  13.  * <h3>1.0 Background</h3>

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

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

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

  17.  * object.

  18.  * <P>

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

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

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

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

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

  24.  * application may add a

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

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

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

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

  29.  * objects and an array of match columns. 

  30.  * <P>

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

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

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

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

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

  36.  * <pre>

  37.  *     class MyRowSetImpl extends BaseRowSet implements CachedRowSet, Joinable {

  38.  *         :

  39.  *         :

  40.  *     }

  41.  * </pre>

  42.  * <P>

  43.  * <h3>2.0 Usage Guidelines</h3>

  44.  * <P>

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

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

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

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

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

  50.  *  be established.

  51.  * <p>

  52.  * <pre>

  53.  *     CachedRowSet crs = new MyRowSetImpl();

  54.  *     crs.populate((ResultSet)rs);

  55.  *     (Joinable)crs.setMatchColumnIndex(1);

  56.  *

  57.  *     JoinRowSet jrs = new JoinRowSetImpl();

  58.  *     jrs.addRowSet(crs);

  59.  * </pre>

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

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

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

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

  64.  * column.

  65.  * <PRE>

  66.  *     CachedRowSet crs2 = new MyRowSetImpl();

  67.  *     crs2.populate((ResultSet)rs);

  68.  *     

  69.  *     JoinRowSet jrs2 = new JoinRowSetImpl();

  70.  *     jrs2.addRowSet(crs2, 1);

  71.  * </PRE>

  72.  * <p>

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

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

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

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

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

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

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

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

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

  82.  * <P>

  83.  * <h3>3.0 Managing Multiple Match Columns</h3>

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

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

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

  87.  * <pre>

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

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

  90.  *     Joinable.setMatchColumn(i);

  91.  * </pre>

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

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

  94.  * interface).

  95.  * <pre>

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

  97.  *     Joinable2.setMatchColumn(w);

  98.  * </pre>

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

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

  101.  * particularly important. Each index of 

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

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

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

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

  106.  * can set multiple match columns in any order, but

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

  108.  * <p>

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

  110.  * rather than column indexes to indicate match columns.

  111.  *

  112.  * @see JoinRowSet

  113.  * @author  Jonathan Bruce

  114.  */

  115. public interface Joinable {

  116.     

  117.     /** 

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

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

  120.      * object based on the match column.

  121.      * <p>

  122.      * Sub-interfaces such as the <code>CachedRowSet</code><sup><font size=-2>TM</font></sup>

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

  124.      * primary key semantics to be enforced on specific columns.

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

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

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

  128.      *

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

  130.      *        set as the match column

  131.      * @throws SQLException if an invalid column index is set

  132.      * @see #setMatchColumn(int[])

  133.      * @see #unsetMatchColumn(int)

  134.      *

  135.      */

  136.     public void setMatchColumn(int columnIdx) throws SQLException;

  137.     

  138.     /**

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

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

  141.      * object based on the match column.

  142.      *

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

  144.      *      columns to be set as the match columns

  145.      * @throws SQLException if an invalid column index is set

  146.      * @see #setMatchColumn(int[])

  147.      * @see #unsetMatchColumn(int[])     

  148.      */

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

  150.     

  151.     /** 

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

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

  154.      * object based on the match column.

  155.      * <p>

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

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

  158.      * primary key semantics to be enforced on specific columns.

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

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

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

  162.      *

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

  164.      *      to be set as the match column

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

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

  167.      * @see #unsetMatchColumn

  168.      * @see #setMatchColumn(int[])

  169.      */

  170.     public void setMatchColumn(String columnName) throws SQLException;

  171.     

  172.     /**

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

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

  175.      * object based on the match column.

  176.      *

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

  178.      *     of the column to be set as the match columns

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

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

  181.      * @see #unsetMatchColumn

  182.      * @see #setMatchColumn(int[])

  183.      */

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

  185.     

  186.     /** 

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

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

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

  190.      *

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

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

  193.      * @throws SQLException if no match column has been set

  194.      * @see #setMatchColumn

  195.      * @see #unsetMatchColumn     

  196.      */

  197.     public int[] getMatchColumnIndexes() throws SQLException;

  198.     

  199.     /** 

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

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

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

  203.      *

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

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

  206.      * @throws SQLException if no match column has been set

  207.      * @see #setMatchColumn

  208.      * @see #unsetMatchColumn

  209.      *

  210.      */

  211.     public String[] getMatchColumnNames() throws SQLException;

  212.     

  213.     /** 

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

  215.      * object.

  216.      * <P>

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

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

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

  220.      * designated column.

  221.      *

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

  223.      *          that is to be unset as a match column

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

  225.      *          the designated column was not previously set as a match

  226.      *          column

  227.      * @see #setMatchColumn     

  228.      */

  229.     public void unsetMatchColumn(int columnIdx) throws SQLException;

  230.     

  231.     /**

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

  233.      * object.

  234.      *

  235.      * @param columnIdxes an arrary of <code>int</code> that identifies the indexes

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

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

  238.      *          the designated column was not previously set as a match

  239.      *          column

  240.      * @see #setMatchColumn       

  241.      */

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

  243.     

  244.     /** 

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

  246.      * object.

  247.      * <P>

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

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

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

  251.      * designated column.

  252.      *

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

  254.      *          that is to be unset as a match column

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

  256.      *          the designated column was not previously set as a match

  257.      *          column

  258.      * @see #setMatchColumn          

  259.      */

  260.     public void unsetMatchColumn(String columnName) throws SQLException;

  261.     

  262.     /**

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

  264.      * object.

  265.      *      

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

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

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

  269.      *     designated column was not previously set as a match column

  270.      * @see #setMatchColumn  

  271.      */

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

  273. }