1/*
2 * Copyright (c) 2000, 2017, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.  Oracle designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Oracle in the LICENSE file that accompanied this code.
10 *
11 * This code is distributed in the hope that it will be useful, but WITHOUT
12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
14 * version 2 for more details (a copy is included in the LICENSE file that
15 * accompanied this code).
16 *
17 * You should have received a copy of the GNU General Public License version
18 * 2 along with this work; if not, write to the Free Software Foundation,
19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20 *
21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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23 * questions.
24 */
25
26package javax.sql;
27
28import java.sql.Connection;
29import java.sql.SQLException;
30
31/**
32 * An object that provides hooks for connection pool management.
33 * A <code>PooledConnection</code> object
34 * represents a physical connection to a data source.  The connection
35 * can be recycled rather than being closed when an application is
36 * finished with it, thus reducing the number of connections that
37 * need to be made.
38 * <P>
39 * An application programmer does not use the <code>PooledConnection</code>
40 * interface directly; rather, it is used by a middle tier infrastructure
41 * that manages the pooling of connections.
42 * <P>
43 * When an application calls the method <code>DataSource.getConnection</code>,
44 * it gets back a <code>Connection</code> object.  If connection pooling is
45 * being done, that <code>Connection</code> object is actually a handle to
46 * a <code>PooledConnection</code> object, which is a physical connection.
47 * <P>
48 * The connection pool manager, typically the application server, maintains
49 * a pool of <code>PooledConnection</code> objects.  If there is a
50 * <code>PooledConnection</code> object available in the pool, the
51 * connection pool manager returns a <code>Connection</code> object that
52 * is a handle to that physical connection.
53 * If no <code>PooledConnection</code> object is available, the
54 * connection pool manager calls the <code>ConnectionPoolDataSource</code>
55 * method <code>getPoolConnection</code> to create a new physical connection.  The
56 *  JDBC driver implementing <code>ConnectionPoolDataSource</code> creates a
57 *  new <code>PooledConnection</code> object and returns a handle to it.
58 * <P>
59 * When an application closes a connection, it calls the <code>Connection</code>
60 * method <code>close</code>. When connection pooling is being done,
61 * the connection pool manager is notified because it has registered itself as
62 * a <code>ConnectionEventListener</code> object using the
63 * <code>ConnectionPool</code> method <code>addConnectionEventListener</code>.
64 * The connection pool manager deactivates the handle to
65 * the <code>PooledConnection</code> object and  returns the
66 * <code>PooledConnection</code> object to the pool of connections so that
67 * it can be used again.  Thus, when an application closes its connection,
68 * the underlying physical connection is recycled rather than being closed.
69 * <p>
70 * If the connection pool manager wraps or provides a proxy to the logical
71 * handle returned from a call to {@code PoolConnection.getConnection}, the pool
72 * manager must do one of the following when the connection pool manager
73 * closes or returns the {@code PooledConnection} to the pool in response to
74 * the application calling {@code Connection.close}:
75 * <ul>
76 * <li>call {@code endRequest} on the logical {@code Connection} handle
77 * <li>call {@code close} on the logical {@code Connection} handle
78 * </ul>
79 * <p>
80 * The physical connection is not closed until the connection pool manager
81 * calls the <code>PooledConnection</code> method <code>close</code>.
82 * This method is generally called to have an orderly shutdown of the server or
83 * if a fatal error has made the connection unusable.
84 *
85 * <p>
86 * A connection pool manager is often also a statement pool manager, maintaining
87 *  a pool of <code>PreparedStatement</code> objects.
88 *  When an application closes a prepared statement, it calls the
89 *  <code>PreparedStatement</code>
90 * method <code>close</code>. When <code>Statement</code> pooling is being done,
91 * the pool manager is notified because it has registered itself as
92 * a <code>StatementEventListener</code> object using the
93 * <code>ConnectionPool</code> method <code>addStatementEventListener</code>.
94 *  Thus, when an application closes its  <code>PreparedStatement</code>,
95 * the underlying prepared statement is recycled rather than being closed.
96 *
97 * @since 1.4
98 */
99
100public interface PooledConnection {
101
102  /**
103   * Creates and returns a <code>Connection</code> object that is a handle
104   * for the physical connection that
105   * this <code>PooledConnection</code> object represents.
106   * The connection pool manager calls this method when an application has
107   * called the method <code>DataSource.getConnection</code> and there are
108   * no <code>PooledConnection</code> objects available. See the
109   * {@link PooledConnection interface description} for more information.
110   *
111   * @return  a <code>Connection</code> object that is a handle to
112   *          this <code>PooledConnection</code> object
113   * @exception SQLException if a database access error occurs
114   * @exception java.sql.SQLFeatureNotSupportedException if the JDBC driver does not support
115   * this method
116   * @since 1.4
117   */
118  Connection getConnection() throws SQLException;
119
120  /**
121   * Closes the physical connection that this <code>PooledConnection</code>
122   * object represents.  An application never calls this method directly;
123   * it is called by the connection pool module, or manager.
124   * <P>
125   * See the {@link PooledConnection interface description} for more
126   * information.
127   *
128   * @exception SQLException if a database access error occurs
129   * @exception java.sql.SQLFeatureNotSupportedException if the JDBC driver does not support
130   * this method
131   * @since 1.4
132   */
133  void close() throws SQLException;
134
135  /**
136   * Registers the given event listener so that it will be notified
137   * when an event occurs on this <code>PooledConnection</code> object.
138   *
139   * @param listener a component, usually the connection pool manager,
140   *        that has implemented the
141   *        <code>ConnectionEventListener</code> interface and wants to be
142   *        notified when the connection is closed or has an error
143   * @see #removeConnectionEventListener
144   */
145  void addConnectionEventListener(ConnectionEventListener listener);
146
147  /**
148   * Removes the given event listener from the list of components that
149   * will be notified when an event occurs on this
150   * <code>PooledConnection</code> object.
151   *
152   * @param listener a component, usually the connection pool manager,
153   *        that has implemented the
154   *        <code>ConnectionEventListener</code> interface and
155   *        been registered with this <code>PooledConnection</code> object as
156   *        a listener
157   * @see #addConnectionEventListener
158   */
159  void removeConnectionEventListener(ConnectionEventListener listener);
160
161        /**
162         * Registers a <code>StatementEventListener</code> with this <code>PooledConnection</code> object.  Components that
163         * wish to be notified when  <code>PreparedStatement</code>s created by the
164         * connection are closed or are detected to be invalid may use this method
165         * to register a <code>StatementEventListener</code> with this <code>PooledConnection</code> object.
166         *
167         * @param listener      an component which implements the <code>StatementEventListener</code>
168         *                                      interface that is to be registered with this <code>PooledConnection</code> object
169         *
170         * @since 1.6
171         */
172        public void addStatementEventListener(StatementEventListener listener);
173
174        /**
175         * Removes the specified <code>StatementEventListener</code> from the list of
176         * components that will be notified when the driver detects that a
177         * <code>PreparedStatement</code> has been closed or is invalid.
178         *
179         * @param listener      the component which implements the
180         *                                      <code>StatementEventListener</code> interface that was previously
181         *                                      registered with this <code>PooledConnection</code> object
182         *
183         * @since 1.6
184         */
185        public void removeStatementEventListener(StatementEventListener listener);
186
187 }
188