ConnectionProvider


1   /*
2    * @(#) ConnectionProvider 1.0 02/08/01
3    */
4   package org.smartlib.pool.core;
5   
6   import java.sql.*;
7   
8   /**
9    * This interface is used to wrap the SmartPool to an existing connection pool.
10   *  
11   * <p>To wrap the SmartPool to an existing pool, provide an instance of 
12   * this interface in the configuration file. SmartPool will then draw 
13   * connection from this pool rather then drawing raw connections to the 
14   * pool. </p>
15   *
16   * <p>Also if the SmartPool is wrapped around another pool
17   * it will draw a connection on every call by calling 
18   * ConnectionProvider.getConnection().</p>
19   *
20   * <p>Similarly when you call Connection.close(), SmartPool returns the 
21   * connection back to the original pool immediately by calling 
22   * ConnectionProvider.returnConnection().</p> 
23   *
24   * <p>In short when this feature is used, SmartPool is just another layer of 
25   * indirection. SmartPool does not maintain any pool. This has been 
26   * specifically designed to do so. This is because the external pool to which
27   * SmartPool is wrapped is expected to do all the pooling. SmartPool can be 
28   * used to detect leaks and monitor live connections etc. <p>
29   *
30   */
31    
32  /* Note from the Author: I realized this when I tested this feature against an
33   * Application Server DataSource pool and to my surprise (I call my self
34   * a J2EE expert :) ) I discovered that the application server requires the
35   * connection to be returned to the pool.
36   * The Application Server manages the state of the connections and thus it is 
37   * imperative to return the connection back to the Application Server after 
38   * each use. 
39   */
40  
41  public interface ConnectionProvider {
42      
43      /**
44       * <p>This method implementation should fetch the connection.
45       * This method is expected to block if a connection is not available untill
46       * a connection a available.</p>
47       *
48       * <p>Whatever preprocessing you want to do, do it here. SmartPool will not 
49       * manuplate the connection state in anyway.</p>
50       * e.g. of preprocessing:<br> 
51       * <li>     1. Testing if the connection is valid.
52       * <li>     2. con.setAutoCommit(false|true)
53       * 
54       * <p>If you throw any Exception while doing this, SmartPool will wrap this 
55       * exception with ConnectionPoolException and throw it back to you in the 
56       * SmartPoolFactory.getConnection() method. So better behave your self and 
57       * handle all the cases here itself.</p>
58       *
59       *  
60       */
61      public Connection getConnection() throws Exception  ;
62  
63      /**
64       *<p>This method implementation should release the connection.</p>   
65       * 
66       * <p>Whatever postprocessing you want to do, do it here.</p>
67       * e.g. of postprocessing<br> 
68       * <li>     1. if (!conn.getAutoCommit()) conn.commit();
69       *  
70       * <p>If you throw any Exception while doing this, SmartPool will wrap this 
71       * exception with SQLException and throw it back to you in the 
72       * Connection.close() method. So better behave your self and 
73       * handle all the cases here itself.</p>
74       *  
75       */
76      public void returnConnection(Connection conn) throws Exception  ;
77  
78  }
79  
80
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