/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */


This package contains two DataSources: PerUserPoolDataSource and
SharedPoolDataSource which provide a database connection pool.
Below are a couple of usage examples.  One shows deployment into a JNDI system.
The other is a simple example initializing the pool using standard java code.

JNDI

Most
J2EE containers will provide some way of deploying resources into JNDI.  The
method will vary among containers, but once the resource is available via
JNDI, the application can access the resource in a container independent
manner.  The following example shows deployment into tomcat (catalina).

In server.xml, the following would be added to the <Context> for your
webapp:


 <Resource name="jdbc/bookstore" auth="Container"
            type="org.apache.commons.dbcp2.datasources.PerUserPoolPoolDataSource"/>
  <ResourceParams name="jdbc/bookstore">
    <parameter>
      <name>factory</name>
      <value>org.apache.commons.dbcp2.datasources.PerUserPoolDataSourceFactory</value>
    </parameter>
    <parameter>
      <name>dataSourceName</name><value>java:comp/env/jdbc/bookstoreCPDS</value>
    </parameter>
    <parameter>
      <name>defaultMaxTotal</name><value>30</value>
    </parameter>
  </ResourceParams>


In web.xml.  Note that elements must be given in the order of the dtd
described in the servlet specification:


<resource-ref>
  <description>
    Resource reference to a factory for java.sql.Connection
    instances that may be used for talking to a particular
    database that is configured in the server.xml file.
  </description>
  <res-ref-name>
    jdbc/bookstore
  </res-ref-name>
  <res-type>
    org.apache.commons.dbcp2.datasources.PerUserPoolDataSource
  </res-type>
  <res-auth>
    Container
  </res-auth>
</resource-ref>


Apache Tomcat deploys all objects configured similarly to above within the
java:comp/env namespace.  So the JNDI path given for
the dataSourceName parameter is valid for a
ConnectionPoolDataSource that is deployed as given in the
cpdsadapter example


The DataSource is now available to the application as shown
below:


    Context ctx = new InitialContext();
    DataSource ds = (DataSource)
        ctx.lookup("java:comp/env/jdbc/bookstore");
    Connection con = null;
    try
    {
        con = ds.getConnection();
        ...
        use the connection
        ...
    }
    finally
    {
        if (con != null)
            con.close();
    }


The reference to the DataSource could be maintained, for
multiple getConnection() requests.  Or the DataSource can be
looked up in different parts of the application code.
PerUserPoolDataSourceFactory and
SharedPoolDataSourceFactory will maintain the state of the pool
between different lookups.  This behavior may be different in other
implementations.

Without JNDI

Connection pooling is useful in applications regardless of whether they run
in a J2EE environment and a DataSource can be used within a
simpler environment.  The example below shows SharedPoolDataSource using
DriverAdapterCPDS as the back end source, though any CPDS is applicable.


public class Pool
{
    private static DataSource ds;
    static
    {
        DriverAdapterCPDS cpds = new DriverAdapterCPDS();
        cpds.setDriver("org.gjt.mm.mysql.Driver");
        cpds.setUrl("jdbc:mysql://localhost:3306/bookstore");
        cpds.setUser("foo");
        cpds.setPassword(null);
        SharedPoolDataSource tds = new SharedPoolDataSource();
        tds.setConnectionPoolDataSource(cpds);
        tds.setMaxTotal(10);
        tds.setMaxWaitMillis(50);
        ds = tds;
    }
    public static getConnection()
    {
        return ds.getConnection();
    }
}


This class can then be used wherever a connection is needed:


    Connection con = null;
    try
    {
        con = Pool.getConnection();
        ...
        use the connection
        ...
    }
    finally
    {
        if (con != null)
            con.close();
    }

/**
 * <p>
 * This package contains two DataSources: <code>PerUserPoolDataSource</code> and
 * <code>SharedPoolDataSource</code> which provide a database connection pool.
 * Below are a couple of usage examples.  One shows deployment into a JNDI system.
 * The other is a simple example initializing the pool using standard java code.
 * </p>
 *
 * <h2>JNDI</h2>
 *
 * <p>
 * Most
 * J2EE containers will provide some way of deploying resources into JNDI.  The
 * method will vary among containers, but once the resource is available via
 * JNDI, the application can access the resource in a container independent
 * manner.  The following example shows deployment into tomcat (catalina).
 * </p>
 * <p>In server.xml, the following would be added to the &lt;Context&gt; for your
 * webapp:
 * </p>
 *
 * <code>
 *  &lt;Resource name="jdbc/bookstore" auth="Container"
 *             type="org.apache.commons.dbcp2.datasources.PerUserPoolPoolDataSource"/&gt;
 *   &lt;ResourceParams name="jdbc/bookstore"&gt;
 *     &lt;parameter&gt;
 *       &lt;name&gt;factory&lt;/name&gt;
 *       &lt;value&gt;org.apache.commons.dbcp2.datasources.PerUserPoolDataSourceFactory&lt;/value&gt;
 *     &lt;/parameter&gt;
 *     &lt;parameter&gt;
 *       &lt;name&gt;dataSourceName&lt;/name&gt;&lt;value&gt;java:comp/env/jdbc/bookstoreCPDS&lt;/value&gt;
 *     &lt;/parameter&gt;
 *     &lt;parameter&gt;
 *       &lt;name&gt;defaultMaxTotal&lt;/name&gt;&lt;value&gt;30&lt;/value&gt;
 *     &lt;/parameter&gt;
 *   &lt;/ResourceParams&gt;
 * </code>
 *
 * <p>
 * In web.xml.  Note that elements must be given in the order of the dtd
 * described in the servlet specification:
 * </p>
 *
 * <code>
 * &lt;resource-ref&gt;
 *   &lt;description&gt;
 *     Resource reference to a factory for java.sql.Connection
 *     instances that may be used for talking to a particular
 *     database that is configured in the server.xml file.
 *   &lt;/description&gt;
 *   &lt;res-ref-name&gt;
 *     jdbc/bookstore
 *   &lt;/res-ref-name&gt;
 *   &lt;res-type&gt;
 *     org.apache.commons.dbcp2.datasources.PerUserPoolDataSource
 *   &lt;/res-type&gt;
 *   &lt;res-auth&gt;
 *     Container
 *   &lt;/res-auth&gt;
 * &lt;/resource-ref&gt;
 * </code>
 *
 * <p>
 * Apache Tomcat deploys all objects configured similarly to above within the
 * <strong>java:comp/env</strong> namespace.  So the JNDI path given for
 * the dataSourceName parameter is valid for a
 * <code>ConnectionPoolDataSource</code> that is deployed as given in the
 * <a href="../cpdsadapter/package.html">cpdsadapter example</a>
 * </p>
 *
 * <p>
 * The <code>DataSource</code> is now available to the application as shown
 * below:
 * </p>
 *
 * <code>
 *
 *     Context ctx = new InitialContext();
 *     DataSource ds = (DataSource)
 *         ctx.lookup("java:comp/env/jdbc/bookstore");
 *     Connection con = null;
 *     try
 *     {
 *         con = ds.getConnection();
 *         ...
 *         use the connection
 *         ...
 *     }
 *     finally
 *     {
 *         if (con != null)
 *             con.close();
 *     }
 *
 * </code>
 *
 * <p>
 * The reference to the <code>DataSource</code> could be maintained, for
 * multiple getConnection() requests.  Or the <code>DataSource</code> can be
 * looked up in different parts of the application code.
 * <code>PerUserPoolDataSourceFactory</code> and
 * <code>SharedPoolDataSourceFactory</code> will maintain the state of the pool
 * between different lookups.  This behavior may be different in other
 * implementations.
 * </p>
 *
 * <h2>Without JNDI</h2>
 *
 * <p>
 * Connection pooling is useful in applications regardless of whether they run
 * in a J2EE environment and a <code>DataSource</code> can be used within a
 * simpler environment.  The example below shows SharedPoolDataSource using
 * DriverAdapterCPDS as the back end source, though any CPDS is applicable.
 * </p>
 *
 * <code>
 *
 * public class Pool
 * {
 *     private static DataSource ds;
 *
 *     static
 *     {
 *         DriverAdapterCPDS cpds = new DriverAdapterCPDS();
 *         cpds.setDriver("org.gjt.mm.mysql.Driver");
 *         cpds.setUrl("jdbc:mysql://localhost:3306/bookstore");
 *         cpds.setUser("foo");
 *         cpds.setPassword(null);
 *
 *         SharedPoolDataSource tds = new SharedPoolDataSource();
 *         tds.setConnectionPoolDataSource(cpds);
 *         tds.setMaxTotal(10);
 *         tds.setMaxWaitMillis(50);
 *
 *         ds = tds;
 *     }
 *
 *     public static getConnection()
 *     {
 *         return ds.getConnection();
 *     }
 * }
 *
 * </code>
 *
 * <p>
 * This class can then be used wherever a connection is needed:
 * </p>
 *
 * <code>
 *     Connection con = null;
 *     try
 *     {
 *         con = Pool.getConnection();
 *         ...
 *         use the connection
 *         ...
 *     }
 *     finally
 *     {
 *         if (con != null)
 *             con.close();
 *     }
 * </code>
 */
package org.apache.commons.dbcp2.datasources;