datasources package.html

jmcnally Sun, 12 Oct 2003 22:29:12 -0700

jmcnally    2003/10/12 22:30:13

  Added:       dbcp/src/java/org/apache/commons/dbcp/datasources
                        package.html
  Log:
  add package.html
  
  Revision  Changes    Path
  1.1                  
jakarta-commons/dbcp/src/java/org/apache/commons/dbcp/datasources/package.html
  
  Index: package.html
  ===================================================================
  <html>
  <body>
  <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>In server.xml, the following would be added to the &lt;Context&gt; for your
  webapp:
  </p>
  
  <code><pre>
  
   &lt;Resource name="jdbc/bookstore" auth="Container"
              type="org.apache.commons.dbcp.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.dbcp.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;defaultMaxActive&lt;/name&gt;&lt;value&gt;30&lt;/value&gt;
      &lt;/parameter&gt;
  
    &lt;/ResourceParams&gt;
  
  </pre></code>
  
  <p>
  In web.xml.  Note that elements must be given in the order of the dtd 
  described in the servlet specification:
  </p>
  
  <code><pre>
  &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.dbcp.datasources.PerUserPoolDataSource
    &lt;/res-type&gt;
    &lt;res-auth&gt;
      Container
    &lt;/res-auth&gt;
  &lt;/resource-ref&gt;
  </pre></code>
  
  
  <p>
  Catalina 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><pre>
  
      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();
      }
  
  </pre></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 backend source, though any CPDS is applicable.
  </p>
  
  <code><pre>
  
  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.setMaxActive(10);
          tds.setMaxWait(50);
  
          ds = tds;
      }
  
      public static getConnection()
      {
          return ds.getConnection();
      }  
  }
  
  </pre></code>
  
  <p>
  This class can then be used wherever a connection is needed:
  </p>
  
  <code><pre>
      Connection con = null;
      try
      {
          con = Pool.getConnection();
          ... 
          use the connection
          ...
      }
      finally
      {
          if (con != null)
              con.close();
      }
  </pre></code>
  
  </body>
  </html>


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