C3P0

Establishing a Connection

                              Creating and establishing a database connections are relatively very expensive. Because it involves processes like establishing a network connection, initializing database session, authorization in the back end database etc.

      Database or DBMS is a Data Source. A legacy file system or some other data source with a corresponding JDBC driver are also data sources.

       When establishing a connection to a database, a JDBC (Java DataBase Client) Application can use any of the two classes

• Driver Manager

                  connects an application to a data source which is specified by its URL (eg:database URL)
                   driver manager class calls the method DriverManager.getConnection to create the connection.The method requires a database URL depending on your DBMS. eg: jdbc:mysql://localhost:3306/

• Data Source   

                 provides a new way for JDBC clients to obtain a database connection. Its the newer and the preferred way.

Advantages of using Data Source over Driver Manager

                        01) portability is increased

                        02) enables the connection pooling and distributed transaction
                              mechanisms
                      
                        03) properties of data source are kept in a configuration file, 
                              so that any change to the data source or data drivers can
                              be made in the configuration file. But in driver manager 
                              properties are hard coded in the application. So after the
                              change the code has to recompiled

             C3P0 provides Data Source implementations

  What is C3P0  ? 

           C3P0 is an easy-to-use library. Increase the functionality of traditional JDBC drivers and make them enterprise ready. The most useful service it provides is when  acquiring database connections it provides newer javax.sql.DataSource  scheme which has many advantages over the traditional DriverManager based JDBC drivers.

 

  Prerequisities

requires level 1.6.x or above Java Runtime environment 

  C3P0 Usage

 For the users c3p0 provides standard jdbc DataSource objects. 3 ways are available to acquire c3p0 pool-backed datasources.
     

• directly instantiate and configure a ComboPooledDataSource

• use DataSources factory class 

• instantiate  PoolBackedDataSource and set its ConectionPoolDataSource and    

        thereby build our own pool backed data source


First method among the above mentioned 3 methods is regarded as the most convenient method. Lets discuss each in detail.


Method 1

Instantiating and Configuring a ComboPooledDataSource

       - instantiate an instance of  com.mchange.v2.c3p0.ComboPooledDataSource.

        -  ComboPooledDataSource() is a public ,no-arg constructor.

        - But before using the DataSource, make sure to set at least the property   
          jdbcUrl.

       - Following shows the code for fully configuring the DataSourceand make a
          usable pooled DataSource.

   
     
       - Above configured DataSource can then be used to make the connection 
         with the database as follows

                 

ComboPooledDataSource dataSource = DatabaseUtility.getDataSource();
Connection connection = dataSource.getConnection();

     
       - Furthermore, we can configure multiple DataSources using named 
         configurations supported by c3p0.

       - For that, construct the ComboPooledDataSource with the configuration
         name as the constructor argument as below.

Method 2

Using the DataSources factory class

  hope detailed explanation on this method soon

 

 

 

 

Using any of the above mentioned methods we can create our  Data Source.
For any Data Source built in, c3p0 use default values for the configuration parameters, if not programmed specifically. But these default values can be overridden using configuration files. Configuration also can be done in 3 ways.

• using a simple java.util.Properties files called c3p0.properties
• using a XML formatted file called c3p0-config.xml
• using more advanced HOCON configuration files  called application.json