Java - DBCP vs JNDI?

Question

I am a newbie and I have created a few simlpe Java Swing applications. I was able to use apache commons DBCP to create a connection pool and access the datasource.

I have recently started to create java web based applciations using JSP and Servlets. I have learnt to use JNDI to access the datasource. I update the XML files and use InitialContext() and lookup("java:comp/env") and that is it!!!! I am using Apache Tomcat as my Servlet/JSP container.

1. But where is the DB connection pool created?

2. If yes, then does that mean JNDI somehow uses the DBCP internally?

When I have to create a DBCP for Swing applications, I had to first create an instance of GenericObjectPool and then create a connection factory object and finally a PoolableConnectionFactory object to create the Datasource which will be used to get a connection.

Answer 1

JNDI is a mechanism to pass objects from one part of the system to another (in technical terms across class loaders). This is most useful for classes and interfaces found in the Java Runtime like String or DataSource.

This means that in your case JNDI is just a transport mechanism and you need to have the actual connection pool defined elsewhere. Most web containers have a mechanism for defining a system wide connection pool, and JNDI then allows you to get to it.

Answer 2

Tomcat use a custom implementation of Apache DBCP and Apache Pool for the JNDI Datasource. These libraries are located in a single JAR at $CATALINA_HOME/lib/tomcat-dbcp.jar.

The main package is org.apache.tomcat.dbcp for avoid conflicts with the regular packages form Apache Commons.

Answer 3

JNDI is a mechanism of locating remote resources via lookup. It has nothing in common with connection pooling libraries. These libraries, of which c3p0, DBCP and BoneCP, are the most famous, allow you to create data sources with ability to pool connections and/or statements. If this data source is used within your application, you don't need to use JNDI, if it is located on a remote system (for instance, in Tomcat), you need to use JNDI to get access to the data source.

As a side note, why did you choose to work with old-school Servlet/JSP combo? It is a better idea to work with JSP successor, facelets that is a preferred view technology in JSF 2.x.

Another comment is to transfer management of your data source to a well-known framework. One direction might be to use an ORM, for example, Hibernate, to manage your data source (which was created with connection pooling in mind).