DriverManager vs. DataSource?

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hank barta - 21 Jan 2004 04:25 GMT

I've been working with some code that accesses a MySQL database with
plans to use it in some web applications (either servlets or JSPs.) I
started with some old code that uses the java.sql.DriverManager
class to establish the connection. Looking at some code in the
J2EE samples, it looks like (and I quote from the documentation)
"The use of a DataSource object is the preferred means of connecting
to a data source."

This leaves me with some questions.

Is it even possible to use DriverManager in a servlet or JSP? I
started looking at the documentation because I could not figure out
how to get my JSP to find mysql.jar.

Can I use DataSource in a console app? It looks like it requires a
JNDI server (again, according to the docs "An object that implements
the DataSource interface will typically be registered with a JNDI
service provider.") I presume that means that I need to run the
servlet/JSP container at a minimum to use a data source (whether
for a console app or JSP.)

I presume that once I have a Connection, it doesn't matter whether
it came from a DriverManager or DataSource, the behavior is pretty
much the same. Is that correct?

I would like to retain the capability to test my database code
from a console application rather than from within a JSP. Will
it be necessary to use different connection methods depending on
the environment or can I switch to the DataSource and use that in
both environments.

Finally, if these are routine questions that are answered somewhere,
please point me to that resource!

thanks,
hank

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Lee Fesperman - 21 Jan 2004 09:21 GMT

> I've been working with some code that accesses a MySQL database with
> plans to use it in some web applications (either servlets or JSPs.) I
[quoted text clipped - 9 lines]
> started looking at the documentation because I could not figure out
> how to get my JSP to find mysql.jar.

Yes, it is possible to use the DriverManager interface. DataSources are preferred
because they make it easy for the JSP/servlet container to provide connection pooling
and other services automatically (under the covers).

JDBC driver jars go in a 'common' directory in the container. The container docs should
specify where to put those jars so that they are accessible.

> Can I use DataSource in a console app? It looks like it requires a
> JNDI server (again, according to the docs "An object that implements
> the DataSource interface will typically be registered with a JNDI
> service provider.") I presume that means that I need to run the
> servlet/JSP container at a minimum to use a data source (whether
> for a console app or JSP.)

You can use DataSource in a 'non-managed' (outside the container server) configuration.
You will need to have the JDBC 2.0 Standard Extension jar or the J2EE jar on the
classpath (to reference javax.sql.DataSource), unless you're using JDK 1.4.x. You don't
need JNDI. You just instantiate the appropriate javax.sql.DataSource implementation, set
connection properties and get the connection (java.sql.Connection). See the javadocs on
javax.sql.DataSource and the docs for your JDBC driver for details.

> I presume that once I have a Connection, it doesn't matter whether
> it came from a DriverManager or DataSource, the behavior is pretty
> much the same. Is that correct?

Yes, that is correct for simple JSP/Servlets.

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Oscar Kind - 21 Jan 2004 09:25 GMT

Place it in the directory WEB-INF/lib. All .jar (and IIRC also .zip) files
in that directory are automatically added to the classpath of the
application.

If it is a driver for all applications, you may instead choose to install
it in the entire application server (for Tomcat 4.x by placing it in the
directory common/lib). This has two obvious consequences:
- That version of the driver is available to all applications.
- Installation becomes more difficult than trivial (i.e. you have to
copy files to two locations, often cannot use a web interface, etc.).

Yes, by using a context provider (the JNDI server of the application
server).

> I presume that once I have a Connection, it doesn't matter whether
> it came from a DriverManager or DataSource, the behavior is pretty
> much the same. Is that correct?

Yes. Behaviour is identical. There is however, one important difference:
getting a connection from a datasource is significantly faster.

> I would like to retain the capability to test my database code
> from a console application rather than from within a JSP. Will
> it be necessary to use different connection methods depending on
> the environment or can I switch to the DataSource and use that in
> both environments.

Since you can use a datasource from a console application, you can use the
same method for both.

> Finally, if these are routine questions that are answered somewhere,
> please point me to that resource!

This is a question I leave to others, since I learned this by doing.

Oscar

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DriverManager vs. DataSource?

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