[javaee-spec users] [jsr342-experts] platform default DataSource and JMS ConnectionFactory

From: Linda DeMichiel <>
Date: Mon, 12 Mar 2012 11:33:52 -0700

The Java EE platform requires that a platform product provide both a
database as well as a JMS provider in the operational environment.

We've gotten a number of requests that the Java EE platform therefore
define both a default data source and a default JMS connection factory
to access these resources.

The JMS spec lead has recently submitted a JIRA issue to us on behalf of the
JMS Expert Group requesting such an enhancement:

We agree that such default, preconfigured resources would facilitate
ease of development, and that they should be added to the platform.

Assuming that the Expert Group agrees with us, we need your input
on how these resources should best be made accessible.

We see two options. For the sake of simplification, I'll describe these
in terms of data sources, but we would expect to treat JMS connection
factories in the same way. The requirements for JMS would of course
only apply in environments in which JMS is required to be supported
(i.e., in the full Java EE platform, but not in the Web Profile).

Approach (1): We require that if a DataSource resource isn't mapped to
a specific database, it is mapped to a preconfigured DataSource for
the product's default database. I.e., in the absence of any action on
the part of the deployer, the following will map to the product's
default database:

    DataSource myDS;

In this approach, there is no special JNDI name and no way to specify
with the lookup element that this is the selected database.

Approach (2): We define a special JNDI name/location at which the
DataSource for the default database is made available, e.g.,
java:comp/defaultDataSource. [Names TBD.]

The application specifies the binding of the resource reference to
this in the usual way, i.e., as follows:

@Resource(name="myDataSource", lookup="java:comp/defaultDataSource")
DataSource myDS;

An advantage of approach (1) is that it is much simpler for beginning
developers since there is no special name that one needs to know.

A disadvantage of approach (1) that it is harder to tell whether the
user made an error and forgot to map the data source reference, or
whether the user left it unmapped on purpose because they wanted it to
be automatically mapped to the default data source.

An additional disadvantage of appraoch (1) is that if a different
lookup name is specified in @Resource, there is no name to replace it
with in the deployment descriptor to refer to the default data source.

The disadvantage of approach (2) is that requiring a special JNDI
name be specified in the lookup element is more verbose.

A possible third--"do both"--approach is that we define a well-known name,
but not require its use. This would result in the flexibility of
approach (2) with the terseness of approach (1), but would not make it
less error-prone.

Please let us know your opinions on these issues.