<s>
DataSource	B-General_Concept
is	O
a	O
name	O
given	O
to	O
the	O
connection	O
set	O
up	O
to	O
a	O
database	O
from	O
a	O
server	B-Application
.	O
</s>
<s>
The	O
data	B-General_Concept
source	I-General_Concept
name	I-General_Concept
(	O
DSN	O
)	O
need	O
not	O
be	O
the	O
same	O
as	O
the	O
filename	O
for	O
the	O
database	O
.	O
</s>
<s>
A	O
factory	O
for	O
connections	O
to	O
the	O
physical	O
data	O
source	O
that	O
this	O
DataSource	B-General_Concept
object	O
represents	O
.	O
</s>
<s>
An	O
alternative	O
to	O
the	O
DriverManager	O
facility	O
,	O
a	O
DataSource	B-General_Concept
object	O
is	O
the	O
preferred	O
means	O
of	O
getting	O
a	O
connection	O
.	O
</s>
<s>
An	O
object	O
that	O
implements	O
the	O
DataSource	B-General_Concept
interface	O
will	O
typically	O
be	O
registered	O
with	O
a	O
naming	O
service	O
based	O
on	O
the	O
Java	B-Language
Naming	I-Language
and	I-Language
Directory	I-Language
Interface	I-Language
(	O
JNDI	B-Language
)	O
API	O
.	O
</s>
<s>
The	O
DataSource	B-General_Concept
interface	O
is	O
implemented	O
by	O
a	O
driver	O
vendor	O
.	O
</s>
<s>
Connection	B-General_Concept
pooling	I-General_Concept
implementation	O
—	O
produces	O
a	O
Connection	O
object	O
that	O
will	O
automatically	O
participate	O
in	O
connection	B-General_Concept
pooling	I-General_Concept
.	O
</s>
<s>
This	O
implementation	O
works	O
with	O
a	O
middle-tier	O
connection	B-General_Concept
pooling	I-General_Concept
manager	O
.	O
</s>
<s>
Distributed	B-General_Concept
transaction	I-General_Concept
implementation	O
—	O
produces	O
a	O
Connection	O
object	O
that	O
may	O
be	O
used	O
for	O
distributed	B-General_Concept
transactions	I-General_Concept
and	O
almost	O
always	O
participates	O
in	O
connection	B-General_Concept
pooling	I-General_Concept
.	O
</s>
<s>
This	O
implementation	O
works	O
with	O
a	O
middle-tier	O
transaction	O
manager	O
and	O
almost	O
always	O
with	O
a	O
connection	B-General_Concept
pooling	I-General_Concept
manager	O
.	O
</s>
<s>
A	O
DataSource	B-General_Concept
object	O
has	O
properties	O
that	O
can	O
be	O
modified	O
when	O
necessary	O
.	O
</s>
<s>
For	O
example	O
,	O
if	O
the	O
data	O
source	O
is	O
moved	O
to	O
a	O
different	O
server	B-Application
,	O
the	O
property	O
for	O
the	O
server	B-Application
can	O
be	O
changed	O
.	O
</s>
<s>
A	O
driver	O
that	O
is	O
accessed	O
via	O
a	O
DataSource	B-General_Concept
object	O
does	O
not	O
register	O
itself	O
with	O
the	O
DriverManager	O
.	O
</s>
<s>
Rather	O
,	O
a	O
DataSource	B-General_Concept
object	O
is	O
retrieved	O
through	O
a	O
lookup	O
operation	O
and	O
then	O
used	O
to	O
create	O
a	O
Connection	O
object	O
.	O
</s>
<s>
With	O
a	O
basic	O
implementation	O
,	O
the	O
connection	O
obtained	O
through	O
a	O
DataSource	B-General_Concept
object	O
is	O
identical	O
to	O
a	O
connection	O
obtained	O
through	O
the	O
DriverManager	O
facility	O
.	O
</s>
<s>
A	O
DataSource	B-General_Concept
object	O
is	O
the	O
representation	O
of	O
a	O
data	O
source	O
in	O
the	O
Java	B-Language
programming	I-Language
language	I-Language
.	O
</s>
<s>
A	O
data	O
source	O
can	O
reside	O
on	O
a	O
remote	O
server	B-Application
,	O
or	O
it	O
can	O
be	O
on	O
a	O
local	O
desktop	O
machine	O
.	O
</s>
<s>
Applications	O
access	O
a	O
data	O
source	O
using	O
a	O
connection	O
,	O
and	O
a	O
DataSource	B-General_Concept
object	O
can	O
be	O
thought	O
of	O
as	O
a	O
factory	O
for	O
connections	O
to	O
the	O
particular	O
data	O
source	O
that	O
the	O
DataSource	B-General_Concept
instance	O
represents	O
.	O
</s>
<s>
The	O
DataSource	B-General_Concept
interface	O
provides	O
two	O
methods	O
for	O
establishing	O
a	O
connection	O
with	O
a	O
data	O
source	O
.	O
</s>
<s>
Using	O
a	O
DataSource	B-General_Concept
object	O
is	O
the	O
preferred	O
alternative	O
to	O
using	O
the	O
DriverManager	O
for	O
establishing	O
a	O
connection	O
to	O
a	O
data	O
source	O
.	O
</s>
<s>
They	O
are	O
similar	O
to	O
the	O
extent	O
that	O
the	O
DriverManager	O
class	O
and	O
DataSource	B-General_Concept
interface	O
both	O
have	O
methods	O
for	O
creating	O
a	O
connection	O
,	O
methods	O
for	O
getting	O
and	O
setting	O
a	O
timeout	O
limit	O
for	O
making	O
a	O
connection	O
,	O
and	O
methods	O
for	O
getting	O
and	O
setting	O
a	O
stream	O
for	O
logging	O
.	O
</s>
<s>
Unlike	O
the	O
DriverManager	O
,	O
a	O
DataSource	B-General_Concept
object	O
has	O
properties	O
that	O
identify	O
and	O
describe	O
the	O
data	O
source	O
it	O
represents	O
.	O
</s>
<s>
Also	O
,	O
a	O
DataSource	B-General_Concept
object	O
works	O
with	O
a	O
Java	B-Language
Naming	I-Language
and	I-Language
Directory	I-Language
Interface	I-Language
(	O
JNDI	B-Language
)	O
naming	O
service	O
and	O
can	O
be	O
created	O
,	O
deployed	O
,	O
and	O
managed	O
separately	O
from	O
the	O
applications	O
that	O
use	O
it	O
.	O
</s>
<s>
A	O
driver	O
vendor	O
will	O
provide	O
a	O
class	O
that	O
is	O
a	O
basic	O
implementation	O
of	O
the	O
DataSource	B-General_Concept
interface	O
as	O
part	O
of	O
its	O
Java	B-Language
Database	I-Language
Connectivity	I-Language
(	O
JDBC	B-Language
)	O
2.0	O
or	O
3.0	O
driver	O
product	O
.	O
</s>
<s>
What	O
a	O
system	O
administrator	O
does	O
to	O
register	O
a	O
DataSource	B-General_Concept
object	O
with	O
a	O
JNDI	B-Language
naming	O
service	O
and	O
what	O
an	O
application	O
does	O
to	O
get	O
a	O
connection	O
to	O
a	O
data	O
source	O
using	O
a	O
DataSource	B-General_Concept
object	O
registered	O
with	O
a	O
JNDI	B-Language
naming	O
service	O
are	O
described	O
later	O
in	O
this	O
chapter	O
.	O
</s>
<s>
Being	O
registered	O
with	O
a	O
JNDI	B-Language
naming	O
service	O
gives	O
a	O
DataSource	B-General_Concept
object	O
two	O
major	O
advantages	O
over	O
the	O
DriverManager	O
.	O
</s>
<s>
A	O
programmer	O
can	O
choose	O
a	O
logical	O
name	O
for	O
the	O
data	O
source	O
and	O
register	O
the	O
logical	O
name	O
with	O
a	O
JNDI	B-Language
naming	O
service	O
.	O
</s>
<s>
The	O
application	O
uses	O
the	O
logical	O
name	O
,	O
and	O
the	O
JNDI	B-Language
naming	O
service	O
will	O
supply	O
the	O
DataSource	B-General_Concept
object	O
associated	O
with	O
the	O
logical	O
name	O
.	O
</s>
<s>
The	O
DataSource	B-General_Concept
object	O
can	O
then	O
be	O
used	O
to	O
create	O
a	O
connection	O
to	O
the	O
data	O
source	O
it	O
represents	O
.	O
</s>
<s>
The	O
second	O
major	O
advantage	O
is	O
that	O
the	O
DataSource	B-General_Concept
facility	O
allows	O
developers	O
to	O
implement	O
a	O
DataSource	B-General_Concept
class	O
to	O
take	O
advantage	O
of	O
features	O
like	O
connection	B-General_Concept
pooling	I-General_Concept
and	O
distributed	B-General_Concept
transactions	I-General_Concept
.	O
</s>
<s>
Connection	B-General_Concept
pooling	I-General_Concept
can	O
increase	O
performance	O
dramatically	O
by	O
reusing	O
connections	O
rather	O
than	O
creating	O
a	O
new	O
physical	O
connection	O
each	O
time	O
a	O
connection	O
is	O
requested	O
.	O
</s>
<s>
The	O
ability	O
to	O
use	O
distributed	B-General_Concept
transactions	I-General_Concept
enables	O
an	O
application	O
to	O
do	O
the	O
heavy	O
duty	O
database	O
work	O
of	O
large	O
enterprises	O
.	O
</s>
<s>
Although	O
an	O
application	O
may	O
use	O
either	O
the	O
DriverManager	O
or	O
a	O
DataSource	B-General_Concept
object	O
to	O
get	O
a	O
connection	O
,	O
using	O
a	O
DataSource	B-General_Concept
object	O
offers	O
significant	O
advantages	O
and	O
is	O
the	O
recommended	O
way	O
to	O
establish	O
a	O
connection	O
.	O
</s>
<s>
Since	O
Java	B-Language
EE	I-Language
6	I-Language
a	O
JNDI-bound	O
DataSource	B-General_Concept
can	O
alternatively	O
be	O
configured	O
in	O
a	O
declarative	O
way	O
directly	O
from	O
within	O
the	O
application	O
.	O
</s>
<s>
A	O
DataSource	B-General_Concept
is	O
an	O
abstract	O
representation	O
of	O
a	O
live	O
set	O
of	O
data	O
that	O
presents	O
a	O
common	O
predictable	O
API	O
for	O
other	O
objects	O
to	O
interact	O
with	O
.	O
</s>
<s>
The	O
nature	O
of	O
your	O
data	O
,	O
its	O
quantity	O
,	O
its	O
complexity	O
,	O
and	O
the	O
logic	O
for	O
returning	O
query	O
results	O
all	O
play	O
a	O
role	O
in	O
determining	O
your	O
type	O
of	O
DataSource	B-General_Concept
.	O
</s>
<s>
For	O
small	O
amounts	O
of	O
simple	O
textual	O
data	O
,	O
a	O
JavaScript	B-Language
array	O
is	O
a	O
good	O
choice	O
.	O
</s>
<s>
If	O
your	O
data	O
has	O
a	O
small	O
footprint	O
but	O
requires	O
a	O
simple	O
computational	O
or	O
transformational	O
filter	O
before	O
being	O
displayed	O
,	O
a	O
JavaScript	B-Language
function	O
may	O
be	O
the	O
right	O
approach	O
.	O
</s>
<s>
For	O
very	O
large	O
datasets	O
—	O
for	O
example	O
,	O
a	O
robust	O
relational	O
database	O
—	O
or	O
to	O
access	O
a	O
third-party	O
webservice	O
you	O
'll	O
certainly	O
need	O
to	O
leverage	O
the	O
power	O
of	O
a	O
Script	O
Node	O
or	O
XHR	O
DataSource	B-General_Concept
.	O
</s>
