On Sep 12, 2012, at 1:52 AM, Kirill Ilyukhin wrote:
Hi!
I am using Tomcat 7.0.29 with a custom JNDI resource factory
(http://tomcat.apache.org/tomcat-7.0-doc/jndi-resources-howto.html#Adding_Custom_Resource_Factories).
The factory creates a connection to data server which then can be
shared between servlets.
Two questions regarding the resource usage.
1. Creation of the resource factory, isn't is supposed to be thread-safe?
As I understand it, your ObjectFactory implementation needs to be thread safe.
See section 4.5 of the link below.
http://docs.oracle.com/javase/1.3/docs/guide/jndi/spec/spi/jndispi.fm.html#1007939
The resource (connection) is used by two servlets which obtains it on
start-up. It works fine if the servlets are loaded one after another -
the first servlet asks JNDI for a connection, JNDI creates a factory,
the factory creates a connection, JNDI gives the connection to the
servlet; the second one ask JNDI for a connection and immediately gets
the same connection, without calling the factory. But if the servlets
are being started exactly at the same time, they get two different
connections created by two different factories. Shouldn't the factory
singleton-ness be managed by Tomcat?
Look at the resource definition...
singleton
Specify whether this resource definition is for a singleton resource, i.e. one
where there is only a single instance of the resource. If this attribute is
true, multiple JNDI lookups for this resource will return the same object. If
this attribute is false, multiple JNDI lookups for this resource will return
different objects. This attribute must be true for javax.sql.DataSource
resources to enable JMX registration of the DataSource. The value of this
attribute must be true or false. By default, this attribute is true.
https://tomcat.apache.org/tomcat-7.0-doc/config/context.html#Resource_Definitions
2. What is the correct way to close the resource?
How should I close the resource if the webapp is being
stopped/undeployed?
Again, look at the resource definition...
closeMethod
Name of the zero-argument method to call on a singleton resource when it is no
longer required. This is intended to speed up clean-up of resources that would
otherwise happen as part of garbage collection. This attribute is ignored if
the singleton attribute is false. If not specificed, no default is defined and
no close method will be called.
https://tomcat.apache.org/tomcat-7.0-doc/config/context.html#Resource_Definitions
Dan
My factory creates a connection on please create
a resource call somewhere from inside JNDI, lets the connection go
and doesn't know how many servlets use it. Users of the resource are
independent, they do not know how many of them are and do not know
when the resource can be closed. So I would expect some kind of it's
time to close the resource(s) call from JNDI. Is there one?
I know that I can track all the resources creation in a
ServletContextListener and then close them in contextDestroyed(), but
I hope there is a nicer way.
Thanks in advance,
Kirill
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