Linda,
Overall, this looks good and is a timely change (I do have some concerns
though). Detailed feedback below:
* ISSUE 1: Should we support the use of annotations for resource
configuration (in addition to DataSourceDefinition) or should we require
that resource configurability metadata be specified in XML?
- The annotations should definitely be supported. Although a majority of
production applications are unlikely to use annotations for resource
configuration, they are very valuable for RoR style RAD development and
minimizing XML.
* ISSUE 2: If we support the use of annotations, which of the above
approaches should we take -- resource-specific or generic?
- The generic annotation approach is very tempting, but does have some
significant problems. Besides being less type-safe, they are also not
very self-contained/self-documenting and hence much less usable. They
could have been workable if the different resource types had more in
common, but they really don't (besides some superficial similarities in
properly names). I think we should avoid the generic annotation approach
or reserve it for cases where containers use them to allow for
configuring resources outside the common types. If we do have a generic
annotation for edge cases, it is probably best to coordinate with an
active JCA EG on that annotation since most if not all resources
configured this way are likely to be JCA resources.
* ISSUE 3: How should we name the standard properties? Do they require
a "package"-specific prefix?
- If we retain the generic annotation approach for provider-specific
edge cases, we should recommend that properties use sensible
"package"-specific prefixes. The issue is that although property names
might be similar, their meaning and usage patterns would likely be very
different depending on the actual resource type, so they should be
categorized and documented separately.
* ISSUE 4: If we take a generic approach, should we use this for
DataSourceDefinition as well, treating the existing DataSourceDefinition
annotation and XML as "legacy"?
- I think it was done right in Java EE 6 in the first place. For
example, Resin has always had cleanly separated XML tags for database,
JMS, etc resource configuration.
* ISSUE 5: Which XML format should we use? Resource-specific or generic?
- Resource specific for "well known" resources and generic for the
others that would be provider specific with some usage guidelines.
* ISSUE 6: Should we support the use of annotations for the
specification of per-tenant reconfigurability?
- As you know, I (and others) expressed concerns around cloud support in
the past. I think this issue crystallizes some of those concerns. What I
see as largely an edge case (multi-tenant Java EE applications that
require a tenant-specific override) would complicate a far more
mundane/common use case (deploying a resource in a vanilla Java EE
application). I think we should reconsider if this particular cloud
feature is really needed. If it is not, we could avoid this bit of
complexity altogether. Multi-tenant enabled application developers would
simply have to let deployers know what resources need to be overriden
via more traditional forms of documentation without any container
intervention (something they would likely need to do anyway). If we
still think this is something that is really needed, it should be
supported in annotations as well as XML. Having something in XML and not
in annotations (or vice versa) is likely to be confusing.
* ISSUE 7: If we support the use of annotations for the specification
of per-tenant reconfigurability, which approach should we take.
- If this feature is indeed needed, I think using resource-specific
annotations with separate typed elements is the least worst. It is the
most type-safe and self-documenting, but it will cause annotation bloat.
All these options cause additional complexity for resource configuration
in non-cloud applications. I could not think of an alternate way that
avoids the complexity while still supporting this feature.
* ISSUE 8: Which approach should we take for the specification of
per-tenant reconfigurability using XML: type-specific XML elements or
generic resource-definition elements?
- As stated above, type-specific elements are far more
readable/self-documenting and less verbose (even more so in XML than in
annotations).
ISSUE 9: Should resource configuration definitions be embedded in the
existing descriptors or should there be a separate XML descriptor?
- I think the decision in Java EE 6 to utilize the existing descriptors
is the correct one. It avoids adding yet another Java EE deployment
descriptor instead of just putting resource definitions in
application.xml, web.xml, beans.xml, etc. Resin has done
application-specific resource deployment for ages and we've never seen a
need to create a separate descriptor for resources. Similarly, Spring
allows for resource definition in it's application context descriptors.
I think creating a separate descriptor adds little value and goes
against the norm for server-side Java development.
Hope this makes sense.
Cheers,
Reza
On 8/26/2011 11:34 AM, Reza Rahman wrote:
> Linda,
>
> Hmm - for some reason I did not get your original email? I'm a bit
> tied up at the moment but will try to get you detailed feedback by
> next week at the latest...
>
> Cheers,
> Reza
>
>
> On 8/26/2011 5:36 AM, Werner Keil wrote:
>> Linda/all,
>>
>> Thanks a lot for the suggestions.
>>
>> I highly appreciate some of these items, especially JMS which I saw
>> recently in a project can be a beast hard to tame. In fact, based on
>> Oracle's (pre EE6) own technologies combined with some Spring which
>> caused many issues, not only due to lack of understanding how to use
>> it properly.
>>
>> I'll try to look into those, probably gather feedback from people who
>> deal with this and reply here, particularly for the JMS Use Case,
>> although it may not be the only one. Is this coordinated with JMS 2.0
>> btw, e.g. by having the Spec Lead on this list?
>>
>> Regards,
>> Werner
>>
>> On Fri, Aug 26, 2011 at 3:13 AM, Linda DeMichiel
>> <linda.demichiel_at_oracle.com <mailto:linda.demichiel_at_oracle.com>> wrote:
>>
>> Aside from Reza's email (thanks, Reza!), we haven't received much
>> feedback on the resource configuration front. Under the assumption
>> that silence implies consent, we'd like to move on to the next steps
>> in this direction.
>>
>> This email contains a number of items that require your input.
>> Briefly, we need feedback on the following aspects:
>>
>> 1. The use of annotations for resource configuration.
>> 2. The form that such annotations (if supported) should take.
>> 3. The form of XML elements for resource configuration.
>> 4. How metadata related to per-tenant (re)configurability should be
>> specified.
>> 5. Whether the XML elements should be embedded in the current
>> descriptors
>> or there should be a separate descriptor.
>>
>> These items are discussed further in the message below. I have
>> flagged specific items on which we need your feedback as "ISSUE:"
>>
>> Since the decision on how to specify metadata for reconfigurability
>> may likely impact the decision on the format to use to specify
>> annotations and XML for resource configuration, I recommend that you
>> make 2 passes to work through this:
>> (1) to review the options and how they interact;
>> (2) to provide your opinions on the issues.
>>
>> thanks,
>>
>> -Linda
>>
>> ---------------------------
>>
>> 1. Annotations for resource configuration
>>
>> Java EE 6 currently supports use of the DataSourceDefinition
>> annotation.
>> This annotation is defined as follows:
>>
>> package javax.annotation.sql;
>>
>> @Retention(RUNTIME)
>> @Target({TYPE})
>> public @interface DataSourceDefinition {
>> String name();
>> String className();
>> String description() default "";
>> String url() default "";
>> String user() default "";
>> String password() default "";
>> String databaseName() default "";
>> int portNumber() default -1;
>> String serverName() default "localhost";
>> int isolationLevel() default -1;
>> boolean transactional() default true;
>> int initialPoolSize() default -1;
>> int maxPoolSize() default -1;
>> int minPoolSize() default -1;
>> int maxIdleTime() default -1;
>> int maxStatements() default -1;
>> String[] properties() default {};
>> int loginTimeout() default 0;
>> }
>>
>>
>> Following this pattern, we might define similar annotations for
>> the other
>> standard resource types -- e.g., define JMSConnectionFactory,
>> JMSDestination,
>> MailSession, and ConnectorResource annotations.
>>
>>
>> An alternative is to take a more generic approach, and instead of
>> these support a generic ResourceDefinition annotation:
>>
>> package javax.annotation.resource;
>>
>> @Retention(RUNTIME)
>> @Target({TYPE})
>> public @interface ResourceDefinition {
>> String description() default "";
>> String name();
>> String className();
>> String[] properties() default {};
>> }
>>
>> With the generic ResourceDefinition approach, all resource-specific
>> information would be provided as properties. For that reason,
>> the generic
>> approach relies heavily on the use of strings and therefore has less
>> type safety. We would need to standardize on the property names
>> to be
>> used, and we would also need to decide whether to require a
>> package-specific prefix on the property names (as illustrated in the
>> examples below) to distinguish them from vendor properties.
>>
>>
>> Examples:
>>
>> Example 1: data sources
>>
>> @DataSourceDefinition(
>> name="java:app/MyDataSource",
>> className="com.foobar.MyDataSource",
>> portNumber=6689,
>> serverName="myserver.com <http://myserver.com>",
>> user="lance",
>> password="secret"
>> )
>>
>> vs
>>
>> @ResourceDefinition(
>> name="java:app/MyDataSource",
>> className="com.foobar.MyDataSource",
>> properties={
>> "javax.sql.portNumber=6689",
>> "javax.sql.serverName=myserver.com <http://myserver.com>",
>> "javax.sql.user=lance",
>> "javax.sql.password=secret"
>> }
>> )
>>
>>
>> Example 2: JMS connection factories
>>
>> @JMSConnectionFactory(
>> name="java:app/MyJMSFactory",
>> resourceType="javax.jms.QueueConnectionFactory",
>> clientId="foo",
>> connectionTimeout=10,
>> initialPoolSize=5,
>> maxPoolSize=15
>> )
>>
>> vs
>>
>> @ResourceDefinition(
>> name="java:app/MyJMSFactory",
>> className="javax.jms.QueueConnectionFactory",
>> properties={
>> "javax.jms.clientId=foo",
>> "javax.jms.connectionTimeout=10",
>> "javax.jms.initialPoolSize=5",
>> "javax.jms.maxPoolSize=15"
>> }
>> )
>>
>>
>> Example 3: JMS destinations
>>
>> @JMSDestination(
>> name="java:app/MyQueue",
>> resourceType="javax.jms.Queue",
>> resourceName="queue124"
>> )
>>
>> vs
>>
>> @ResourceDefinition(
>> name="java:app/MyQueue",
>> className="javax.jms.Queue",
>> properties={
>> "javax.jms.resourceName=queue124"
>> }
>> )
>>
>>
>> ISSUE 1: Should we support the use of annotations for resource
>> configuration
>> (in addition to DataSourceDefinition) or should we require that
>> resource
>> configurability metadata be specified in XML?
>>
>> ISSUE 2: If we support the use of annotations, which of the above
>> approaches should we take -- resource-specific or generic?
>>
>> ISSUE 3: How should we name the standard properties? Do they require
>> a "package"-specific prefix?
>>
>> ISSUE 4: If we take a generic approach, should we use this for
>> DataSourceDefinition as well, treating the existing
>> DataSourceDefinition
>> annotation and XML as "legacy"?
>>
>>
>> ------------------
>>
>>
>> 2. XML for resource configuration
>>
>> We currently support the use of the data-source element in the
>> Java EE 6
>> descriptors as part of the jndiEnvironmentRefsGroup type. (See
>> http://java.sun.com/xml/ns/javaee/javaee_6.xsd for the details..)
>>
>> For the new elements, the choices are again whether to have elements
>> that are resource-specific or generic.
>>
>>
>> Example:
>>
>> Resource-specific approach, JMS connection factory:
>>
>> <jms-connection-factory>
>> <name>MyJMSFactory</name>
>> <resource-type>javax.jms.QueueConnectionFactory</resource-type>
>> <client-id>foo</client-id>
>> <connection-timeout>10</connection-timeout>
>> <initial-pool-size>5</initial-pool-size>
>> <max-pool-size>15</max-pool-size>
>> </jms-connection-factory>
>>
>>
>> Generic approach:
>>
>> <resource-definition>
>> <name>MyJMSFactory</name>
>> <resource-type>javax.jms.QueueConnectionFactory</resource-type>
>> <property>
>> <name>clientId</name>
>> <value>foo</value>
>> </property>
>> <property>
>> <name>connectionTimeout</name>
>> <value>10</value>
>> </property>
>> <property>
>> <name>initialPoolSize</name>
>> <value>5</value>
>> </property>
>> <property>
>> <name>maxPoolSize</name>
>> <value>15</value>
>> </property>
>> </resource-definition>
>>
>>
>> Note that the specification of properties could be made somewhat less
>> verbose by the use of attributes. The example above uses elements
>> to be more consistent with the current style of our deployment
>> descriptors.
>>
>>
>> With XML, we again have the issue as to whether properties in the
>> generic approach should use a resource-specific prefix, e.g.,
>>
>> <resource-definition>
>> <name>MyJMSFactory</name>
>> <resource-type>javax.jms.QueueConnectionFactory</resource-type>
>> <property>
>> <name>javax.jms.clientId</name>
>> <value>foo</value>
>> </property>
>> <property>
>> <name>javax.jms.connectionTimeout</name>
>> <value>10</value>
>> </property>
>> <property>
>> <name>javax.jms.initialPoolSize</name>
>> <value>5</value>
>> </property>
>> <property>
>> <name>javax.jms.maxPoolSize</name>
>> <value>15</value>
>> </property>
>> </resource-definition>
>>
>>
>> ISSUE 5: Which XML format should we use? Resource-specific or
>> generic ?
>>
>>
>> ----------------------------
>>
>>
>> 3. Specification of per-tenant reconfigurability
>>
>> In the resource configuration document that I circulated several
>> weeks
>> ago, I noted that we needed a means to include information about
>> which
>> attributes of a resource definition must be modified by a tenant,
>> which
>> must not be modified, and which may be modified.
>>
>> The remainder of this message outlines how that might be handled in
>> the various approaches.
>>
>> If we take a generic approach (@ResourceDefinition), the property
>> elements
>> could be expanded to specify a configurability element. For example:
>>
>> @Retention(RUNTIME)
>> @Target({TYPE})
>> public @interface ResourceDefinition {
>> String description() default "";
>> String name();
>> String className();
>> ConfigProperty[] configProperties() default {};
>> }
>>
>> @Retention(RUNTIME)
>> @Target({})
>> public @interface ConfigProperty {
>> String name();
>> String value();
>> Configurability configurability() default
>> Configurability.MAY_MODIFY;
>> }
>>
>> public enum Configurability {
>> MUST_MODIFY,
>> MUST_NOT_MODIFY,
>> MAY_MODIFY,
>> }
>>
>>
>>
>> Example:
>>
>> @ResourceDefinition(
>> name="java:app/MyJMSFactory",
>> className="javax.jms.QueueConnectionFactory",
>> configProperties={
>> @ConfigProperty(
>> name="clientId",
>> value="foo",
>> configurability=MUST_MODIFY),
>> @ConfigProperty(
>> name="connectionTimeout",
>> value="10"),
>> @ConfigProperty(
>> name="initialPoolSize",
>> value="5"),
>> @ConfigProperty(
>> name="maxPoolSize",
>> value="15")
>> }
>> )
>>
>>
>> A possible alternative to the use of the embedded @ConfigProperty
>> annotation approach might be to embed further syntax into the
>> property
>> specification to capture configurabilty semantics. For example:
>>
>> @ResourceDefinition(
>> name="java:app/MyJMSFactory",
>> className="javax.jms.QueueConnectionFactory",
>> properties={
>> "javax.jms.clientId=foo", // must modify
>> "javax.jms.connectionTimeout=?10", // may modify
>> "javax.jms.transactional==true" // must not modify
>> }
>> )
>>
>>
>>
>> Things get more complicated with the typed resource definition
>> approach. Consider what happens to JMSConnectionFactory, where some
>> of the non-property elements are optional.
>>
>> Maintaining typing using the separate elements approach leads to
>> a proliferation of annotations.
>>
>> For example:
>>
>> @JMSConnectionFactory(
>> name="java:app/MyJMSFactory",
>> resourceType="javax.jms.QueueConnectionFactory",
>> clientId=_at_ClientId(value="foo",
>> configurability=Configurability.MUST_MODIFY),
>> connectionTimeout=_at_ConnectionTimeout(10),
>> initialPoolSize=_at_PoolSize(5),
>> maxPoolSize=_at_PoolSize(15)
>> )
>>
>>
>> An alternative is that only string-valued elements are used, and all
>> elements are of type ResourceElement:
>>
>> @Retention(RUNTIME) @Target({})
>> public @interface ResourceElement {
>> String value();
>> Configurability configurability() default
>> Configurability.MAY_MODIFY;
>> }
>>
>>
>> Example:
>>
>> @JMSConnectionFactory(
>> name="java:app/MyJMSFactory",
>> resourceType="javax.jms.QueueConnectionFactory",
>> clientId=_at_ResourceElement(value="foo", configurability=MUST_MODIFY),
>> connectionTimeout=_at_ResourceElement("10"),
>> initialPoolSize=_at_ResourceElement("5"),
>> maxPoolSize=_at_ResourceElement("15")
>> )
>>
>>
>> ISSUE 6: Should we support the use of annotations for the
>> specification
>> of per-tenant reconfigurability?
>>
>> ISSUE 7: If we support the use of annotations for the
>> specification of
>> per-tenant reconfigurability, which approach should we take:
>> (1) Generic ResourceDefinition annotation
>> (2) Resource-specific annotations, using separate typed elements
>> (3) Resource-specific annotations, using ResourceElement approach
>> (4) Other?
>>
>>
>> ---------------------------
>>
>>
>> 4. Specification of per-tenant reconfigurability using XML
>>
>> With XML on the other hand, extension is fairly straightforward. The
>> various types could be augmented with attributes.
>>
>>
>> Example:
>>
>> <jms-connection-factory>
>> <name configurability=MUST_NOT_MODIFY>java:app/MyJMSFactory</name>
>> <resource-type configurability=MUST_NOT_MODIFY>
>> javax.jms.QueueConnectionFactory
>> </resource-type>
>> <client-id configurability=MUST_MODIFY>foo</client-id>
>> <connection-timeout>10</connection-timeout>
>> <initial-pool-size>5</initial-pool-size>
>> <max-pool-size>15</max-pool-size>
>> </jms-connection-factory>
>>
>>
>>
>> With the generic approach, this would look as follows, assuming
>> again a default of MAY_MODIFY if no attribute is specified:
>>
>> <resource-definition>
>> <name configurability=MUST_NOT_MODIFY>java:app/MyJMSFactory</name>
>> <resource-type configurability=MUST_NOT_MODIFY>
>> javax.jms.QueueConnectionFactory
>> </resource-type>
>> <property configurability=MUST_MODIFY>
>> <name>clientId</name>
>> <value>foo</value>
>> </property>
>> <property>
>> <name>connectionTimeout</name>
>> <value>10</value>
>> </property>
>> <property>
>> <name>initialPoolSize</name>
>> <value>5</value>
>> </property>
>> <property>
>> <name>maxPoolSize</name>
>> <value>15</value>
>> </property>
>> </resource-definition>
>>
>>
>> ISSUE 8: Which approach should we take for the specification of
>> per-tenant reconfigurability using XML: type-specific XML elements
>> or generic resource-definition elements?
>>
>>
>> ---------------------------------------
>>
>> 5. XML Descriptors for the specification of resource configuration.
>>
>> A further item pertains to where the XML elements for resource
>> configuration should be located -- i.e., in the existing Java EE
>> descriptors, or in a separate resources.xml (or services.xml)
>> descriptor. In our view, the fact that these resource configuration
>> elements are applicable to the application as a whole argues that
>> there
>> should be a separate descriptor.
>>
>> ISSUE 9: Should resource configuration definitions be embedded in
>> the existing descriptors or should there be a separate XML
>> descriptor?
>>
>> ---------------------------
>>
>>
>> RECAP OF THE ISSUES. ALL OF THESE NEED YOUR INPUT:
>>
>>
>> ISSUE 1: Should we support the use of annotations for resource
>> configuration
>> (in addition to DataSourceDefinition) or should we require that
>> resource
>> configurability metadata be specified in XML?
>>
>> ISSUE 2: If we support the use of annotation, which of the above
>> approaches should we take -- resource-specific or generic?
>>
>> ISSUE 3: How should we name the standard properties? Do they require
>> a "package"-specific prefix?
>>
>> ISSUE 4: If we take a generic approach, should we use this for
>> DataSourceDefinition as well, treating the existing
>> DataSourceDefinition
>> annotation and XML as "legacy"?
>>
>> ISSUE 5: Which XML format should we use? Resource-specific or
>> generic ?
>>
>> ISSUE 6: Should we support the use of annotations for the
>> specification
>> of per-tenant reconfigurability?
>>
>> ISSUE 7: If we support the use of annotations for the
>> specification of
>> per-tenant reconfigurability, which approach should we take:
>> (1) Generic ResourceDefinition annotation
>> (2) Resource-specific annotations, using separate typed elements
>> (3) Resource-specific annotations, using ResourceElement approach
>> (4) Other?
>>
>> ISSUE 8: Which approach should we take for the specification of
>> per-tenant reconfigurability using XML: type-specific XML elements
>> or generic resource-definition elements?
>>
>> ISSUE 9: Should resource configuration definitions be embedded in
>> the existing descriptors or should there be a separate XML
>> descriptor?
>>
>> --------
>>
>> Thanks in advance for your feedback!
>>
>> -Linda
>>
>>
>> ------------------------------------------------------------------------
>>
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