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",
user="lance",
password="secret"
)
vs
@ResourceDefinition(
name="java:app/MyDataSource",
className="com.foobar.MyDataSource",
properties={
"javax.sql.portNumber=6689",
"javax.sql.serverName=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