Hi Michael,
Thanks for this analysis.
On Apr 28, 2005, at 11:16 AM, Michael Watzek wrote:
Hi,
Micheal Bouschen raised the issue to get rid of the compile time dependencies between ri11 runtime and ri11 query. The benefit would be:
1) Runtime and query could be separated into 2 different projects. 2) ri11 runtime could be executed with another query implementation. 3) ri11 query could be executed with another runtime implementation.
Below, I summerize what code changes have to be done to achieve issue 2).
There are only 2 dependencies from runtime implementation to query implementation:
- PersistenceManagerFactoryImpl calls Tree constructor - PersistenceManagerImpl calls QueryImpl constructors
What if we move the method newQueryTree from PMFImpl to the FOStorePMF class?
Similarly, we can move the nine newQueryXXX methods from PMImpl to FOStorePM.
If we break this dependency, we could keep the dependency from Query to Runtime. And not implement part 3 as outlined below. I think part 3 is a lot of work and still doesn't remove the dependencies.
(The proposal below still requires the Query to know about StateManagerInternal, FieldManager, and StoreManager which I guess are still defined in Runtime.)
So the new proposal is to break out ri11 into
core20 (model plus utility): no dependencies enhancer20: depends on core runtime20: depends on core query20: depends on runtime and core fostore20: depends on core, runtime, and query
Craig
The proposal is to introduce a new runtime interface QueryFactory which defines methods creating QueryTree instances and Query instances, e.g.
public interface QueryFactory { QueryTree createTree(); Query createQuery(...); }
This interface is implemented by query implementations. The ri11 query implementation calls the Tree and QueryImpl constructors.
Additionally, ri11 runtime defines a new PMFInternal property containing the class name of the QueryFactory implementation. The property may be specified by a Properties instance which is passed to JDOHelper.getPersistenceManagerFactory, or it may be set calling a setter on the PMFInternal instance. The PMFInternal instance looks up the implementation class and calls newInstance() in order to create a QueryFactory instance. The class object is kept in an instance variable. The Tree and QueryImpl constructor calls in PersistenceManagerFactoryImpl and PersistenceManagerImpl are replaced by corresponding calls on the QueryFactory instance.
Constraints on the QueryFactory implementation class: It must implement a public no argument constructor.
Below, I summerize what code changes have to be done to achieve issue 3).
The ri11 query implementation does not have references into runtime implementation packages, such as "org.apache.jdo.impl.pm" or "org.apache.jdo.impl.state". However, it has some references into runtime specific interfaces like PersistenceManagerInternal (PMI) and StateManagerInternal (SMI):
- PMI.findStateManager(...) - PMI.loadClass(...) - PMI.assertIsOpen() - PMI.getStoreManager() - PMI.getCurrentWrapper() - SMI.provideField(...)
Additionally, there is a dependency to the FieldManager interface: As query implementation calls method SMI.provideField(...) having a field manager parameter, it provides an implementation for that interface and passes an instance of that implementation.
The proposal is to define a new query interface RuntimeContext defining all of the methods above, e.g.
interface RuntimeContext
{
StateManager findStateManager(PersistenceCapable pc);
Class loadClass(String name, ClassLoader given) throws ClassNotFoundException;
void assertIsOpen();
StoreManager getStoreManager();
PersistenceManager getCurrentWrapper();
void provideField(int fieldNumber, FieldManager fieldManager, boolean identifying);
}
This interface is implemented by runtime implementations. A query instance has an instance of this interface which it gets through a parameter of query factory method "createQuery", e.g.
QueryFactory.createQuery(..., RuntimeContext context);
All calls of the methods above are replaced by corresponding method calls on RuntimeContext instance.
Drawbacks of this proposal: It does not eliminate the dependency to the FieldManager interface.
Advantages of this proposal: It gathers all runtime calls in an single instance implementing a small API, rather than having calls on 2 different instances each of which implements a big API (PMI defines 23 methods, SMI defines 33 meethods).
Regards, Michael -- ------------------------------------------------------------------- Michael Watzek [EMAIL PROTECTED] Engineering GmbH mailto:[EMAIL PROTECTED] Buelowstr. 66 Tel.: ++49/30/235 520 36 10783 Berlin - Germany Fax.: ++49/30/217 520 12 http://www.spree.de/ -------------------------------------------------------------------
Craig Russell Architect, Sun Java Enterprise System http://java.sun.com/products/jdo 408 276-5638 mailto:[EMAIL PROTECTED] P.S. A good JDO? O, Gasp!
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