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
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
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Michael Watzek Tech@Spree Engineering GmbH
mailto:mwa.tech@spree.de Buelowstr. 66
Tel.: ++49/30/235 520 36 10783 Berlin - Germany
Fax.: ++49/30/217 520 12 http://www.spree.de/
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