Craig,
before we talk about the Datamapper specifically I think it would help
to settle a couple more general things about what we are planning to do
for the new persistence implementation ...
primarily, I think we need to figure out what we are going to implement.
so far you have talked about JDO and JPA, and we already have
Hibernate, so those are the options on the table right now. as far as
I'm concerned we should be picking one of them and focus there because I
am still not interested in planning multiple backend implementations.
that's not really useful to people who are running roller and it's more
overhead to maintain for us roller developers.
assuming we agree that we are only focusing on implementing one of the
options, we then need to decide which one. just so it's known, i think
it's entirely lame that we are getting rid of Hibernate over a silly
licensing issue. as a large roller customer i consider it more of a
pain than a benefit to have to replace the backend. regardless of that
fact, it appears that's what everyone wants to do, so i consider
Hibernate to no longer be an option. that leaves JDO and JPA as you
mentioned, and i don't really have any preference between the two.
-- Allen
Craig L Russell wrote:
Hi,
Here's what I propose as a starting point for the query interface
between Datamapper Managers and Datamapper Persistence.
There are enough differences between JDO, JPA, and Hibernate that I
found it really awkward to define a set of methods on
PersistenceStrategy that covered the functionality. In particular, there
are two methods in JPA that both execute the query and determine the
result shape, and parameters are passed one by one. In JDO, there is an
API that determines the result shape and one method to execute the
query, passing parameter values. It's trivial to encapsulate these
differences in a Query instance.
I've included the Query API below for discussion, along with calling
sequence from Mapper.
Craig
public class DatamapperPersistenceStrategy {
...
/**
* Create query.
* @param clazz the class of instances to find
* @param queryName the name of the query
* @throws org.apache.roller.RollerException on any error
*/
public DatamapperQuery newQuery(Class clazz, String queryName)
throws RollerException;
}
public class DatamapperUserManagerImpl {
...
public WebsiteData getWebsiteByHandle(String handle, Boolean enabled)
throws RollerException {
// XXX cache websites by handle?
return (WebsiteData)strategy.newQuery(WebsiteData.class,
"getByHandle&&Enabled")
.execute(new Object[]{handle, enabled});
}
public interface DatamapperQuery {
/** Execute the query with no parameters.
* @return the results of the query
*/
Object execute();
/** Execute the query with one parameter.
* @param param the parameter
* @return the results of the query
*/
Object execute(Object param);
/** Execute the query with parameters.
* @param params the parameters
* @return the results of the query
*/
Object execute(Object[] params);
/** Remove instances selected by the query with no parameters.
* @return the results of the query
*/
void removeAll();
/** Remove instances selected by the query with one parameter.
* @param param the parameter
* @return the results of the query
*/
void removeAll(Object param);
/** Remove instances selected by the query with parameters.
* @param params the parameters
* @return the results of the query
*/
void removeAll(Object[] params);
/** Set the result to be a single instance (not a List).
* @result the instance on which this method is called
*/
DatamapperQuery setUnique();
/** Set the types of the parameters. This is only needed if the
* parameter types are temporal types, e.g. Date, Time, Calendar.
* @param the types of the parameters in corresponding positions.
* @result the instance on which this method is called
*/
DatamapperQuery setTypes(Object[] types);
/** Set the range of results for this query.
* @fromIncl the beginning row number
* @toExcl the ending row number
* @return the instance on which this method is called
*/
DatamapperQuery setRange(long fromIncl, long toExcl);
}
Craig Russell
[EMAIL PROTECTED] http://db.apache.org/jdo
