What is ENC

There is a difference between component namespace and appserver (global) namespace.

Each "component" has it's own ENC at java:/comp/env

When it declares a dependency, it binds it to a name in here, eg. java:/comp/env/ejb/SomeEJB
It looks it up using this name. It is up to the deployer to bind this name with the global appserver name of the required resource eg below of a sun-web.xml. The resource could physically be in another server.


jdbc/FooDS -- relative to java:/comp/env
jdbc/OracleDS -- global jndi name


They say directo global lookups are not portable because appserver global namespace is implementation-specific.

Mappend name in @Resource annotation is the global jndi name (gets rid of need for sun-web.xml). Name (has a default of classname/fieldname) is the name in java:comp/env

If you don't suppy a mappedname, and don't provide a mapping in xml, it will look up global jndi name which is the same as the resource dependency's name in java:comp/env

https://glassfish.dev.java.net/javaee5/ejb/compdependencies_xmlforum_nov15.pdf

Stick to commen-sense conventions

I implemented an update by deleting and recreating an entity, thinking this would have no consequences (mainly because the weak foreign keys stayed the same and I expected access would happen through these keys). But I added another independent guid, and then there was a problem that because the guid changed, a client could no longer retrieve the object.

XCS clustering problem

XCS wasn't responding. Logs showed things about GMSImpl, wrongMethod() suspect(). It was trying to join cluster but something was going wrong.

Removing XmotionSessionCache-service.xml stoppedt his.

java.lang.OutOfMemoryError: PermGen space

Monitor memory sizes through jboss by invoking listMemoryPools() of ServerInfo jmx object in the jmx-console

wire up your relationships!

Again I got caught by not wiring up my ejb bidirectional relationships. As an example I had GeoFence (gf) and GeoFenceDataSet (ds). gf has one ref to ds and ds has lazy collection of gf's.

I never understood why I need to do a ds.getGeoFences().add(gf). I thought this should be magically looked after whenever I create a gf with gf.setDataSet(ds). In particular what I saw was, I would do the following within a transaction

em.persist(gf)
em.flush()

and then

for (gf : ds.getGeoFences() )

in a separate transaction. Since my collection was lazy-loaded, I expected the newly added gf to be in that collection, since it should have been loading the collection from the database, but it didn't. It looks like the entity manager knows whether to read in collection or not. It seems to keep track of the ds verison number and the last gf id it should know about.

sql server and collation

http://www.databasejournal.com/features/mssql/article.php/10894_3302341_2
http://blogs.msdn.com/michkap/archive/2005/11/08/490305.aspx
http://www.madprops.org/cs/blogs/mabster/archive/2007/07/02/sql-collation-made-easy.aspx

Default collation depends on how sql server was installed.

Looks like SQL collations were just for sql server, and windows collations are for the whole of windows.