Hi Marcel,
I'll handle question #2. I'll let the folks that work on the
container answer the other ones.
#2 The javaagent is used to allow us to do dynamic weaving of domain
classes that use fetch=LAZY for OneToOne and ManyToOne mappings. Those
classes are weaved to contain som TopLink-specific data structures that
allow us to provide LAZY loading of those relationships. If you do not
want to (or cannot use the agent), a flag can be provided in the
properties of your persitence unit to avoid the weaving. The property
"toplink.weaving" can be set to "false". This will disable the
weaving. The consequences of setting this property is that the LAZY
hint will not be observed for OneToOne and ManyToOne relationships and
they will be loaded EAGERly.
-Tom
Marcel Overdijk wrote:
>Hi,
>
>I'm adding JPA support to a framework and have some questions.
>Currently I'm using the Toplink Essentials and javaee.jar from GlassFish M6.
>
>1. The javaee.jar contains more then only the persistence related classes
>and therefor is 1mb big. Is there a official Sun jar downloadable containing
>only persistence classes. In Spring 2.0 distribution a persistence.jar
>(58kb) is included. I can use this but I don't know the origin of it.
>
>2. In the persistence example on the GlassFish page the
>toplinks-essentials-agent.jar is used in combination with -javaagent (SE
>example). What does the toplink-essentials-agent do? If I just put
>toplink-essentials and javaee.jar on the classpath everything seems to work
>fine. Is there any drawback?
>
>3. When I want to get an EntityManager based on an persistence unit Name I
>don't know at compile time. The only option (I believe) is to create an emf
>first:
>String pu = "some dynamic pu name";
>Persistence.createEntityManagerFactory(pu);
>However to create a emf each time is expensive. I could keep a reference to
>a pu once created.
>But what I'm wondering is how JEE 5 containers handle this. Do they create
>subsequent emf's or are they smart that they know it was already created in
>a previous call?
>
>Hope you can hekp me on this.
>
>Regards,
>Marcel Overdijk
>
>
>