CDI + jo4neo = Neo4j on Java EE 6
Pascal Salg
Here I want to present a project I
have been working on for the past few weeks.
As my app server of choice is JBoss AS 7 I started experimenting with CDI
Extensions.
(CDI = Context & Dependency Injection)
CDI implements extensibility by Portable Extensions which can be used by
dropping the jar in your WEB-INF7lib directory..
Actually there is a whole lot more ways to extend the CDI framework (like
custom qualifiers, stereotypes etc but for now let's stick to the subject
"portable extensions" )
By implementing a cdi portable extension you can leverage the power of the JEE
environment (like transactions, lifecycle mgmt by the container..)
So by implementing different listeners for lifecycle events we can perform
startup tasks like initialization, validation, instanciation or cleanup and
shutdown tasks
For including Neo4j in a project please have a look at
http://docs.neo4j.org/chunked/stable/tutorials-java-embedded-setup.html
Basically what I did is this:
- Introduced a new Environment parameter "neo.path". The value for this system property will be set at server startup if proper configuration has been done. It is either passed as a parameter or it is contained in a neo.properties file.
- You can pass the parameter when running your server by appending "-Dneo.path=/path/to/file/neo.properties"
- You can pass it contained in a neo.properties file located in the src/META-INF directory (like persistence.xml would do..)
- I wrote a small container class (NeoORM.java) for the jo4neo object graph (this container later could be filled with other neo4j addons as well)
- NeoORM.getObjectGraph() returns the jo4neo object graph
- I created a cutom qualifier annotation: "@NeoEntityManager". This annotation optionally takes a String as an argument which either points to a directory (where the neo4j db will reside) or it points to a neo.properties file.
- By using the annotation on a class member of type NeoORM a configured instance will be injected.
- Implemented some fallback strategies for instanciation e.g. the neo.path system property was not set and annotations don't use the String argument (from where would the neo4j db know where to run put its files)
I have used jo4neo in a larger project and was happy with it as I was looking for an object-graph mapper other than Spring Data (one that is lightweight but still gets the job done).
But you know how it is, you always find new spots in your own code to "refactor" ;) That's when my idea of this portable extension was born.
Please let me know who to talk to regarding committing this to the current git repo.
Greetings from Germany,
p.salg
Peter Neubauer
great to hear you are finding jo4neo useful! It has been a bit dormant
during the last months, so I would suggest to clone the repo, do your
changes, write up a blog post and promote it - we would certainly help
to get people to try your fork!
WDYT?
/peter
Cheers,
/peter neubauer
G: neubauer.peter
S: peter.neubauer
P: +46 704 106975
L: http://www.linkedin.com/in/neubauer
T: @peterneubauer
Neo4j 1.8 GA - http://www.dzone.com/links/neo4j_18_release_fluent_graph_literacy.html
Taylor
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Peter Neubauer
yes, the project is still on Google Code. I was thinking that a move
might be good since there is a lot more infrastructure on Github?
/peter
Cheers,
/peter neubauer
G: neubauer.peter
S: peter.neubauer
P: +46 704 106975
L: http://www.linkedin.com/in/neubauer
T: @peterneubauer
Neo4j 1.8 GA - http://www.dzone.com/links/neo4j_18_release_fluent_graph_literacy.html
Pascal Salg
I found a github repo here (which just looks like a github clone of the svn repo at google code):
https://github.com/joostbaas/jo4neo
I then cloned the trunk and created a new github repo:
https://github.com/salgmachine/neoorm
So .. I'm good, I think I don't need commit privileges for jo4neo for now ;)
Greetings from Germany,
pascal
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