Nice work Nacho! Some cool new features... love the meta-data
reloader idea
On 13 Sep 2010, at 18:53, Nacho Coloma wrote:
We are excited to announce the 1.0 release of SimpleDS. SimpleDS is a
simple persistence framework for Google AppEngine that provides an
alternative to JDO or JPA.
This release includes a lot of new features:
Cached queries
==============
This is the star feature of this release. Starting with 1.0, all query
results can be cached. To maximize cache performance only the returned
primary keys will be cached, so you still have to use @Cacheable to
cache the entity itself.
There are cases were this feature is killer, e.g. to retrieve a User
given the email:
User user = entityManager.createQuery(User.class)
.equal("email", googleUser.getEmail())
.withCacheSeconds(3600)
.asSingleResult()
;
DEBUG CacheManagerImpl - Level 2 cache hit:
qdata{kind=User,pred=[email = t...@example.com]}
DEBUG CacheManagerImpl - Level 2 cache hit: User(5)
DEBUG Level1Cache - Level 1 cache hit: User(5)
Cached queries work with FetchOptions (cursors, limit and offset) and
support only count(), asSingleEntity(), asList() and asPagedList().
Any invocation to asIterable() / asIterator() will ignore the cache.
To clear cached data, just prepare the same query and invoke
clearCache().
More about cache here [2].
Better fluent interfaces
========================
The syntax has been simplified from this (older version):
SimpleQuery query =
entityManager.createQuery(User.class).equal("name", "foo");
return entityManager.find(query);
To this:
return entityManager.createQuery(User.class)
.equal("email", email)
.equal("enabled", true)
.sortAsc("email")
.asList()
;
Now we rarely use more than one line for most queries. In this
example, if email is null it will just be ignored.
Several methods have been added: asList(), asSingleResult(),
asIterator(), asIterable() and PagedQuery.asPagedList(). The old
EntityManager methods have been deprecated.
More about queries here [3].
New Functions
=============
We are also adding some new Functions for transforming persistent
entities. Some examples of use:
// save space for your relationships by storing Set<Long> instead of
Set<Key>
Set<Long> userIds = user.getFriends();
Collection<Key> userKeys = Collections2.transform(userIds, new
IdToKeyFunction(User.class));
Collection<User> users = entityManager.get(userKeys);
// transform back
CompositeFunction<User, Long> func = new CompositeFunction(
new EntityToKeyFunction(User.class),
new KeyToIdFunction()
);
user.setFriends(Collections2.transform(users, func));
// just return a collection of email addresses
return Collections2.transform(users, new
EntityToPropertyFunction(User.class, "email"));
More about functions and transformations here [4]
Added JRebel support
====================
I personally use JRebel for development, which means that I rarely
restart my development server. This was a problem with SimpleDS, which
was unable to detect changes such as new persistent attributes, etc.
SimpleDS can now be used with JRebel just by adding this to your
startup code:
if (SystemProperty.environment.get().equals("Development"))
ClassMetadataReloader.register();
Then in eclipse ("Go to your launcher config -> Arguments -> VM
Arguments")
-javaagent:/usr/local/java/appengine-java-sdk/lib/agent/appengine-
agent.jar -noverify
"-javaagent:${env_var:REBEL_HOME}/jrebel.jar"
Minor changes
=============
* Added @Property.converter to override the default converter for one
persistent property. You can, for example, store a String attribute as
Text.
* Added new methods SimpleQuery.withReadPolicy(ReadPolicy) and
SimpleQuery.withDeadline(double)
* Added new methods SimpleQuery.withStartCursor(Cursor) and
SimpleQuery.withEndCursor(Cursor)
* Cache settings will be ignored when invoked within a transaction.
* We have moved from commons-logging to slf4j. This may break binary
compatibility, but is a huge boost in performance.
Next on the roadmap: we are already playing with appengine-mapper and
expect to deprecate our own dirty hack (BackgroundTasks) for our next
release.
I hope you find it interesting. All feedback is welcome.
Nacho.
[1] http://code.google.com/p/simpleds/wiki/ReleaseAnnouncements
[2] http://code.google.com/p/simpleds/wiki/Cache
[3] http://code.google.com/p/simpleds/wiki/SimpleQuery
[4] http://code.google.com/p/simpleds/wiki/Functions
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