Mysema Blog

A very good post!

2011-10-06T08:04:02.910+03:00

A very good post!

Sorry for the late reply. Here is a related ticket...

2011-08-31T14:17:22.130+03:00

Sorry for the late reply. Here is a related ticket : https://bugs.launchpad.net/querydsl/+bug/837998

There are various Querydsl tutorials on this blog ...

2011-08-15T11:42:14.493+03:00

There are various Querydsl tutorials on this blog and the reference docs : http://source.mysema.com/static/querydsl/2.2.0/reference/html/

They are all meant for beginners and intermediate users.

Hi Abhishek. Sorry for the late reply. Answered on...

2011-08-15T11:40:48.743+03:00

Hi Abhishek. Sorry for the late reply. Answered on SO.

Hi, I am facing an issue when i am trying to acces...

2011-06-17T15:32:06.193+03:00

Hi,
I am facing an issue when i am trying to access 2nd level nested element in an entity,I am getting a NullPointerException. I saw this link https://bugs.launchpad.net/querydsl/+bug/500163 but could not use it. Maybe some help. I already posted my question in http://stackoverflow.com/questions/6385036/querydsl-generated-classes-not-able-to-access-second-level-elements-for-querying .

I followed your instructions for Eclipse Helios, b...

2011-06-08T14:24:07.477+03:00

I followed your instructions for Eclipse Helios, but I get an exception:

java.lang.NullPointerException
at org.eclipse.jdt.internal.compiler.apt.dispatch.RoundEnvImpl.getElementsAnnotatedWith(RoundEnvImpl.java:122)
at org.eclipse.jdt.internal.compiler.apt.dispatch.RoundEnvImpl.getElementsAnnotatedWith(RoundEnvImpl.java:186)
at com.mysema.query.apt.DefaultConfiguration.(DefaultConfiguration.java:111)
at com.mysema.query.apt.jpa.JPAConfiguration.(JPAConfiguration.java:57)
at com.mysema.query.apt.hibernate.HibernateConfiguration.(HibernateConfiguration.java:33)
at com.mysema.query.apt.hibernate.HibernateAnnotationProcessor.createConfiguration(HibernateAnnotationProcessor.java:28)
at com.mysema.query.apt.jpa.JPAAnnotationProcessor.process(JPAAnnotationProcessor.java:45)
at org.eclipse.jdt.internal.compiler.apt.dispatch.RoundDispatcher.handleProcessor(RoundDispatcher.java:139)
at org.eclipse.jdt.internal.compiler.apt.dispatch.RoundDispatcher.round(RoundDispatcher.java:110)
at org.eclipse.jdt.internal.compiler.apt.dispatch.BaseAnnotationProcessorManager.processAnnotations(BaseAnnotationProcessorManager.java:159)
at org.eclipse.jdt.internal.apt.pluggable.core.dispatch.IdeAnnotationProcessorManager.processAnnotations(IdeAnnotationProcessorManager.java:134)
at org.eclipse.jdt.internal.compiler.Compiler.processAnnotations(Compiler.java:836)
at org.eclipse.jdt.internal.compiler.Compiler.compile(Compiler.java:428)
at org.eclipse.jdt.internal.core.builder.AbstractImageBuilder.compile(AbstractImageBuilder.java:364)
at org.eclipse.jdt.internal.core.builder.BatchImageBuilder.compile(BatchImageBuilder.java:178)
at org.eclipse.jdt.internal.core.builder.AbstractImageBuilder.compile(AbstractImageBuilder.java:301)
at org.eclipse.jdt.internal.core.builder.BatchImageBuilder.build(BatchImageBuilder.java:60)
at org.eclipse.jdt.internal.core.builder.JavaBuilder.buildAll(JavaBuilder.java:254)
at org.eclipse.jdt.internal.core.builder.JavaBuilder.build(JavaBuilder.java:173)
at org.eclipse.core.internal.events.BuildManager$2.run(BuildManager.java:629)
at org.eclipse.core.runtime.SafeRunner.run(SafeRunner.java:42)
at org.eclipse.core.internal.events.BuildManager.basicBuild(BuildManager.java:172)
at org.eclipse.core.internal.events.BuildManager.basicBuild(BuildManager.java:203)
at org.eclipse.core.internal.events.BuildManager$1.run(BuildManager.java:255)
at org.eclipse.core.runtime.SafeRunner.run(SafeRunner.java:42)
at org.eclipse.core.internal.events.BuildManager.basicBuild(BuildManager.java:258)
at org.eclipse.core.internal.events.BuildManager.basicBuild(BuildManager.java:220)
at org.eclipse.core.internal.events.BuildManager.build(BuildManager.java:362)
at org.eclipse.core.internal.resources.Project$1.run(Project.java:545)
at org.eclipse.core.internal.resources.Workspace.run(Workspace.java:1975)
at org.eclipse.core.internal.resources.Project.internalBuild(Project.java:524)
at org.eclipse.core.internal.resources.Project.build(Project.java:115)
at org.eclipse.jdt.internal.ui.util.CoreUtility$BuildJob.run(CoreUtility.java:160)
at org.eclipse.core.internal.jobs.Worker.run(Worker.java:54)

Never mind to the anonymous above. I figured it o...

2011-04-18T00:58:04.449+03:00

Never mind to the anonymous above. I figured it out:) I was just a little confused about which backend I had to use - JPA, JDO, Hibernate, etc..

I ended up generating the code using code like the above and was able to do queries using SQLTemplates and SQLQuery.

Great library. Thanks

Is there a beginner's tutorial somewhere? I&#...

2011-04-17T15:08:07.488+03:00

Is there a beginner's tutorial somewhere? I'm familiar with Java, but not so familiar with working with databases with Java.

For example, what are my imports for

" java.sql.Connection conn = ...;
MetaDataExporter exporter = new MetaDataExporter();
exporter.setPackageName("com.myproject.mydomain");
exporter.setTargetFolder(new File("src/main/java"));
exporter.export(conn.getMetaData());"

I need to reverse map a database and I'm assuming this MetaDataExporter stuff is what I need to use, but I just need a little more info.

Thanks

Werner, thanks for the hint. Fixed this in the blo...

2011-04-05T08:39:08.172+03:00

Werner, thanks for the hint. Fixed this in the blog post.

It looks like that fragment of your sample code wa...

2011-04-04T19:58:57.812+03:00

It looks like that fragment of your sample code was never run:
men.relationshipStatus.eq(RelationshipStatsu.SINGLE),
women.gender.eq(Gender.FEMALE),
women.relationshipStatsu.eq(RelationshipStatus.SINGLE));

Find the error, it shouldn't be too hard ;-)

Miguel, just add the element true to the configura...

2011-03-05T10:05:30.081+02:00

Miguel, just add the element true to the configuration. For more information see the reference documentation.

Hi, great post! I was wondering: is there any way ...

2011-03-04T20:15:44.446+02:00

Hi, great post!
I was wondering: is there any way of generating the Bean classes directly from maven as well, instead of java?

Thanks for the correction. Fixed and published.

2011-02-10T20:55:43.326+02:00

Thanks for the correction. Fixed and published.

I believe there is a typo in the first section of ...

2011-02-10T16:52:16.430+02:00

I believe there is a typo in the first section of this blog. It looks like you mistakenly copied the Maven dependencies from http://blog.mysema.com/2010/07/querying-hibernate-with-querydsl.html

There is no mention of querydsl-sql anywhere and I'm pretty sure we don't need to depend on querydsl-hql for SQL code.

SQLAlchemy is for Python. Who cares? Great work,...

2010-08-24T20:28:51.571+03:00

SQLAlchemy is for Python. Who cares?

Great work, Timo!

The query extensions with static delegates are rea...

2010-08-02T14:38:12.005+03:00

The query extensions with static delegates are really clever Querydsl feature, beyond my expectations on the original request.
I wish standard java could have such an extension mechanism, so all static helpers / utils (commons lang and so many others) would be used as instance methods on types themselves.
Congrats again, Timo and the Querydsl team!

Actually you can do that in Querydsl since two yea...

2010-07-25T20:18:40.131+03:00

Actually you can do that in Querydsl since two years as well. I just didn't describe it before in a blog post.

The XML overhead for Java builds is regrettable, but Maven and Ant are the standard build tools for Java, so I added integration guides for them.

Querydsl itself doesn't require any XML configuration. All it needs is the APT configuration in the build tool of choice, which can be XML-based or not, and the Querydsl library dependencies.

For a non-XML-based build tool for Java, consider using Apache Buildr. It uses a Ruby DSL for declaring builds.

you can do that in SQLAchemy since two years ... a...

2010-07-23T21:28:10.616+03:00

you can do that in SQLAchemy since two years ... and you don't need all this xml shit

Andy, here is a discussion related to Parameter us...

2010-06-30T22:26:07.599+03:00

Andy, here is a discussion related to Parameter usage : Query parameters

> With any standardised interface we'd likely go via a factory API, with newVariable(), newParameter() methods.

Let's see some further examples as code. The standalone expression model of Querydsl has many benefits, for example the default variables.

But I guess getting queries, parameters and root variables from a factory is still acceptable.

Thx Timo. I worked out how you currently handle pa...

2010-06-28T10:35:52.570+03:00

Thx Timo. I worked out how you currently handle params/vars. With any standardised interface we'd likely go via a factory API, with newVariable(), newParameter() methods.

I am currently on vacation, so I keep the response...

2010-06-24T17:43:48.498+03:00

I am currently on vacation, so I keep the response brief.

Parameters are supported via the Param class, both unnamed and named parameters are supported.

Querydsl JDO has only query sources, the first becomes the actual source and the others act as variables.

I will provider pointers etc after my holidays.

Timo, how does QueryDSL allows parameters/variable...

2010-06-23T10:59:35.924+03:00

Timo,
how does QueryDSL allows parameters/variables to be used in queries ? You have a "Param" class, but how do I get hold of one of those to use it in a query e.g as part of a filter ? Got an example URL ? Same goes for variables in JDO (does QueryDSL support them currently?). Thx

"unique" is just an example. The point i...

2010-06-22T21:23:08.439+03:00

"unique" is just an example. The point is that you need different methods for multiple row and single row results. Otherwise it is not type-safe.

> What about queries which return customer.firs...

2010-06-22T21:18:11.539+03:00

> What about queries which return customer.firstName results?

Obviously the user could set the type parameter of the query as that of the result class. The disadvantage of that is that the user needs to know it at the point of creating the query, though likely they ought to know at that point anyway. The advantage of setting it in execute() (your next option) is that you can reuse a query and change the result and also result class. So option 2 likely would be better for that reason alone.

Not sure Option 3 (no explicit execute()) would get many votes, from a backwards compatibility point-of-view never mind anything else.