Develop Reference

Running OptaPlanner on the module path

I would like to make my OptaPlanner project run on the module path.
I created an example repository (mwkroening/optaplanner-modulepath-example) based on the cloud balancing demo in the docs.
The example project is running well on the classpath but there is an issue I can't workaround when trying to make it run on the module path. You can see the progress so far in PR #1.
The scoreDrl specified in the solverConfig.xml fails to load with the following exception:
Exception in thread "main" java.lang.IllegalArgumentException: The scoreDrl (io/github/mwkroening/optaplannermodulepathexample/cloudBalancingScoreRules.drl) does not exist as a classpath resource in the classLoader (jdk.internal.loader.ClassLoaders$AppClassLoader#7c16905e).
at org.optaplanner.core#7.18.0.Final/org.optaplanner.core.config.score.director.ScoreDirectorFactoryConfig.buildDroolsScoreDirectorFactory(ScoreDirectorFactoryConfig.java:519)
at org.optaplanner.core#7.18.0.Final/org.optaplanner.core.config.score.director.ScoreDirectorFactoryConfig.buildScoreDirectorFactory(ScoreDirectorFactoryConfig.java:351)
at org.optaplanner.core#7.18.0.Final/org.optaplanner.core.config.solver.SolverConfig.buildSolver(SolverConfig.java:255)
at org.optaplanner.core#7.18.0.Final/org.optaplanner.core.impl.solver.AbstractSolverFactory.buildSolver(AbstractSolverFactory.java:61)
at io.github.mwkroening.optaplannermodulepathexample/io.github.mwkroening.optaplannermodulepathexample.App.main(App.java:14)
I got a similar exception before when calling SolverFactory.createFromXmlResource.
My workaround for that problem was instead calling:
SolverFactory.createFromXmlInputStream(
App.class.getResourceAsStream("cloudBalancingSolverConfig.xml"));
I looked at PLANNER-883 and psiroky/optaplanner-cloudbalancing-jdk9, but I think a classpath resource was used in that case and not one on the module path.
How could I resolve this issue?
Perhaps I should open an issue instead of posting this here, right?

There's an overloaded method of every SolverFactory.createFrom*(...) that accepts a classloader: SolverFactory.createFrom*(..., classloader). That class loader isn't just used for loading the XML resources, but also the DRL resource.
So try:
SolverFactory.createFromXmlResource("/.../cloudBalancingSolverConfig.xml",
App.class.getClassLoader())
I haven't tested this out yet myself, but if it works, I'd love to see this added to the "jigsaw" section in the manual (PR welcome :).

baffling logback bug TimeBasedArchiveRemover$ArhiveRemoverRunnable

Logback 1.1.7
This was during a "production" run: stack trace from Exception (actually NoClassDefFoundError is an Error):
Exception in thread "main" java.lang.NoClassDefFoundError: ch/qos/logback/core/rolling/helper/TimeBasedArchiveRemover$ArhiveRemoverRunnable
at ch.qos.logback.core.rolling.helper.TimeBasedArchiveRemover.cleanAsynchronously(TimeBasedArchiveRemover.java:231)
at ch.qos.logback.core.rolling.TimeBasedRollingPolicy.rollover(TimeBasedRollingPolicy.java:178)
at ch.qos.logback.core.rolling.RollingFileAppender.attemptRollover(RollingFileAppender.java:204)
at ch.qos.logback.core.rolling.RollingFileAppender.rollover(RollingFileAppender.java:183)
at ch.qos.logback.core.rolling.RollingFileAppender.subAppend(RollingFileAppender.java:224)
at ch.qos.logback.core.OutputStreamAppender.append(OutputStreamAppender.java:100)
So I looked at the source: that class ArhiveRemoverRunnable does indeed exist in the .java file where it should have been instantiated on l. 231 (with that mis-spelling)...
Then I unpacked the executable jar (logback-core-1.1.7.jar): again, the file TimeBasedArchiveRemover$ArhiveRemoverRunnable.class exists in the package, as does file TimeBasedArchiveRemover.class.
This error is not going to happen that often: it is obviously when the "rolling" logger decides it's time to clean up the directory.
Anyone got any idea why this might happen? Troublingly I find no evidence of anyone else experiencing this...!

Potential workaround (pending):
I thought the answer to this might be to extract the source files for this .jar, edit the offending class, compile and repackage as an executable jar, and then use instead of the downloaded jar. In order to do this I started a new Gradle project in Eclipse, imported the entire source package, etc. The thing compiles (builds) OK in Eclipse-with-Gradle, with no complaints of the "NoClassDef" type...
But I'm having difficulties actually producing this executable jar. It'd be a nice thing to be able to accomplish: ability to tweak and test a downloaded dependency in some way (if really necessary).
Current not so satisfactory workaround:
In fact I have no need for a "time-based" archive remover. I'm quite happy just having archives removed on the basis of the size of all the files in the logging directory. This answer appears to solve this. However, logback is quite a beast: I'm not entirely sure: is "archive removal" the same thing as "rollover"?
If the Error occurs again, of course, I shall have to make a special utility method to log every LOGGER.xxx command within a try...catch.

Grails 2.1.1 - How to develop a plugin with an AstTransformer?

I want to replace the auto injected log object, which is of type org.apache.commons.logging.Log with an object of type org.slf4j.Logger, so that I can use it properly with Logback.
Therefore I need to create a ...Transformer class (written in Java) - that's what I got from Graeme Rocher over at the "grails-user" mailing list. I'm also aware that I have to pack this ...Transformer class within a plugin and make it a *.jar archive which I can load within the lib/ folder of the plugin. But I guess I'm doing something wrong here as I have the class, along with a META-INF folder which contains the MANIFEST.MF file as well as another folder services which holds the following file org.codehaus.groovy.transform.ASTTransformation which holds just one String: the canonical name of the ...Transformer class.
Now, if I try to do a grails clean everything is fine, BUT if I try to run grails package-plugin the console comes up with a java.lang.ClassNotFoundException.
Clipping from Stacktrace:
| Packaging Grails application...
| Error Fatal error during compilation org.codehaus.groovy.control.MultipleCompilationErrorsException: startup failed:
Could not instantiate global transform class my.package.ast.LoggingTransformation specified at jar:file:/C:/Source/MyGrailsAST/lib/replace-logging-logback-ast.jar!/META-INF/services/org.codehaus.groovy.transform.ASTTransformation because of exception java.lang.ClassNotFoundException: my.package.ast.LoggingTransformation
1 error
org.codehaus.groovy.control.MultipleCompilationErrorsException: startup failed:
Could not instantiate global transform class my.package.ast.LoggingTransformation specified at jar:file:/C:/Source/MyGrailsAST/lib/replace-logging-logback-ast.jar!/META-INF/services/org.codehaus.groovy.transform.ASTTransformation because of exception java.lang.ClassNotFoundException: my.package.ast.LoggingTransformation
Does anybody have some experience with Grails plugins which handle with AstTransformer and could give me some advice on this? Is there a good tutorial out there which I haven't seen so far?
Please let me know ;)

so, after some research, browsing and finally asking at the Grails Mailing List (see the mailing list archives at: http://grails.1312388.n4.nabble.com/Grails-user-f1312389.html I found a solution.
my goal was to create a Globals ASTTransformation, to inject a org.slf4j.Logger object instead of the usual org.apache.commons.logging.Log object into every Artefact class without annotation.
so, here are the steps:
I created Java class similar to https://github.com/grails/grails-core/blob/master/grails-logging/src/main/groovy/org/codehaus/groovy/grails/compiler/logging/LoggingTransformer.java but with my own implementation of the org.slf4j.Logger object. It is crucial that you place the Java.class under the following package: org.codehaus.groovy.grails.compiler as
Grails scans for classes that are annotated with #AstTransformer in this package. (Graeme Rocher)
and pack it into a JAR along with its MANIFEST.MF file within the META-INF/ folder. A META-INF/services directory with all its stuff is not needed as Graeme Rocher stated:
You do not need the META-INF/services stuff and I would remove it as it is probably complicating matters.
So, I guess this statement was more related to my specific problem as I only have one #AstTransformer class within my plugin, but that's just a guess. And I haven't searched for further informations on this topic. Maybe some other developer here who needs this could do some research and share his solution within this thread...
The JAR should be imported to the plugin and placed under the lib/ directory. After this you should be able to do grails clean, grails compile and grails package-plugin.
If you want to replace the log implementation, as I did, you should exclude the grails-logging and grails-plugin-log4j JARs from your designated project's classpath. This is done in the BuildConfig.groovy file:
inherits("global") {
excludes "grails-plugin-log4j", "grails-logging"
}
Now install your plugin grails install-plugin \path\to\plugin.zip and everthing should work as expected.
Hope this helps...

GWT super-source gives unable to resolve class java/lang/Object in development mode

I am trying to emulate some java.lang and java.io classes, e.g. OutputStream within GWT.
I have created a "super" package in my module and referenced it using super-source.
My package structure looks like
com/example/gwt/client
com/example/gwt/server
com/example/gwt/shared
com/example/gwt/super
com/example/gwt/super/java/io/OutputStream.java
com/example/gwt/mymodule.get.xml
and mymodule.xml contains an entry
<super-source path="super" />
Within Eclipse all of the files within the super folder are in error - to be expected because the package structure is wrong. .class files are being generated in the WEB-INF/classes folder, again with the "wrong" package structure so should be ignored.
When I run my application in development mode I get lots of
unable to resolve class java/lang/Object
errors. What am I doing wrong?

Rename ....get.xml to ....gwt.xml?
You can exclude "super" from the eclipse build path.
Try right-clicking or the build path menu exclusion options..

There was nothing wrong with the approach - just the execution.
I had compile errors in the emulated classes which were being masked by the fact that Eclipse was showing errors because of the "incorrect" package structure. Running the compiler from within Eclipse flushed these out.
It also seems that deleting the gwt-unitCache might have helped. As I was moving code around it seems that there were stale entries in here that were still being referenced.

Hibernate in Servlet causesNoClassDefFoundError: org/slf4j/LoggerFactory

I have a Java (6) application which uses Hibernate (V3.3.2) to read data from HSQLDB, which i build and debug/run with Eclipse (V3.5.1), and it works fine.
I then created a GWT (V1.7) Servlet web app, copied my hibernate classes into it, and added the same User Libraries dependencies. However when i run the servlet and try to access a URL which invokes my code i get this:
java.lang.NoClassDefFoundError: org/slf4j/LoggerFactory
at org.hibernate.cfg.Configuration.<clinit>(Configuration.java:152)
at xxx.daoimpl.DAOSession.initialise(DAOSession.java:40)
where DAOSession.java:40 is :
AnnotationConfiguration config = new AnnotationConfiguration ();
Googling for this error suggests i am missing slf4j-api.jar from the classpath, however if i look at the command line for the Debug properties i can see this jar there:
C:\java\jsedk_6\jre\bin\javaw.exe
-agentlib:jdwp=transport=dt_socket,suspend=y,address=localhost:54541
-Xmx512m -Dfile.encoding=Cp1252
-classpath
D:\dev\workspace\xxx\src;
D:\dev\workspace\xxx\resources;
D:\dev\workspace\xxx\war\WEB-INF\classes;
C:\java\eclipse\plugins\com.google.gwt.eclipse.sdkbundle.win32_1.7.1.v200909221731\gwt-windows-1.7.1\gwt-user.jar;
C:\java\eclipse\plugins\com.google.gwt.eclipse.sdkbundle.win32_1.7.1.v200909221731\gwt-windows-1.7.1\gwt-dev-windows.jar;
C:\java\hibernate-annotations-3.4.0.GA\hibernate-annotations.jar;
C:\java\hibernate-annotations-3.4.0.GA\lib\ejb3-persistence.jar;
C:\java\hibernate-annotations-3.4.0.GA\lib\hibernate-commons-annotations.jar;
C:\java\hibernate-distribution-3.3.2.GA\hibernate3.jar;
C:\java\hibernate-distribution-3.3.2.GA\lib\required\antlr-2.7.6.jar;
C:\java\hibernate-distribution-3.3.2.GA\lib\required\commons-collections-3.1.jar;
C:\java\hibernate-distribution-3.3.2.GA\lib\required\dom4j-1.6.1.jar;
C:\java\hibernate-distribution-3.3.2.GA\lib\required\javassist-3.9.0.GA.jar;
C:\java\hibernate-distribution-3.3.2.GA\lib\required\jta-1.1.jar;
C:\java\hibernate-validator-4.0.1.GA\hibernate-validator-4.0.1.GA.jar;
C:\java\hibernate-validator-4.0.1.GA\lib\validation-api-1.0.0.GA.jar;
C:\java\hibernate-validator-4.0.1.GA\lib\log4j-1.2.14.jar;
C:\java\hsqldb\lib\hsqldb.jar;
C:\java\restlet-jse-2.0m5\lib\org.restlet.jar;
C:\java\restlet-jee-2.0m5\lib\org.restlet.ext.servlet.jar;
C:\java\restlet-jse-2.0m5\lib\org.restlet.ext.xml.jar;
C:\java\slf4j-1.5.8\slf4j-api-1.5.8.jar;
C:\java\slf4j-1.5.8\slf4j-log4j12-1.5.8.jar
com.google.gwt.dev.HostedMode
...
If i open the jar i can see the LoggerFactory class in there.
Any idea why it isn't being found by the class loader?
Edit 1: If try to access org.slf4j.LoggerFactory from my code, Eclipse compiles it ok, but i get the same error at runtime.
Edit 2: If i add a Test class with a main which calls the same code and run it, it works. So this classpath problem seems specific to the Servlet.
thanks,
jon

It seems that copying the two slf4j jars to the war/WEB-INF/lib sub-project/dir fixed the problem. I'm not really sure why i should need to do this for these two jars and not for all the other Hibernate, Restlet etc jars that the project also uses, though i suppose for consistency i will do that anyway - i guess it will make deployment easier as well.
If someone can provide some sort of explanation as to why this worked and why exactly i need to do it i will select it as the "correct" answer, otherwise i'll select this one.

Can you please reconfirm that you have at least two slf4j.jar files in the classpath, the slf4j-api.jar and exactly one implementation, such as slf4j-jdk14.jar?
You must not have multiple sflj4-implementations in the classpath.

You have a runtime dependency issue so everything compiles fine but the dependency is in your jars. You need to visit the Hibernate site and look at the compatibility matrix and make sure you are matched up correctly then check the dependencies for annotations and core. You log4J jars look fine so it's definitely some quirk.
If it works in Eclipse then logically it's definitely some diff between the 2 runtimes (eclipse and non-eclipse), if the matrix checks out fine then see if you can factor out the commonalities in the 2 then work out the differences -- your answer should be in there.

I had a similar issue except I was using Tomcat and the NoClassDefFound error was on the juli logger. I fixed it by removing the Tomcat dependencies from my classpath when running in hosted mode because hosted mode embeds a Tomcat server that was conflicting. So I would see what happens if you remove some or all of the restlet jars from your classpath to see if they conflict.