The problem is how your app (or the memory measuit lib) is loading classes. It does not seem to use the classloader from your application main class (which is the one maven provides prepared with your dependencies).
Maybe it helps to set the thread context classloader with the app classloader (not sure if the maven plugin does that or not). But it might just not be possible to make your external code use this classloader, in that case starting a stand alone java might be easier. Gruss Bernd -- http://bernd.eckenfels.net ________________________________ Von: Siddharth Jain <siddh...@gmail.com> Gesendet: Monday, July 25, 2022 2:13:30 AM An: Maven Users List <users@maven.apache.org> Betreff: Re: java.lang.ClassNotFoundException: com.google.common.base.Preconditions could you explain this to me? we have tried running without configuring any agent mvn exec:java -X -Dexec.mainClass=com.example.App and the exception is still there. and maven:exec works for other projects. On Sun, Jul 24, 2022 at 1:19 PM Bernd Eckenfels <e...@zusammenkunft.net> wrote: > Since exec:java executes in the running JVM it does not reconfigure the > (boot)classpath but provides a configured classloader. It looks like the > measuring agent does not like that. In that Case you need either > exec:exec or a plug-in for that purpose. > > Gruss > Bernd > > > -- > http://bernd.eckenfels.net > ________________________________ > Von: Siddharth Jain <siddh...@gmail.com> > Gesendet: Sunday, July 24, 2022 8:46:04 PM > An: users@maven.apache.org <users@maven.apache.org> > Betreff: java.lang.ClassNotFoundException: > com.google.common.base.Preconditions > > we are running into the dreaded ClassNotFoundException in a project. Here > is the setup. Using JDK 11 and Maven 3.8.5. Trying to create sample test > project that uses memory-measurer > <https://github.com/DimitrisAndreou/memory-measurer> to measure memory. > First we mvn packaged and installed the memory-measurer artifact into M2 > repository. Then we created a test project in which we add dependency on > memory-measurer. The project compiles fine but gives error on running (we > run using mvn exec:java plugin): > > Caused by: java.lang.ClassNotFoundException: > com.google.common.base.Preconditions > at jdk.internal.loader.BuiltinClassLoader.loadClass > (BuiltinClassLoader.java:581) > at jdk.internal.loader.ClassLoaders$AppClassLoader.loadClass > (ClassLoaders.java:178) > at java.lang.ClassLoader.loadClass (ClassLoader.java:521) > at objectexplorer.InstrumentationGrabber.checkSetup > (InstrumentationGrabber.java:20) > at objectexplorer.InstrumentationGrabber.instrumentation > (InstrumentationGrabber.java:25) > at objectexplorer.MemoryMeasurer.<clinit> (MemoryMeasurer.java:24) > at com.example.App.main (App.java:20) > at org.codehaus.mojo.exec.ExecJavaMojo$1.run (ExecJavaMojo.java:254) > at java.lang.Thread.run (Thread.java:834) > > > What have we tried? Here is output of mvn dependency:build-classpath: > > > /Users/xxx/.m2/repository/objectexplorer/memory-measurer/1.0-SNAPSHOT/memory-measurer-1.0-SNAPSHOT.jar:/Users/xxx/.m2/repository/com/google/code/findbugs/jsr305/3.0.2/jsr305-3.0.2.jar:/Users/xxx/.m2/repository/com/google/guava/guava/19.0/guava-19.0.jar:/Users/xxx/.m2/repository/junit/junit/4.11/junit-4.11.jar:/Users/xxx/.m2/repository/org/hamcrest/hamcrest-core/1.3/hamcrest-core-1.3.jar > > we unpacked guava-19.0.jar in a temp directory and can see > > -rw-r--r-- 1 xxx staff 5252 Aug 25 2014 > /Users/xxx/temp/com/google/common/base/Preconditions.class > > in it. The next thing we tried is printing > System.getProperty("java.class.path"). This gives: > > /Library/Downloads/apache-maven-3.8.5/boot/plexus-classworlds-2.6.0.jar > > above does not contain the classpath calculated by mvn dependency plugin. > Question 1: Why? > > Question 2: When we printed System.getProperty("java.class.path") in > another working project we got same result. It seems the classpath when > using mvn exec:java is always > > /Library/Downloads/apache-maven-3.8.5/boot/plexus-classworlds-2.6.0.jar > > How is the other project able to load classes from above classpath? Why is > mvn > exec:java not using correct classpath? How do we fix this? > > > Here <https://gist.github.com/siddjain/5d2afee15a756b689c5231488e6c29be> > is > output of maven with the -X switch. You can see following debug info: > > > [DEBUG] Adding project dependency artifact: memory-measurer to classpath > [DEBUG] Adding project dependency artifact: jsr305 to classpath > *[DEBUG] Adding project dependency artifact: guava to classpath* here > <https://gist.github.com/siddjain/2ceaca405acdaf460df94a064e07c17f> is > pom.xml. would be great if someone could help us out. >
