Maven - ClassNotFoundException

[Graeme Byers]

This may be a simple Java ClassNotFoundException rather than Maven but I can't spot it.

Thank you for any help.

I'm following 'Maven - The Definitive Guide' page 54.

Step 1 :

Directory of C:\ch-custom

24/01/2012  16:08    <DIR>          .
24/01/2012  16:08    <DIR>          ..
24/01/2012  16:08               428 ch-custom.txt
12/01/2011  17:40               635 pom.xml
24/01/2012  16:10    <DIR>          simple-weather

Step 2 :

 Directory of C:\ch-custom\simple-weather

24/01/2012  15:12    <DIR>          .
24/01/2012  15:12    <DIR>          ..
24/01/2012  15:12    <DIR>          org
12/01/2011  17:40             3,497 pom.xml
24/01/2012  15:03    <DIR>          src
24/01/2012  15:04    <DIR>          target
24/01/2012  15:04             6,081 velocity.log

Step 3 :

Directory of C:\ch-custom\simple-weather\target\classes\org\sonatype\mavenbook\weather

24/01/2012  15:04    <DIR>          .
24/01/2012  15:04    <DIR>          ..
24/01/2012  15:04             1,721 Main.class
24/01/2012  15:04             1,667 Weather.class
24/01/2012  15:04             1,750 WeatherFormatter.class
24/01/2012  15:04             2,556 YahooParser.class
24/01/2012  15:04             1,308 YahooRetriever.class

Step 4 :

cd c:\ch-custom
c:\ch-custom>mvn exec:java -Dexec.mainClass=org.sonatype.mavenbook.weather.Main

[INFO] Scanning for projects...
[WARNING] 
[WARNING] Some problems were encountered while building the effective model for org.sonatype.mavenbook.custom:simple-weather:jar:0.8-SNAPSHOT
[WARNING] 'build.plugins.plugin.version' for org.apache.maven.plugins:maven-compiler-plugin is missing. @ line 49, column 15
[WARNING] 'build.plugins.plugin.version' for org.apache.maven.plugins:maven-surefire-plugin is missing. @ line 69, column 15
[WARNING] 'build.plugins.plugin.version' for org.apache.maven.plugins:maven-jar-plugin is missing. @ line 57, column 15
[WARNING] 
[WARNING] It is highly recommended to fix these problems because they threaten the stability of your build.
[WARNING] 
[WARNING] For this reason, future Maven versions might no longer support building such malformed projects.
[WARNING] 
[INFO] ------------------------------------------------------------------------
[INFO] Reactor Build Order:
[INFO] 
[INFO] Customizing Chapter Parent Project
[INFO] Customizing Chapter Simple Weather Project
[INFO]                                                                         
[INFO] ------------------------------------------------------------------------
[INFO] Building Customizing Chapter Parent Project 0.8-SNAPSHOT
[INFO] ------------------------------------------------------------------------
[INFO] 
[INFO] >>> exec-maven-plugin:1.2.1:java (default-cli) @ parent >>>
[INFO] 
[INFO] <<< exec-maven-plugin:1.2.1:java (default-cli) @ parent <<<
[INFO] 
[INFO] --- exec-maven-plugin:1.2.1:java (default-cli) @ parent ---
[WARNING] 
java.lang.ClassNotFoundException: org.sonatype.mavenbook.weather.Main
	at java.net.URLClassLoader$1.run(URLClassLoader.java:202)
	at java.security.AccessController.doPrivileged(Native Method)
	at java.net.URLClassLoader.findClass(URLClassLoader.java:190)
	at java.lang.ClassLoader.loadClass(ClassLoader.java:306)
	at java.lang.ClassLoader.loadClass(ClassLoader.java:247)
	at org.codehaus.mojo.exec.ExecJavaMojo$1.run(ExecJavaMojo.java:285)
	at java.lang.Thread.run(Thread.java:662)
[INFO] ------------------------------------------------------------------------
[INFO] Reactor Summary:
[INFO] 
[INFO] Customizing Chapter Parent Project ................ FAILURE [0.438s]
[INFO] Customizing Chapter Simple Weather Project ........ SKIPPED
[INFO] ------------------------------------------------------------------------
[INFO] BUILD FAILURE
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 1.141s
[INFO] Finished at: Tue Jan 24 16:23:07 GMT 2012
[INFO] Final Memory: 4M/15M
[INFO] ------------------------------------------------------------------------
[ERROR] Failed to execute goal org.codehaus.mojo:exec-maven-plugin:1.2.1:java (default-cli) on project parent: An exception occured while executing the Java class. org.sonatype.mavenbook.weather.Main -> [Help 1]
[ERROR] 
[ERROR] To see the full stack trace of the errors, re-run Maven with the -e switch.
[ERROR] Re-run Maven using the -X switch to enable full debug logging.
[ERROR] 
[ERROR] For more information about the errors and possible solutions, please read the following articles:
[ERROR] [Help 1] http://cwiki.apache.org/confluence/display/MAVEN/MojoExecutionException

[Graeme Byers]

Forgot to mention : %CLASSPATH% contains C:\ch-custom\simple-weather\target\classes

[Peter Johnson]

You are using the Exec plugin. You need to post the entire definition of that plugin from your pom.xml file (Maven - The Definitive Guide, page 54, doesn't show the Exec plugin being used). Apparently, you didn't set the classpath, or you used the wrong target (you should be using exec:java, not exec:exec).

Also, "The Definitive Guide" has be superceeded by "The Complete Reference": http://www.sonatype.com/books/mvnref-book/reference/

[Peter Johnson]

Graeme Byers wrote:Forgot to mention : %CLASSPATH% contains C:\ch-custom\simple-weather\target\classes

Never set CLASSPATH, that's a sure way to get yourself into trouble because you will at some point accidentally pick up the wrong class file. Besides, you should not have to do that when using Maven.