Startup Error: java.lang.IncompatibleClassChangeError: org/apache/struts2/convention/DefaultClassFinder$InfoBuildingVisitor

Question

I have a Struts2 application, originally XML-based, but now for the first time I introduced an Annotation-based action, and the application broke on startup.

Given the following Action mapping, on startup of the application, I get the error

java.lang.InstantiationError: com.opensymphony.xwork2.util.finder.ClassFinder
    at org.apache.struts2.convention.PackageBasedActionConfigBuilder.findActions(PackageBasedActionConfigBuilder.java:390)
    at org.apache.struts2.convention.PackageBasedActionConfigBuilder.buildActionConfigs(PackageBasedActionConfigBuilder.java:347)
    at org.apache.struts2.convention.ClasspathPackageProvider.loadPackages(ClasspathPackageProvider.java:53)
    at com.opensymphony.xwork2.config.impl.DefaultConfiguration.reloadContainer(DefaultConfiguration.java:199)
    at com.opensymphony.xwork2.config.ConfigurationManager.getConfiguration(ConfigurationManager.java:67)
    at org.apache.struts2.dispatcher.Dispatcher.getContainer(Dispatcher.java:906)
    at org.apache.struts2.dispatcher.Dispatcher.init_PreloadConfiguration(Dispatcher.java:445)
    at org.apache.struts2.dispatcher.Dispatcher.init(Dispatcher.java:486)
    at org.apache.struts2.dispatcher.InitOperations.initDispatcher(InitOperations.java:75)
    at org.apache.struts2.dispatcher.filter.StrutsPrepareAndExecuteFilter.init(StrutsPrepareAndExecuteFilter.java:63)
    at org.apache.catalina.core.ApplicationFilterConfig.initFilter(ApplicationFilterConfig.java:279)

There was a similar question here, but no one responded, Issue with Struts2 Filter Exception

Libraries Used:

• struts2-convention-plugin-2.3.14.3.jar
• struts2-core-2.5.10.1.jar
• struts2-json-plugin-2.5.10.1.jar
• struts2-spring-plugin-2.5.10.1.jar
• struts2-tiles-plugin-2.5.10.1.jar
• xwork-core-2.1.6.jar

Update: I thought the Convention-Plugin-JAR 2.3.14.3 was incompatible with the other 2.5.10.1 ones, so I downloaded: struts2-convention-plugin-2.5.10.1.jar

Now on startup getting

java.lang.IncompatibleClassChangeError: org/apache/struts2/convention/DefaultClassFinder$InfoBuildingVisitor
    at org.apache.struts2.convention.DefaultClassFinder.readClassDef(DefaultClassFinder.java:459) ~[struts2-convention-plugin-2.5.10.1.jar:2.5.10.1]
    at org.apache.struts2.convention.DefaultClassFinder.<init>(DefaultClassFinder.java:90) [struts2-convention-plugin-2.5.10.1.jar:2.5.10.1]
    at org.apache.struts2.convention.PackageBasedActionConfigBuilder.buildClassFinder(PackageBasedActionConfigBuilder.java:397) [struts2-convention-plugin-2.5.10.1.jar:2.5.10.1]
    at org.apache.struts2.convention.PackageBasedActionConfigBuilder.findActions(PackageBasedActionConfigBuilder.java:379) [struts2-convention-plugin-2.5.10.1.jar:2.5.10.1]
    at org.apache.struts2.convention.PackageBasedActionConfigBuilder.buildActionConfigs(PackageBasedActionConfigBuilder.java:335) [struts2-convention-plugin-2.5.10.1.jar:2.5.10.1]
    at org.apache.struts2.convention.ClasspathPackageProvider.loadPackages(ClasspathPackageProvider.java:53) [struts2-convention-plugin-2.5.10.1.jar:2.5.10.1]
    at com.opensymphony.xwork2.config.impl.DefaultConfiguration.reloadContainer(DefaultConfiguration.java:199) [struts2-core-2.5.10.1.jar:2.5.10.1]

SOLUTION The solution was to add ASM 5.x JARs which are a dependency of the Struts-Convention JAR for annotations. We were using ASM 3.3. I added the ASM-Core, -Common, -Tree Version 5.1 JARs.

Answer 1

struts2-convention plugin 2.5.10.1 has compile dependencies

<dependency>
    <groupId>org.apache.commons</groupId>
    <artifactId>commons-lang3</artifactId>
    <version>3.4</version>
</dependency>
<dependency>
    <groupId>org.ow2.asm</groupId>
    <artifactId>asm</artifactId>
    <version>5.1</version>
</dependency>
<dependency>
    <groupId>org.ow2.asm</groupId>
    <artifactId>asm-commons</artifactId>
    <version>5.1</version>
</dependency>

---

Note: if you don't need asm and asm-commons dependencies you can downgrade to Struts 2.5.5.

Answer 2

Struts2 uses ASM 5x for the Convention plugin. Check you classpath and make sure you have appropriate version of ASM jars.