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How do I fix NoClassDefFoundError, the class path in the error is incorrect, but it's not in code I've written

EDIT: Just realised it's caused by a ClassNotFoundException, would still like some help.
I'm trying to update keycloak from version 12.0.3 to version 13.0.0, however when I make that change I get the following error:
Exception in thread "main" java.lang.NoClassDefFoundError: com/fasterxml/jackson/databind/jsontype/PolymorphicTypeValidator
at java.lang.Class.getDeclaredConstructors0(Native Method)
at java.lang.Class.privateGetDeclaredConstructors(Class.java:2671)
at java.lang.Class.getConstructors(Class.java:1651)
at org.jboss.resteasy.util.PickConstructor.pickSingletonConstructor(PickConstructor.java:30)
at org.jboss.resteasy.spi.ResteasyProviderFactory.createConstructorInjector(ResteasyProviderFactory.java:2821)
at org.jboss.resteasy.spi.ResteasyProviderFactory.createProviderInstance(ResteasyProviderFactory.java:2813)
at org.jboss.resteasy.spi.ResteasyProviderFactory.addMessageBodyReader(ResteasyProviderFactory.java:1048)
at org.jboss.resteasy.spi.ResteasyProviderFactory.registerProvider(ResteasyProviderFactory.java:1821)
at org.jboss.resteasy.spi.ResteasyProviderFactory.register(ResteasyProviderFactory.java:3026)
at org.jboss.resteasy.client.jaxrs.ResteasyClientBuilder.register(ResteasyClientBuilder.java:559)
at org.jboss.resteasy.client.jaxrs.ResteasyClientBuilder.register(ResteasyClientBuilder.java:48)
at org.keycloak.admin.client.Keycloak.newRestEasyClient(Keycloak.java:71)
at org.keycloak.admin.client.Keycloak.<init>(Keycloak.java:53)
at org.keycloak.admin.client.KeycloakBuilder.build(KeycloakBuilder.java:147)
at socsan.myapp.v1.mymodule.keycloak.KeycloakUserManager.createKeycloakInstance(KeycloakUserManager.java:187)
at socsan.myapp.v1.mymodule.keycloak.KeycloakUserManager.<init>(KeycloakUserManager.java:36)
at socsan.myapp.v1.mymodule.mymodule.startServices(mymodule.java:51)
at socsan.myapp.common.lifecycle.ProcessStarter.runStartupTasks(ProcessStarter.java:61)
at socsan.myapp.common.lifecycle.ProcessStarter.start(ProcessStarter.java:48)
at socsan.myapp.v1.mymodule.mymodule.main(mymodule.java:34)
Caused by: java.lang.ClassNotFoundException: com.fasterxml.jackson.databind.jsontype.PolymorphicTypeValidator
at java.net.URLClassLoader.findClass(URLClassLoader.java:382)
at java.lang.ClassLoader.loadClass(ClassLoader.java:418)
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:352)
at java.lang.ClassLoader.loadClass(ClassLoader.java:351)
... 20 more
I tried updating the fasterxml databind package too, but it didn't make any difference.
I noticed that the path to the correct jar in the maven repository is different to the path in the error.
In the maven repository there are stored at com/fasterxml/jackson/core/databind.
Does that have any baring on the issue?
How can I fix this?
EDIT 2:
In the parent pom we have this:
<dependency>
<groupId>com.fasterxml.jackson.datatype</groupId>
<artifactId>jackson-datatype-jsr310</artifactId>
<version>2.9.8</version>
</dependency>
The only change made to the module pom was to increase the version as stated above.
looking at the dependency analyser for jackson-databind it does look a bit of a mess, I should also point out that we're using the maven shade plugin:

Getting java.lang.NoClassDefFoundError: org/apache/axiom/om/util/StAXParserConfiguration in SoapBuilder

Below is my stack trace.
Caused by: java.lang.NoClassDefFoundError: org/apache/axiom/om/util/StAXParserConfiguration
at org.apache.axis2.builder.SOAPBuilder.processDocument(SOAPBuilder.java:64)
at org.apache.axis2.transport.TransportUtils.createDocumentElement(TransportUtils.java:197)
at org.apache.axis2.transport.TransportUtils.createSOAPMessage(TransportUtils.java:145)
at org.apache.axis2.transport.TransportUtils.createSOAPMessage(TransportUtils.java:108)
at org.apache.axis2.transport.TransportUtils.createSOAPMessage(TransportUtils.java:67)
at org.apache.axis2.description.OutInAxisOperationClient.handleResponse(OutInAxisOperation.java:354)
at org.apache.axis2.description.OutInAxisOperationClient.send(OutInAxisOperation.java:417)
at org.apache.axis2.description.OutInAxisOperationClient.executeImpl(OutInAxisOperation.java:229)
at org.apache.axis2.client.OperationClient.execute(OperationClient.java:165)

After a bit searching found that, the dependencies in my project for org.apache.axis2 were been upgraded from 1.5.1 to 1.5.3.
After 1.5.1 version had a transitive dependency on the library having the StAXParserConfiguration class.
But the later(newer) one does not have it. As such, I have to add the artifact explicitly in my pom.

You probably need to bundle the missing library with your deployed artifact,
<dependency>
<groupId>org.apache.ws.commons.axiom</groupId>
<artifactId>axiom-api</artifactId>
<version>1.2.14</version>
</dependency>

ClassNotFoundException oracle.i18n.util.LocaleMapper on tomcat TLD scanning. ojdbc7 maven dep (xmlparserv2-12.1.0.2.jar transitive) causes this error

I am receiving an error when running my spring-boot application with embedded-tomcat (haven't tried with server tomcat yet).
java.lang.IllegalStateException: Tomcat 7 reflection failed
at org.springframework.boot.context.embedded.tomcat.SkipPatternJarScanner.scan(SkipPatternJarScanner.java:77)
at org.apache.catalina.startup.TldConfig.execute(TldConfig.java:271)
at org.apache.catalina.startup.TldConfig.lifecycleEvent(TldConfig.java:590)
at org.apache.catalina.util.LifecycleSupport.fireLifecycleEvent(LifecycleSupport.java:117)
at org.apache.catalina.util.LifecycleBase.fireLifecycleEvent(LifecycleBase.java:90)
at org.apache.catalina.core.StandardContext.startInternal(StandardContext.java:5522)
at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:145)
at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1571)
at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1561)
at java.util.concurrent.FutureTask.run(FutureTask.java:266)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
at java.lang.Thread.run(Thread.java:748)
Caused by: java.lang.reflect.InvocationTargetException: null
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at org.springframework.boot.context.embedded.tomcat.SkipPatternJarScanner.scan(SkipPatternJarScanner.java:73)
... 12 common frames omitted
Caused by: java.lang.NoClassDefFoundError: oracle/i18n/util/LocaleMapper
at oracle.xml.parser.v2.XMLReader.setEncoding(XMLReader.java:980)
at oracle.xml.parser.v2.XMLReader.checkXMLDecl(XMLReader.java:3284)
at oracle.xml.parser.v2.XMLReader.pushXMLReader(XMLReader.java:570)
at oracle.xml.parser.v2.XMLReader.pushXMLReader(XMLReader.java:274)
at oracle.xml.parser.v2.XMLParser.parse(XMLParser.java:232)
at org.apache.tomcat.util.digester.Digester.parse(Digester.java:1576)
at org.apache.catalina.startup.TldConfig.tldScanStream(TldConfig.java:565)
at org.apache.catalina.startup.TldConfig.tldScanJar(TldConfig.java:513)
at org.apache.catalina.startup.TldConfig.access$200(TldConfig.java:61)
at org.apache.catalina.startup.TldConfig$TldJarScannerCallback.scan(TldConfig.java:300)
at org.apache.tomcat.util.scan.StandardJarScanner.process(StandardJarScanner.java:259)
at org.apache.tomcat.util.scan.StandardJarScanner.scan(StandardJarScanner.java:221)
... 17 common frames omitted
Caused by: java.lang.ClassNotFoundException: oracle.i18n.util.LocaleMapper
at java.net.URLClassLoader.findClass(URLClassLoader.java:381)
at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:335)
at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
... 29 common frames omitted
On further inspection, It appears as though the previous version of the orai18n.jar depended on by the ojdbc7 maven dep contained this class in vesion 11.2.0.3 but the newer (12.1.0.2) file does not contain it.

After much hassle, I've found the root cause (Edit: Actually the better answer provided has a more appropriate cause/solution, see Serri's answer):
according to this bug comment in spring-boot The Oracle SaxParserFactory impl and the (later run into after solving the first) DocumentBuilderFactory implementations are picked up instead of the default xerces impls. Changing the implementation using the META-INF/services/<class-name> files solved the issue:
in my.jar:
and each file:
// javax.xml.parsers.DocumentBuilderFactory
com.sun.org.apache.xerces.internal.jaxp.DocumentBuilderFactoryImpl
// javax.xml.parsers.SAXParserFactory
com.sun.org.apache.xerces.internal.jaxp.SAXParserFactoryImpl
This causes each service finder to resolve the default xerces implementation in the standard java library.

It's a conflict with xmlparserv2.
Try this :
<dependency>
<groupId>com.oracle.jdbc</groupId>
<artifactId>ojdbc7</artifactId>
<version>12.1.0.2</version>
<exclusions>
<exclusion>
<groupId>com.oracle.jdbc</groupId>
<artifactId>xmlparserv2</artifactId>
</exclusion>
</exclusions>
</dependency>

In my case I had the Oracle Jars installed under $CATALINA_HOME/lib to be able to set up a JNDI DB connection in Tomcat, simply removing xmlparserv2.jar from the $CATALINA_HOME/lib directory resolved the problem.

New change for xdb instead com.oracle.jdbc use: com.oracle.ojdbc.
<dependency>
<groupId>com.oracle.ojdbc</groupId>
<artifactId>xdb</artifactId>
<version>19.3.0.0</version>
<exclusions>
<exclusion>
<groupId>com.oracle.ojdbc</groupId>
<artifactId>xmlparserv2</artifactId>
</exclusion>
</exclusions>
</dependency>

The cause of the problem is as Serri said, except for the solution given by Serri I think if you use IntelliJ IDEA as a coding tool, please check Project Structure Artifacts to remove the dependency on xmlparserv2, this worked for me
Remove conflicting dependencies

Getting java.lang.ClassNotFoundException:MalformedPatternException

While trying to marshal the java object to xml i am getting below exception .
java.lang.ClassNotFoundException: org.apache.oro.text.regex.MalformedPatternException
at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1645)
at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1491)
at java.lang.Class.forName0(Native Method)
at java.lang.Class.forName(Class.java:186)
at org.castor.xml.AbstractInternalContext.getRegExpEvaluator(AbstractInternalContext.java:325)
at org.exolab.castor.xml.validators.PatternValidator.initEvaluator(PatternValidator.java:262)
at org.exolab.castor.xml.validators.PatternValidator.validate(PatternValidator.java:200)
at org.exolab.castor.xml.validators.StringValidator.validate(StringValidator.java:302)
at org.exolab.castor.xml.validators.StringValidator.validate(StringValidator.java:340)
at org.exolab.castor.xml.FieldValidator.validateInstance(FieldValidator.java:324)
at org.exolab.castor.xml.FieldValidator.validate(FieldValidator.java:271)
at org.exolab.castor.xml.util.XMLClassDescriptorImpl.validate(XMLClassDescriptorImpl.java:1072)
at org.exolab.castor.xml.Validator.validate(Validator.java:135)
at org.exolab.castor.xml.Marshaller.validate(Marshaller.java:2594)
at org.exolab.castor.xml.Marshaller.marshal(Marshaller.java:826)
at in.mywebapp.util.XMLUnmarshaller.getStatusRequestParam(XMLUnmarshaller.java:266)
Not sure which jar is missing .

you are probably missing oro.jar. You can add maven dependency
<dependency>
<groupId>oro</groupId>
<artifactId>oro</artifactId>
<version>2.0.8</version>
</dependency>
or download the jar from maven repository

Please make sure oro jar file is in classpath. It is not there. So, class loading is failing

java.lang.ClassNotFoundException: org.quartz.DisallowConcurrentExecution

I've developed some code that executes a quartz job.At first the code was outside the tomcat and it executes very well, but when I tried to embed the same code inside a web application I get java.lang.NoClassDefFoundError: org/quartz/DisallowConcurrentExecution.
I'm using quartz 2.1.5 and it's already in the class path.
Here is the stack trace:
Exception in thread "DefaultQuartzScheduler_QuartzSchedulerThread" java.lang.NoClassDefFoundError: org/quartz/DisallowConcurrentExecution
INFO: Illegal access: this web application instance has been stopped already. Could not load org.quartz.DisallowConcurrentExecution. The eventual following stack trace is caused by an error thrown for debugging purposes as well as to attempt to terminate the thread which caused the illegal access, and has no functional impact.
at org.quartz.impl.JobDetailImpl.isConcurrentExectionDisallowed(JobDetailImpl.java:390)
java.lang.IllegalStateException
at org.quartz.simpl.RAMJobStore.acquireNextTriggers(RAMJobStore.java:1447)
at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1273)
at org.quartz.core.QuartzSchedulerThread.run(QuartzSchedulerThread.java:264)
at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1233)
Caused by: java.lang.ClassNotFoundException: org.quartz.DisallowConcurrentExecution
at java.lang.ClassLoader.loadClassInternal(ClassLoader.java:320)
at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1387)
at org.quartz.impl.JobDetailImpl.isConcurrentExectionDisallowed(JobDetailImpl.java:390)
at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1233)
at org.quartz.simpl.RAMJobStore.acquireNextTriggers(RAMJobStore.java:1447)
at java.lang.ClassLoader.loadClassInternal(ClassLoader.java:320)
at org.quartz.core.QuartzSchedulerThread.run(QuartzSchedulerThread.java:264)

make sure you have only 1 quartz-all-.jar in your classpath (maybe you have 2 : 1 in Tomcat lib folder + 1 in your war)

NoClassDefFoundErrors point to a missing JAR or class on the classpath. In this case the problem is likely that in Tomcat you have quartz-<ver>.jar on your classpath when you actually need quartz-all-<ver>.jar.

for them who use maven can use the new version by add
<dependency>
<groupId>org.quartz-scheduler</groupId>
<artifactId>quartz</artifactId>
<version>2.1.7</version>
</dependency>

It should be keep the .jar file inside of the project location. Import .jar file from the outside from the location which the project have is the reason for getting this error. also verified that if the project is a maven project, then it should include the maven dependency in the pom.xml to add the dependency to the project
<dependency>
<groupId>org.quartz-scheduler</groupId>
<artifactId>quartz</artifactId>
<version>2.3.2</version>
</dependency>
<dependency>
<groupId>org</groupId>
<artifactId>quartz_job</artifactId>
<version>2.2.1</version>
</dependency>