# APM-Plugin: java.lang.ClassNotFoundException: net.bytebuddy.matcher.ElementMatcher **URL:** \ **Category:** APM\ **Tags:** java\ **Created:** [October 28, 2021, 7:24am UTC](https://discuss.elastic.co/t/apm-plugin-java-lang-classnotfoundexception-net-bytebuddy-matcher-elementmatcher/287889 "2021-10-28T07:24:27Z")\ **Posts on this page:** 4\ **Page:** 1
**Author:** ![Matthias\_W](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/matthias_w/32/96451_2.png) [@Matthias\_W](https://discuss.elastic.co/u/Matthias_W)\ **Post date:** [October 28, 2021, 7:24am UTC](https://discuss.elastic.co/t/apm-plugin-java-lang-classnotfoundexception-net-bytebuddy-matcher-elementmatcher/287889/1 "2021-10-28T07:24:27Z")
I am trying to create a plugin for the elastic apm-agent-java. I have closely followed the external plugin example: [apm-agent-java/integration-tests/external-plugin-test/external-plugin at master · elastic/apm-agent-java · GitHub](https://github.com/elastic/apm-agent-java/tree/master/integration-tests/external-plugin-test/external-plugin) However, I am getting an exception when trying to attach the agent: ```auto 2021-10-28 08:54:14,082 [main] INFO co.elastic.apm.agent.bci.ElasticApmAgent - Loading plugin apm-test-plugin-1.0.0-SNAPSHOT.jar [elastic-apm-agent] ERROR Failed to start agent java.lang.reflect.InvocationTargetException at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) at java.base/java.lang.reflect.Method.invoke(Method.java:566) at co.elastic.apm.agent.premain.AgentMain.loadAndInitializeAgent(AgentMain.java:149) at co.elastic.apm.agent.premain.AgentMain.init(AgentMain.java:94) at co.elastic.apm.agent.premain.AgentMain.premain(AgentMain.java:50) at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) at java.base/java.lang.reflect.Method.invoke(Method.java:566) at java.instrument/sun.instrument.InstrumentationImpl.loadClassAndStartAgent(InstrumentationImpl.java:513) at java.instrument/sun.instrument.InstrumentationImpl.loadClassAndCallPremain(InstrumentationImpl.java:525) Caused by: java.lang.NoClassDefFoundError: net/bytebuddy/matcher/ElementMatcher at java.base/java.lang.Class.forName0(Native Method) at java.base/java.lang.Class.forName(Class.java:398) at co.elastic.apm.agent.util.DependencyInjectingServiceLoader.instantiate(DependencyInjectingServiceLoader.java:128) at co.elastic.apm.agent.util.DependencyInjectingServiceLoader.instantiate(DependencyInjectingServiceLoader.java:118) at co.elastic.apm.agent.util.DependencyInjectingServiceLoader.(DependencyInjectingServiceLoader.java:69) at co.elastic.apm.agent.util.DependencyInjectingServiceLoader.load(DependencyInjectingServiceLoader.java:89) at co.elastic.apm.agent.bci.ElasticApmAgent.loadInstrumentations(ElasticApmAgent.java:171) at co.elastic.apm.agent.bci.ElasticApmAgent.initInstrumentation(ElasticApmAgent.java:163) at co.elastic.apm.agent.bci.ElasticApmAgent.initialize(ElasticApmAgent.java:149) ... 13 more Caused by: java.lang.ClassNotFoundException: net.bytebuddy.matcher.ElementMatcher at java.base/java.net.URLClassLoader.findClass(URLClassLoader.java:471) at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:588) at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:521) ... 22 more ``` Any ideas what is going wrong? Thank you! ---
**Author:** ![Matthias\_W](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/matthias_w/32/96451_2.png) [@Matthias\_W](https://discuss.elastic.co/u/Matthias_W)\ **Post date:** [October 28, 2021, 8:21am UTC](https://discuss.elastic.co/t/apm-plugin-java-lang-classnotfoundexception-net-bytebuddy-matcher-elementmatcher/287889/2 "2021-10-28T08:21:54Z")
I think I have figured it out: `integration-tests/external-plugin-test/external-plugin/pom.xml` was recently changed (after the latest release). Before the change, it contained the following configuration for the maven-shade-plugin: ```auto net.bytebuddy co.elastic.apm.agent.shaded.bytebuddy ``` Adding these lines to my plugin seems to fix the issue. ---
**Author:** ![felixbarny](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/felixbarny/32/27341_2.png) [@felixbarny](https://discuss.elastic.co/u/felixbarny)\ **Post date:** [October 28, 2021, 10:41am UTC](https://discuss.elastic.co/t/apm-plugin-java-lang-classnotfoundexception-net-bytebuddy-matcher-elementmatcher/287889/3 "2021-10-28T10:41:58Z")
Yes, this will change in the next version of the agent. The current version requires Byte Buddy to be shaded. The next version requires it not to be shaded. We're working towards a more stable API so that there won't be breaking changes after the plugin API has been declared stable. ---
**Author:** ![system](https://us1.discourse-cdn.com/elastic/original/3X/1/a/1ac57faf039f6b580b3f104ef42a2a89e41014de.png) [@system](https://discuss.elastic.co/u/system)\ **Post date:** [November 18, 2021, 6:42am UTC](https://discuss.elastic.co/t/apm-plugin-java-lang-classnotfoundexception-net-bytebuddy-matcher-elementmatcher/287889/4 "2021-11-18T06:42:55Z")
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