[FIXED] JMeter ClassNotFoundException on Java Request Sampler class

Issue

JMeter (5.5) doesn't see sampler class in Java request despite steps below being done:

• Sampler is in uber jar
• Jar was added to /lib and /lib/ext
• jmeter.properties user.classpath and search_path were tested (no luck)
• href="https://i.stack.imgur.com/AnvCk.png" rel="nofollow noreferrer">Jar was added in test plan in GUI
• Sampler is extending AbstractJavaSamplerClient

2022-08-30 15:27:34,324 ERROR o.a.j.p.j.c.g.JavaConfigGui: Error creating class:'package.SseSampler' in JavaSampler ${__threadNum}  SSE ${Username}, check for a missing jar in your jmeter 'search_paths' and 'plugin_dependency_paths' properties
java.lang.ClassNotFoundException: package.SseSampler
    at java.net.URLClassLoader.findClass(URLClassLoader.java:445) ~[?:?]
    at java.lang.ClassLoader.loadClass(ClassLoader.java:587) ~[?:?]
    at java.lang.ClassLoader.loadClass(ClassLoader.java:520) ~[?:?]
    at java.lang.Class.forName0(Native Method) ~[?:?]
    at java.lang.Class.forName(Class.java:467) ~[?:?]
    at org.apache.jmeter.protocol.java.config.gui.JavaConfigGui.classOk(JavaConfigGui.java:272) ~[ApacheJMeter_java.jar:5.5]
    at org.apache.jmeter.protocol.java.config.gui.JavaConfigGui.configure(JavaConfigGui.java:260) ~[ApacheJMeter_java.jar:5.5]
    at org.apache.jmeter.protocol.java.control.gui.JavaTestSamplerGui.configure(JavaTestSamplerGui.java:89) ~[ApacheJMeter_java.jar:5.5]
    at org.apache.jmeter.gui.GuiPackage.refreshCurrentGui(GuiPackage.java:468) ~[ApacheJMeter_core.jar:5.5]
    at org.apache.jmeter.gui.GuiPackage.updateCurrentGui(GuiPackage.java:452) ~[ApacheJMeter_core.jar:5.5]
    at org.apache.jmeter.gui.action.ActionRouter.performAction(ActionRouter.java:79) ~[ApacheJMeter_core.jar:5.5]
    at org.apache.jmeter.gui.action.ActionRouter.doActionNow(ActionRouter.java:124) ~[ApacheJMeter_core.jar:5.5]
    at org.apache.jmeter.gui.MainFrame.actionPerformed(MainFrame.java:899) ~[ApacheJMeter_core.jar:5.5]
    at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:1972) ~[?:?]
    at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2313) ~[?:?]
    at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:405) ~[?:?]
    at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:262) ~[?:?]
    at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonListener.java:279) ~[?:?]
    at com.github.weisj.darklaf.ui.button.DarkButtonListener.mouseReleased(DarkButtonListener.java:72) ~[darklaf-core-2.7.3.jar:2.7.3]
    at java.awt.AWTEventMulticaster.mouseReleased(AWTEventMulticaster.java:297) ~[?:?]
    at java.awt.Component.processMouseEvent(Component.java:6626) ~[?:?]
    at javax.swing.JComponent.processMouseEvent(JComponent.java:3389) ~[?:?]
    at java.awt.Component.processEvent(Component.java:6391) ~[?:?]
    at java.awt.Container.processEvent(Container.java:2266) ~[?:?]
    at java.awt.Component.dispatchEventImpl(Component.java:5001) ~[?:?]
    at java.awt.Container.dispatchEventImpl(Container.java:2324) ~[?:?]
    at java.awt.Component.dispatchEvent(Component.java:4833) ~[?:?]
    at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4948) ~[?:?]
    at java.awt.LightweightDispatcher.processMouseEvent(Container.java:4575) ~[?:?]
    at java.awt.LightweightDispatcher.dispatchEvent(Container.java:4516) ~[?:?]
    at java.awt.Container.dispatchEventImpl(Container.java:2310) ~[?:?]
    at java.awt.Window.dispatchEventImpl(Window.java:2780) ~[?:?]
    at java.awt.Component.dispatchEvent(Component.java:4833) ~[?:?]
    at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:773) ~[?:?]
    at java.awt.EventQueue$4.run(EventQueue.java:722) ~[?:?]
    at java.awt.EventQueue$4.run(EventQueue.java:716) ~[?:?]
    at java.security.AccessController.doPrivileged(AccessController.java:399) ~[?:?]
    at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:86) ~[?:?]
    at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:97) ~[?:?]
    at java.awt.EventQueue$5.run(EventQueue.java:746) ~[?:?]
    at java.awt.EventQueue$5.run(EventQueue.java:744) ~[?:?]
    at java.security.AccessController.doPrivileged(AccessController.java:399) ~[?:?]
    at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:86) ~[?:?]
    at java.awt.EventQueue.dispatchEvent(EventQueue.java:743) ~[?:?]
    at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:203) ~[?:?]
    at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:124) ~[?:?]
    at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:113) ~[?:?]
    at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:109) ~[?:?]
    at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:101) ~[?:?]
    at java.awt.EventDispatchThread.run(EventDispatchThread.java:90) ~[?:?]

Everything worked in 5.4.1 version, but for some reason it cannot run right now on my machine, so I would like to try use newest one.

Env:

• Windows 10 Enterprise
• Java 11 openjdk version "11.0.14" 2022-01-18 LTS

Solution

1. Put your .jar to "lib/ext" folder of your JMeter installation
2. Restart JMeter to pick it up
3. No other actions are required, i.e. don't amend Classpath, don't include it in Test Plan, etc.

If you want reference implementation you can take a look at RSAEncrypt.java and RSADecrypt.java

If you follow installation instructions from Beanshell vs. JSR223 vs. Java For JMeter: Complete Showdown article you should see the next 2 guys there:

If you see them - then there is something wrong with your jar, take a look at jmeter.log file and see if there are any suspicious entries there.

If you don't see them - then something is wrong with your JMeter installation, it's better to reinstall it from scratch.

Answered By - Dmitri T
Answer Checked By - David Goodson (JavaFixing Volunteer)