I have JMeter 3.3 and I added [ElasticSearch backend listener](https://github.com/delirius325/JMeter_ElasticsearchBackendListener) plugin.

I opened JMeter GUI and tried create back end listener and it failed with error:

```
2017-10-17 14:35:24,785 ERROR o.a.j.g.GuiPackage: Problem retrieving gui for org.apache.jmeter.visualizers.backend.BackendListenerGui
java.lang.NoClassDefFoundError: okhttp3/MediaType
    at net.kvak.jmeter.backendlistener.elasticsearch.ElasticsearchBackend.<clinit>(ElasticsearchBackend.java:50) ~[elasticsearch-backend-listener-1.5.jar:?]
    at java.lang.Class.forName0(Native Method) ~[?:1.8.0_144]
    at java.lang.Class.forName(Unknown Source) ~[?:1.8.0_144]
    at org.apache.jmeter.visualizers.backend.BackendListenerGui.actionPerformed(BackendListenerGui.java:166) ~[ApacheJMeter_components.jar:3.3 r1808647]
    at javax.swing.JComboBox.fireActionEvent(Unknown Source) ~[?:1.8.0_144]
    at javax.swing.JComboBox.setSelectedItem(Unknown Source) ~[?:1.8.0_144]
    at javax.swing.JComboBox.setSelectedIndex(Unknown Source) ~[?:1.8.0_144]
    at org.apache.jmeter.visualizers.backend.BackendListenerGui.clearGui(BackendListenerGui.java:281) ~[ApacheJMeter_components.jar:3.3 r1808647]
    at org.apache.jmeter.gui.GuiPackage.createTestElement(GuiPackage.java:348) ~[ApacheJMeter_core.jar:3.3 r1808647]
    at org.apache.jmeter.gui.action.AddToTree.doAction(AddToTree.java:68) ~[ApacheJMeter_core.jar:3.3 r1808647]
    at org.apache.jmeter.gui.action.ActionRouter.performAction(ActionRouter.java:80) ~[ApacheJMeter_core.jar:3.3 r1808647]
    at org.apache.jmeter.gui.action.ActionRouter.lambda$actionPerformed$0(ActionRouter.java:65) ~[ApacheJMeter_core.jar:3.3 r1808647]
    at java.awt.event.InvocationEvent.dispatch(Unknown Source) [?:1.8.0_144]
    at java.awt.EventQueue.dispatchEventImpl(Unknown Source) [?:1.8.0_144]
    at java.awt.EventQueue.access$500(Unknown Source) [?:1.8.0_144]
    at java.awt.EventQueue$3.run(Unknown Source) [?:1.8.0_144]
    at java.awt.EventQueue$3.run(Unknown Source) [?:1.8.0_144]
    at java.security.AccessController.doPrivileged(Native Method) ~[?:1.8.0_144]
    at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(Unknown Source) [?:1.8.0_144]
    at java.awt.EventQueue.dispatchEvent(Unknown Source) [?:1.8.0_144]
    at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source) [?:1.8.0_144]
    at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source) [?:1.8.0_144]
    at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source) [?:1.8.0_144]
    at java.awt.EventDispatchThread.pumpEvents(Unknown Source) [?:1.8.0_144]
    at java.awt.EventDispatchThread.pumpEvents(Unknown Source) [?:1.8.0_144]
    at java.awt.EventDispatchThread.run(Unknown Source) [?:1.8.0_144]
Caused by: java.lang.ClassNotFoundException: okhttp3.MediaType
    at java.net.URLClassLoader.findClass(Unknown Source) ~[?:1.8.0_144]
    at java.lang.ClassLoader.loadClass(Unknown Source) ~[?:1.8.0_144]
    at java.lang.ClassLoader.loadClass(Unknown Source) ~[?:1.8.0_144]
    ... 26 more
2017-10-17 14:35:30,212 ERROR o.a.j.g.a.AddToTree: Exception while adding a component to tree.
java.lang.RuntimeException: java.lang.NoClassDefFoundError: okhttp3/MediaType
    at org.apache.jmeter.gui.GuiPackage.createTestElement(GuiPackage.java:359) ~[ApacheJMeter_core.jar:3.3 r1808647]
    at org.apache.jmeter.gui.action.AddToTree.doAction(AddToTree.java:68) ~[ApacheJMeter_core.jar:3.3 r1808647]
    at org.apache.jmeter.gui.action.ActionRouter.performAction(ActionRouter.java:80) ~[ApacheJMeter_core.jar:3.3 r1808647]
    at org.apache.jmeter.gui.action.ActionRouter.lambda$actionPerformed$0(ActionRouter.java:65) ~[ApacheJMeter_core.jar:3.3 r1808647]
    at java.awt.event.InvocationEvent.dispatch(Unknown Source) [?:1.8.0_144]
    at java.awt.EventQueue.dispatchEventImpl(Unknown Source) [?:1.8.0_144]
    at java.awt.EventQueue.access$500(Unknown Source) [?:1.8.0_144]
    at java.awt.EventQueue$3.run(Unknown Source) [?:1.8.0_144]
    at java.awt.EventQueue$3.run(Unknown Source) [?:1.8.0_144]
    at java.security.AccessController.doPrivileged(Native Method) ~[?:1.8.0_144]
    at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(Unknown Source) [?:1.8.0_144]
    at java.awt.EventQueue.dispatchEvent(Unknown Source) [?:1.8.0_144]
    at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source) [?:1.8.0_144]
    at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source) [?:1.8.0_144]
    at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source) [?:1.8.0_144]
    at java.awt.EventDispatchThread.pumpEvents(Unknown Source) [?:1.8.0_144]
    at java.awt.EventDispatchThread.pumpEvents(Unknown Source) [?:1.8.0_144]
    at java.awt.EventDispatchThread.run(Unknown Source) [?:1.8.0_144]
Caused by: java.lang.NoClassDefFoundError: okhttp3/MediaType
    at net.kvak.jmeter.backendlistener.elasticsearch.ElasticsearchBackend.<clinit>(ElasticsearchBackend.java:50) ~[elasticsearch-backend-listener-1.5.jar:?]
    at java.lang.Class.forName0(Native Method) ~[?:1.8.0_144]
    at java.lang.Class.forName(Unknown Source) ~[?:1.8.0_144]
    at org.apache.jmeter.visualizers.backend.BackendListenerGui.actionPerformed(BackendListenerGui.java:166) ~[ApacheJMeter_components.jar:3.3 r1808647]
    at javax.swing.JComboBox.fireActionEvent(Unknown Source) ~[?:1.8.0_144]
    at javax.swing.JComboBox.setSelectedItem(Unknown Source) ~[?:1.8.0_144]
    at javax.swing.JComboBox.setSelectedIndex(Unknown Source) ~[?:1.8.0_144]
    at org.apache.jmeter.visualizers.backend.BackendListenerGui.clearGui(BackendListenerGui.java:281) ~[ApacheJMeter_components.jar:3.3 r1808647]
    at org.apache.jmeter.gui.GuiPackage.createTestElement(GuiPackage.java:348) ~[ApacheJMeter_core.jar:3.3 r1808647]
    ... 17 more
Caused by: java.lang.ClassNotFoundException: okhttp3.MediaType
    at java.net.URLClassLoader.findClass(Unknown Source) ~[?:1.8.0_144]
    at java.lang.ClassLoader.loadClass(Unknown Source) ~[?:1.8.0_144]
    at java.lang.ClassLoader.loadClass(Unknown Source) ~[?:1.8.0_144]
    at net.kvak.jmeter.backendlistener.elasticsearch.ElasticsearchBackend.<clinit>(ElasticsearchBackend.java:50) ~[elasticsearch-backend-listener-1.5.jar:?]
    at java.lang.Class.forName0(Native Method) ~[?:1.8.0_144]
    at java.lang.Class.forName(Unknown Source) ~[?:1.8.0_144]
    at org.apache.jmeter.visualizers.backend.BackendListenerGui.actionPerformed(BackendListenerGui.java:166) ~[ApacheJMeter_components.jar:3.3 r1808647]
    at javax.swing.JComboBox.fireActionEvent(Unknown Source) ~[?:1.8.0_144]
    at javax.swing.JComboBox.setSelectedItem(Unknown Source) ~[?:1.8.0_144]
    at javax.swing.JComboBox.setSelectedIndex(Unknown Source) ~[?:1.8.0_144]
    at org.apache.jmeter.visualizers.backend.BackendListenerGui.clearGui(BackendListenerGui.java:281) ~[ApacheJMeter_components.jar:3.3 r1808647]
    at org.apache.jmeter.gui.GuiPackage.createTestElement(GuiPackage.java:348) ~[ApacheJMeter_core.jar:3.3 r1808647]
    ... 17 more

```

Sent question in [plugin group](https://groups.google.com/forum/#!forum/jmeter-plugins) but didn't receive any answer.

Is it working only with additional plugin/jars? on different version?

Also why doesn't it have page in https://jmeter-plugins.org/ (although it displayed in search results in site)?