Deploying Jenkins Sectioned View Plugin extension - jenkins

Question

I want to create new view for Sectioned View Plugin for Jenkins. How should I deploy my extension? I was trying to deploy it as new plugin in .jpi file but it didn't work. Where should I put my class/jar/jpi (I don't know which is right) file?
UPD: I tried to put jar to \jenkins\plugin\sectioned-view\WEB-INF\lib directory and it works but I doubt it's a right way to deploy that extension
UPD2: When I try to deploy extension as a new plugin I get these exception on startup:
WARNING: Failed to load <packageName>.<mainExtensionClassName>$DescriptorImpl
java.lang.InstantiationException:<jenkinsDirectory>\plugins\installedapplicationssection\WEB-INF\lib\classes.jar might need to be rebuilt: java.lang.ClassNotFoundException: <packageName>.<mainExtensionClassName>$DescriptorImpl
at net.java.sezpoz.IndexItem.element(IndexItem.java:144)
at hudson.ExtensionFinder$Sezpoz._find(ExtensionFinder.java:628)
at hudson.ExtensionFinder$Sezpoz.find(ExtensionFinder.java:617)
at hudson.ExtensionFinder._find(ExtensionFinder.java:151)
at hudson.ClassicPluginStrategy.findComponents(ClassicPluginStrategy.java:316)
at hudson.ExtensionList.load(ExtensionList.java:295)
at hudson.ExtensionList.ensureLoaded(ExtensionList.java:248)
at hudson.ExtensionList.iterator(ExtensionList.java:138)
at hudson.ClassicPluginStrategy.findComponents(ClassicPluginStrategy.java:309)
at hudson.ExtensionList.load(ExtensionList.java:295)
at hudson.ExtensionList.ensureLoaded(ExtensionList.java:248)
at hudson.ExtensionList.get(ExtensionList.java:153)
at hudson.PluginManager$PluginUpdateMonitor.getInstance(PluginManager.java:1109)
at hudson.maven.PluginImpl.init(PluginImpl.java:54)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at hudson.init.InitializerFinder.invoke(InitializerFinder.java:120)
at hudson.init.InitializerFinder$TaskImpl.run(InitializerFinder.java:184)
at org.jvnet.hudson.reactor.Reactor.runTask(Reactor.java:259)
at jenkins.model.Jenkins$7.runTask(Jenkins.java:906)
at org.jvnet.hudson.reactor.Reactor$2.run(Reactor.java:187)
at org.jvnet.hudson.reactor.Reactor$Node.run(Reactor.java:94)
at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
at java.lang.Thread.run(Unknown Source)
Caused by: java.lang.ClassNotFoundException: <packageName>.<mainExtensionClassName>$DescriptorImpl
at hudson.PluginManager$UberClassLoader.findClass(PluginManager.java:985)
at java.lang.ClassLoader.loadClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
at net.java.sezpoz.IndexItem.element(IndexItem.java:134)
But I already have this in my class:
#Extension
public static final class DescriptorImpl extends SectionedViewSectionDescriptor {
#Override
public String getDisplayName() {
return "My Section";
}
}