Steps to reproduce:

1 Login to Jenkins (localhost:8080)

2. Select Manage Jenkins

3. Go to JIRA sites and click on Add

4. Enter your Jira URL, user name and password

5. Click on Validate Settings

Result: the following error message is displayed

Stack trace

java.lang.ClassNotFoundException: com.atlassian.fugue.Effect
    at jenkins.util.AntClassLoader.findClassInComponents(AntClassLoader.java:1374)
    at jenkins.util.AntClassLoader.findClass(AntClassLoader.java:1327)
    at jenkins.util.AntClassLoader.loadClass(AntClassLoader.java:1080)
    at java.lang.ClassLoader.loadClass(Unknown Source)
Caused: java.lang.NoClassDefFoundError: com/atlassian/fugue/Effect
    at com.atlassian.httpclient.apache.httpcomponents.DefaultHttpClientFactory.doCreate(DefaultHttpClientFactory.java:68)
    at com.atlassian.httpclient.apache.httpcomponents.DefaultHttpClientFactory.create(DefaultHttpClientFactory.java:35)
    at com.atlassian.jira.rest.client.internal.async.AsynchronousHttpClientFactory.createClient(AsynchronousHttpClientFactory.java:63)
    at com.atlassian.jira.rest.client.internal.async.AsynchronousJiraRestClientFactory.create(AsynchronousJiraRestClientFactory.java:35)
    at com.atlassian.jira.rest.client.internal.async.AsynchronousJiraRestClientFactory.createWithBasicHttpAuthentication(AsynchronousJiraRestClientFactory.java:42)
    at hudson.plugins.jira.JiraSite.createSession(JiraSite.java:280)
    at hudson.plugins.jira.JiraSite$DescriptorImpl.doValidate(JiraSite.java:782)
    at java.lang.invoke.MethodHandle.invokeWithArguments(Unknown Source)
    at org.kohsuke.stapler.Function$MethodFunction.invoke(Function.java:343)
    at org.kohsuke.stapler.Function.bindAndInvoke(Function.java:184)
    at org.kohsuke.stapler.Function.bindAndInvokeAndServeResponse(Function.java:117)
    at org.kohsuke.stapler.MetaClass$1.doDispatch(MetaClass.java:129)
    at org.kohsuke.stapler.NameBasedDispatcher.dispatch(NameBasedDispatcher.java:58)
    at org.kohsuke.stapler.Stapler.tryInvoke(Stapler.java:715)
Caused: javax.servlet.ServletException
    at org.kohsuke.stapler.Stapler.tryInvoke(Stapler.java:765)
    at org.kohsuke.stapler.Stapler.invoke(Stapler.java:845)
    at org.kohsuke.stapler.MetaClass$5.doDispatch(MetaClass.java:248)
    at org.kohsuke.stapler.NameBasedDispatcher.dispatch(NameBasedDispatcher.java:58)
    at org.kohsuke.stapler.Stapler.tryInvoke(Stapler.java:715)
    at org.kohsuke.stapler.Stapler.invoke(Stapler.java:845)
    at org.kohsuke.stapler.Stapler.invoke(Stapler.java:649)
    at org.kohsuke.stapler.Stapler.service(Stapler.java:238)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:790)
    at org.eclipse.jetty.servlet.ServletHolder.handle(ServletHolder.java:812)
    at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1669)
    at hudson.util.PluginServletFilter$1.doFilter(PluginServletFilter.java:135)
    at hudson.util.PluginServletFilter.doFilter(PluginServletFilter.java:138)
    at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1652)
    at hudson.security.csrf.CrumbFilter.doFilter(CrumbFilter.java:80)
    at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1652)
    at hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:84)
    at hudson.security.UnwrapSecurityExceptionFilter.doFilter(UnwrapSecurityExceptionFilter.java:51)
    at hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:87)
    at jenkins.security.ExceptionTranslationFilter.doFilter(ExceptionTranslationFilter.java:117)
    at hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:87)
    at org.acegisecurity.providers.anonymous.AnonymousProcessingFilter.doFilter(AnonymousProcessingFilter.java:125)
    at hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:87)
    at org.acegisecurity.ui.rememberme.RememberMeProcessingFilter.doFilter(RememberMeProcessingFilter.java:142)
    at hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:87)
    at org.acegisecurity.ui.AbstractProcessingFilter.doFilter(AbstractProcessingFilter.java:271)
    at hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:87)
    at jenkins.security.BasicHeaderProcessor.doFilter(BasicHeaderProcessor.java:92)
    at hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:87)
    at org.acegisecurity.context.HttpSessionContextIntegrationFilter.doFilter(HttpSessionContextIntegrationFilter.java:249)
    at hudson.security.HttpSessionContextIntegrationFilter2.doFilter(HttpSessionContextIntegrationFilter2.java:67)
    at hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:87)
    at hudson.security.ChainedServletFilter.doFilter(ChainedServletFilter.java:90)
    at hudson.security.HudsonFilter.doFilter(HudsonFilter.java:171)
    at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1652)
    at org.kohsuke.stapler.compression.CompressionFilter.doFilter(CompressionFilter.java:49)
    at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1652)
    at hudson.util.CharacterEncodingFilter.doFilter(CharacterEncodingFilter.java:82)
    at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1652)
    at org.kohsuke.stapler.DiagnosticThreadNameFilter.doFilter(DiagnosticThreadNameFilter.java:30)
    at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1652)
    at org.eclipse.jetty.servlet.ServletHandler.doHandle(ServletHandler.java:585)
    at org.eclipse.jetty.server.handler.ScopedHandler.handle(ScopedHandler.java:143)
    at org.eclipse.jetty.security.SecurityHandler.handle(SecurityHandler.java:553)
    at org.eclipse.jetty.server.session.SessionHandler.doHandle(SessionHandler.java:223)
    at org.eclipse.jetty.server.handler.ContextHandler.doHandle(ContextHandler.java:1127)
    at org.eclipse.jetty.servlet.ServletHandler.doScope(ServletHandler.java:515)
    at org.eclipse.jetty.server.session.SessionHandler.doScope(SessionHandler.java:185)
    at org.eclipse.jetty.server.handler.ContextHandler.doScope(ContextHandler.java:1061)
    at org.eclipse.jetty.server.handler.ScopedHandler.handle(ScopedHandler.java:141)
    at org.eclipse.jetty.server.handler.HandlerWrapper.handle(HandlerWrapper.java:97)
    at org.eclipse.jetty.server.Server.handle(Server.java:499)
    at org.eclipse.jetty.server.HttpChannel.handle(HttpChannel.java:311)
    at org.eclipse.jetty.server.HttpConnection.onFillable(HttpConnection.java:257)
    at org.eclipse.jetty.io.AbstractConnection$2.run(AbstractConnection.java:544)
    at winstone.BoundedExecutorService$1.run(BoundedExecutorService.java:77)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
    at java.lang.Thread.run(Unknown Source)

I have also tried the following:

• different browsers
• http instead of https
• adding also the Link URL (JIRA alternative URL)
• Checking and unchecking the Use HTTP authentication checkbox
• a random website
• removing and reinstalling the JIRA plugin

The same error message is generated