Hudson plugin for Yammer-API Stapler Exception?

I am using Hudson-yammer plugin for sending notification on yammer & Uses following jar

Hudson jar = hudson-core-1.384.jar

Stapler jar = stapler1.87 Jar

Hudson-yammer plugin = http://code.google.com/p/hudson-yammer/

Exception in thread "main" java.lang.NoClassDefFoundError: or开发者_如何学Gog/kohsuke/stapler/StaplerFallback
    at java.lang.ClassLoader.defineClass1(Native Method)
    at java.lang.ClassLoader.defineClass(ClassLoader.java:634)
    at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:142)
    at java.net.URLClassLoader.defineClass(URLClassLoader.java:277)
    at java.net.URLClassLoader.access$000(URLClassLoader.java:73)
    at java.net.URLClassLoader$1.run(URLClassLoader.java:212)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.net.URLClassLoader.findClass(URLClassLoader.java:205)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:321)
    at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:294)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:266)
    at hudson.tasks.Publisher.getDescriptor(Publisher.java:123)
    at hudson.plugins.yammer.YammerPublisher.<init>(YammerPublisher.java:66)
    at hudson.plugins.yammer.NotifyToYammer.main(NotifyToYammer.java:22)
Caused by: java.lang.ClassNotFoundException: org.kohsuke.stapler.StaplerFallback
    at java.net.URLClassLoader$1.run(URLClassLoader.java:217)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.net.URLClassLoader.findClass(URLClassLoader.java:205)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:321)
    at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:294)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:266)
    ... 14 more

Hudson-yammer plugin = http://code.google.com/p/hudson-yammer/

What's wrong with the code ? Which jar is required ?

please do the needful !!

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I would try the JAR file at version 1.96, the SVN source tree indicates that the class file is there at that version (java.net is horribly slow at the moment, so I wasn't able to check 1.87)