java.lang.ClassNotFoundException: org.apache.lucene.codecs.PostingsFormat

I'm trying to implement an Java program using EmbeddedSolrServer and when I run my program I get an exception :

Jul 03, 2013 12:13:49 PM org.apache.solr.core.CoreContainer <init>
INFO: New CoreContainer 2120829822
Jul 03, 2013 12:13:49 PM org.apache.solr.core.CoreContainer load
INFO: Loading CoreContainer using Solr Home: '/home/usersolr/solr-4.2.1/indexation_test1/solr'
Jul 03, 2013 12:13:49 PM org.apache.solr.core.SolrResourceLoader <init>
INFO: new SolrResourceLoader for directory: '/home/usersolr/solr-4.2.1/indexation_test1/solr/'
Exception in thread "main" java.lang.reflect.InvocationTargetException
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:601)
    at org.eclipse.jdt.internal.jarinjarloader.JarRsrcLoader.main(JarRsrcLoader.java:58)
Caused by: java.lang.NoClassDefFoundError: org/apache/lucene/codecs/PostingsFormat
    at org.apache.solr.core.SolrResourceLoader.reloadLuceneSPI(SolrResourceLoader.java:181)
    at org.apache.solr.core.SolrResourceLoader.<init>(SolrResourceLoader.java:114)
    at org.apache.solr.core.SolrResourceLoader.<init>(SolrResourceLoader.java:231)
    at org.apache.solr.core.CoreContainer.load(CoreContainer.java:422)
    at org.apache.solr.core.CoreContainer.load(CoreContainer.java:405)
    at org.apache.solr.core.CoreContainer.<init>(CoreContainer.java:189)
    at Main.Main.main(Main.java:35)
    ... 5 more
Caused by: java.lang.ClassNotFoundException: org.apache.lucene.codecs.PostingsFormat
    at java.net.URLClassLoader$1.run(URLClassLoader.java:366)
    at java.net.URLClassLoader$1.run(URLClassLoader.java:355)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.net.URLClassLoader.findClass(URLClassLoader.java:354)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:423)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:356)
    ... 12 more

Have someone already met this exception ? In witch JAR file can found the PostingsFormat class ?

Edit (Solved):

If you're like me and you don't know exactly where to find some jars you need, it's possible to find some jars files under these paths :

• solr-X.X.X/example/solr-webapp/webapp/WEB-INF/lib/
• solr-X.X.X/example/lib (particularly : servlet-api-X.X.jar)

Hope it helps !

Thank Marvin Emil Brach & Jayendra

Corentin