Solr not loading a custom filter

I have written a custom KeepWord filter factory and have put the resultant jar under solr/lib directory. But when starting solr I am getting this error

SEVERE: org.apache.solr.common.SolrException: Error loading class 'org.custom.solr.analysis.MyKeepWordFilterFactory'
    at org.apache.solr.core.SolrResourceLoader.findClass(SolrResourceLoader.java:389)
    at org.apache.solr.core.SolrResourceLoader.newInstance(SolrResourceLoader.java:404)
    at org.apache.solr.util.plugin.AbstractPluginLoader.create(AbstractPluginLoader.java:83)
    at org.apache.solr.util.plugin.AbstractPluginLoader.load(AbstractPluginLoader.java:140)
    at org.apache.solr.schema.IndexSchema.readAnalyzer(IndexSchema.java:941)
    at org.apache.solr.schema.IndexSchema.access$100(IndexSchema.java:62)
    at org.apache.solr.schema.IndexSchema$1.create(IndexSchema.java:450)
    at org.apache.solr.schema.IndexSchema$1.create(IndexSchema.java:435)
    at org.apache.solr.util.plugin.AbstractPluginLoader.load(AbstractPluginLoader.java:140)
    at org.apache.solr.schema.IndexSchema.readSchema(IndexSchema.java:480)
    at org.apache.solr.schema.IndexSchema.<init>(IndexSchema.java:125)
    at org.apache.solr.core.CoreContainer.create(CoreContainer.java:461)
    at org.apache.solr.core.CoreContainer.load(CoreContainer.java:316)
    ...
    Caused by: java.lang.ClassNotFoundException: org.custom.solr.analysis.MyKeepWordFilterFactory
    at java.net.URLClassLoader$1.run(URLClassLoader.java:202)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.net.URLClassLoader.findClass(URLClassLoader.java:190)
    ...

This is the content of my solr instance directory.

>$ ls solr/*
solr/README.txt

solr/conf:
admin-extra.html             mapping-ISOLatin1Accent.txt  scripts.conf                    stopwords.txt                velocity/ elevate.xml                  protwords.txt               solrconfig.xml               stopwords_en.txt             xslt/ mapping-FoldToASCII.txt      schema.xml                   spellings.txt                synonyms.txt

solr/data:
index/        spellchecker/

solr/lib:
my-solr-analyserfilter.jar

The content of the jar file

>$ unzip -l solr/lib/my-solr-analyserfilter.jar 
Archive:  solr/lib/ctown-solr-analyserfilter.jar
  Length     Date   Time    Name
 --------    ----   ----    ----
        0  09-23-11 23:07   META-INF/
       60  09-23-11 23:07   META-INF/MANIFEST.MF
     3330  09-23-11 23:07   org/custom/analysis/MyKeepWordFilterFactory.class
 --------                   -------
     3390                   3 files

I am using solr version 3.4.0. As per documentation - https://wiki.apache.org/solr/SolrPlugins#How_to_Load_Plugins - keeping the jar file under lib directory sho开发者_开发百科uld have made solr detect the jar. But apparently it's not happening. What am I doing wrong? Kindly help me in resolving this issue.

Couple of things -
1. org.custom.solr.analysis.MyKeepWordFilterFactory does not match the contents of your jar file org/custom/analysis/MyKeepWordFilterFactory.class. The solr package is missing.
2. If it still does not find it. Check if the entry in solrconfig.xml is uncommented and the jar file is loaded when the server starts up.