title: ClassNotFoundException: org.apache.xml.serializer.TreeWalker
body: <p>I wrote a simple app with xml database &amp; appache tomcat. I worked fine, till I tried to zip the workspace while it was open. After that anytime I try to create tomcat server promptly I get this error:  </p>
  
  <blockquote>
    <p><code>ClassNotFoundException: org.apache.xml.serializer.TreeWalker</code></p>
  </blockquote>
  
  <p>So I left this. Now I was working on xmlspy, trying to generate a pdf file using tomcat FO engine. I installed new tomcat &amp; pointed to this in the xmlspy. Now when I try to run fo in xmlspy I get the following error. </p>
  
  <p>Note: The <code>serializer.jar</code> &amp; xalan jar files are already in lib folder. </p>
  
  <blockquote>
  <pre><code>log4j:WARN No appenders could be found for logger (org.apache.fop.util.ContentHandlerFactoryRegistry).
  log4j:WARN Please initialize the log4j system properly.
  log4j:WARN See http://logging.apache.org/log4j/1.2/faq.html#noconfig for more info.
  Exception in thread "main" java.lang.NoClassDefFoundError: org/apache/xml/serializer/TreeWalker
    at org.apache.xalan.processor.TransformerFactoryImpl.newTransformer(TransformerFactoryImpl.java:823)
    at org.apache.fop.cli.InputHandler.transformTo(InputHandler.java:278)
    at org.apache.fop.cli.InputHandler.renderTo(InputHandler.java:130)
    at org.apache.fop.cli.Main.startFOP(Main.java:174)
    at org.apache.fop.cli.Main.main(Main.java:205)
  Caused by: java.lang.ClassNotFoundException: org.apache.xml.serializer.TreeWalker
    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)
    ... 5 more
  </code></pre>
  </blockquote>