title: Hibernate in Servlet causesNoClassDefFoundError: org/slf4j/LoggerFactory
body: <p>I have a Java (6) application which uses Hibernate (V3.3.2) to read data from HSQLDB, which i build and debug/run with Eclipse (V3.5.1), and it works fine.</p>
  
  <p>I then created a GWT (V1.7) Servlet web app, copied my hibernate classes into it, and added the same User Libraries dependencies. However when i run the servlet and try to access a URL which invokes my code i get this:</p>
  
  <pre><code>java.lang.NoClassDefFoundError: org/slf4j/LoggerFactory
      at org.hibernate.cfg.Configuration.&lt;clinit&gt;(Configuration.java:152)
      at xxx.daoimpl.DAOSession.initialise(DAOSession.java:40)
  </code></pre>
  
  <p>where DAOSession.java:40 is :</p>
  
  <pre><code>AnnotationConfiguration config = new AnnotationConfiguration ();
  </code></pre>
  
  <p>Googling for this error suggests i am missing slf4j-api.jar from the classpath, however if i look at the command line for the Debug properties i can see this jar there:</p>
  
  <pre><code>C:\java\jsedk_6\jre\bin\javaw.exe
  -agentlib:jdwp=transport=dt_socket,suspend=y,address=localhost:54541
  -Xmx512m -Dfile.encoding=Cp1252
  -classpath
      D:\dev\workspace\xxx\src;
      D:\dev\workspace\xxx\resources;
      D:\dev\workspace\xxx\war\WEB-INF\classes;
      C:\java\eclipse\plugins\com.google.gwt.eclipse.sdkbundle.win32_1.7.1.v200909221731\gwt-windows-1.7.1\gwt-user.jar;
      C:\java\eclipse\plugins\com.google.gwt.eclipse.sdkbundle.win32_1.7.1.v200909221731\gwt-windows-1.7.1\gwt-dev-windows.jar;
      C:\java\hibernate-annotations-3.4.0.GA\hibernate-annotations.jar;
      C:\java\hibernate-annotations-3.4.0.GA\lib\ejb3-persistence.jar;
      C:\java\hibernate-annotations-3.4.0.GA\lib\hibernate-commons-annotations.jar;
      C:\java\hibernate-distribution-3.3.2.GA\hibernate3.jar;
      C:\java\hibernate-distribution-3.3.2.GA\lib\required\antlr-2.7.6.jar;
      C:\java\hibernate-distribution-3.3.2.GA\lib\required\commons-collections-3.1.jar;
      C:\java\hibernate-distribution-3.3.2.GA\lib\required\dom4j-1.6.1.jar;
      C:\java\hibernate-distribution-3.3.2.GA\lib\required\javassist-3.9.0.GA.jar;
      C:\java\hibernate-distribution-3.3.2.GA\lib\required\jta-1.1.jar;
      C:\java\hibernate-validator-4.0.1.GA\hibernate-validator-4.0.1.GA.jar;
      C:\java\hibernate-validator-4.0.1.GA\lib\validation-api-1.0.0.GA.jar;
      C:\java\hibernate-validator-4.0.1.GA\lib\log4j-1.2.14.jar;
      C:\java\hsqldb\lib\hsqldb.jar;
      C:\java\restlet-jse-2.0m5\lib\org.restlet.jar;
      C:\java\restlet-jee-2.0m5\lib\org.restlet.ext.servlet.jar;
      C:\java\restlet-jse-2.0m5\lib\org.restlet.ext.xml.jar;
      C:\java\slf4j-1.5.8\slf4j-api-1.5.8.jar;
      C:\java\slf4j-1.5.8\slf4j-log4j12-1.5.8.jar
      com.google.gwt.dev.HostedMode
      ...
  </code></pre>
  
  <p>If i open the jar i can see the LoggerFactory class in there.</p>
  
  <p>Any idea why it isn't being found by the class loader?</p>
  
  <p><strong>Edit 1:</strong> If try to access org.slf4j.LoggerFactory from my code, Eclipse compiles it ok, but i get the same error at runtime.</p>
  
  <p><strong>Edit 2:</strong> If i add a Test class with a main which calls the same code and run it, it works. So this classpath problem seems specific to the Servlet.</p>
  
  <p>thanks,
  jon</p>