NoClassDefFoundError with Restlet AppEngine andJackson - google-app-engine

Question

I get a NoClassDefFoundError using Restlet with Google App Engine and GWT.
I'm trying to get Json respresentations of my objects. The error I get is:
java.lang.NoClassDefFoundError: org/codehaus/jackson/JsonGenerator$Feature
A basic skeleton of the method where I get the error is:
#Get("json")
public Representation getProduct() {
Product product = new Product("whatever");
return new JacksonRepresentation<Product>(MediaType.APPLICATION_JSON, product);
}
Initially I got an error for the JsonFactory class when using only the Restlet provided JAR's. I then downloaded the `jackson-all-1.9.7.jar. That error has since been replaced by this new one.
Any idea what's going on ?? Maybe I'm missing some libraries but I can figure out which ones.
EDIT: Including the stacktrace. I removed all the libs and just ran off the Restlet org.restlet.ext.jackson JAR. Also, to check if the class is available at compile time as implied by the answer below, I tried check for autocomplete for the class and package in Eclipse and it doesn't show anything. I'm assuming this means that its not available at compile time either.
java.lang.NoClassDefFoundError: org/codehaus/jackson/JsonFactory
at org.restlet.ext.jackson.JacksonRepresentation.createObjectMapper(JacksonRepresentation.java:118)
at org.restlet.ext.jackson.JacksonRepresentation.getObjectMapper(JacksonRepresentation.java:164)
at org.restlet.ext.jackson.JacksonRepresentation.write(JacksonRepresentation.java:205)
at org.restlet.representation.WriterRepresentation.write(WriterRepresentation.java:104)
at org.restlet.engine.http.ServerCall.writeResponseBody(ServerCall.java:550)
at org.restlet.engine.http.ServerCall.sendResponse(ServerCall.java:488)
at org.restlet.ext.servlet.internal.ServletCall.sendResponse(ServletCall.java:492)
at org.restlet.engine.http.adapter.ServerAdapter.commit(ServerAdapter.java:197)
at org.restlet.engine.http.HttpServerHelper.handle(HttpServerHelper.java:151)
at org.restlet.ext.servlet.ServerServlet.service(ServerServlet.java:1028)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
at org.mortbay.jetty.servlet.ServletHolder.handle(ServletHolder.java:511)
at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1166)
at com.google.appengine.tools.development.HeaderVerificationFilter.doFilter(HeaderVerificationFilter.java:35)
at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
at com.google.appengine.api.blobstore.dev.ServeBlobFilter.doFilter(ServeBlobFilter.java:60)
at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
at com.google.apphosting.utils.servlet.TransactionCleanupFilter.doFilter(TransactionCleanupFilter.java:43)
at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
at com.google.appengine.tools.development.StaticFileFilter.doFilter(StaticFileFilter.java:122)
at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
at com.google.appengine.tools.development.BackendServersFilter.doFilter(BackendServersFilter.java:97)
at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
at org.mortbay.jetty.servlet.ServletHandler.handle(ServletHandler.java:388)
at org.mortbay.jetty.security.SecurityHandler.handle(SecurityHandler.java:216)
at org.mortbay.jetty.servlet.SessionHandler.handle(SessionHandler.java:182)
at org.mortbay.jetty.handler.ContextHandler.handle(ContextHandler.java:765)
at org.mortbay.jetty.webapp.WebAppContext.handle(WebAppContext.java:418)
at com.google.appengine.tools.development.DevAppEngineWebAppContext.handle(DevAppEngineWebAppContext.java:78)
at org.mortbay.jetty.handler.HandlerWrapper.handle(HandlerWrapper.java:152)
at com.google.appengine.tools.development.JettyContainerService$ApiProxyHandler.handle(JettyContainerService.java:369)
at org.mortbay.jetty.handler.HandlerWrapper.handle(HandlerWrapper.java:152)
at org.mortbay.jetty.Server.handle(Server.java:326)
at org.mortbay.jetty.HttpConnection.handleRequest(HttpConnection.java:542)
at org.mortbay.jetty.HttpConnection$RequestHandler.headerComplete(HttpConnection.java:923)
at org.mortbay.jetty.HttpParser.parseNext(HttpParser.java:547)
at org.mortbay.jetty.HttpParser.parseAvailable(HttpParser.java:212)
at org.mortbay.jetty.HttpConnection.handle(HttpConnection.java:404)
at org.mortbay.io.nio.SelectChannelEndPoint.run(SelectChannelEndPoint.java:409)
at org.mortbay.thread.QueuedThreadPool$PoolThread.run(QueuedThreadPool.java:582)
Caused by: java.lang.ClassNotFoundException: org.codehaus.jackson.JsonFactory
at java.net.URLClassLoader$1.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
at com.google.appengine.tools.development.IsolatedAppClassLoader.loadClass(IsolatedAppClassLoader.java:176)
at java.lang.ClassLoader.loadClass(Unknown Source)
... 40 more

Answer 1

Also, if you look in the lib directory of the Restlet version that you downloaded, you will see a readme.txt that will tell you some of the jars that you need to include when you use various Restlet Extensions. For example, the readme.txt should have something like the following:
org.restlet.ext.jackson (Restlet Extension - Jackson)
org.codehaus.jackson.core_1.9
org.codehaus.jackson.mapper_1.9
Thus, if you are using Jackson with Restlet (org.restlet.ext.jackson.jar), you will also need to include the two other jars listed below it.

Answer 2

This is similar to this problem here: Objectify NoClassDefFoundError
You need to put the jar file under WEB-INF/lib/ and make sure include that the library in your build path. And for the clue, NoClassDefFound means that the library is available on compile time but not on the runtime

Answer 3

I updated the to Restlet 2.0.14 and used the org.codehaus.jackson libraries provided with it instead of the ones from the website.
That seems to fix the problem though I don't know which of the two actions actually did this.