Eclipse Juno EE NoClassDefFoundError when using external Jar - apache

Question

I added an external jar in my eclipse dynamic webproject via Folder -> properties -> build path -> Libraries -> add external jar.
The code is working fine on compile time.
package servlet;
import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.ServletException;
import javax.servlet.annotation.MultipartConfig;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.apache.tika.Tika;
#WebServlet(name="UploadServlet", urlPatterns={"/uploadFile"}) // specify urlPattern for servlet
#MultipartConfig //Specify that this servlet will receive a multipart data
public class UploadServlet extends HttpServlet {
protected void doPost(HttpServletRequest req, HttpServletResponse res) throws IOException, ServletException{
Tika tika = new Tika();
res.setContentType("text/html");
PrintWriter writer = res.getWriter();
writer.write(mediaType);
}
}
I added Apache Tika but when I run my application. these exception occured.
root cause
java.lang.NoClassDefFoundError: org/apache/tika/Tika
servlet.UploadServlet.doPost(UploadServlet.java:19)
javax.servlet.http.HttpServlet.service(HttpServlet.java:641)
javax.servlet.http.HttpServlet.service(HttpServlet.java:722)
root cause
java.lang.ClassNotFoundException: org.apache.tika.Tika
org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1714)
org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1559)
servlet.UploadServlet.doPost(UploadServlet.java:19)
javax.servlet.http.HttpServlet.service(HttpServlet.java:641)
javax.servlet.http.HttpServlet.service(HttpServlet.java:722)
I am using Apache Tika to determine what file has been upload, I want to use it for validating if a file is an image, or audio file

Answer 1

You forgot to add that jar to the Deployment Assembly page. It's not deployed to the server when you run your application, hence the NoClassDefFoundErrors.