java.lang.noclassdefounderror:com/hp/hpl/jena/shared/baduriException on running servlet

当运行一个非常简单的servlet时,我得到一个“java.lang.noclassdefounderror:com/hp/hpl/jena/shared/baduriException”。错误指向“tagger”类的初始化。代码如下

import java.io.IOException;
import java.io.PrintWriter;

import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import my.package.Tagger;

public class NormaliserServlet extends HttpServlet{
    public void doGet(HttpServletRequest req, HttpServletResponse response) throws IOException{
        Tagger pot = new Tagger("");

        response.setContentType("text");
        PrintWriter out = response.getWriter();
        out.println("hello");
        out.println(pot.someMethod());
        out.close();

        this.log("Request for normaliser");
    }
}

war文件包含在WEB-INF/lib中定义“tagger”的JAR文件,类似的调用在servlet之外工作。我似乎找不到问题所在。web.xml也是相当标准的:

<servlet>
    <servlet-name>normalise</servlet-name>
    <servlet-class>NormaliserServlet</servlet-class>
</servlet>
<servlet-mapping>
    <servlet-name>normalise</servlet-name>
    <url-pattern>/normalise</url-pattern>
</servlet-mapping>

我使用Winstone作为servlet容器,但在Tomcat中得到了完全相同的错误。stacktrace是:

java.lang.NoClassDefFoundError: com/hp/hpl/jena/shared/BadURIException
    at NormaliserServlet.doGet(NormaliserServlet.java:13)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:104)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:45)
    at winstone.ServletConfiguration.execute(ServletConfiguration.java:249)
    at winstone.RequestDispatcher.forward(RequestDispatcher.java:335)
    at winstone.RequestHandlerThread.processRequest(RequestHandlerThread.java:244)
    at winstone.RequestHandlerThread.run(RequestHandlerThread.java:150)
    at java.lang.Thread.run(Thread.java:619)