Servlet：java.lang.ClassNotFoundException：org.json.simple.parser.ParseException

我正在为Android实施Google Cloud Messaging服务。我创建了一个测试服务器，该服务器将推送通知发送给应用程序用户。但是我创建的服务器正在生成以下错误。我在服务器端使用Java Servlet，并且在项目中包含了gcm-server.jar文件。

这是日志：

java.lang.ClassNotFoundException: org.json.simple.parser.ParseException
    at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1680)
    at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1526)
    at com.mgcm.SendGCMMessage.processRequest(SendGCMMessage.java:48)
    at com.mgcm.SendGCMMessage.doPost(SendGCMMessage.java:40)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:637)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:298)
    at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:859)
    at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:588)
    at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:489)
    at java.lang.Thread.run(Unknown Source)

知道这有什么问题吗？