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javamongodbservletsmongo-java

Why I can't initialize a Mongo in Servlet

I'm making java web project , and try to use mongodb. but I found a problem,

Mongo mongo = new Mongo("localhost", 27017)

when I use it in a main method, it is ok. but when I use it in Servlet init() or doGet, doPost it throws exceptions, it is like:

    Allocate exception for servlet RegServlet
java.lang.ClassNotFoundException: com.mongodb.MongoException
    at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1680)
    at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1526)
    at java.lang.Class.getDeclaredConstructors0(Native Method)
    at java.lang.Class.privateGetDeclaredConstructors(Class.java:2389)
    at java.lang.Class.getConstructor0(Class.java:2699)
    at java.lang.Class.newInstance0(Class.java:326)
    at java.lang.Class.newInstance(Class.java:308)
    at org.apache.catalina.core.StandardWrapper.loadServlet(StandardWrapper.java:1116)
    at org.apache.catalina.core.StandardWrapper.allocate(StandardWrapper.java:809)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:129)
    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(Thread.java:662)
2011-5-19 20:44:39 org.apache.catalina.startup.HostConfig checkResources
Solution

  • That's because you have not included a jar containing class com.mongodb.MongoException (hence why you're having java.lang.ClassNotFoundException). There are no jars that is needed by your application to run MongoDB. Add the relevant Mongo jars in your WEB-INF/lib folder or your webapp server/container lib folder.