为什么我无法在Servlet中初始化Mongo
我正在制作java web项目，并尝试使用mongodb。 但是我发现一个问题，
Mongo mongo = new Mongo("localhost", 27017)
当我在main方法中使用它时，就可以了。 但是当我在 Servlet init() 或 doGet、doPost 中使用它时 它抛出异常，就像：
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
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
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这是因为您没有包含包含类
com.mongodb.MongoException的 jar（因此您会遇到java.lang.ClassNotFoundException）。您的应用程序不需要任何 jar 来运行 MongoDB。在您的WEB-INF/lib文件夹或 webapp 服务器/容器lib文件夹中添加相关的 Mongo jar。That's because you have not included a jar containing class
com.mongodb.MongoException(hence why you're havingjava.lang.ClassNotFoundException). There are no jars that is needed by your application to run MongoDB. Add the relevant Mongo jars in yourWEB-INF/libfolder or your webapp server/containerlibfolder.