jsp项目开发全程实录中第二章图书馆的问题（可以进到登陆界面，登陆后出错）

已经打了JAR包了-9个那个，JDK是C:\Program Files\Java\jdk1.6.0_07和C:\Program Files\Java\jre1.6.0_07

tomcat：apache-tomcat-6.0.18



HTTP Status 500 - 

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type Exception report

message 

description The server encountered an internal error () that prevented it from fulfilling this request.

exception 

javax.servlet.ServletException: java.lang.NullPointerException
org.apache.struts.action.RequestProcessor.processException(RequestProcessor.java:523)
org.apache.struts.action.RequestProcessor.processActionPerform(RequestProcessor.java:421)
org.apache.struts.action.RequestProcessor.process(RequestProcessor.java:224)
org.apache.struts.action.ActionServlet.process(ActionServlet.java:1194)
org.apache.struts.action.ActionServlet.doPost(ActionServlet.java:432)
javax.servlet.http.HttpServlet.service(HttpServlet.java:637)
javax.servlet.http.HttpServlet.service(HttpServlet.java:717)


root cause 

java.lang.NullPointerException
com.core.ConnDB.executeQuery(ConnDB.java:53)
com.dao.ManagerDAO.checkManager(ManagerDAO.java:73)
com.action.Manager.managerLogin(Manager.java:51)
com.action.Manager.execute(Manager.java:24)
org.apache.struts.action.RequestProcessor.processActionPerform(RequestProcessor.java:419)
org.apache.struts.action.RequestProcessor.process(RequestProcessor.java:224)
org.apache.struts.action.ActionServlet.process(ActionServlet.java:1194)
org.apache.struts.action.ActionServlet.doPost(ActionServlet.java:432)
javax.servlet.http.HttpServlet.service(HttpServlet.java:637)
javax.servlet.http.HttpServlet.service(HttpServlet.java:717)


note The full stack trace of the root cause is available in the Apache Tomcat/6.0.18 logs.


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Apache Tomcat/6.0.18