Servlet连接jdbc总是错误java.lang.NullPointerException

Question

错误信息
SEVERE: Servlet.service() for servlet [com.homework.register.Register] in context with path [/homework] threw exception
java.lang.NullPointerException
at com.homework.register.DAO.Query(DAO.java:81)
at com.homework.register.Register.doPost(Register.java:56)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:647)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:728)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:305)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:222)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:123)
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:502)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:171)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:99)
at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:953)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:408)
at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1023)
at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:589)
at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:310)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
at java.lang.Thread.run(Thread.java:724)

Answer 1

conn = getConnection();
            st = null;
            ResultSet res  = null;
            try {
                st = conn.createStatement();
                res = st.executeQuery(queryString);
 conn  为空，楼主断点进去getConnection();方法检查吧。
connection = DriverManager.getConnection(dburl, user, pwd);  检查这句。

Answer 2

确认 下
jdbc:mysql://localhost:3306/register", "Fenice", "930709")是否写正确确认下WebRoot/WEB-INF/lib 目下的是否把正确的包导入了