我一直在做一个J2EE项目，我正在使用连接池，通过在heroku上部署的数据库访问它。 我正在使用以下代码来设置连接对象：
Context initContext=new InitialContext(); Context envContext=(Context)initContext.lookup("java:comp/env"); DataSource ds=(DataSource)envContext.lookup("jdbc/DB"); con=ds.getConnection(); 我的META-INF文件夹中有一个context.xml文件，其值为：
<?xml version="1.0" encoding="UTF-8"?> <Context> <Resource name="jdbc/DB" auth="Container" type="javax.sql.DataSource" maxActive="100" maxIdle="30" maxWait="10000" driverClassName="org.postgresql.Driver" url="<connection_url>" username="<user_name>" password="<password>"/> </Context>
数据库连接在我的本地tomcat v8服务器上完美运行，但是当我在heroku上部署了我的.war文件时，我的日志中出现以下错误，并且无法在我的网页中看到我的数据库数据。
javax.naming.NoInitialContextException: Need to specify class name in environment or system property, or as an applet parameter, or in an application resource file: java.naming.factory.initial at javax.naming.spi.NamingManager.getInitialContext(NamingManager.java:662) at javax.naming.InitialContext.getDefaultInitCtx(InitialContext.java:313) at javax.naming.InitialContext.getURLOrDefaultInitCtx(InitialContext.java:350) at javax.naming.InitialContext.lookup(InitialContext.java:417) at com.controller.A.doPost(A.java:48) at javax.servlet.http.HttpServlet.service(HttpServlet.java:648) at javax.servlet.http.HttpServlet.service(HttpServlet.java:729) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:291) at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:219) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:106) at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:502) at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:142) at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:79) at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:88) at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:518) at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1091) at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:668) at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1521) at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.run(NioEndpoint.java:1478) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617) at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142) at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) at java.lang.Thread.run(Thread.java:745) java.lang.NullPointerException at com.controller.A.doPost(A.java:81) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:291) at javax.servlet.http.HttpServlet.service(HttpServlet.java:729) at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:142) at javax.servlet.http.HttpServlet.service(HttpServlet.java:648) at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:219) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:106) at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:88) at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:518) at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:668) at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1521) at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:502) at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:79) at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1091) at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.run(NioEndpoint.java:1478) at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617) at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) at java.lang.Thread.run(Thread.java:745)
我的A.java文件中的标记exception行是：
48:Context initContext=new InitialContext(); 81:{ try { st.close(); con.close(); } }