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HTTP Status 500 - An exception occurred processing JSP page /index.jsp at line 20

HTTP Status 500 - An exception occurred processing JSP page /index.jsp at line 20
type Exception report
message An exception occurred processing JSP page /index.jsp at line 20
description The server encountered an internal error that prevented it from fulfilling this request.
exception
org.apache.jasper.JasperException: An exception occurred processing JSP page /index.jsp at line 20

17:     <%
18:       ItemsDao itemsDao = new ItemsDao();
19:       ArrayList<Items> list = itemsDao.getAllItems();
20:       for (int i = 0; i < list.size(); i++) {
21:     %>
22:     <center>
23:       <table width="750" height="60" cellpadding="0" cellspacing="0" border="0">


Stacktrace:
	org.apache.jasper.servlet.JspServletWrapper.handleJspException(JspServletWrapper.java:568)
	org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:470)
	org.apache.jasper.servlet.JspServlet._serviceJspFile(JspServlet.java:395)
	org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java)
	org.apache.jasper.servlet.JspServlet.service(JspServlet.java:339)
	javax.servlet.http.HttpServlet.service(HttpServlet.java:727)
	org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)

root cause
java.lang.NullPointerException
	org.apache.jsp.index_jsp._jspService(index_jsp.java:80)
	org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
	javax.servlet.http.HttpServlet.service(HttpServlet.java:727)
	org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:432)
	org.apache.jasper.servlet.JspServlet._serviceJspFile(JspServlet.java:395)
	org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java)
	org.apache.jasper.servlet.JspServlet.service(JspServlet.java:339)
	javax.servlet.http.HttpServlet.service(HttpServlet.java:727)
	org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)

note The full stack trace of the root cause is available in the Apache Tomcat/7.0.57 logs.
Apache Tomcat/7.0.57


隔壁王爷爷

2015-04-15

源自：JAVA遇见HTML——JSP篇  8-6

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7 回答

demo_h
2015-04-15

同学你问题表述的不是很清楚 麻烦你说清楚点 不能只把异常显示出来 要把源代码一起贴出来 别人才好可以给你解答 

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#1

隔壁王爷爷 提问者

源代码跟老师一的大同小异，版本不一样，问题就是配置问题
2015-04-15 回复 有任何疑惑可以回复我~
#2

隔壁王爷爷 提问者

谢谢你~问题解决啦~源代码太多 就不贴了
2015-04-15 回复 有任何疑惑可以回复我~
#3

xiulangzi 回复 隔壁王爷爷 提问者

这个问题是如何解决的呢？ 我也遇到 空指针问题，报错跟你一样
2016-06-03 回复 有任何疑惑可以回复我~
weixin_慕虎6515297
2019-02-28

我这边有个问题，点击任意一个产品后，出现如下错过是什么回事

求各位大神帮忙指点。

https://img1.sycdn.imooc.com//5c77781f00016de908300486.jpg


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隔壁王爷爷 提问者
2015-04-15

Class.forName(） 能执行之后

重启之后DriverManager.getConnection(）爆错

吃完饭回来

才想起来 重启之后没开启服务

开启MySQL之后就OK了

http://img1.sycdn.imooc.com//552e898f0001e77c10220726.jpg


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隔壁王爷爷 提问者
2015-04-15

现在是Class.forName(） 能执行

DriverManager.getConnection(）爆错

一直在循环爆这个错误

2015-04-15 21:09:02 JRebel: Could not open/create prefs root node Software\JavaSoft\Prefs at root 0x80000002. Windows RegCreateKeyEx(...) returned error code 5.
com.mysql.jdbc.CommunicationsException: Communications link failure due to underlying exception: 

** BEGIN NESTED EXCEPTION ** 

java.net.ConnectException
MESSAGE: Connection refused: connect

STACKTRACE:

java.net.ConnectException: Connection refused: connect
	at java.net.DualStackPlainSocketImpl.connect0(Native Method)
	at java.net.DualStackPlainSocketImpl.socketConnect(DualStackPlainSocketImpl.java:79)
	at java.net.AbstractPlainSocketImpl.doConnect(AbstractPlainSocketImpl.java:345)
	at java.net.AbstractPlainSocketImpl.connectToAddress(AbstractPlainSocketImpl.java:206)
	at java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:188)
	at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:172)
	at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:392)
	at java.net.Socket.connect(Socket.java:589)
	at java.net.Socket.connect(Socket.java:538)
	at java.net.Socket.<init>(Socket.java:434)
	at java.net.Socket.<init>(Socket.java:244)
	at com.mysql.jdbc.StandardSocketFactory.connect(StandardSocketFactory.java:256)
	at com.mysql.jdbc.MysqlIO.<init>(MysqlIO.java:271)
	at com.mysql.jdbc.Connection.createNewIO(Connection.java:2771)
	at com.mysql.jdbc.Connection.<init>(Connection.java:1555)
	at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:285)
	at java.sql.DriverManager.getConnection(DriverManager.java:664)
	at java.sql.DriverManager.getConnection(DriverManager.java:247)
	at shop.util.DBHelper.getInstance(DBHelper.java:41)
	at shop.dao.ItemsDao.getAllItems(ItemsDao.java:35)
	at org.apache.jsp.index_jsp._jspService(index_jsp.java:115)
	at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:727)
	at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:432)
	at org.apache.jasper.servlet.JspServlet._serviceJspFile(JspServlet.java:395)
	at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java)
	at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:339)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:727)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:303)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
	at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
	at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:220)
	at org.apache.catalina.core.StandardContextValve.__invoke(StandardContextValve.java:122)
	at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java)
	at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:503)
	at org.apache.catalina.core.StandardHostValve.__invoke(StandardHostValve.java:170)
	at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java)
	at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:103)
	at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:950)
	at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:116)
	at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:421)
	at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1070)
	at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:611)
	at org.apache.tomcat.util.net.AprEndpoint$SocketProcessor.doRun(AprEndpoint.java:2466)
	at org.apache.tomcat.util.net.AprEndpoint$SocketProcessor.run(AprEndpoint.java:2455)
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
	at java.util.concurrent.ThreadPoolExecutor$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)


** END NESTED EXCEPTION **



Last packet sent to the server was 0 ms ago.
	at com.mysql.jdbc.Connection.createNewIO(Connection.java:2847)
	at com.mysql.jdbc.Connection.<init>(Connection.java:1555)
	at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:285)
	at java.sql.DriverManager.getConnection(DriverManager.java:664)
	at java.sql.DriverManager.getConnection(DriverManager.java:247)
	at shop.util.DBHelper.getInstance(DBHelper.java:41)
	at shop.dao.ItemsDao.getAllItems(ItemsDao.java:35)
	at org.apache.jsp.index_jsp._jspService(index_jsp.java:115)
	at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:727)
	at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:432)
	at org.apache.jasper.servlet.JspServlet._serviceJspFile(JspServlet.java:395)
	at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java)
	at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:339)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:727)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:303)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
	at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
	at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:220)
	at org.apache.catalina.core.StandardContextValve.__invoke(StandardContextValve.java:122)
	at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java)
	at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:503)
	at org.apache.catalina.core.StandardHostValve.__invoke(StandardHostValve.java:170)
	at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java)
	at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:103)
	at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:950)
	at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:116)
	at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:421)
	at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1070)
	at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:611)
	at org.apache.tomcat.util.net.AprEndpoint$SocketProcessor.doRun(AprEndpoint.java:2466)
	at org.apache.tomcat.util.net.AprEndpoint$SocketProcessor.run(AprEndpoint.java:2455)
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
	at java.util.concurrent.ThreadPoolExecutor$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)
com.mysql.jdbc.CommunicationsException: Communications link failure due to underlying exception: 

** BEGIN NESTED EXCEPTION ** 

java.net.ConnectException
MESSAGE: Connection refused: connect

STACKTRACE:

java.net.ConnectException: Connection refused: connect
	at java.net.DualStackPlainSocketImpl.connect0(Native Method)
	at java.net.DualStackPlainSocketImpl.socketConnect(DualStackPlainSocketImpl.java:79)
	at java.net.AbstractPlainSocketImpl.doConnect(AbstractPlainSocketImpl.java:345)
	at java.net.AbstractPlainSocketImpl.connectToAddress(AbstractPlainSocketImpl.java:206)
	at java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:188)
	at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:172)
	at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:392)
	at java.net.Socket.connect(Socket.java:589)
	at java.net.Socket.connect(Socket.java:538)
	at java.net.Socket.<init>(Socket.java:434)
	at java.net.Socket.<init>(Socket.java:244)
	at com.mysql.jdbc.StandardSocketFactory.connect(StandardSocketFactory.java:256)
	at com.mysql.jdbc.MysqlIO.<init>(MysqlIO.java:271)
	at com.mysql.jdbc.Connection.createNewIO(Connection.java:2771)
	at com.mysql.jdbc.Connection.<init>(Connection.java:1555)
	at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:285)
	at java.sql.DriverManager.getConnection(DriverManager.java:664)
	at java.sql.DriverManager.getConnection(DriverManager.java:247)
	at shop.util.DBHelper.getInstance(DBHelper.java:41)
	at shop.dao.ItemsDao.getAllItems(ItemsDao.java:35)
	at org.apache.jsp.index_jsp._jspService(index_jsp.java:115)
	at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:727)
	at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:432)
	at org.apache.jasper.servlet.JspServlet._serviceJspFile(JspServlet.java:395)
	at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java)
	at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:339)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:727)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:303)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
	at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
	at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:220)
	at org.apache.catalina.core.StandardContextValve.__invoke(StandardContextValve.java:122)
	at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java)
	at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:503)
	at org.apache.catalina.core.StandardHostValve.__invoke(StandardHostValve.java:170)
	at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java)
	at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:103)
	at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:950)
	at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:116)
	at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:421)
	at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1070)
	at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:611)
	at org.apache.tomcat.util.net.AprEndpoint$SocketProcessor.doRun(AprEndpoint.java:2466)
	at org.apache.tomcat.util.net.AprEndpoint$SocketProcessor.run(AprEndpoint.java:2455)
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
	at java.util.concurrent.ThreadPoolExecutor$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)


** END NESTED EXCEPTION **


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隔壁王爷爷 提问者
2015-04-15

debug加搜索 用了三个小时，发现tomcat跟java的classloader不一样

把mysql-connector-*.jar 复制到tomcat/lib下 还是显示不出正确结果

先去吃晚饭，吃完饭继续debug

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隔壁王爷爷 提问者
2015-04-15

开始以为是编码的问题，把所有文件搞成utf-8

又把数据库搞成utf-8,还是爆错

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