shangrila-xiu

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sqlquestion1

jsp处理过程中遇到的问题

1、报错内容如下：

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信息: At least one JAR was scanned for TLDs yet contained no TLDs. Enable debug logging for this logger for a complete list of JARs that were scanned but no TLDs were found in them. Skipping unneeded JARs during scanning can improve startup time and JSP compilation time.
java.lang.NullPointerException
	at cn.itcast.DB.DBHelper.query(DBHelper.java:95)
	at servlet.ModifyPasswordServlet.doPost(ModifyPasswordServlet.java:64)
	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:312)
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
	at java.lang.Thread.run(Thread.java:745)

百度上讲的解决方案1是：把没有用处的标签去掉就行了

2、下面的这个错是空指针

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HTTP Status 500 - An exception occurred processing JSP page /details.jsp at line 102
type Exception report
message An exception occurred processing JSP page /details.jsp at line 102
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 /details.jsp at line 102
99:           <!-- 鍟嗗搧璇︽儏 -->
100:           <%
101:           	ItemsDAO itemDao = new ItemsDAO();
102:                        Items item = itemDao.getItemsById(Integer.parseInt(request.getParameter("id")));
103:                        if(item!=null)
104:                        {
105:           %>
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:390)
	org.apache.jasper.servlet.JspServlet.service(JspServlet.java:334)
	javax.servlet.http.HttpServlet.service(HttpServlet.java:728)
root cause
java.lang.NumberFormatException: null
	java.lang.Integer.parseInt(Integer.java:542)
	java.lang.Integer.parseInt(Integer.java:615)
	org.apache.jsp.details_jsp._jspService(details_jsp.java:172)
	org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
	javax.servlet.http.HttpServlet.service(HttpServlet.java:728)
	org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:432)
	org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:390)
	org.apache.jasper.servlet.JspServlet.service(JspServlet.java:334)
	javax.servlet.http.HttpServlet.service(HttpServlet.java:728)
note The full stack trace of the root cause is available in the Apache Tomcat/7.0.42 logs.
Apache Tomcat/7.0.42

解决方法是：导入它的数据库连接的包就好了。

3、对于我这次来说，是摊上事了，我的还是报错的。报错如下：500状态码的错

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HTTP Status 500 - java.lang.NumberFormatException: null
type Exception report
message java.lang.NumberFormatException: null
description The server encountered an internal error that prevented it from fulfilling this request.
exception
org.apache.jasper.JasperException: java.lang.NumberFormatException: null
	org.apache.jasper.servlet.JspServletWrapper.handleJspException(JspServletWrapper.java:549)
	org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:470)
	org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:390)
	org.apache.jasper.servlet.JspServlet.service(JspServlet.java:334)
	javax.servlet.http.HttpServlet.service(HttpServlet.java:728)
root cause
java.lang.NumberFormatException: null
	java.lang.Integer.parseInt(Integer.java:542)
	java.lang.Integer.parseInt(Integer.java:615)
	org.apache.jsp.details_jsp._jspService(details_jsp.java:172)
	org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
	javax.servlet.http.HttpServlet.service(HttpServlet.java:728)
	org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:432)
	org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:390)
	org.apache.jasper.servlet.JspServlet.service(JspServlet.java:334)
	javax.servlet.http.HttpServlet.service(HttpServlet.java:728)
note The full stack trace of the root cause is available in the Apache Tomcat/7.0.42 logs.
Apache Tomcat/7.0.42

500的错误，似乎想到了什么。我的web.xml没有生成。

我重新创建了servlet。先重新部署下项目再在浏览器打开。原来是我的index.jsp没有对象给它。而它的值是从index.jsp得来的.哎，刚才吓得我不轻。