我跟大家差不多错误，都是输入管理员账号密码后就出现错误：
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: org.apache.jasper.JasperException: java.lang.NullPointerException
org.apache.struts.chain.ComposableRequestProcessor.process(ComposableRequestProcessor.java:286)
org.apache.struts.action.ActionServlet.process(ActionServlet.java:1913)
org.apache.struts.action.ActionServlet.doPost(ActionServlet.java:462)
javax.servlet.http.HttpServlet.service(HttpServlet.java:637)
javax.servlet.http.HttpServlet.service(HttpServlet.java:717)


root cause 

org.apache.jasper.JasperException: java.lang.NullPointerException
org.apache.jasper.servlet.JspServletWrapper.handleJspException(JspServletWrapper.java:522)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:416)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:342)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:267)
javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
org.apache.struts.chain.commands.servlet.PerformForward.handleAsForward(PerformForward.java:113)
org.apache.struts.chain.commands.servlet.PerformForward.perform(PerformForward.java:96)
org.apache.struts.chain.commands.AbstractPerformForward.execute(AbstractPerformForward.java:54)
org.apache.struts.chain.commands.ActionCommandBase.execute(ActionCommandBase.java:51)
org.apache.commons.chain.impl.ChainBase.execute(ChainBase.java:190)
org.apache.commons.chain.generic.LookupCommand.execute(LookupCommand.java:304)
org.apache.commons.chain.impl.ChainBase.execute(ChainBase.java:190)
org.apache.struts.chain.ComposableRequestProcessor.process(ComposableRequestProcessor.java:283)
org.apache.struts.action.ActionServlet.process(ActionServlet.java:1913)
org.apache.struts.action.ActionServlet.doPost(ActionServlet.java:462)
javax.servlet.http.HttpServlet.service(HttpServlet.java:637)
javax.servlet.http.HttpServlet.service(HttpServlet.java:717)


root cause 

java.lang.NullPointerException
sun.misc.FloatingDecimal.readJavaFormatString(FloatingDecimal.java:991)
java.lang.Float.valueOf(Float.java:388)
com.dao.BorrowDAO.bookBorrowSort(BorrowDAO.java:204)
org.apache.jsp.main_jsp._jspService(main_jsp.java:192)
org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:374)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:342)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:267)
javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
org.apache.struts.chain.commands.servlet.PerformForward.handleAsForward(PerformForward.java:113)
org.apache.struts.chain.commands.servlet.PerformForward.perform(PerformForward.java:96)
org.apache.struts.chain.commands.AbstractPerformForward.execute(AbstractPerformForward.java:54)
org.apache.struts.chain.commands.ActionCommandBase.execute(ActionCommandBase.java:51)
org.apache.commons.chain.impl.ChainBase.execute(ChainBase.java:190)
org.apache.commons.chain.generic.LookupCommand.execute(LookupCommand.java:304)
org.apache.commons.chain.impl.ChainBase.execute(ChainBase.java:190)
org.apache.struts.chain.ComposableRequestProcessor.process(ComposableRequestProcessor.java:283)
org.apache.struts.action.ActionServlet.process(ActionServlet.java:1913)
org.apache.struts.action.ActionServlet.doPost(ActionServlet.java:462)
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


然后tomcat日志是：
2009-6-1 12:52:45 org.apache.catalina.core.StandardWrapperValve invoke
严重: Servlet.service() for servlet action threw exception
java.lang.NullPointerException
        at sun.misc.FloatingDecimal.readJavaFormatString(FloatingDecimal.java:991)
        at java.lang.Float.valueOf(Float.java:388)
        at com.dao.BorrowDAO.bookBorrowSort(BorrowDAO.java:204)
        at org.apache.jsp.main_jsp._jspService(main_jsp.java:192)
        at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
        at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:374)
        at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:342)
        at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:267)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290)
        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
        at org.apache.catalina.core.ApplicationDispatcher.invoke(ApplicationDispatcher.java:630)
        at org.apache.catalina.core.ApplicationDispatcher.processRequest(ApplicationDispatcher.java:436)
        at org.apache.catalina.core.ApplicationDispatcher.doForward(ApplicationDispatcher.java:374)
        at org.apache.catalina.core.ApplicationDispatcher.forward(ApplicationDispatcher.java:302)
        at org.apache.struts.chain.commands.servlet.PerformForward.handleAsForward(PerformForward.java:113)
        at org.apache.struts.chain.commands.servlet.PerformForward.perform(PerformForward.java:96)
        at org.apache.struts.chain.commands.AbstractPerformForward.execute(AbstractPerformForward.java:54)
        at org.apache.struts.chain.commands.ActionCommandBase.execute(ActionCommandBase.java:51)
        at org.apache.commons.chain.impl.ChainBase.execute(ChainBase.java:190)
        at org.apache.commons.chain.generic.LookupCommand.execute(LookupCommand.java:304)
        at org.apache.commons.chain.impl.ChainBase.execute(ChainBase.java:190)
        at org.apache.struts.chain.ComposableRequestProcessor.process(ComposableRequestProcessor.java:283)
        at org.apache.struts.action.ActionServlet.process(ActionServlet.java:1913)
        at org.apache.struts.action.ActionServlet.doPost(ActionServlet.java:462)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:637)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290)
        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
        at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233)
        at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191)
        at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:128)
        at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)
        at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
        at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:286)
        at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:845)
        at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:583)
        at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:447)
        at java.lang.Thread.run(Thread.java:619)

是空指针，但是我不知道错误在哪，麻烦能跟我说下吗？谢谢

我的数据库是自己找着书里的表打进去的，因为我的Mysql是vista的没有data文件夹，呵呵
应该不会有什么错误啊
请帮我解答下，谢谢，在线等