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所以我试图从文件读取器中填充两个数组。我相信这需要嵌套循环。我认为我走的是正确的道路，但自昨天以来我一直陷入困境。此程序的目的是通过jsp启动程序并动态读取值。任何帮助真的会被赞赏。我想我正走在正确的轨道上，但我似乎无法完成自己的事业。 fxRates.csv的第一行应该填充到currencyCodes数组中，其余行应该填充到2d数组fxExchangeRates中。我得到的代码没有任何错误，但现在我得到的是这样的，当我尝试运行程序：
分割为字符串数组时空指针异常
以下是错误日志：
Info: visiting unvisited references
Info: visiting unvisited references
Info: visiting unvisited references
Warning: Ignore WEB-INF/sun-web.xml in archive /G:/School/Java II/Labs/MidtermAD/build/web/, as WLS counterpart runtime xml WEB-INF/glassfish-web.xml is present in the same archive.
Info: Loading application [MidtermAD] at [/MidtermAD]
Info: MidtermAD was successfully deployed in 464 milliseconds.
Warning: StandardWrapperValve[jsp]: Servlet.service() for servlet jsp threw exception
java.lang.NullPointerException
at java.lang.String.split(String.java:2337)
at java.lang.String.split(String.java:2422)
at data.FxDataModel.<init>(FxDataModel.java:38)
at org.apache.jsp.fxCalc_jsp.jspInit(fxCalc_jsp.java:45)
at org.apache.jasper.runtime.HttpJspBase.init(HttpJspBase.java:92)
at org.apache.jasper.servlet.JspServletWrapper.getServlet(JspServletWrapper.java:210)
at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:388)
at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:473)
at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:377)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:790)
at org.apache.catalina.core.StandardWrapper.service(StandardWrapper.java:1682)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:318)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:160)
at org.apache.catalina.core.StandardPipeline.doInvoke(StandardPipeline.java:734)
at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:673)
at com.sun.enterprise.web.WebPipeline.invoke(WebPipeline.java:99)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:174)
at org.apache.catalina.connector.CoyoteAdapter.doService(CoyoteAdapter.java:415)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:282)
at com.sun.enterprise.v3.services.impl.ContainerMapper$HttpHandlerCallable.call(ContainerMapper.java:459)
at com.sun.enterprise.v3.services.impl.ContainerMapper.service(ContainerMapper.java:167)
at org.glassfish.grizzly.http.server.HttpHandler.runService(HttpHandler.java:201)
at org.glassfish.grizzly.http.server.HttpHandler.doHandle(HttpHandler.java:175)
at org.glassfish.grizzly.http.server.HttpServerFilter.handleRead(HttpServerFilter.java:235)
at org.glassfish.grizzly.filterchain.ExecutorResolver$9.execute(ExecutorResolver.java:119)
at org.glassfish.grizzly.filterchain.DefaultFilterChain.executeFilter(DefaultFilterChain.java:284)
at org.glassfish.grizzly.filterchain.DefaultFilterChain.executeChainPart(DefaultFilterChain.java:201)
at org.glassfish.grizzly.filterchain.DefaultFilterChain.execute(DefaultFilterChain.java:133)
at org.glassfish.grizzly.filterchain.DefaultFilterChain.process(DefaultFilterChain.java:112)
at org.glassfish.grizzly.ProcessorExecutor.execute(ProcessorExecutor.java:77)
at org.glassfish.grizzly.nio.transport.TCPNIOTransport.fireIOEvent(TCPNIOTransport.java:561)
at org.glassfish.grizzly.strategies.AbstractIOStrategy.fireIOEvent(AbstractIOStrategy.java:112)
at org.glassfish.grizzly.strategies.WorkerThreadIOStrategy.run0(WorkerThreadIOStrategy.java:117)
at org.glassfish.grizzly.strategies.WorkerThreadIOStrategy.access$100(WorkerThreadIOStrategy.java:56)
at org.glassfish.grizzly.strategies.WorkerThreadIOStrategy$WorkerThreadRunnable.run(WorkerThreadIOStrategy.java:137)
at org.glassfish.grizzly.threadpool.AbstractThreadPool$Worker.doWork(AbstractThreadPool.java:565)
at org.glassfish.grizzly.threadpool.AbstractThreadPool$Worker.run(AbstractThreadPool.java:545)
at java.lang.Thread.run(Thread.java:745)
fxInit.jsp：
<%@page import="java.io.*"%>
<%@page import="java.util.*"%>
<%@ page import="data.FxDataModel"%>
<%!
private FxDataModel fxDataModel;
public void jspInit(){
Properties fxProps = new Properties();
ServletContext context = getServletContext();
fxProps.getProperty(FxDataModel.FX_PRP_FILE_NAME_KEY);
context.getRealPath(context.getInitParameter(FxDataModel.FX_PRP_FILE_NAME_KEY));
try{
FileInputStream input = new FileInputStream(FxDataModel.FX_PRP_FILE_NAME_KEY);
fxProps.load(input);
input.close();
}catch(IOException e){
FileInputStream input = null;
}
context.getRealPath(fxProps.getProperty(FxDataModel.FX_RATE_FILE_NAME_KEY));
try{
FileInputStream input = new FileInputStream(FxDataModel.FX_RATE_FILE_NAME_KEY);
fxProps.load(input);
input.close();
}catch(IOException e){
FileInputStream input = null;
}
fxDataModel = new FxDataModel(fxProps);
}
%>
FxDataModel.Java：
package data;
import java.util.*;
public class FxDataModel {
public static final String FX_PRP_FILE_NAME_KEY = "fx.prp.file.name";
public static final String FX_RATE_FILE_NAME_KEY = "fx.rates.file.name";
public static final String FX_RATES_FILE_DLMTR_KEY = "fx.rates.file.dlmtr";
public static final String SRC_AMT_KEY = "src.amt";
public static final String SRC_CUCY_KEY = "src.cucy";
public static final String DST_AMT_KEY = "dst.amt";
public static final String DST_CUCY_KEY = "dst.cucy";
private Properties fxProps = new Properties();
private double [][] fxExchangeRates;
private String[] fxCurrencies;
public FxDataModel(Properties fxProps)
{
this.fxProps = fxProps;
String[] rateStrings;
String record;
fxProps .setProperty(FX_RATES_FILE_DLMTR_KEY,"fx.rates.file.dlmtr");
String delimiter = fxProps.getProperty(FX_RATES_FILE_DLMTR_KEY);
Scanner reader = new Scanner(FX_RATE_FILE_NAME_KEY);
fxCurrencies = reader.nextLine().split(delimiter);
for(int i = 0 ; i < fxCurrencies.length ; i++){
record= reader.nextLine();
rateStrings = record.split(delimiter);
fxExchangeRates[i] = new double[fxCurrencies.length];
for(int j = 0 ; j < rateStrings.length ; j++){
fxExchangeRates[i][j]= Double.parseDouble(rateStrings[j]);
}
reader.close();
}
}
public Properties getFxProps()
{
return fxProps;
}
public String[] getFxCurrencies(){
return fxCurrencies;
}
public double getFxRate(final String inNumber, final String outNumber){
int Currency1;
int Currency2;
double rate;
for(Currency1 = 0; Currency1 <getFxCurrencies().length; Currency1++){
if(inNumber.equals(fxCurrencies[Currency1])){
break;
}
}
for(Currency2 = 0; Currency2 <getFxCurrencies().length; Currency2++){
if(outNumber.equals(fxCurrencies[Currency2])){
break;
}
}
rate = fxExchangeRates[Currency1][Currency2];
return rate;
}
}
fxCalc.jsp
<%@include file="fxInit.jsp"%>
<%
Properties fxProps = fxDataModel.getFxProps();
String srcAmtName = fxProps.getProperty(FxDataModel.SRC_AMT_KEY);
String dstAmtName = fxProps.getProperty(FxDataModel.DST_AMT_KEY);
String srcCucyName = fxProps.getProperty(FxDataModel.SRC_CUCY_KEY);
String dstCucyName = fxProps.getProperty(FxDataModel.DST_CUCY_KEY);
String Curr1 = request.getParameter(srcAmtName);
String Curr2 = request.getParameter(dstAmtName);
String formInput;
String formOutput;
String[] currencies = fxDataModel.getFxCurrencies();
try {
formInput = request.getParameter(srcAmtName);
Double formDouble = Double.parseDouble(formInput);
Double Conversion = fxDataModel.getFxRate(Curr1,Curr2)*formDouble;
formOutput = String.valueOf(Conversion);
} catch (NumberFormatException ex) {
Curr1= Curr2 = currencies[0];
formInput = ("");
formOutput = ("");
} catch (NullPointerException npe){
Curr1= Curr2 = currencies[0];
formInput = ("");
formOutput = ("");
}
%>
<html>
<head>
<title>F/X Calculator</title>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
</head>
<style>
h1{
color: white;
font-family: verdana;
font-size: 200%;
font-style: italic;
text-align: center;
}
hr{
color:white;
}
select{
margin-top: 30px;
margin-right:10px;
}
input{
margin-top: 30px;
margin-right:10px;
}
</style>
<body bgcolor = "blue">
<h1>
Money Banks F/X Calculator<br>
</h1>
<hr>
<div align="center">
<form name ="fxCalc" action="fxCalc.jsp" method="POST">
<select name="<%=srcCucyName%>">
<% for (String currency : currencies) { %>
<option value="<%=currency%>" <%=currency.equals(Curr1)?"selected":""%>><%=currency%></option>
<%}%>
</select>
<input name="<%=srcAmtName%>" type="text" value = <%=formInput%> >
<select name="<%=dstCucyName%>">
<% for (String currency : currencies) { %>
<option value="<%=currency%>" <%=currency.equals(Curr2)?"selected":""%>><%=currency%></option>
<%}%>
</select>
<input name="<%=dstAmtName%>" type="text" disabled="disabled" value = <%=formOutput%>>
<br>
<input name="submitbutton" type="submit" value="Convert" name="Convert"/>
<input name="resetbutton" type="reset" value="Reset"/>
<form/>
<div/>
</body>
</html>
我真的不理解的一件事是我不应该在html中“硬编码”表单控件，所以这就是为什么这些“SRC_AMT_KEY”键被提供。我只是不确定如何实现它们。尽我所能，但我完全不理解这一部分。键是否应该替换“Curr1”和“Curr2”等变量？这是应用程序以前的工作方式，但我们现在正在更新它，以便没有硬编码。我非常感谢任何帮助理解这个项目。我已经坚持了几天，现在我会继续更新代码，如果我取得任何进展。谢谢！
这里也是fxCalc.prp文件的内容：
dst.amt=dstAmt
dst.cucy=dstCucy
fx.rates.file.dlmtr=,
fx.rates.file.name=/WEB-INF/fxRates.csv
src.amt=srcAmt
src.cucy=srcCucy
的fxRates.csv文件还包含这些代码：
CAD,EUR,GBP,USD
1.0,0.624514066,0.588714763,0.810307
1.601244959,1.0,0.942676548,1.2975
1.698615463,1.060809248,1.0,1.3764
1.234100162,0.772200772,.726532984,1.0
太多的代码。只提供相关的内容。 [MCVE]（http://stackoverflow.com/help/mcve）。 – YoungHobbit
好的..谢谢。我删除了一些东西并缩小了问题的范围。 – DeathWish
您从未使用任何值填充'fxProps'属性。 –