分割为字符串数组

时间：2015-10-15 18:46:54

标签： java jsp multidimensional-array nullpointerexception filereader

所以我试图从文件阅读器填充两个数组。我认为这需要嵌套循环。我觉得我走在正确的轨道上，但自昨天以来我一直处于困境。该程序的目的是通过jsp启动程序并动态读取值。真的很感激任何帮助。我觉得我走在正确的轨道上，但我似乎无法自己完成它。应将fxRates.csv的第一行填充到currencyCodes数组中，其余行应填充到2d数组fxExchangeRates中。我得到的代码没有任何错误，但现在我得到的是当我尝试运行程序时：enter image description here

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，这就是提供这些“SRC_AMT_KEY”键的原因。我只是不确定如何实现它们。我尽我所能，但我完全不了解这一部分。键应该替换像“Curr1”和“Curr2”这样的变量吗？这是应用程序之前的工作方式，但我们现在正在更新它，以便没有任何硬编码。在理解这个项目时，我真的很感激。我已经坚持了几天，如果我取得任何进展，我会继续更新代码。谢谢！

以下是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

fxRates.csv文件还包含以下代码：

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

1 个答案:

答案 0 :(得分：2)

在FxDataModel.Java类中 您将属性引用声明为private Properties fxProps;

但您没有分配属性对象。默认情况下，它使用null分配，在空值上，您调用fxProps.getProperty( FX_RATES_FILE_DLMTR_KEY );。因此，在运行时，JVM会抛出NullPointerException。

<强>解决方案： 

private Properties fxProps = new Properties();
fxProps .setProperty(FX_RATES_FILE_DLMTR_KEY,"fx.rates.file.dlmtr");
private String delimiter = fxProps.getProperty( FX_RATES_FILE_DLMTR_KEY );
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