私はEJBを初めて使用するため、JavaEE6チュートリアルのチュートリアルのようにサンプルEJBプロジェクトを実行していました。
Beanの外観は次のとおりです。
Converter.java
package converter.ejb;
import java.math.BigDecimal;
import javax.ejb.Remote;
@Remote
public interface Converter {
public BigDecimal dollarToYen(BigDecimal dollars);
public BigDecimal yenToEuro(BigDecimal yen);
}
ConverterBean.java
package converter.ejb;
import java.math.BigDecimal;
import javax.ejb.LocalBean;
import javax.ejb.Stateless;
@Stateless
public class ConverterBean {
private BigDecimal yenRate = new BigDecimal("115.3100");
private BigDecimal euroRate = new BigDecimal("0.0071");
public BigDecimal dollarToYen(BigDecimal dollars) {
BigDecimal result = dollars.multiply(yenRate);
return result.setScale(2, BigDecimal.ROUND_UP);
}
public BigDecimal yenToEuro(BigDecimal yen) {
BigDecimal result = yen.multiply(euroRate);
return result.setScale(2, BigDecimal.ROUND_UP);
}
}
ConverterClient.java
package converter.ejb;
import java.math.BigDecimal;
import javax.ejb.EJB;
public class ConverterClient {
@EJB
private static Converter converter;
public ConverterClient(String[] args) {
}
public static void main(String[] args) {
ConverterClient client = new ConverterClient(args);
client.doConversion();
}
public void doConversion() {
try {
BigDecimal param = new BigDecimal("100.00");
BigDecimal yenAmount = converter.dollarToYen(param);
System.out.println("$" + param + " is " + yenAmount
+ " Yen.");
BigDecimal euroAmount = converter.yenToEuro(yenAmount);
System.out.println(yenAmount + " Yen is " + euroAmount
+ " Euro.");
System.exit(0);
} catch (Exception ex) {
System.err.println("Caught an unexpected exception!");
ex.printStackTrace();
}
}
}
JSPページであるWebクライアントがあります：converterweb.jsp
<%@ page import="converter.ejb.Converter,
java.math.*, javax.naming.*"%>
<%!
private Converter converter = null;
public void jspInit() {
try {
InitialContext ic = new InitialContext();
converter = (Converter)
ic.lookup(Converter.class.getName());
} catch (Exception ex) {
System.out.println("Couldn’t create converter bean."+
ex.getMessage());
}
}
public void jspDestroy() {
converter = null;
}
%>
<html>
<head>
<title>Converter</title>
</head>
<body bgcolor="white">
<h1>Converter</h1>
<hr>
<p>Enter an amount to convert:</p>
<form method="get">
<input type="text" name="amount" size="25">
<br>
<p>
<input type="submit" value="Submit">
<input type="reset" value="Reset">
</form>
<%
String amount = request.getParameter("amount");
if ( amount != null && amount.length() > 0 ) {
BigDecimal d = new BigDecimal(amount);
BigDecimal yenAmount = converter.dollarToYen(d);
%>
<p>
<%= amount %> dollars are <%= yenAmount %> Yen.
<p>
<%
BigDecimal euroAmount =
converter.yenToEuro(yenAmount);
%>
<%= amount %> Yen are <%= euroAmount %> Euro.
<%
}
%>
</body>
</html>
しかし、このプロジェクトを実行しようとすると、NullPointerExceptionが発生します。Websphereアプリケーションサーバーを使用しています。誰かがこれが起こっている理由と私がそれを修正する方法についていくつかの光を当てることができますか？
編集：エラーログ
[12/10/12 14:21:26:956 IST] 0000001f webapp E com.ibm.ws.webcontainer.webapp.WebApp logServletError SRVE0293E: [Servlet Error]-[/converterweb.jsp]: java.lang.NullPointerException
at com.ibm._jsp._converterweb._jspService(_converterweb.java:118)
at com.ibm.ws.jsp.runtime.HttpJspBase.service(HttpJspBase.java:99)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:668)
at com.ibm.ws.webcontainer.servlet.ServletWrapper.service(ServletWrapper.java:1188)
at com.ibm.ws.webcontainer.servlet.ServletWrapper.handleRequest(ServletWrapper.java:763)
at com.ibm.ws.webcontainer.servlet.ServletWrapper.handleRequest(ServletWrapper.java:454)
at com.ibm.ws.webcontainer.servlet.ServletWrapperImpl.handleRequest(ServletWrapperImpl.java:178)
at com.ibm.wsspi.webcontainer.servlet.GenericServletWrapper.handleRequest(GenericServletWrapper.java:122)
at com.ibm.ws.jsp.webcontainerext.AbstractJSPExtensionServletWrapper.handleRequest(AbstractJSPExtensionServletWrapper.java:205)
at com.ibm.ws.webcontainer.filter.WebAppFilterManager.invokeFilters(WebAppFilterManager.java:1020)
at com.ibm.ws.webcontainer.servlet.CacheServletWrapper.handleRequest(CacheServletWrapper.java:87)
at com.ibm.ws.webcontainer.WebContainer.handleRequest(WebContainer.java:895)
at com.ibm.ws.webcontainer.WSWebContainer.handleRequest(WSWebContainer.java:1662)
at com.ibm.ws.webcontainer.channel.WCChannelLink.ready(WCChannelLink.java:195)
at com.ibm.ws.http.channel.inbound.impl.HttpInboundLink.handleDiscrimination(HttpInboundLink.java:452)
at com.ibm.ws.http.channel.inbound.impl.HttpInboundLink.handleNewRequest(HttpInboundLink.java:511)
at com.ibm.ws.http.channel.inbound.impl.HttpInboundLink.processRequest(HttpInboundLink.java:305)
at com.ibm.ws.http.channel.inbound.impl.HttpICLReadCallback.complete(HttpICLReadCallback.java:83)
at com.ibm.ws.tcp.channel.impl.AioReadCompletionListener.futureCompleted(AioReadCompletionListener.java:165)
at com.ibm.io.async.AbstractAsyncFuture.invokeCallback(AbstractAsyncFuture.java:217)
at com.ibm.io.async.AsyncChannelFuture.fireCompletionActions(AsyncChannelFuture.java:161)
at com.ibm.io.async.AsyncFuture.completed(AsyncFuture.java:138)
at com.ibm.io.async.ResultHandler.complete(ResultHandler.java:204)
at com.ibm.io.async.ResultHandler.runEventProcessingLoop(ResultHandler.java:775)
at com.ibm.io.async.ResultHandler$2.run(ResultHandler.java:905)
at com.ibm.ws.util.ThreadPool$Worker.run(ThreadPool.java:1659)