-3
Dies ist ein einfacher Rechner mit 2 Operationen: '+' & '-'. Als ich es vor einiger Zeit ausgeführt habe, hat alles funktioniert. Aber irgendwann bin ich auf Fehler gestoßen und kann nicht verstehen, was passiert ist.java.lang.NumberFormatException im Servlet
Dies ist meine Quelle:
html
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
<title>Calculator</title>
</head>
<body>
<h1>Calculator</h1>
<form action="./" method="get">
<label>First number:</label> <input type="text" name="num1" /> <br />
<label>Second number: </label> <input type="text" name="num2" /> <br />
<select name="operator">
<option value="+">+</option>
<option value="-">-</option>
</select>
<input type="submit" value="submit" />
</form>
</body>
</html>
xml
<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd" id="WebApp_ID" version="3.0">
<display-name>Calculator</display-name>
<welcome-file-list>
<welcome-file>index.html</welcome-file>
<welcome-file>index.htm</welcome-file>
<welcome-file>index.jsp</welcome-file>
<welcome-file>default.html</welcome-file>
<welcome-file>default.htm</welcome-file>
<welcome-file>default.jsp</welcome-file>
</welcome-file-list>
<servlet>
<servlet-name>Calculator</servlet-name>
<servlet-class>ua.nure.nechyporuk.Calculator</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>Calculator</servlet-name>
<url-pattern>/</url-pattern>
</servlet-mapping>
</web-app>
.java-
package ua.nure.nechyporuk;
import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
public class Calculator extends HttpServlet {
private static final long serialVersionUID = 1L;
public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
try {
response.setContentType("text/html");
int a1 = Integer.parseInt(request.getParameter("num1"));
int a2 = Integer.parseInt(request.getParameter("num2"));
String operator = request.getParameter("operator");
if (operator.equals("+")&& operator != null) {
request.setAttribute("operation", "addition");
request.setAttribute("res", a1+a2);
request.getRequestDispatcher("index.jsp").forward(request, response);
}
if (operator.equals("-")&& operator != null) {
request.setAttribute("operation", "subtract");
request.setAttribute("res", a1-a2);
request.getRequestDispatcher("index.jsp").forward(request, response);
}
} catch (Exception e) {
e.printStackTrace();
}
}
}
jsp
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
<title>Result of calculation:</title>
</head>
<body>
<h1>Result of ${operation}</h1>
<h1>${res}</h1>
<a href= "http://localhost:8081/Calculator">back to calculator</a>;
</body>
</html>
Ich kann nicht verstehen, warum diesen Fehler bekommen. Wie HTML-Seite hat keine Zeit zu arbeiten. Tomkat ich auf Port 8081.
Ausnahmen:
java.lang.NumberFormatException: For input string: "null"
at java.lang.NumberFormatException.forInputString(NumberFormatException.java:65)
at java.lang.Integer.parseInt(Integer.java:580)
at java.lang.Integer.parseInt(Integer.java:615)
at ua.nure.nechyporuk.Calculator.doGet(Calculator.java:17)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:624)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:731)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:303)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:218)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:122)
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:505)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:169)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:103)
at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:956)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:116)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:442)
at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1082)
at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:623)
at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:316)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
at java.lang.Thread.run(Thread.java:745)
fügen Sie die complate Fehlermeldung – Jens
Sie nicht den Parameter an das Servlet übergeben. Deshalb sehen Sie Null – Apostolos
'sysout' die' request.getParameter ("num1") 'und' request.getParameter ("num2") 'und sehen, was es zuerst druckt. – Apostolos