Einfacher Taschenrechner mit Java Server Pages (JSP) erstellen und Tomcat unter Ubuntu installieren

Oktober 14, 2023 admin

apt update
apt install default-jdk
apt install tomcat9
systemctl start tomcat9
systemctl enable tomcat9

// Usernames und Passworte anpassen:
nano /etc/tomcat9/tomcat-users.xml

systemctl restart tomcat9

nano /var/lib/tomcat9/webapps/ROOT/index.jsp
cd /var/lib/tomcat9/webapps/ROOT/
ls
mv index.html index.html_bak
ls
nano index.jsp

Quellcode index.jsp:

<%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8"%>
<!DOCTYPE html>
<html>
<head>
    <title>Einfacher Taschenrechner</title>
</head>
<body>
    <h1>Einfacher Taschenrechner</h1>
    <form method="post" action="index.jsp">
        <input type="text" name="num1" placeholder="Zahl 1" required>
        <select name="operator" required>
            <option value="+">+</option>
            <option value="-">-</option>
            <option value="*">*</option>
            <option value="/">/</option>
        </select>
        <input type="text" name="num2" placeholder="Zahl 2" required>
        <input type="submit" value="Berechnen">
    </form>

    <%-- Java-Code für die Berechnung --%>
    <%
        String num1Str = request.getParameter("num1");
        String num2Str = request.getParameter("num2");
        String operator = request.getParameter("operator");
        double result = 0;

        if (num1Str != null && num2Str != null && operator != null) {
            try {
                double num1 = Double.parseDouble(num1Str);
                double num2 = Double.parseDouble(num2Str);

                switch (operator) {
                    case "+":
                        result = num1 + num2;
                        break;
                    case "-":
                        result = num1 - num2;
                        break;
                    case "*":
                        result = num1 * num2;
                        break;
                    case "/":
                        if (num2 != 0) {
                            result = num1 / num2;
                        } else {
                            out.println("<p style='color:red;'>Fehler: Division durch Null.</p>");
                        }
                        break;
                    default:
                        out.println("<p style='color:red;'>Ungültiger Operator.</p>");
                        break;
                }
            } catch (NumberFormatException e) {
                out.println("<p style='color:red;'>Fehler: Bitte geben Sie gültige Zahlen ein.</p>");
            }
        }
    %>

    <%-- Anzeige des Ergebnisses --%>
    <%
        if (num1Str != null && num2Str != null && operator != null) {
            out.println("<p>Ergebnis: " + result + "</p>");
        }
    %>

</body>
</html>

Webapplikation im Browser aufrufen:

http://10.0.0.5:8080/index.jsp

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