Failed to convert value of type 'java.lang.String' to required type 'double'; nested exception is java.lang.NumberFormatException: empty String

Sharman Jeurkar

I am new to Spring boot. I am trying to calculate moles when the user inputs 2 of the three values. I have tried to make a dropdown, where if one of the link is clicked , then one of the textbox becomes read-only. But while doing this I am getting this error

 There was an unexpected error (type=Bad Request, status=400).
    Failed to convert value of type 'java.lang.String' to required type 'double'; nested exception is java.lang.NumberFormatException: empty String
Failed to convert value of type 'java.lang.String' to required type 'double'; nested exception is java.lang.NumberFormatException: empty String
org.springframework.web.method.annotation.MethodArgumentTypeMismatchException: Failed to convert value of type 'java.lang.String' to required type 'double'; nested exception is java.lang.NumberFormatException: empty String
    at org.springframework.web.method.annotation.AbstractNamedValueMethodArgumentResolver.resolveArgument(AbstractNamedValueMethodArgumentResolver.java:133)
    at org.springframework.web.method.support.HandlerMethodArgumentResolverComposite.resolveArgument(HandlerMethodArgumentResolverComposite.java:121)
    at org.springframework.web.method.support.InvocableHandlerMethod.getMethodArgumentValues(InvocableHandlerMethod.java:179)
    at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:146)
    at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:117)
    at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:895)
    at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:808)
    at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:87)
    at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1067)
    at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:963)
    at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1006)
    at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:898)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:655)
    at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:883)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:764)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:227)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162)
    at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:189)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162)
    at org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:100)
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:117)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:189)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162)
    at org.springframework.web.filter.FormContentFilter.doFilterInternal(FormContentFilter.java:93)
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:117)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:189)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162)
    at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:201)
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:117)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:189)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:197)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:97)
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:540)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:135)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:92)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:78)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:357)
    at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:382)
    at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:65)
    at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:895)
    at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1732)
    at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
    at org.apache.tomcat.util.threads.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1191)
    at org.apache.tomcat.util.threads.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:659)
    at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
    at java.base/java.lang.Thread.run(Thread.java:831)
Caused by: java.lang.NumberFormatException: empty String
    at java.base/jdk.internal.math.FloatingDecimal.readJavaFormatString(FloatingDecimal.java:1842)
    at java.base/jdk.internal.math.FloatingDecimal.parseDouble(FloatingDecimal.java:110)
    at java.base/java.lang.Double.parseDouble(Double.java:556)
    at java.base/java.lang.Double.valueOf(Double.java:519)
    at org.springframework.util.NumberUtils.parseNumber(NumberUtils.java:223)
    at org.springframework.beans.propertyeditors.CustomNumberEditor.setAsText(CustomNumberEditor.java:115)
    at org.springframework.beans.TypeConverterDelegate.doConvertTextValue(TypeConverterDelegate.java:429)
    at org.springframework.beans.TypeConverterDelegate.doConvertValue(TypeConverterDelegate.java:402)
    at org.springframework.beans.TypeConverterDelegate.convertIfNecessary(TypeConverterDelegate.java:155)
    at org.springframework.beans.TypeConverterSupport.convertIfNecessary(TypeConverterSupport.java:73)
    at org.springframework.beans.TypeConverterSupport.convertIfNecessary(TypeConverterSupport.java:53)
    at org.springframework.validation.DataBinder.convertIfNecessary(DataBinder.java:700)
    at org.springframework.web.method.annotation.AbstractNamedValueMethodArgumentResolver.resolveArgument(AbstractNamedValueMethodArgumentResolver.java:125)
    ... 47 more

This is my Java controller code:

package com.sharman.controller;

import org.springframework.stereotype.Controller;
import org.springframework.ui.Model;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestParam;

import com.sharman.service.Calculator;

@Controller
@RequestMapping("/Chemistry-Calculator/")
public class HomeController {
    @RequestMapping("/")
    public String callHome() {
        return "home";
    }

    @RequestMapping("/about")
    public String callAbout() {
        return "about";
    }

    @RequestMapping("/Mole-Calculator")
    public String callMoleCalculator() {
        return "Mole-Calculator";
    }

    @RequestMapping("/Number-Of-Moles")
    public String calculateMoles(@RequestParam(value = "givenMass",  required=false) double givenMassInput,
            @RequestParam(value = "molarMass",  required=false) double molarMassInput,
            @RequestParam(value = "moles",  required=false) double molesInput, Model model) {

        Calculator calculate = new Calculator();

        if (molesInput == 0) {
            double moles = calculate.calculateMoles(givenMassInput, molarMassInput);
            model.addAttribute("givenMass", givenMassInput);
            model.addAttribute("molarMass", molarMassInput);
            model.addAttribute("moles", moles);
            
        }else if (givenMassInput == 0) {
            double givenMass = calculate.calculateGivenMass(molarMassInput, molesInput);
            model.addAttribute("molarMass", molarMassInput);
            model.addAttribute("moles", molesInput);
            model.addAttribute("givenMass", givenMass);
        }else if (molarMassInput == 0) {
            double molarMass = calculate.calculateMolarMass(givenMassInput, molesInput);
            model.addAttribute("givenMass", givenMassInput);
            model.addAttribute("moles", molesInput);
            model.addAttribute("molarMass", molarMass);
        }

        return "Mole-Calculator";
    }

    @RequestMapping("/Avagadros-Number")
    public String callAvagadrosNumber() {
        return "Avagadros-Number";
    }

    @RequestMapping("/Avagadro's-Number-Result")
    public String calculateAvagadrosNumber(@RequestParam(value = "moles") double moles, Model model) {

        Calculator calculate = new Calculator();
        double result = calculate.calculateAvagadrosNumber(moles);
        String power = "10\u00b2\u00b3";
        System.out.println(power);
        model.addAttribute("result", result + "x" + power);
        model.addAttribute("moles", moles);
        return "Avagadros-Number";
    }

}

I am here trying to send the values in a model variable. This is my jsp page:

<!DOCTYPE html>
<html>
<head>
<!-- Required meta tags -->
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, initial-scale=1">

<!-- Bootstrap CSS -->
<link
    href="https://cdn.jsdelivr.net/npm/[email protected]/dist/css/bootstrap.min.css"
    rel="stylesheet"
    integrity="sha384-1BmE4kWBq78iYhFldvKuhfTAU6auU8tT94WrHftjDbrCEXSU1oBoqyl2QvZ6jIW3"
    crossorigin="anonymous">

<title>Mole Calculator | Chemistry Calculator</title>

</head>



<body>

    <nav class="navbar fixed-top navbar-expand-lg navbar-dark bg-black">

        <div class="container-fluid">
            <a class="navbar-brand" href="#"><h4>
                    <b>Chemistry Calculator</b>
                </h4></a>

            <button class="navbar-toggler" type="button"
                data-bs-toggle="collapse" data-bs-target="#navbarSupportedContent"
                aria-controls="navbarSupportedContent" aria-expanded="false"
                aria-label="Toggle navigation">
                <span class="navbar-toggler-icon"></span>
            </button>

            <div class="collapse navbar-collapse" id="navbarSupportedContent">

                <ul class="navbar-nav  text-uppercase">

                    <li class="nav-item"><a class="nav-link active"
                        aria-current="page" href="/Chemistry-Calculator/">Home</a></li>

                    <li class="nav-item"><a class="nav-link active"
                        aria-current="page" href="/Chemistry-Calculator/about">About</a></li>


                </ul>

            </div>
        </div>
    </nav>

    <div class="container" style="padding-top: 5%;">

        <div class="card px-4 py-5" style="width: 650px;">
            <div class="card-block">

                <form action="/Chemistry-Calculator/Number-Of-Moles">

                    <div class="mb-3">
                        <label for="givenMass" class="form-label">Given Mass of
                            Substance</label> <input type="number" class="form-control" id="givenMass"
                            aria-describedby="emailHelp" name="givenMass"
                            value="${givenMass}" style="width: 600px">
                    </div>
                    <div class="mb-3">
                        <label for="molarMass" class="form-label">Molar Mass</label> <input
                            type="number" class="form-control" id="molarMass" name="molarMass"
                            value="${molarMass}" style="width: 600px">
                    </div>

                    <div class="mb-3">
                        <label for="moles" class="form-label">Moles</label> <input
                            type="number" class="form-control" id="moles" name="moles"
                            value="${moles}" style="width: 600px">
                    </div>

                    <input class="btn btn-outline-success" type="submit"
                        value="Calculate">

                    <div class="btn-group">
                        <button type="button" class="btn btn-success dropdown-toggle"
                            data-bs-toggle="dropdown" aria-expanded="false">Choose
                            what to calculate</button>
                        <ul class="dropdown-menu">
                            <li><a class="dropdown-item" onclick="readonlyForMoles()"
                                href="#">Calculate Moles</a></li>
                            <li><a class="dropdown-item"
                                onclick="readonlyForMolarMass()"
                                href="#">Calculate Molar
                                    Mass</a></li>
                            <li><a class="dropdown-item"
                                onclick="readonlyForGivenMass()"
                                href="#">Calculate Given
                                    mass</a></li>
                        </ul>
                    </div>

                </form>
            </div>
        </div>
    </div>

    <script
        src="https://cdn.jsdelivr.net/npm/[email protected]/dist/js/bootstrap.bundle.min.js"
        integrity="sha384-ka7Sk0Gln4gmtz2MlQnikT1wXgYsOg+OMhuP+IlRH9sENBO0LRn5q+8nbTov4+1p"
        crossorigin="anonymous"></script>
    <script type="text/javascript"src="/javascript/script.js"></script>

</body>
</html>

Please help me sove this error

Hopey One

Make the parameters Double (class type) rather than double primitive type. I think spring will then convert an empty string from your form request (or no parameter) to a null rather than throwing an exception.

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