Hibernate Spring Object Wrapper not passing values

I am struggling to create a form where I can insert multiple readings of electric meters. I have constructed a wrapper that holds all the values. All looks good until the moment I submit the readings as I get java.lang.NullPointerException.

Here is part of a controller:

@RequestMapping("/registerEnergyReadings")
public ModelAndView registerEnergyReadings(
        @ModelAttribute("energyReadingWrapper") EnergyReadingWrapper, energyReadingWrapper, BindingResult result) {
    // loading available meters from DB:
    List<EnergyMeters> energyMeters= meterService.getMeters();
    List<EnergyReading> readings= new ArrayList<EnergyReading>();
    //preparing the wrapper           
    for (int i = 0; i < energyMeters.size(); i++) {
        EnergyReading reading = new EnergyReading();
        reading.setMeter(energyMeters.get(i));
    //the two lines below done temporary so I don't have to fill the form every time   
    // I test it now
        reading.setReading(23);
        reading.setDate(new Date());
        readings.add(reading);
    }
    energyReadingWrapper.setEnergyReadings(readings);
    Map<String, Object> model = new HashMap<String, Object>();
    model.put("energyReadingWrapper", energyReadingWrapper);

    return new ModelAndView("RegisterEnergyReadings", "model", model);
}

@RequestMapping("/saveEnergyReadings")
public ModelAndView saveEnergyReadings( @ModelAttribute("energyReadingWrapper") EnergyReadingWrapper energyReadingWrapper, BindingResult result) {
    System.out.println("this is the point I reach before the null exception");
    System.out.println(energyReadingWrapper.toString());
    List<EnergyReadings> readings= energyReadingWrapper.getEnergyReadings();
    for (EnergyReadingsi : readings) {
        readingService.saveReading(i);
    }

    return new ModelAndView("redirect:/readingList.html");
}

And the jsp form (the crucial part of it):

<c:url var="readings" value="saveEnergyReadings.html" />
<form:form id="energyReadingWrapper"
    modelAttribute="energyReadingWrapper" method="post"
    action="${readings}">
    <table width="400px" height="150px">
        <c:forEach items="${energyReadingWrapper.energyReadings}"
            varStatus="i" var="energyReadings">
            <tr>
                <td><c:out value="${energyReadings.meter.description}" /></td>

                <td><form:input
                        path="energyReadings[${i.index}].readingValue" /></td>
                <td><form:input path="energyReadings[${i.index}].date"
                        type="date" /></td>
            </tr>
        </c:forEach>
        <tr>
            <td colspan="6" align="center"><input type="submit"
                value="Save" /></td>
    </table>
</form:form>

All looks fine. The jsp page generates table with rows matching the number of meters and all of them have the default values that I set (23 and the current date) I don't understand why the wrapper is not being passed to the controller when I press save button. What have I missed?

Regards, Maciej

EDIT: The stack trace (unfortunately I am writing the program in Polish):

type Exception report

message Request processing failed; nested exception is java.lang.NullPointerException

description The server encountered an internal error that prevented it from fulfilling this request.

exception

org.springframework.web.util.NestedServletException: Request processing failed; nested exception is java.lang.NullPointerException org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:659) org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:563) javax.servlet.http.HttpServlet.service(HttpServlet.java:648) javax.servlet.http.HttpServlet.service(HttpServlet.java:729) org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52) root cause

java.lang.NullPointerException forms.OdczytEnergiaFormularz.toString(OdczytEnergiaFormularz.java:20) kamienica.controller.HomeController.zapiszOdczytEnergia(HomeController.java:511) sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source) sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source) java.lang.reflect.Method.invoke(Unknown Source) org.springframework.web.bind.annotation.support.HandlerMethodInvoker.doInvokeMethod(HandlerMethodInvoker.java:710) org.springframework.web.bind.annotation.support.HandlerMethodInvoker.invokeHandlerMethod(HandlerMethodInvoker.java:167) org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter.invokeHandlerMethod(AnnotationMethodHandlerAdapter.java:414) org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter.handle(AnnotationMethodHandlerAdapter.java:402) org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:77 1) org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:716) org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:647) org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:563) javax.servlet.http.HttpServlet.service(HttpServlet.java:648) javax.servlet.http.HttpServlet.service(HttpServlet.java:729) org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)

Here is the wrapper class:

public class EnergyReadingWrapper{

    private List<EnergyReading> energyReadings;

(setters and getters)
}

链接地址: http://www.djcxy.com/p/27888.html

上一篇: 无法将命令发送到SMTP主机

下一篇: Hibernate Spring Object Wrapper不传递值