Question

我有以下转换器代码：

@FacesConverter("konverter")
public class Konverter implements Converter {

@EJB
private BenutzerAendernLocal benutzer;

@Override
public Object getAsObject(FacesContext fc, UIComponent uic, String value) {
    if (value != null && value.trim().length() > 0) {
        try {
            System.out.println("KONVERTER: " + Integer.parseInt(value));

            return benutzer.finde(Integer.parseInt(value));
        } catch (NumberFormatException e) {
            throw new ConverterException(
                    new FacesMessage(FacesMessage.SEVERITY_ERROR, "Konvertier Fehler", "Nicht valide"));
        }
    } else {
        return null;
    }
 }

@Override
public String getAsString(FacesContext fc, UIComponent uic, Object object) {
    if (object != null) {
        return String.valueOf(((Benutzer) object).getId());
    } else {
        return null;
    }
}

}

我的@Stateless SessionBean中的代码：

@Override
public Benutzer finde(Integer id) {
    try {
        Benutzer b = em.find(Benutzer.class, id);
        return b;
    } catch (NoResultException e) {
        return null;
    }

}

我遇到的问题是，在返回语句的Konverter类的'getAsObject（）'方法中，我得到了一个NullPointerException。奇怪 - 在System.out中我得到了正确的id，因此值不为空。

错误：

2016-09-15T10：43：55.622 + 0200 | Schwerwiegend：java.lang.NullPointerException at de.Bean.Konverter.getAsObject（Konverter.java:26） at com.sun.faces.renderkit.html_basic.HtmlBasicInputRenderer.getConvertedValue（HtmlBasicInputRenderer.java:171） at com.sun.faces.renderkit.html_basic.MenuRenderer.convertSelectOneValue（MenuRenderer.java:201） at com.sun.faces.renderkit.html_basic.MenuRenderer.getConvertedValue（MenuRenderer.java:318） at org.primefaces.component.selectonelistbox.SelectOneListboxRenderer.getConvertedValue（SelectOneListboxRenderer.java:36） at javax.faces.component.UIInput.getConvertedValue（UIInput.java:1045）在javax.faces.component.UIInput.validate（UIInput.java:975）在javax.faces.component.UIInput.executeValidate（UIInput.java:1248）在javax.faces.component.UIInput.processValidators（UIInput.java:712）在javax.faces.component.UIComponentBase.processValidators（UIComponentBase.java:1261）在org.primefaces.component.panel.Panel.processValidators（Panel.java:287）在javax.faces.component.UIComponentBase.processValidators（UIComponentBase.java:1261）在org.primefaces.component.dialog.Dialog.processValidators（Dialog.java:403）在javax.faces.component.UIForm.processValidators（UIForm.java:253）在javax.faces.component.UIComponentBase.processValidators（UIComponentBase.java:1261）在javax.faces.component.UIComponentBase.processValidators（UIComponentBase.java:1261）在javax.faces.component.UIViewRoot.processValidators（UIViewRoot.java:1195） at com.sun.faces.lifecycle.ProcessValidationsPhase.execute（ProcessValidationsPhase.java:76）在com.sun.faces.lifecycle.Phase.doPhase（Phase.java:101）在com.sun.faces.lifecycle.LifecycleImpl.execute（LifecycleImpl.java:198）在javax.faces.webapp.FacesServlet.service（FacesServlet.java:658）在org.apache.catalina.core.StandardWrapper.service（StandardWrapper.java:1682）在org.apache.catalina.core.StandardWrapperValve.invoke（StandardWrapperValve.java:318） at org.apache.catalina.core.StandardContextValve.invoke（StandardContextValve.java:160）在org.apache.catalina.core.StandardPipeline.doInvoke（StandardPipeline.java:734）在org.apache.catalina.core.StandardPipeline.invoke（StandardPipeline.java:673）在com.sun.enterprise.web.WebPipeline.invoke（WebPipeline.java:99）在org.apache.catalina.core.StandardHostValve.invoke（StandardHostValve.java:174）在org.apache.catalina.connector.CoyoteAdapter.doService（CoyoteAdapter.java:416）在org.apache.catalina.connector.CoyoteAdapter.service（CoyoteAdapter.java:283） at com.sun.enterprise.v3.services.impl.ContainerMapper $ HttpHandlerCallable.call（ContainerMapper.java:459） at com.sun.enterprise.v3.services.impl.ContainerMapper.service（ContainerMapper.java:167）在org.glassfish.grizzly.http.server.HttpHandler.runService（HttpHandler.java:206）在org.glassfish.grizzly.http.server.HttpHandler.doHandle（HttpHandler.java:180）在org.glassfish.grizzly.http.server.HttpServerFilter.handleRead（HttpServerFilter.java:235）在org.glassfish.grizzly.filterchain.ExecutorResolver $ 9.execute（ExecutorResolver.java:119）在org.glassfish.grizzly.filterchain.DefaultFilterChain.executeFilter（DefaultFilterChain.java:284）在org.glassfish.grizzly.filterchain.DefaultFilterChain.executeChainPart（DefaultFilterChain.java:201）在org.glassfish.grizzly.filterchain.DefaultFilterChain.execute（DefaultFilterChain.java:133）在org.glassfish.grizzly.filterchain.DefaultFilterChain.process（DefaultFilterChain.java:112）在org.glassfish.grizzly.ProcessorExecutor.execute（ProcessorExecutor.java:77） at org.glassfish.grizzly.nio.transport.TCPNIOTransport.fireIOEvent（TCPNIOTransport.java:526）在org.glassfish.grizzly.strategies.AbstractIOStrategy.fireIOEvent（AbstractIOStrategy.java:112）在org.glassfish.grizzly.strategies.WorkerThreadIOStrategy.run0（WorkerThreadIOStrategy.java:117）在org.glassfish.grizzly.strategies.WorkerThreadIOStrategy.access $ 100（WorkerThreadIOStrategy.java:56）在org.glassfish.grizzly.strategies.WorkerThreadIOStrategy $ WorkerThreadRunnable.run（WorkerThreadIOStrategy.java:137）在org.glassfish.grizzly.threadpool.AbstractThreadPool $ Worker.doWork（AbstractThreadPool.java:591）在org.glassfish.grizzly.threadpool.AbstractThreadPool $ Worker.run（AbstractThreadPool.java:571）在java.lang.Thread.run（Thread.java:745）

JSF转换器 - NullPointerException

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