Question

我正在使用PrimeFaces 4.0，与两个xhtml页面关联的NetBeans。 xhtml呈现选择的一个无线电菜单，用户可以从中选择他们想要更多信息的实验。当他们这样做时，我希望xhtml将实验作为字符串传递回java。在用户点击提交后，我想要打开另一个xhtml页面，用户可以从中进一步缩小搜索条件。截至目前，当用户单击“提交”时，会出现空指针异常。此外，使用System.out.println（），我可以看到java没有从网页上获取字符串，因为我的Glassfish服务器输出打印（部分）：＆＃34;信息：nullaaaaaaaaaaaaaaaaaaaaa＆＃34;。它根本不打印其他println（）。

XHTML部分

            <h:form>
                <h:panelGrid>
                    <p:selectOneRadio id="Test"  value="Please Selecte a Test">
                        <p:ajax update="Test"  partialSubmit="#{targetBeantFranz.selectedNameOfExperiments}"/>
                        <f:selectItems  value="#{targetBeantFranz.nameofexperiments}" />
                    </p:selectOneRadio>
                    <h:commandButton value="Select" action="open" />

                </h:panelGrid>
            </h:form>

以下是受影响的Java方法（整个JAVA文件比这长得多）：

@ManagedBean(name = "targetBeantFranz", eager = true)
@SessionScoped

public class TargetBeanFranz implements Serializable {

public String selectedNameOfExperiments;
private final Map<String, String> nameofexperiments;

public TargetBeanFranz() throws SQLException {

        nameofexperiments = new HashMap<String, String>();

        XYexpdataServiceAdapter xydata = new XYexpdataServiceAdapterImpl();

        List<String> dbnameofexperiments = xydata.getNameofexperiments();
        for (String ta : dbnameofexperiments) {
            nameofexperiments.put(ta, ta);
        }
    }

    public String getSelectedNameOfExperiments() {
        System.out.println(selectedNameOfExperiments + "aaaaaaaaaaaaaaaaaaaaa");
        return selectedNameOfExperiments;
    }

    public void setSelectedNameOfExperiments(String selectedNameOfExperiments) {
        System.out.println(selectedNameOfExperiments + "bbbbbbbbbbbbbbbbbbbbbbbbb");
        this.selectedNameOfExperiments = selectedNameOfExperiments;
    }
}
    public Map<String, String> getNameofexperiments() {
        return nameofexperiments;
    }
}

ETA：我的堆栈跟踪看起来像这样：

显示java.lang.NullPointerException at javax.faces.component.SelectItemsIterator $ MapIterator.next（SelectItemsIterator.java:346） at javax.faces.component.SelectItemsIterator $ MapIterator.next（SelectItemsIterator.java:315）在javax.faces.component.SelectItemsIterator.next（SelectItemsIterator.java:155）在javax.faces.component.SelectItemsIterator.next（SelectItemsIterator.java:64）在javax.faces.component.SelectUtils.matchValue（SelectUtils.java:86）在javax.faces.component.UISelectOne.validateValue（UISelectOne.java:153）在javax.faces.component.UIInput.validate（UIInput.java:983） at javax.faces.component.UIInput.executeValidate（UIInput.java:1249）在javax.faces.component.UIInput.processValidators（UIInput.java:712）在javax.faces.component.UIComponentBase.processValidators（UIComponentBase.java:1261）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org.primefaces.component.layout.Layout.processValidators（Layout.java:233）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:646）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:357）在org.apache.catalina.connector.CoyoteAdapter.service（CoyoteAdapter.java:260）在com.sun.enterprise.v3.services.impl.ContainerMapper.service（ContainerMapper.java:188）在org.glassfish.grizzly.http.server.HttpHandler.runService（HttpHandler.java:191）在org.glassfish.grizzly.http.server.HttpHandler.doHandle（HttpHandler.java:168）在org.glassfish.grizzly.http.server.HttpServerFilter.handleRead（HttpServerFilter.java:189）在org.glassfish.grizzly.filterchain.ExecutorResolver $ 9.execute（ExecutorResolver.java:119）在org.glassfish.grizzly.filterchain.DefaultFilterChain.executeFilter（DefaultFilterChain.java:288）在org.glassfish.grizzly.filterchain.DefaultFilterChain.executeChainPart（DefaultFilterChain.java:206）在org.glassfish.grizzly.filterchain.DefaultFilterChain.execute（DefaultFilterChain.java:136）在org.glassfish.grizzly.filterchain.DefaultFilterChain.process（DefaultFilterChain.java:114）在org.glassfish.grizzly.ProcessorExecutor.execute（ProcessorExecutor.java:77）在org.glassfish.grizzly.nio.transport.TCPNIOTransport.fireIOEvent（TCPNIOTransport.java:838）在org.glassfish.grizzly.strategies.AbstractIOStrategy.fireIOEvent（AbstractIOStrategy.java:113）在org.glassfish.grizzly.strategies.WorkerThreadIOStrategy.run0（WorkerThreadIOStrategy.java:115）在org.glassfish.grizzly.strategies.WorkerThreadIOStrategy.access $ 100（WorkerThreadIOStrategy.java:55）在org.glassfish.grizzly.strategies.WorkerThreadIOStrategy $ WorkerThreadRunnable.run（WorkerThreadIOStrategy.java:135）在org.glassfish.grizzly.threadpool.AbstractThreadPool $ Worker.doWork（AbstractThreadPool.java:564）在org.glassfish.grizzly.threadpool.AbstractThreadPool $ Worker.run（AbstractThreadPool.java:544）在java.lang.Thread.run（Thread.java:745）

Answer 1

检查此article以获取有关JSF UI组件<h:selectOneMenu>的更多信息。

Answer 2

可能是你需要在bean的构造函数中初始化：selectedNameOfExperiments

我需要帮助确定我的空指针异常来自哪里

2 个答案: