如何根据 selectOneMenu 的当前选择验证 selectManyCheckbox 的最大检查值数量？

Question

我正在使用 JSF 2.0 和 PrimeFaces。我有一个 selectOneMenu 和一个 selectManyCheckbox。我想实现这个场景：

当用户选择时：

• option1(PieChart)，则允许用户最多勾选一个复选框
• option2(BarChart)，则允许用户最多勾选两个复选框

这是我目前的尝试，观点：

<h:selectOneMenu value="#{bean.chartType}">
    <f:selectItem itemValue="PieChart" itemLabel="PieChart" />
    <f:selectItem itemValue="BarChart" itemLabel="BarChart" />
    <p:ajax event="keyup" update="checkbox" listener="#{bean.checkboxHandler}" />
</h:selectOneMenu>

<h:selectManyCheckbox id="checkbox" value="#{bean.selectedItemscheckbox}">
    <f:selectItem itemValue="priority" itemLabel="By priority" />
    <f:selectItem itemValue="project" itemLabel="By project" />
    <f:selectItem itemValue="issuetype" itemLabel="By IssueType" />
    <f:selectItem itemValue="group" itemLabel="By group" />
</h:selectManyCheckbox>

（注意：我不确定<p:ajax event> 是否正确）

豆子：

public void checkboxHandler() {
    Iterator it1 = selectedItemscheckbox.iterator();
    if (chartType.equals("PieChart")) {
        while (it1.hasNext()) {
            if (selectedItemscheckbox.size() > 1) {
                // Here should be somthing that shows a message to the user.
            }
        }
    }
}

在tring BalusC的解决方案后，出现了这个错误：

java.lang.InstantiationException: DAOKPI.TestAjax$MyCheckboxValidator
at java.lang.Class.newInstance0(Class.java:340)
at java.lang.Class.newInstance(Class.java:308)
at com.sun.faces.application.ApplicationImpl.newThing(ApplicationImpl.java:1699)
at com.sun.faces.application.ApplicationImpl.createValidator(ApplicationImpl.java:1557)
at com.sun.faces.facelets.tag.jsf.ValidatorTagHandlerDelegateImpl.createValidator(ValidatorTag     HandlerDelegateImpl.java:238)
at com.sun.faces.facelets.tag.jsf.ValidatorTagHandlerDelegateImpl.applyAttachedObject(Validato    rTagHandlerDelegateImpl.java:132)
at com.sun.faces.facelets.tag.jsf.ValidatorTagHandlerDelegateImpl.applyNested(ValidatorTagHand    lerDelegateImpl.java:205)
at com.sun.faces.facelets.tag.jsf.ValidatorTagHandlerDelegateImpl.apply(ValidatorTagHandlerDel    egateImpl.java:87)
at javax.faces.view.facelets.DelegatingMetaTagHandler.apply(DelegatingMetaTagHandler.java:120)
at javax.faces.view.facelets.CompositeFaceletHandler.apply(CompositeFaceletHandler.java:98)
at javax.faces.view.facelets.DelegatingMetaTagHandler.applyNextHandler(DelegatingMetaTagHandle     r.java:137)
at com.sun.faces.facelets.tag.jsf.ComponentTagHandlerDelegateImpl.apply(ComponentTagHandlerDel    egateImpl.java:188)
at javax.faces.view.facelets.DelegatingMetaTagHandler.apply(DelegatingMetaTagHandler.java:120)
at javax.faces.view.facelets.CompositeFaceletHandler.apply(CompositeFaceletHandler.java:98)
at javax.faces.view.facelets.DelegatingMetaTagHandler.applyNextHandler(DelegatingMetaTagHandler.java:137)
at com.sun.faces.facelets.tag.jsf.ComponentTagHandlerDelegateImpl.apply(ComponentTagHandlerDelegateImpl.java:188)
at javax.faces.view.facelets.DelegatingMetaTagHandler.apply(DelegatingMetaTagHandler.java:120)
at javax.faces.view.facelets.CompositeFaceletHandler.apply(CompositeFaceletHandler.java:98)
at javax.faces.view.facelets.DelegatingMetaTagHandler.applyNextHandler(DelegatingMetaTagHandler.java:137)
at com.sun.faces.facelets.tag.jsf.ComponentTagHandlerDelegateImpl.apply(ComponentTagHandlerDelegateImpl.java:188)
at javax.faces.view.facelets.DelegatingMetaTagHandler.apply(DelegatingMetaTagHandler.java:120)
at javax.faces.view.facelets.DelegatingMetaTagHandler.applyNextHandler(DelegatingMetaTagHandler.java:137)
at com.sun.faces.facelets.tag.jsf.ComponentTagHandlerDelegateImpl.apply(ComponentTagHandlerDelegateImpl.java:188)
at javax.faces.view.facelets.DelegatingMetaTagHandler.apply(DelegatingMetaTagHandler.java:120)
at javax.faces.view.facelets.CompositeFaceletHandler.apply(CompositeFaceletHandler.java:98)
at javax.faces.view.facelets.DelegatingMetaTagHandler.applyNextHandler(DelegatingMetaTagHandler.java:137)
at com.sun.faces.facelets.tag.jsf.ComponentTagHandlerDelegateImpl.apply(ComponentTagHandlerDelegateImpl.java:188)
at javax.faces.view.facelets.DelegatingMetaTagHandler.apply(DelegatingMetaTagHandler.java:120)
at javax.faces.view.facelets.CompositeFaceletHandler.apply(CompositeFaceletHandler.java:98)
at com.sun.faces.facelets.compiler.NamespaceHandler.apply(NamespaceHandler.java:93)
at javax.faces.view.facelets.CompositeFaceletHandler.apply(CompositeFaceletHandler.java:98)
at com.sun.faces.facelets.compiler.EncodingHandler.apply(EncodingHandler.java:86)
at com.sun.faces.facelets.impl.DefaultFacelet.apply(DefaultFacelet.java:152)
at com.sun.faces.application.view.FaceletViewHandlingStrategy.buildView(FaceletViewHandlingStrategy.java:769)
at com.sun.faces.lifecycle.RenderResponsePhase.execute(RenderResponsePhase.java:100)
at com.sun.faces.lifecycle.Phase.doPhase(Phase.java:101)
at com.sun.faces.lifecycle.LifecycleImpl.render(LifecycleImpl.java:139)
at javax.faces.webapp.FacesServlet.service(FacesServlet.java:410)
at org.apache.catalina.core.StandardWrapper.service(StandardWrapper.java:1534)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:281)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:175)
at org.apache.catalina.core.StandardPipeline.doInvoke(StandardPipeline.java:655)
at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:595)
at com.sun.enterprise.web.WebPipeline.invoke(WebPipeline.java:98)
at com.sun.enterprise.web.PESessionLockingStandardPipeline.invoke(PESessionLockingStandardPipeline.java:91)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:162)
at org.apache.catalina.connector.CoyoteAdapter.doService(CoyoteAdapter.java:326)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:227)
at com.sun.enterprise.v3.services.impl.ContainerMapper.service(ContainerMapper.java:170)
at com.sun.grizzly.http.ProcessorTask.invokeAdapter(ProcessorTask.java:822)
at com.sun.grizzly.http.ProcessorTask.doProcess(ProcessorTask.java:719)
at com.sun.grizzly.http.ProcessorTask.process(ProcessorTask.java:1013)
at com.sun.grizzly.http.DefaultProtocolFilter.execute(DefaultProtocolFilter.java:225)
at com.sun.grizzly.DefaultProtocolChain.executeProtocolFilter(DefaultProtocolChain.java:137)
at com.sun.grizzly.DefaultProtocolChain.execute(DefaultProtocolChain.java:104)
at com.sun.grizzly.DefaultProtocolChain.execute(DefaultProtocolChain.java:90)
at com.sun.grizzly.http.HttpProtocolChain.execute(HttpProtocolChain.java:79)
at com.sun.grizzly.ProtocolChainContextTask.doCall(ProtocolChainContextTask.java:54)
at com.sun.grizzly.SelectionKeyContextTask.call(SelectionKeyContextTask.java:59)
at com.sun.grizzly.ContextTask.run(ContextTask.java:71)
at com.sun.grizzly.util.AbstractThreadPool$Worker.doWork(AbstractThreadPool.java:532)
at com.sun.grizzly.util.AbstractThreadPool$Worker.run(AbstractThreadPool.java:513)
at java.lang.Thread.run(Thread.java:662)

更新

谢谢你的问题解决了:)

Answer 1

您需要一个自定义的Validator，当复选框包含太多选中的项目时，它会抛出一个ValidatorException。这个Validator 需要附加到复选框组件，并且应该在视图中的某处可以显示验证错误的<h:message> 或<h:messages> 组件。

ajax 事件错误。在下拉列表中，您想挂接change 事件。在复选框或单选按钮内，您想挂上click 事件。当您将 event 属性保留为默认值时，这两者已经是默认值。每个组件应该依次提交自己和另一个组件，最后重新渲染消息组件以反映验证错误。

为了在自定义验证器中计算选定的下拉值，最简洁的方法是将整个下拉组件设置为复选框组件的自定义属性。这可以通过binding 属性将下拉列表绑定到视图并在复选框内指定为<f:attribute> 的值来实现。然后可以在自定义验证器中获取下拉组件及其值。

总之，下面的启动示例应该可以工作（请注意，我使用 <f:ajax> 作为 <p:ajax> 在这种特殊情况下没有增加任何额外的优势，我承认我无法从头顶告诉我如何以及是否会起作用）：

<h:selectOneMenu id="chartType" binding="#{chartType}" value="#{bean.chartType}">
    <f:selectItem itemValue="PieChart" itemLabel="PieChart" />
    <f:selectItem itemValue="BarChart" itemLabel="BarChart" />
    <f:ajax execute="chartType checkbox" render="checkboxmessage" />
</h:selectOneMenu>
<h:selectManyCheckbox id="checkbox" value="#{bean.selectedItemscheckbox}">
    <f:selectItem itemValue="priority" itemLabel="By priority" />
    <f:selectItem itemValue="project" itemLabel="By project" />
    <f:selectItem itemValue="issuetype" itemLabel="By IssueType" />
    <f:selectItem itemValue="group" itemLabel="By group" />
    <f:validator validatorId="myCheckboxValidator" />
    <f:attribute name="chartType" value="#{chartType}" />
    <f:ajax execute="chartType checkbox" render="checkboxmessage" />
</h:selectManyCheckbox>
<h:message id="checkboxmessage" for="checkbox" />

有

@FacesValidator("myCheckboxValidator")
public class MyCheckboxValidator implements Validator {

    @Override
    public void validate(FacesContext context, UIComponent component, Object value) throws ValidatorException {
        UIInput chartTypeComponent = (UIInput) component.getAttributes().get("chartType");
        String chartType = (String) chartTypeComponent.getValue();
        List<String> selectedItemscheckbox = (List<String>) value;

        if ("PieChart".equals(chartType) && selectedItemscheckbox.size() > 1) {
            throw new ValidatorException(new FacesMessage("Max 1 item allowed"));
        }
        else if ("BarChart".equals(chartType) && selectedItemscheckbox.size() > 2) {
            throw new ValidatorException(new FacesMessage("Max 2 items allowed"));
        }
    }

}

请注意，我假设 #{bean.selectedItemscheckbox} 是 List<String>。如果它实际上是String[]，那么您需要相应地更改验证器代码。