java.lang.IllegalStateException: java.lang.InstantiationExce

给定以下标签处理程序类

public final class ViewParamValidationFailed extends TagHandler implements ComponentSystemEventListener
{
    private final String redirect;
    public ViewParamValidationFailed(TagConfig config) {
        super(config);
        redirect = getRequiredAttribute("redirect").getValue();
    }
    @Override
    public void apply(FaceletContext context, UIComponent parent) throws IOException {
        if (parent instanceof UIViewRoot && !context.getFacesContext().isPostback()) {
            ((UIViewRoot) parent).subscribeToEvent(PostValidateEvent.class, this);
        }
    }
    @Override
    public void processEvent(ComponentSystemEvent event) throws AbortProcessingException {
        FacesContext context = FacesContext.getCurrentInstance();
        if (context.isValidationFailed()) {
            try {
                ExternalContext externalContext = context.getExternalContext();
                externalContext.redirect(externalContext.getRequestContextPath() + redirect);
            }
            catch (IOException e) {
                throw new AbortProcessingException(e);
            }
        }
    }
}

标签处理程序只是为了在转换失败时重定向到一个页面。

在XHTML页面上的用法如下:

<?xml version='1.0' encoding='UTF-8' ?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml"
      xmlns:h="http://xmlns.jcp.org/jsf/html"
      xmlns:p="http://primefaces.org/ui"
      xmlns:my="http://example.com/ui"
      xmlns:f="http://xmlns.jcp.org/jsf/core">
    <h:head>
        <title>Test</title>
    </h:head>
    <h:body>
        <f:metadata>
            <f:viewParam name="id" required="true" value="#{testManagedBean.id}"/>
            <my:viewParamValidationFailed redirect="/public_resources/PageNotFound.jsf"/>
        </f:metadata>
        <h:form id="form" prependId="true">
            <p:commandButton value="Submit" actionListener="#{testManagedBean.submitAction}"/>
        </h:form>
    </h:body>
</html>

我们可以为<f:viewParam>设置一个可选的转换器属性，就像converter="javax.faces.Long"

一样

_{在现实中，存在<f:metadata>包在<ui:define name="metaData">内的模板}

关联的JSF托管bean:

@ManagedBean
@RequestScoped
public final class TestManagedBean
{
    private Long id; // Getter and setter.
    public TestManagedBean() {}
    public void submitAction() {
        System.out.println("submitAction() called.");
    }
}

当给定的<p:commandButton>被按下时，抛出以下异常:

SEVERE:   java.lang.IllegalStateException: java.lang.InstantiationException: tags.ViewParamValidationFailed
    at javax.faces.component.StateHolderSaver.restore(StateHolderSaver.java:153)
    at javax.faces.component.UIComponent$ComponentSystemEventListenerAdapter.restoreState(UIComponent.java:2633)
    at javax.faces.component.StateHolderSaver.restore(StateHolderSaver.java:165)
    at javax.faces.component.UIComponentBase.restoreAttachedState(UIComponentBase.java:1793)
    at javax.faces.component.UIComponentBase.restoreSystemEventListeners(UIComponentBase.java:1911)
    at javax.faces.component.UIComponentBase.restoreState(UIComponentBase.java:1607)
    at javax.faces.component.UIViewRoot.restoreState(UIViewRoot.java:1771)
    at com.sun.faces.application.view.FaceletPartialStateManagementStrategy$2.visit(FaceletPartialStateManagementStrategy.java:380)
    at com.sun.faces.component.visit.FullVisitContext.invokeVisitCallback(FullVisitContext.java:151)
    at javax.faces.component.UIComponent.visitTree(UIComponent.java:1690)
    at com.sun.faces.application.view.FaceletPartialStateManagementStrategy.restoreView(FaceletPartialStateManagementStrategy.java:367)
    at com.sun.faces.application.StateManagerImpl.restoreView(StateManagerImpl.java:138)
    at com.sun.faces.application.view.ViewHandlingStrategy.restoreView(ViewHandlingStrategy.java:123)
    at com.sun.faces.application.view.FaceletViewHandlingStrategy.restoreView(FaceletViewHandlingStrategy.java:590)
    at com.sun.faces.application.view.MultiViewHandler.restoreView(MultiViewHandler.java:150)
    at javax.faces.application.ViewHandlerWrapper.restoreView(ViewHandlerWrapper.java:353)
    at org.omnifaces.viewhandler.RestorableViewHandler.restoreView(RestorableViewHandler.java:66)
    at javax.faces.application.ViewHandlerWrapper.restoreView(ViewHandlerWrapper.java:353)
    at com.sun.faces.lifecycle.RestoreViewPhase.execute(RestoreViewPhase.java:197)
    at com.sun.faces.lifecycle.Phase.doPhase(Phase.java:101)
    at com.sun.faces.lifecycle.RestoreViewPhase.doPhase(RestoreViewPhase.java:121)
    at com.sun.faces.lifecycle.LifecycleImpl.execute(LifecycleImpl.java:198)
    at javax.faces.webapp.FacesServlet.service(FacesServlet.java:646)
    at org.apache.catalina.core.StandardWrapper.service(StandardWrapper.java:1682)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:344)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:214)
    at org.primefaces.webapp.filter.FileUploadFilter.doFilter(FileUploadFilter.java:70)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:256)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:214)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:316)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:160)
    at org.apache.catalina.core.StandardPipeline.doInvoke(StandardPipeline.java:734)
    at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:673)
    at com.sun.enterprise.web.WebPipeline.invoke(WebPipeline.java:99)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:174)
    at org.apache.catalina.connector.CoyoteAdapter.doService(CoyoteAdapter.java:357)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:260)
    at com.sun.enterprise.v3.services.impl.ContainerMapper.service(ContainerMapper.java:188)
    at org.glassfish.grizzly.http.server.HttpHandler.runService(HttpHandler.java:191)
    at org.glassfish.grizzly.http.server.HttpHandler.doHandle(HttpHandler.java:168)
    at org.glassfish.grizzly.http.server.HttpServerFilter.handleRead(HttpServerFilter.java:189)
    at org.glassfish.grizzly.filterchain.ExecutorResolver$9.execute(ExecutorResolver.java:119)
    at org.glassfish.grizzly.filterchain.DefaultFilterChain.executeFilter(DefaultFilterChain.java:288)
    at org.glassfish.grizzly.filterchain.DefaultFilterChain.executeChainPart(DefaultFilterChain.java:206)
    at org.glassfish.grizzly.filterchain.DefaultFilterChain.execute(DefaultFilterChain.java:136)
    at org.glassfish.grizzly.filterchain.DefaultFilterChain.process(DefaultFilterChain.java:114)
    at org.glassfish.grizzly.ProcessorExecutor.execute(ProcessorExecutor.java:77)
    at org.glassfish.grizzly.nio.transport.TCPNIOTransport.fireIOEvent(TCPNIOTransport.java:838)
    at org.glassfish.grizzly.strategies.AbstractIOStrategy.fireIOEvent(AbstractIOStrategy.java:113)
    at org.glassfish.grizzly.strategies.WorkerThreadIOStrategy.run0(WorkerThreadIOStrategy.java:115)
    at org.glassfish.grizzly.strategies.WorkerThreadIOStrategy.access$100(WorkerThreadIOStrategy.java:55)
    at org.glassfish.grizzly.strategies.WorkerThreadIOStrategy$WorkerThreadRunnable.run(WorkerThreadIOStrategy.java:135)
    at org.glassfish.grizzly.threadpool.AbstractThreadPool$Worker.doWork(AbstractThreadPool.java:564)
    at org.glassfish.grizzly.threadpool.AbstractThreadPool$Worker.run(AbstractThreadPool.java:544)
    at java.lang.Thread.run(Thread.java:722)
Caused by: java.lang.InstantiationException: tags.ViewParamValidationFailed
    at java.lang.Class.newInstance0(Class.java:357)
    at java.lang.Class.newInstance(Class.java:325)
    at javax.faces.component.StateHolderSaver.restore(StateHolderSaver.java:150)
    ... 54 more

这个标签处理程序应该只与<f:viewParam>相关联，并且应该完全跳过，例如，当进行回发时。

有解决办法吗?

至关重要:

在apply()方法内部的条件检查中，

if (parent instanceof UIViewRoot && !context.getFacesContext().isPostback()) {
    System.out.println("Inside if");
    ((UIViewRoot) parent).subscribeToEvent(PostValidateEvent.class, this);
}

当给定的按钮被单击时，这个条件被评估为false，因为很明显。因此，应该不会有任何问题。

令人惊讶的是，当if语句中唯一的一行被删除时，异常消失了，如下所示。

if (parent instanceof UIViewRoot && !context.getFacesContext().isPostback()) {
    //Debug statements only.
}

在本例中，当给定的<p:commandButton>被按下时，尽管条件被求值为false，但它不会抛出如上所述的异常。

从未见过这种情况

默认情况下，JSF序列化视图中任何<h:form>(作为<input type="hidden" name="javax.faces.ViewState">)的视图状态(组件树状态)。这将在该表单上的回发请求的恢复视图阶段恢复。JSF视图状态覆盖了树中组件的组件系统事件监听器。

这条线

((UIViewRoot) parent).subscribeToEvent(PostValidateEvent.class, this);

为UIViewRoot组件添加一个，然后需要序列化。

你有4个选项:

让它实现Serializable。
让它实现Externalizable。
当监听器完成它的工作时取消订阅。
用SystemEventListener代替ComponentSystemEventListener

在这种特殊情况下，只要您不需要在单个<f:viewParam>中支持标记嵌套，而只在<f:metadata>中支持，那么选项4应该足够了。用SystemEventListener代替ComponentSystemEventListener接口，实现isListenerForSource()方法只对UIViewRoot返回true，最后用UIViewRoot#subscribeToViewEvent()代替订阅侦听器。

public final class ViewParamValidationFailed extends TagHandler implements SystemEventListener {
    private final String redirect;
    public ViewParamValidationFailed(TagConfig config) {
        super(config);
        redirect = getRequiredAttribute("redirect").getValue();
    }
    @Override
    public void apply(FaceletContext context, UIComponent parent) throws IOException {
        if (parent instanceof UIViewRoot && !context.getFacesContext().isPostback()) {
            ((UIViewRoot) parent).subscribeToViewEvent(PostValidateEvent.class, this);
        }
    }
    @Override
    public boolean isListenerForSource(Object source) {
        return source instanceof UIViewRoot;
    }
    @Override
    public void processEvent(SystemEvent event) throws AbortProcessingException {
        FacesContext context = FacesContext.getCurrentInstance();
        if (context.isValidationFailed()) {
            try {
                ExternalContext externalContext = context.getExternalContext();
                externalContext.redirect(externalContext.getRequestContextPath() + redirect);
            }
            catch (IOException e) {
                throw new AbortProcessingException(e);
            }
        }
    }
}

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