托管bean的托管bean类java.time.ZonedDateTime managedBean不声明公共无参数构造函数

时间：2016-01-18 11:11:16

标签： jsf managed-bean java-time faces-config

为了获得当前日期，我在faces-config.xml中声明了一个托管bean，如下所示。

<managed-bean>
    <managed-bean-name>currentDate</managed-bean-name>
    <managed-bean-class>java.time.ZonedDateTime</managed-bean-class>
    <managed-bean-scope>request</managed-bean-scope>
</managed-bean>

早些时候，我一直在使用org.joda.time.DateTime并且工作正常。这个bean可以在EL中访问，就像下面这样。

<h:outputText value="#{currentDate}" converter="#{converter}"/>

然而，这会导致抛出以下异常。

16:15:29,984 SEVERE [javax.enterprise.resource.webcontainer.jsf.application] (default task-16) Error Rendering View[/admin_side/Home.xhtml]: com.sun.faces.mgbean.ManagedBeanCreationException: Unable to create managed bean currentDate.  The following problems were found:
     - Managed bean class java.time.ZonedDateTime for managed bean currentDate doesnt declare a public no-argument constructor.
    at com.sun.faces.mgbean.BeanManager.create(BeanManager.java:265)
    at com.sun.faces.el.ManagedBeanELResolver.resolveBean(ManagedBeanELResolver.java:257)
    at com.sun.faces.el.ManagedBeanELResolver.getValue(ManagedBeanELResolver.java:117)
    at com.sun.faces.el.DemuxCompositeELResolver._getValue(DemuxCompositeELResolver.java:176)
    at com.sun.faces.el.DemuxCompositeELResolver.getValue(DemuxCompositeELResolver.java:203)
    at com.sun.el.parser.AstIdentifier.getValue(AstIdentifier.java:116)
    at com.sun.el.ValueExpressionImpl.getValue(ValueExpressionImpl.java:226)
    at org.jboss.weld.el.WeldValueExpression.getValue(WeldValueExpression.java:50)
    at org.jboss.weld.el.WeldValueExpression.getValue(WeldValueExpression.java:50)
    at com.sun.faces.facelets.el.TagValueExpression.getValue(TagValueExpression.java:109)
    at javax.faces.component.ComponentStateHelper.eval(ComponentStateHelper.java:194)
    at javax.faces.component.ComponentStateHelper.eval(ComponentStateHelper.java:182)
    at javax.faces.component.UIOutput.getValue(UIOutput.java:174)
    at com.sun.faces.renderkit.html_basic.HtmlBasicInputRenderer.getValue(HtmlBasicInputRenderer.java:205)
    at com.sun.faces.renderkit.html_basic.HtmlBasicRenderer.getCurrentValue(HtmlBasicRenderer.java:355)
    at com.sun.faces.renderkit.html_basic.HtmlBasicRenderer.encodeEnd(HtmlBasicRenderer.java:164)
    at javax.faces.component.UIComponentBase.encodeEnd(UIComponentBase.java:920)
    at javax.faces.component.UIComponent.encodeAll(UIComponent.java:1863)
    at javax.faces.render.Renderer.encodeChildren(Renderer.java:176)
    at javax.faces.component.UIComponentBase.encodeChildren(UIComponentBase.java:890)
    at com.sun.faces.renderkit.html_basic.HtmlBasicRenderer.encodeRecursive(HtmlBasicRenderer.java:304)
    at com.sun.faces.renderkit.html_basic.HtmlBasicRenderer.encodeRecursive(HtmlBasicRenderer.java:309)
    at com.sun.faces.renderkit.html_basic.GroupRenderer.encodeChildren(GroupRenderer.java:114)
    at javax.faces.component.UIComponentBase.encodeChildren(UIComponentBase.java:890)
    at javax.faces.component.UIComponent.encodeAll(UIComponent.java:1856)
    at javax.faces.component.UIComponent.encodeAll(UIComponent.java:1859)
    at javax.faces.component.UIComponent.encodeAll(UIComponent.java:1859)
    at com.sun.faces.application.view.FaceletViewHandlingStrategy.renderView(FaceletViewHandlingStrategy.java:458)
    at com.sun.faces.application.view.MultiViewHandler.renderView(MultiViewHandler.java:134)
    at javax.faces.application.ViewHandlerWrapper.renderView(ViewHandlerWrapper.java:337)
    at javax.faces.application.ViewHandlerWrapper.renderView(ViewHandlerWrapper.java:337)
    at javax.faces.application.ViewHandlerWrapper.renderView(ViewHandlerWrapper.java:337)
    at javax.faces.application.ViewHandlerWrapper.renderView(ViewHandlerWrapper.java:337)
    at com.sun.faces.lifecycle.RenderResponsePhase.execute(RenderResponsePhase.java:120)
    at com.sun.faces.lifecycle.Phase.doPhase(Phase.java:101)
    at com.sun.faces.lifecycle.LifecycleImpl.render(LifecycleImpl.java:219)
    at javax.faces.webapp.FacesServlet.service(FacesServlet.java:659)
    at io.undertow.servlet.handlers.ServletHandler.handleRequest(ServletHandler.java:86)
    at io.undertow.servlet.handlers.FilterHandler$FilterChainImpl.doFilter(FilterHandler.java:130)
    at org.primefaces.webapp.filter.FileUploadFilter.doFilter(FileUploadFilter.java:78)
    at io.undertow.servlet.core.ManagedFilter.doFilter(ManagedFilter.java:60)
    at io.undertow.servlet.handlers.FilterHandler$FilterChainImpl.doFilter(FilterHandler.java:132)
    at io.undertow.websockets.jsr.JsrWebSocketFilter.doFilter(JsrWebSocketFilter.java:151)
    at io.undertow.servlet.core.ManagedFilter.doFilter(ManagedFilter.java:60)
    at io.undertow.servlet.handlers.FilterHandler$FilterChainImpl.doFilter(FilterHandler.java:132)
    at org.omnifaces.facesviews.FacesViewsForwardingFilter.filterExtensionLess(FacesViewsForwardingFilter.java:128)
    at org.omnifaces.facesviews.FacesViewsForwardingFilter.doFilter(FacesViewsForwardingFilter.java:89)
    at org.omnifaces.filter.HttpFilter.doFilter(HttpFilter.java:108)
    at io.undertow.servlet.core.ManagedFilter.doFilter(ManagedFilter.java:60)
    at io.undertow.servlet.handlers.FilterHandler$FilterChainImpl.doFilter(FilterHandler.java:132)
    at filter.NoCacheFilter.doFilter(NoCacheFilter.java:33)
    at io.undertow.servlet.core.ManagedFilter.doFilter(ManagedFilter.java:60)
    at io.undertow.servlet.handlers.FilterHandler$FilterChainImpl.doFilter(FilterHandler.java:132)
    at org.omnifaces.filter.CharacterEncodingFilter.doFilter(CharacterEncodingFilter.java:122)
    at org.omnifaces.filter.HttpFilter.doFilter(HttpFilter.java:108)
    at io.undertow.servlet.core.ManagedFilter.doFilter(ManagedFilter.java:60)
    at io.undertow.servlet.handlers.FilterHandler$FilterChainImpl.doFilter(FilterHandler.java:132)
    at io.undertow.servlet.handlers.FilterHandler.handleRequest(FilterHandler.java:85)
    at io.undertow.servlet.handlers.security.ServletSecurityRoleHandler.handleRequest(ServletSecurityRoleHandler.java:62)
    at io.undertow.servlet.handlers.ServletDispatchingHandler.handleRequest(ServletDispatchingHandler.java:36)
    at org.wildfly.extension.undertow.security.SecurityContextAssociationHandler.handleRequest(SecurityContextAssociationHandler.java:78)
    at io.undertow.server.handlers.PredicateHandler.handleRequest(PredicateHandler.java:43)
    at io.undertow.servlet.handlers.security.SSLInformationAssociationHandler.handleRequest(SSLInformationAssociationHandler.java:131)
    at io.undertow.servlet.handlers.security.ServletAuthenticationCallHandler.handleRequest(ServletAuthenticationCallHandler.java:57)
    at io.undertow.server.handlers.DisableCacheHandler.handleRequest(DisableCacheHandler.java:33)
    at io.undertow.server.handlers.PredicateHandler.handleRequest(PredicateHandler.java:43)
    at io.undertow.security.handlers.AuthenticationConstraintHandler.handleRequest(AuthenticationConstraintHandler.java:51)
    at io.undertow.security.handlers.AbstractConfidentialityHandler.handleRequest(AbstractConfidentialityHandler.java:46)
    at io.undertow.servlet.handlers.security.ServletConfidentialityConstraintHandler.handleRequest(ServletConfidentialityConstraintHandler.java:64)
    at io.undertow.servlet.handlers.security.ServletSecurityConstraintHandler.handleRequest(ServletSecurityConstraintHandler.java:56)
    at io.undertow.security.handlers.AuthenticationMechanismsHandler.handleRequest(AuthenticationMechanismsHandler.java:58)
    at io.undertow.servlet.handlers.security.CachedAuthenticatedSessionHandler.handleRequest(CachedAuthenticatedSessionHandler.java:72)
    at io.undertow.security.handlers.NotificationReceiverHandler.handleRequest(NotificationReceiverHandler.java:50)
    at io.undertow.security.handlers.SecurityInitialHandler.handleRequest(SecurityInitialHandler.java:76)
    at io.undertow.server.handlers.PredicateHandler.handleRequest(PredicateHandler.java:43)
    at org.wildfly.extension.undertow.security.jacc.JACCContextIdHandler.handleRequest(JACCContextIdHandler.java:61)
    at io.undertow.server.handlers.PredicateHandler.handleRequest(PredicateHandler.java:43)
    at io.undertow.server.handlers.PredicateHandler.handleRequest(PredicateHandler.java:43)
    at io.undertow.servlet.handlers.ServletInitialHandler.handleFirstRequest(ServletInitialHandler.java:282)
    at io.undertow.servlet.handlers.ServletInitialHandler.dispatchRequest(ServletInitialHandler.java:261)
    at io.undertow.servlet.handlers.ServletInitialHandler.access$000(ServletInitialHandler.java:80)
    at io.undertow.servlet.handlers.ServletInitialHandler$1.handleRequest(ServletInitialHandler.java:172)
    at io.undertow.server.Connectors.executeRootHandler(Connectors.java:199)
    at io.undertow.server.HttpServerExchange$1.run(HttpServerExchange.java:774)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
    at java.lang.Thread.run(Thread.java:745)

他们称他们为Value-based Classes。因此，这些类是不可变的，因此没有公共无参数构造函数，例外。

具体问题不需要整个参考。

  

某些类，例如java.util.Optional和   java.time.LocalDateTime，是基于价值的。基于价值的实例   类：

     
      
  • 是final和immutable （尽管可能包含对可变对象的引用）;实现equals()，hashCode()，   和toString()仅由实例的状态计算   而不是来自其身份或任何其他物体的状态或   变量;
    •   
  • 不使用身份敏感操作，例如实例之间的引用相等性（==），实例的身份哈希代码，或者   实例的内部锁定同步;
    •   
  • 仅基于equals()被视为相等，不基于引用相等（==）;
    •   
  • 没有可访问的构造函数，而是通过工厂方法实例化，而工厂方法没有做出任何承诺   返回实例的身份;
    •   
  • 在相等时可自由替换，这意味着根据x交换任意两个y和equals()实例   任何计算或方法调用都不应该产生可见的   改变行为。
    •   
     

如果尝试，程序可能会产生不可预测的结果   将两个引用区分为基于值的类的相等值，   是直接通过参考平等还是间接通过上诉   同步，身份哈希，序列化或任何其他   身份敏感机制。使用此类身份敏感   对基于值的类的实例的操作可能具有不可预测性   效果，应该避免。

救援是什么，转向java.util.Date / java.util.Calendar？

在WildFly 9.0.2 final中使用Mojarra 2.2.12。

1 个答案:

答案 0 :(得分：4)

不幸的是，这确实是一种技术限制，无法通过“老式”<managed-bean>方法解决。

鉴于JSF bean管理可能会在未来的Java EE版本中被弃用而不赞成使用CDI，并且您使用WildFly实际运行支持CDI的容器，您最好转向CDI方法。在CDI中，这可以通过所谓的producer来实现。 

@RequestScoped
public class CurrentDateProducer {

    @Produces
    @Named
    public ZonedDateTime getCurrentDate() {
        return ZonedDateTime.now();
    }

}

它将以#{currentDate}的预期方式提供。

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