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java - 弄清楚为什么当我不希望调用 JSF getter 时会调用它们

转载 作者：太空宇宙 更新时间：2023-11-04 08:32:59 26 4
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我正在与 jsf 2 合作我发现有些行为很难解释或理解。

我有几个独立的h:form s。

其中一个看起来像这样:

<h:form>
    <h:commandButton value="#{text.General_Wipe_Now}" action="#{bean.doThate}" >
        <f:ajax execute="@form" render="@form" />
    </h:commandButton>
    <h:selectBooleanCheckbox value="#{bean.ignoreErrors}">Ignore Errors</h:selectBooleanCheckbox>
</h:form>

我的问题是，每当我按下上述按钮时，我都会看到其他不相关的 bean 成员 getter(它们是其他形式的一部分)被调用。 (通过日志记录)

任何 getter 中都没有业务逻辑，但我想了解其原因。通过打印stacktrace我确定JSF确实是调用他们的人。

你建议我如何关注 JSF了解为什么他们被称为？可能是什么原因？

谢谢!本。

更新

这是由正在运行但不应该运行的 getter 之一打印的堆栈跟踪。正如评论中所讨论的，在这个问题中包含所有相关的细节将非常复杂，因此我宁愿获得有关工具的帮助来自己找到答案。

java.lang.Exception
    at com.aCompanyName.applicationName.beans.aBean.getSomethingFromBean(CurrentDevice.java:382)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
    at java.lang.reflect.Method.invoke(Method.java:597)
    at javax.el.BeanELResolver.getValue(BeanELResolver.java:302)
    at javax.el.CompositeELResolver.getValue(CompositeELResolver.java:175)
    at org.apache.myfaces.el.unified.resolver.FacesCompositeELResolver.getValue(FacesCompositeELResolver.java:142)
    at com.sun.el.parser.AstValue.getValue(AstValue.java:116)
    at com.sun.el.parser.AstValue.getValue(AstValue.java:163)
    at com.sun.el.ValueExpressionImpl.getValue(ValueExpressionImpl.java:219)
    at org.apache.myfaces.view.facelets.el.TagValueExpression.getValue(TagValueExpression.java:85)
    at org.apache.myfaces.view.facelets.component.UIRepeat.getValue(UIRepeat.java:248)
    at org.apache.myfaces.view.facelets.component.UIRepeat.getDataModel(UIRepeat.java:211)
    at org.apache.myfaces.view.facelets.component.UIRepeat._validateAttributes(UIRepeat.java:530)
    at org.apache.myfaces.view.facelets.component.UIRepeat.visitTree(UIRepeat.java:763)
    at javax.faces.component.UIComponent.visitTree(UIComponent.java:797)
    at javax.faces.component.UIComponentBase.visitTree(UIComponentBase.java:992)
    at javax.faces.component.UIComponent.visitTree(UIComponent.java:797)
    at javax.faces.component.UIComponentBase.visitTree(UIComponentBase.java:992)
    at javax.faces.component.UIComponent.visitTree(UIComponent.java:797)
    at javax.faces.component.UIComponentBase.visitTree(UIComponentBase.java:992)
    at javax.faces.component.UIComponent.visitTree(UIComponent.java:797)
    at javax.faces.component.UIComponentBase.visitTree(UIComponentBase.java:992)
    at javax.faces.component.UIComponent.visitTree(UIComponent.java:797)
    at javax.faces.component.UIComponentBase.visitTree(UIComponentBase.java:992)
    at javax.faces.component.UIComponent.visitTree(UIComponent.java:797)
    at javax.faces.component.UIComponentBase.visitTree(UIComponentBase.java:992)
    at javax.faces.component.UIComponent.visitTree(UIComponent.java:797)
    at javax.faces.component.UIComponentBase.visitTree(UIComponentBase.java:992)
    at javax.faces.component.UIComponent.visitTree(UIComponent.java:797)
    at javax.faces.component.UIComponentBase.visitTree(UIComponentBase.java:992)
    at javax.faces.component.UIComponent.visitTree(UIComponent.java:797)
    at javax.faces.component.UIComponentBase.visitTree(UIComponentBase.java:992)
    at javax.faces.component.UIComponent.visitTree(UIComponent.java:797)
    at javax.faces.component.UIComponentBase.visitTree(UIComponentBase.java:992)
    at javax.faces.component.UIComponent.visitTree(UIComponent.java:797)
    at javax.faces.component.UIComponentBase.visitTree(UIComponentBase.java:992)
    at javax.faces.component.UIComponent.visitTree(UIComponent.java:797)
    at javax.faces.component.UIComponentBase.visitTree(UIComponentBase.java:992)
    at org.apache.myfaces.view.facelets.tag.ui.DebugPhaseListener._doTreeVisit(DebugPhaseListener.java:310)
    at org.apache.myfaces.view.facelets.tag.ui.DebugPhaseListener.afterPhase(DebugPhaseListener.java:286)
    at org.apache.myfaces.lifecycle.PhaseListenerManager.informPhaseListenersAfter(PhaseListenerManager.java:111)
    at org.apache.myfaces.lifecycle.LifecycleImpl.executePhase(LifecycleImpl.java:185)
    at org.apache.myfaces.lifecycle.LifecycleImpl.execute(LifecycleImpl.java:118)
    at javax.faces.webapp.FacesServlet.service(FacesServlet.java:189)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191)
    at org.apache.openejb.tomcat.catalina.OpenEJBValve.invoke(OpenEJBValve.java:45)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:298)
    at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:852)
    at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:588)
    at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:489)
    at java.lang.Thread.run(Thread.java:662)

更新2

正在制作 SSCCE，一旦我有了，就会更新。

更新3

问题似乎出现在 <ui:repeat> 上值属性。这是说明问题的 SSCCE 代码:

<h:body>
    <ui:repeat var="str" value="#{admin.SList}">
        STRING: #{str}
    </ui:repeat>

    <h:form>
        <h:commandButton value="pressie" action="#{admin.doThat}">
            <f:ajax execute="@form"/>
        </h:commandButton>
    </h:form>
</h:body>

Bean 代码:

@PostConstruct
public void init()
{
    slist.add("Testing");
    slist.add("This");
    slist.add("Thing");
}

private List<String> slist = new ArrayList<String>();

public List<String> getSList(){
    logger.trace("Getting LIST");
    return slist;
}

public void doThat(){
    logger.trace("DoThat Was Run");
}

按下按钮时，将输出到日志:

2011-08-16 16:55:55,853 TRACE [http-80-2] (AdminBean.java:80) - Getting LIST
2011-08-16 16:55:55,865 TRACE [http-80-2] (AdminBean.java:85) - DoThat Was Run

为什么要运行列表？这不是多余的吗？

最佳答案

我不使用 MyFaces，所以我不会详细介绍它。但值得一提的是，在 Mojarra 上 setter/getter 也被称为 <ui:repeat> 。然而，在我看来，堆栈对于正在发生的事情更加清楚。这是Thread#dumpStack()直到FacesServlet#service() :

java.lang.Exception: Stack trace
    at java.lang.Thread.dumpStack(Thread.java:1249)
    at mypackage.Bean.getList(Bean.java:21)
    at sun.reflect.GeneratedMethodAccessor51.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
    at java.lang.reflect.Method.invoke(Method.java:597)
    at javax.el.BeanELResolver.getValue(BeanELResolver.java:302)
    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.AstValue.getValue(AstValue.java:116)
    at com.sun.el.parser.AstValue.getValue(AstValue.java:163)
    at com.sun.el.ValueExpressionImpl.getValue(ValueExpressionImpl.java:219)
    at com.sun.faces.facelets.el.TagValueExpression.getValue(TagValueExpression.java:109)
    at com.sun.faces.facelets.component.UIRepeat.getValue(UIRepeat.java:272)
    at com.sun.faces.facelets.component.UIRepeat.getDataModel(UIRepeat.java:248)
    at com.sun.faces.facelets.component.UIRepeat.setIndex(UIRepeat.java:442)
    at com.sun.faces.facelets.component.UIRepeat.doVisitChildren(UIRepeat.java:661)
    at com.sun.faces.facelets.component.UIRepeat.visitTree(UIRepeat.java:619)
    at javax.faces.component.UIComponent.visitTree(UIComponent.java:1600)
    at javax.faces.component.UIComponent.visitTree(UIComponent.java:1600)
    at com.sun.faces.application.view.StateManagementStrategyImpl.restoreView(StateManagementStrategyImpl.java:240)
    at com.sun.faces.application.StateManagerImpl.restoreView(StateManagerImpl.java:188)
    at com.sun.faces.application.view.ViewHandlingStrategy.restoreView(ViewHandlingStrategy.java:123)
    at com.sun.faces.application.view.FaceletViewHandlingStrategy.restoreView(FaceletViewHandlingStrategy.java:452)
    at com.sun.faces.application.view.MultiViewHandler.restoreView(MultiViewHandler.java:148)
    at javax.faces.application.ViewHandlerWrapper.restoreView(ViewHandlerWrapper.java:303)
    at com.sun.faces.lifecycle.RestoreViewPhase.execute(RestoreViewPhase.java:189)
    at com.sun.faces.lifecycle.Phase.doPhase(Phase.java:101)
    at com.sun.faces.lifecycle.RestoreViewPhase.doPhase(RestoreViewPhase.java:113)
    at com.sun.faces.lifecycle.LifecycleImpl.execute(LifecycleImpl.java:118)
    at javax.faces.webapp.FacesServlet.service(FacesServlet.java:409)
    // Remnant omitted for brevity.

因此，当状态管理需要访问整个组件树时，就会在恢复 View 阶段发生这种情况。 UIRepeat反过来，当要访问其子级时，需要设置行索引。

根据UIRepeat#doVisitChildren()将行索引设置为 -1 。最终目标是仅访问树中的子级，而不是迭代模型值或渲染任何内容。它只需要 DataModel为了能够设置行索引。数据模型的值是您看到正在调用 getter 的列表。如果一切正常，这个 getter 应该在恢复 View 阶段只调用一次。但是，如果它也在渲染响应阶段被调用，那么您可能会担心这一点，因为它完全没有必要。

关于java - 弄清楚为什么当我不希望调用 JSF getter 时会调用它们，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/7078477/

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