在JSF 2.2中，从请求范围更改为视图范围会导致ManagedBeanResolver错误

我正在从Myfaces 1.2升级到Myfaces 2.2

我遇到了一个问题，当bean值由于重新初始化bean而丢失时。所以我尝试将bean的作用域从请求作用域更改为视图作用域，但我发现了以下错误

控制台中的错误：-

java.lang.NullPointerException
    at org.apache.myfaces.el.unified.resolver.ManagedBeanResolver$5.put(ManagedBeanResolver.java:101) [myfaces-impl-2.2.2.jar]
    at org.apache.myfaces.el.unified.resolver.ManagedBeanResolver.putInScope(ManagedBeanResolver.java:367) [myfaces-impl-2.2.2.jar]
    at org.apache.myfaces.el.unified.resolver.ManagedBeanResolver.createManagedBean(ManagedBeanResolver.java:340) [myfaces-impl-2.2.2.jar]
    at org.apache.myfaces.el.unified.resolver.ManagedBeanResolver.getValue(ManagedBeanResolver.java:296) [myfaces-impl-2.2.2.jar]
    at javax.el.CompositeELResolver.getValue(CompositeELResolver.java:67) [el-api.jar:2.2.FR]
    at org.apache.myfaces.el.unified.resolver.FacesCompositeELResolver.getValue(FacesCompositeELResolver.java:179) [myfaces-impl-2.2.2.jar]
    at org.apache.el.parser.AstIdentifier.getValue(AstIdentifier.java:72) [jasper-el.jar:7.0.39]
    at org.apache.el.ValueExpressionImpl.getValue(ValueExpressionImpl.java:185) [jasper-el.jar:7.0.39]

    at org.apache.myfaces.lifecycle.PhaseListenerManager.informPhaseListenersBefore(PhaseListenerManager.java:77) [myfaces-impl-2.2.2.jar]
    at org.apache.myfaces.lifecycle.LifecycleImpl.executePhase(LifecycleImpl.java:184) [myfaces-impl-2.2.2.jar]
    at org.apache.myfaces.lifecycle.LifecycleImpl.execute(LifecycleImpl.java:143) [myfaces-impl-2.2.2.jar]
    at javax.faces.webapp.FacesServlet.service(FacesServlet.java:198) [myfaces-api-2.2.2.jar]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:305) [catalina.jar:7.0.39]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210) [catalina.jar:7.0.39]
    at org.apache.myfaces.webapp.filter.ExtensionsFilter.doFilter(ExtensionsFilter.java:349) [tomahawk20-1.1.10.jar]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:243) [catalina.jar:7.0.39]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210) [catalina.jar:7.0.39]
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:222) [catalina.jar:7.0.39]
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:123) [catalina.jar:7.0.39]
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:472) [catalina.jar:7.0.39]
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:171) [catalina.jar:7.0.39]
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:99) [catalina.jar:7.0.39]
    at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:947) [catalina.jar:7.0.39]
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118) [catalina.jar:7.0.39]
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:408) [catalina.jar:7.0.39]
    at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1009) [tomcat-coyote.jar:7.0.39]
    at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:589) [tomcat-coyote.jar:7.0.39]
    at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:310) [tomcat-coyote.jar:7.0.39]
    at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886) [1.6.0_35]
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908) [1.6.0_35]
    at java.lang.Thread.run(Thread.java:662) [1.6.0_35]

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如果您试图从视图范围bean访问数据，请尝试通过调用页面预呈现事件上的方法来加载包含数据的bean。

看起来您试图在创建视图之前访问视图范围bean，这是无效的。从请求范围更改为查看范围将没有帮助。您需要以另一种方式解决最初的问题。当我在请求范围内使用JSF1.2时，应用程序运行良好。只是在升级之后，我开始面临问题snd，然后我改为查看范围。查看范围和请求范围不一样，所以你不应该做那个更改。我知道它们不一样，但随着bean值丢失，我尝试增加要查看的范围。您应该使用一个bean来存储视图范围中的值，使用另一个bean来处理请求范围逻辑，在本例中是绑定到phase listener方法。这样就行了。