使用Custom ViewHandler时抛出NullPointerException

时间：2012-03-06 18:29:09

标签： jsf-2 glassfish-3

我正在尝试在我的应用程序中使用自定义ViewHandler，该应用程序使用JSF2，PrimeFaces 3.2.x构建并部署在Glassfish AS v3.1.1上。一旦我在faces-config.xml中添加了自定义ViewHandler，第一页就可以正常呈现，但任何操作都会导致NPE。我修改了我的ViewHandler，所以除了代理父ViewHandler之外什么也没做，但问题仍然存在。

CustomViewHandler的代码

import java.io.IOException;
import java.util.Locale;
import javax.faces.FacesException;
import javax.faces.application.ViewHandler;
import javax.faces.component.UIViewRoot;
import javax.faces.context.FacesContext;

public class CustomViewHandler extends ViewHandler {
    private ViewHandler parent;

    public CustomViewHandler(ViewHandler parent) {
        this.parent = parent;
    }

    @Override
    public UIViewRoot restoreView(FacesContext facesContext, String viewId) {
        return parent.restoreView(facesContext, viewId);
    }

    @Override
    public Locale calculateLocale(FacesContext facesContext) {
        return parent.calculateLocale(facesContext);
    }

    @Override
    public String calculateRenderKitId(FacesContext facesContext) {
        return parent.calculateRenderKitId(facesContext);
    }

    @Override
    public UIViewRoot createView(FacesContext facesContext, String viewId) {
        return parent.createView(facesContext, viewId);
    }

    @Override
    public String getActionURL(FacesContext facesContext, String actionId) {
        return parent.getActionURL(facesContext, actionId);
    }

    @Override
    public String getResourceURL(FacesContext facesContext, String resId) {
        return parent.getResourceURL(facesContext, resId);
    }

    @Override
    public void renderView(FacesContext facesContext, UIViewRoot viewId) throws IOException, FacesException {
        parent.renderView(facesContext, viewId);

    }

    @Override
    public void writeState(FacesContext facesContext) throws IOException {
        parent.writeState(facesContext);
    }

    public ViewHandler getParent() {
        return parent;
    }
}

我的faces-config.xml 

<application>
    <view-handler>com.util.CustomViewHandler</view-handler>
    <message-bundle>messages</message-bundle>
    <locale-config>
        <default-locale>en</default-locale>
        <supported-locale>en</supported-locale>
    </locale-config>
    <resource-bundle>
       <base-name>messages</base-name>
       <var>msg</var>
     </resource-bundle>
</application>

堆栈跟踪

java.lang.NullPointerException
at javax.faces.component.UIComponentBase.getRenderer(UIComponentBase.java:1402)
at javax.faces.component.UIComponentBase.decode(UIComponentBase.java:785)
at javax.faces.component.UIComponentBase.processDecodes(UIComponentBase.java:1181)
at javax.faces.component.UIComponentBase.processDecodes(UIComponentBase.java:1176)
at javax.faces.component.UIComponentBase.processDecodes(UIComponentBase.java:1176)
at javax.faces.component.UIViewRoot.processDecodes(UIViewRoot.java:933)
at com.sun.faces.lifecycle.ApplyRequestValuesPhase.execute(ApplyRequestValuesPhase.java:78)
at com.sun.faces.lifecycle.Phase.doPhase(Phase.java:101)
at com.sun.faces.lifecycle.LifecycleImpl.execute(LifecycleImpl.java:118)
at javax.faces.webapp.FacesServlet.service(FacesServlet.java:593)
at org.apache.catalina.core.StandardWrapper.service(StandardWrapper.java:1539)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:343)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:217)
at org.primefaces.webapp.filter.FileUploadFilter.doFilter(FileUploadFilter.java:79)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:256)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:217)
at com.seer.filter.CharacterEncodingFilter.doFilter(CharacterEncodingFilter.java:21)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:256)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:217)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:279)
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:330)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:231)
at com.sun.enterprise.v3.services.impl.ContainerMapper.service(ContainerMapper.java:232)
at com.sun.grizzly.http.ProcessorTask.invokeAdapter(ProcessorTask.java:828)
at com.sun.grizzly.http.ProcessorTask.doProcess(ProcessorTask.java:725)
at com.sun.grizzly.http.ProcessorTask.process(ProcessorTask.java:1019)
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:722)

由于

1 个答案:

答案 0 :(得分：2)

我遇到了同样的错误，但是通过扩展ViewHandlerWrapper而不是ViewHandler来解决错误。

以下是我CustomViewHandler的示例（不是一个完整的示例，但是在我们的应用程序中构建为概念证明）：

import javax.faces.application.ViewExpiredException;
import javax.faces.application.ViewHandler;
import javax.faces.application.ViewHandlerWrapper;
import javax.faces.component.UIViewRoot;
import javax.faces.context.FacesContext;

import org.apache.log4j.Logger;

public class CustomViewHandler extends ViewHandlerWrapper {

    private ViewHandler wrapped;
    private static Logger LOGGER = Logger.getLogger(CustomViewHandler.class);

    public CustomViewHandler(ViewHandler wrapped) {
        LOGGER.info("CustomViewHandler.CustomViewHandler():wrapped View Handler:"+wrapped.getClass());
        this.wrapped = wrapped;
    }

    @Override
    public UIViewRoot restoreView(FacesContext context, String viewId) {
        UIViewRoot root;
        try {
            LOGGER.info("restoring view : " + viewId);
            root = wrapped.restoreView(context, viewId);
        } catch (ViewExpiredException e) {
            LOGGER.error("View Expired : " + e.getMessage() + " -> recreating");
            root = wrapped.createView(context, viewId);
        }
        return root;
    }

    @Override
    public ViewHandler getWrapped() {
        return wrapped;
    }
}

如果您想要一个更完整且功能更强的自定义视图处理程序，请查看OmniFaces RestorableViewHandler。源代码可在该页面上找到。

来自Java Doc

  

javax.faces.application.ViewHandlerWrapper

     

提供ViewHandler的简单实现，可以由希望为现有ViewHandler实例提供专门行为的开发人员进行子类化。所有方法的默认实现是调用包装的ViewHandler。

     

用法：扩展此类并覆盖getWrapped以返回我们正在包装的实例。

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