Null Pointer exception occurs when using the flash scoped value as the f:param value
2018/4/25
Codes to replicate the exception
index.xhtml
<?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:f="http://xmlns.jcp.org/jsf/core">
<h:head>
<title>index</title>
</h:head>
<h:body>
<h:form>
<h:panelGrid columns="2">
<h:outputLabel for="username" >Name: </h:outputLabel>
<h:inputText id="username" value="#{flash.username}" />
<h:outputLabel for="email" >email: </h:outputLabel>
<h:inputText id="email" value="#{flash.email}" />
<h:outputLabel for="age" >age: </h:outputLabel>
<h:inputText id="age" value="#{flash.age}" />
</h:panelGrid>
<h:commandButton value="Submit" action="confirm?faces-redirect=true" />
</h:form>
</h:body>
</html>
confirm.xhtml
<?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:f="http://xmlns.jcp.org/jsf/core"
xmlns:ui="http://xmlns.jcp.org/jsf/facelets"
xmlns:c="http://xmlns.jcp.org/jsp/jstl/core" >
<h:head>
<title>confirm</title>
<!--<link rel="stylesheet" href="http://maxcdn.bootstrapcdn.com/bootstrap/3.3.6/css/bootstrap.min.css"/>-->
</h:head>
<h:body>
<p class="text-success"> username: <h:outputText value="#{flash.keep.username}" /> </p>
<p class="text-info" > email: <h:outputText value="#{flash.keep.email}" /> </p>
<p class="text-danger"> age: <h:outputText value="#{flash.keep.age}" /> </p>
<br />
<h:link value="Confirm" outcome="done">
<f:param name="username" value="#{flash.username}" />
</h:link>
</h:body>
</html>
When clicking the Submit button in the index.xhtml, the following exception occurs:
Severe: Error Rendering View[/confirm.xhtml]
java.lang.NullPointerException
at java.net.URLEncoder.encode(URLEncoder.java:204)
at com.sun.faces.context.UrlBuilder.addValuesToParameter(UrlBuilder.java:318)
at com.sun.faces.context.UrlBuilder.addParameters(UrlBuilder.java:127)
at com.sun.faces.context.ExternalContextImpl.encodeBookmarkableURL(ExternalContextImpl.java:1055)
at com.sun.faces.application.view.MultiViewHandler.getBookmarkableURL(MultiViewHandler.java:407)
at javax.faces.application.ViewHandlerWrapper.getBookmarkableURL(ViewHandlerWrapper.java:272)
at org.jboss.weld.jsf.ConversationAwareViewHandler.getBookmarkableURL(ConversationAwareViewHandler.java:132)
at com.sun.faces.renderkit.html_basic.OutcomeTargetRenderer.getEncodedTargetURL(OutcomeTargetRenderer.java:194)
at com.sun.faces.renderkit.html_basic.OutcomeTargetLinkRenderer.renderAsActive(OutcomeTargetLinkRenderer.java:158)
at com.sun.faces.renderkit.html_basic.OutcomeTargetLinkRenderer.encodeBegin(OutcomeTargetLinkRenderer.java:96)
at javax.faces.component.UIComponentBase.encodeBegin(UIComponentBase.java:864)
at javax.faces.component.UIComponent.encodeAll(UIComponent.java:1854)
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:456)
at com.sun.faces.application.view.MultiViewHandler.renderView(MultiViewHandler.java:133)
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:647)
at org.apache.catalina.core.StandardWrapper.service(StandardWrapper.java:1682)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:318)
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:415)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:282)
at com.sun.enterprise.v3.services.impl.ContainerMapper$HttpHandlerCallable.call(ContainerMapper.java:459)
at com.sun.enterprise.v3.services.impl.ContainerMapper.service(ContainerMapper.java:167)
at org.glassfish.grizzly.http.server.HttpHandler.runService(HttpHandler.java:201)
at org.glassfish.grizzly.http.server.HttpHandler.doHandle(HttpHandler.java:175)
at org.glassfish.grizzly.http.server.HttpServerFilter.handleRead(HttpServerFilter.java:235)
at org.glassfish.grizzly.filterchain.ExecutorResolver$9.execute(ExecutorResolver.java:119)
at org.glassfish.grizzly.filterchain.DefaultFilterChain.executeFilter(DefaultFilterChain.java:284)
at org.glassfish.grizzly.filterchain.DefaultFilterChain.executeChainPart(DefaultFilterChain.java:201)
at org.glassfish.grizzly.filterchain.DefaultFilterChain.execute(DefaultFilterChain.java:133)
at org.glassfish.grizzly.filterchain.DefaultFilterChain.process(DefaultFilterChain.java:112)
at org.glassfish.grizzly.ProcessorExecutor.execute(ProcessorExecutor.java:77)
at org.glassfish.grizzly.nio.transport.TCPNIOTransport.fireIOEvent(TCPNIOTransport.java:561)
at org.glassfish.grizzly.strategies.AbstractIOStrategy.fireIOEvent(AbstractIOStrategy.java:112)
at org.glassfish.grizzly.strategies.WorkerThreadIOStrategy.run0(WorkerThreadIOStrategy.java:117)
at org.glassfish.grizzly.strategies.WorkerThreadIOStrategy.access$100(WorkerThreadIOStrategy.java:56)
at org.glassfish.grizzly.strategies.WorkerThreadIOStrategy$WorkerThreadRunnable.run(WorkerThreadIOStrategy.java:137)
at org.glassfish.grizzly.threadpool.AbstractThreadPool$Worker.doWork(AbstractThreadPool.java:565)
at org.glassfish.grizzly.threadpool.AbstractThreadPool$Worker.run(AbstractThreadPool.java:545)
at java.lang.Thread.run(Thread.java:745)
FATAL: JSF1073: java.lang.NullPointerException caught during processing of RENDER_RESPONSE 6 : UIComponent-ClientId=, Message=null
FATAL: No associated message
java.lang.NullPointerException
at java.net.URLEncoder.encode(URLEncoder.java:204)
at com.sun.faces.context.UrlBuilder.addValuesToParameter(UrlBuilder.java:318)
at com.sun.faces.context.UrlBuilder.addParameters(UrlBuilder.java:127)
at com.sun.faces.context.ExternalContextImpl.encodeBookmarkableURL(ExternalContextImpl.java:1055)
at com.sun.faces.application.view.MultiViewHandler.getBookmarkableURL(MultiViewHandler.java:407)
at javax.faces.application.ViewHandlerWrapper.getBookmarkableURL(ViewHandlerWrapper.java:272)
at org.jboss.weld.jsf.ConversationAwareViewHandler.getBookmarkableURL(ConversationAwareViewHandler.java:132)
at com.sun.faces.renderkit.html_basic.OutcomeTargetRenderer.getEncodedTargetURL(OutcomeTargetRenderer.java:194)
at com.sun.faces.renderkit.html_basic.OutcomeTargetLinkRenderer.renderAsActive(OutcomeTargetLinkRenderer.java:158)
at com.sun.faces.renderkit.html_basic.OutcomeTargetLinkRenderer.encodeBegin(OutcomeTargetLinkRenderer.java:96)
at javax.faces.component.UIComponentBase.encodeBegin(UIComponentBase.java:864)
at javax.faces.component.UIComponent.encodeAll(UIComponent.java:1854)
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:456)
at com.sun.faces.application.view.MultiViewHandler.renderView(MultiViewHandler.java:133)
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:647)
at org.apache.catalina.core.StandardWrapper.service(StandardWrapper.java:1682)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:318)
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:415)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:282)
at com.sun.enterprise.v3.services.impl.ContainerMapper$HttpHandlerCallable.call(ContainerMapper.java:459)
at com.sun.enterprise.v3.services.impl.ContainerMapper.service(ContainerMapper.java:167)
at org.glassfish.grizzly.http.server.HttpHandler.runService(HttpHandler.java:201)
at org.glassfish.grizzly.http.server.HttpHandler.doHandle(HttpHandler.java:175)
at org.glassfish.grizzly.http.server.HttpServerFilter.handleRead(HttpServerFilter.java:235)
at org.glassfish.grizzly.filterchain.ExecutorResolver$9.execute(ExecutorResolver.java:119)
at org.glassfish.grizzly.filterchain.DefaultFilterChain.executeFilter(DefaultFilterChain.java:284)
at org.glassfish.grizzly.filterchain.DefaultFilterChain.executeChainPart(DefaultFilterChain.java:201)
at org.glassfish.grizzly.filterchain.DefaultFilterChain.execute(DefaultFilterChain.java:133)
at org.glassfish.grizzly.filterchain.DefaultFilterChain.process(DefaultFilterChain.java:112)
at org.glassfish.grizzly.ProcessorExecutor.execute(ProcessorExecutor.java:77)
at org.glassfish.grizzly.nio.transport.TCPNIOTransport.fireIOEvent(TCPNIOTransport.java:561)
at org.glassfish.grizzly.strategies.AbstractIOStrategy.fireIOEvent(AbstractIOStrategy.java:112)
at org.glassfish.grizzly.strategies.WorkerThreadIOStrategy.run0(WorkerThreadIOStrategy.java:117)
at org.glassfish.grizzly.strategies.WorkerThreadIOStrategy.access$100(WorkerThreadIOStrategy.java:56)
at org.glassfish.grizzly.strategies.WorkerThreadIOStrategy$WorkerThreadRunnable.run(WorkerThreadIOStrategy.java:137)
at org.glassfish.grizzly.threadpool.AbstractThreadPool$Worker.doWork(AbstractThreadPool.java:565)
at org.glassfish.grizzly.threadpool.AbstractThreadPool$Worker.run(AbstractThreadPool.java:545)
at java.lang.Thread.run(Thread.java:745)
The problem seems at rendering the <h:link> facelet. The flash scoped value cannot be added to <f:param> and that results in URL encoding fails.
Workaround
Store the flash scoped value to request scoped bean and use the bean property as the value for <f:param>.
When you are at the confirm.xhml page, you can refresh the page (submit multiple requests). The page shows the same result because of using flash.keep to reserve the flash values for next JSF request lifecycle.
However, when you navigate back to comfirm.xhtml from done.xhtml using the Browser's previous-page button, refershing the page will result in Null Pointer exception because the flash scope has been cleared. The null value in the value attribute of f:param causes the exception.
The modified confirm.xhtml is as the following:
confirm.xhtml
<?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:f="http://xmlns.jcp.org/jsf/core"
xmlns:c="http://xmlns.jcp.org/jsp/jstl/core"
xmlns:ui="http://xmlns.jcp.org/jsf/facelets">
<h:head>
<title>Facelet Title</title>
</h:head>
<h:body>
<ui:debug hotkey="x" />
<c:set target="#{login}" property="username" value="#{flash.keep.uname}" />
<c:set target="#{login}" property="email" value="#{flash.keep.email}" />
<c:set target="#{login}" property="age" value="#{flash.keep.age}" />
<p> username: <h:outputText value="#{login.username}" /> </p>
<p> email: <h:outputText value="#{login.email}" /> </p>
<p> age: <h:outputText value="#{login.age}" /> </p>
<br />
<h:link outcome="done" value="Confirm">
<f:param name="username" value="#{login.username}" />
<f:param name="email" value="#{login.email}" />
</h:link>
</h:body>
The corresponding login managed bean:
import javax.inject.Named;
import javax.enterprise.context.RequestScoped;
@Named(value = "login")
@RequestScoped
public class login {
private String username;
private String email;
private String age;
public login() {
}
public String getUsername() {
return username;
}
public void setUsername(String username) {
this.username = username;
}
public String getEmail() {
return email;
}
public void setEmail(String email) {
this.email = email;
}
public String getAge() {
return age;
}
public void setAge(String age) {
this.age = age;
}
}
