ArrayIndexOutOfBoundsException when handling array on view - jsf

Question

actualy my question is how to display a collection in my view :
ex:
<h:outputText value="#{item.machineCollection.get(0).id != null ? item.machineCollection.get(0).id : ''}"/>
even after testing my code if the result is null i got this error
Array index out of range: 0
java.lang.ArrayIndexOutOfBoundsException: Array index out of range: 0
at java.util.Vector.get(Vector.java:694) at
org.eclipse.persistence.indirection.IndirectList.get(IndirectList.java:401)
at sun.reflect.GeneratedMethodAccessor194.invoke(Unknown Source) at
sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597) at
javax.el.BeanELResolver.invokeMethod(BeanELResolver.java:779) at
javax.el.BeanELResolver.invoke(BeanELResolver.java:528) at
javax.el.CompositeELResolver.invoke(CompositeELResolver.java:257) at
com.sun.el.parser.AstValue.getValue(AstValue.java:134) at
com.sun.el.parser.AstValue.getValue(AstValue.java:183) at
com.sun.el.parser.AstNotEqual.getValue(AstNotEqual.java:58) at
com.sun.el.parser.AstChoice.getValue(AstChoice.java:64) at
com.sun.el.parser.AstDeferredExpression.getValue(AstDeferredExpression.java:63)
at
com.sun.el.parser.AstCompositeExpression.getValue(AstCompositeExpression.java:68)
at
com.sun.el.ValueExpressionImpl.getValue(ValueExpressionImpl.java:224)
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:169) 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:875)
at javax.faces.component.UIComponent.encodeAll(UIComponent.java:1764)
at javax.faces.component.UIComponent.encodeAll(UIComponent.java:1760)
at
org.primefaces.component.datatable.DataTableRenderer.encodeRegularCell(DataTableRenderer.java:741)
at
org.primefaces.component.datatable.DataTableRenderer.encodeRow(DataTableRenderer.java:693)
at
org.primefaces.component.datatable.DataTableRenderer.encodeTbody(DataTableRenderer.java:601)
at
org.primefaces.component.datatable.DataTableRenderer.encodeRegularTable(DataTableRenderer.java:220)
at
org.primefaces.component.datatable.DataTableRenderer.encodeMarkup(DataTableRenderer.java:192)
at
org.primefaces.component.datatable.DataTableRenderer.encodeEnd(DataTableRenderer.java:74)
at
javax.faces.component.UIComponentBase.encodeEnd(UIComponentBase.java:875)
at
org.primefaces.renderkit.CoreRenderer.renderChild(CoreRenderer.java:59)
at
org.primefaces.renderkit.CoreRenderer.renderChildren(CoreRenderer.java:43)
at
org.primefaces.component.panel.PanelRenderer.encodeContent(PanelRenderer.java:198)
at
org.primefaces.component.panel.PanelRenderer.encodeMarkup(PanelRenderer.java:115)
at
org.primefaces.component.panel.PanelRenderer.encodeEnd(PanelRenderer.java:55)
at
javax.faces.component.UIComponentBase.encodeEnd(UIComponentBase.java:875)
at javax.faces.component.UIComponent.encodeAll(UIComponent.java:1764)
at javax.faces.render.Renderer.encodeChildren(Renderer.java:168) at
javax.faces.component.UIComponentBase.encodeChildren(UIComponentBase.java:845)
at
org.primefaces.renderkit.CoreRenderer.renderChild(CoreRenderer.java:55)
at
org.primefaces.renderkit.CoreRenderer.renderChildren(CoreRenderer.java:43)
at
org.primefaces.component.layout.LayoutUnitRenderer.encodeEnd(LayoutUnitRenderer.java:51)
at
javax.faces.component.UIComponentBase.encodeEnd(UIComponentBase.java:875)
at javax.faces.component.UIComponent.encodeAll(UIComponent.java:1764)
at javax.faces.component.UIComponent.encodeAll(UIComponent.java:1760)
at javax.faces.component.UIComponent.encodeAll(UIComponent.java:1760)
at javax.faces.component.UIComponent.encodeAll(UIComponent.java:1760)
at
com.sun.faces.application.view.FaceletViewHandlingStrategy.renderView(FaceletViewHandlingStrategy.java:402)
at
com.sun.faces.application.view.MultiViewHandler.renderView(MultiViewHandler.java:131)
at
javax.faces.application.ViewHandlerWrapper.renderView(ViewHandlerWrapper.java:288)
at
com.sun.faces.lifecycle.RenderResponsePhase.execute(RenderResponsePhase.java:121)
at com.sun.faces.lifecycle.Phase.doPhase(Phase.java:101) at
com.sun.faces.lifecycle.LifecycleImpl.render(LifecycleImpl.java:139)
at javax.faces.webapp.FacesServlet.service(FacesServlet.java:594) at
org.apache.catalina.core.StandardWrapper.service(StandardWrapper.java:1550)
at
org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:281)
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
org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:161)
at
org.apache.catalina.connector.CoyoteAdapter.doService(CoyoteAdapter.java:331)
at
org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:231)
at
com.sun.enterprise.v3.services.impl.ContainerMapper$AdapterCallable.call(ContainerMapper.java:317)
at
com.sun.enterprise.v3.services.impl.ContainerMapper.service(ContainerMapper.java:195)
at
com.sun.grizzly.http.ProcessorTask.invokeAdapter(ProcessorTask.java:860)
at
com.sun.grizzly.http.ProcessorTask.doProcess(ProcessorTask.java:757)
at
com.sun.grizzly.http.ProcessorTask.process(ProcessorTask.java:1056)
at
com.sun.grizzly.http.DefaultProtocolFilter.execute(DefaultProtocolFilter.java:229)
at
com.sun.grizzly.DefaultProtocolChain.executeProtocolFilter(DefaultProtocolChain.java:137)
at
com.sun.grizzly.DefaultProtocolChain.execute(DefaultProtocolChain.java:104)
at
com.sun.grizzly.DefaultProtocolChain.execute(DefaultProtocolChain.java:90)
at
com.sun.grizzly.http.HttpProtocolChain.execute(HttpProtocolChain.java:79)
at
com.sun.grizzly.ProtocolChainContextTask.doCall(ProtocolChainContextTask.java:54)
at
com.sun.grizzly.SelectionKeyContextTask.call(SelectionKeyContextTask.java:59)
at com.sun.grizzly.ContextTask.run(ContextTask.java:71) at
com.sun.grizzly.util.AbstractThreadPool$Worker.doWork(AbstractThreadPool.java:532)
at
com.sun.grizzly.util.AbstractThreadPool$Worker.run(AbstractThreadPool.java:513)
at java.lang.Thread.run(Thread.java:680)
if someone have a solution urgently pleas and thanks

Answer 1

The problem is that you have
item.machineCollection.get(0).id
If you have an empty collection, item.machineCollection.get(0) will not work.
In primeface datatable you can use the var attribute. So if you add var="row" you can do
<p:datatable var="row" value="#{item.machineCollection}" >
<p:column>
<f:facet name="header">
<h:outputText value="Id" />
</f:facet>
<h:outputText value="#{row.id}"/>
</p:column>
....
</p:datatable>

Answer 2

Use not empty operator:
<h:outputText value="#{not empty item.machineCollection ? item.machineCollection.get(0).id : ''}
or write custom JSF function, as described in this topic:
How to create a custom EL function to invoke a static method?