Error with two selectManyListbox

I have two selectManyListbox related(the second is generated accordind the first) ,but when I run the application an error occure:

JSF:

<h:selectManyListbox   value="#{TestAjax.selectedProjects}"  id="project" size="3">
  <f:selectItem itemLabel="-- Select Projects -- " itemValue="0"/> 
  <f:selectItems value="#{TestAjax.getMyListProject()}" />
  <f:ajax event="change"  render="status" />
 </h:selectManyListbox>

 <h:selectManyListbox   value="#{TestAjax.selectedstatus}" id="status"  size="3">
  <f:selectItem itemLabel="-- Select status -- " itemValue="0"/> 
  <f:selectItems value="#{TestAjax.StepsByProject()}" />
 </h:selectManyListbox>

The error:

java.lang.NullPointerException
at DAOKPI.TestAjax.FormattingVar(TestAjax.java:342)
at DAOKPI.TestAjax.StepsByProject(TestAjax.java:367)
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.invokeMethod(BeanELResolver.java:737)
at javax.el.BeanELResolver.invoke(BeanELResolver.java:467)
at javax.el.CompositeELResolver.invoke(CompositeELResolver.java:254)
at com.sun.el.parser.AstValue.getValue(AstValue.java:111)
at com.sun.el.parser.AstValue.getValue(AstValue.java:163)
at com.sun.el.ValueExpressionImpl.getValue(ValueExpressionImpl.java:21开发者_如何学Python9)
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.UISelectItems.getValue(UISelectItems.java:129)
at com.sun.faces.renderkit.SelectItemsIterator.initializeItems(SelectItemsIterator.java:202)
at com.sun.faces.renderkit.SelectItemsIterator.hasNext(SelectItemsIterator.java:135)
at com.sun.faces.renderkit.html_basic.MenuRenderer.renderOptions(MenuRenderer.java:762)
at com.sun.faces.renderkit.html_basic.MenuRenderer.renderSelect(MenuRenderer.java:844)
at com.sun.faces.renderkit.html_basic.MenuRenderer.encodeEnd(MenuRenderer.java:298)
at javax.faces.component.UIComponentBase.encodeEnd(UIComponentBase.java:875)
at com.sun.faces.renderkit.html_basic.HtmlBasicRenderer.encodeRecursive(HtmlBasicRenderer.java    :312)
at com.sun.faces.renderkit.html_basic.GridRenderer.renderRow(GridRenderer.java:185)
at com.sun.faces.renderkit.html_basic.GridRenderer.encodeChildren(GridRenderer.java:129)
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.panel.PanelRenderer.encodeContent(PanelRenderer.java:229)
at org.primefaces.component.panel.PanelRenderer.encodeMarkup(PanelRenderer.java:152)
at org.primefaces.component.panel.PanelRenderer.encodeEnd(PanelRenderer.java:75)
at javax.faces.component.UIComponentBase.encodeEnd(UIComponentBase.java:875)
at javax.faces.component.UIComponent.encodeAll(UIComponent.java:1763)
at javax.faces.render.Renderer.encodeChildren(Renderer.java:168)
at javax.faces.component.UIComponentBase.encodeChildren(UIComponentBase.java:845)
at javax.faces.component.UIComponent.encodeAll(UIComponent.java:1756)
at javax.faces.component.UIComponent.encodeAll(UIComponent.java:1759)
at javax.faces.component.UIComponent.encodeAll(UIComponent.java:1759)
at com.sun.faces.application.view.FaceletViewHandlingStrategy.renderView(FaceletViewHandlingSt     rategy.java:401)
at com.sun.faces.application.view.MultiViewHandler.renderView(MultiViewHandler.java:131)
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)

---

java.lang.NullPointerException
at DAOKPI.TestAjax.FormattingVar(TestAjax.java:342)
at DAOKPI.TestAjax.StepsByProject(TestAjax.java:367)

This tells you all you need to know. A null pointer exception occured in your class TestAjax, the method was FormattingVar() and the line number is 342. From your JSF page, the error occured in the 2nd selectManyListbox, as seen by the StepsByProject() in the stacktrace as well