Using Map to populate multiple SelectManyCheckboxes - ClassCastException - jsf

Question

In my controller, there is a Collection of "questions" with possible answer-options. My view iterates the questions with an ui:repeat. When I try to read the selected options, I get a java.lang.ClassCastException:
javax.faces.FacesException: #{cbtestController.submit}: java.lang.ClassCastException: [Ljava.lang.String; cannot be cast to java.util.List
at com.sun.faces.application.ActionListenerImpl.processAction(ActionListenerImpl.java:118)
at javax.faces.component.UICommand.broadcast(UICommand.java:315)
at javax.faces.component.UIViewRoot.broadcastEvents(UIViewRoot.java:790)
at javax.faces.component.UIViewRoot.processApplication(UIViewRoot.java:1282)
at com.sun.faces.lifecycle.InvokeApplicationPhase.execute(InvokeApplicationPhase.java:81)
at com.sun.faces.lifecycle.Phase.doPhase(Phase.java:101)
at com.sun.faces.lifecycle.LifecycleImpl.execute(LifecycleImpl.java:198)
at javax.faces.webapp.FacesServlet.service(FacesServlet.java:646)
at org.apache.catalina.core.StandardWrapper.service(StandardWrapper.java:1682)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:344)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:214)
at org.omnifaces.facesviews.FacesViewsForwardingFilter.doFilter(FacesViewsForwardingFilter.java:130)
at org.omnifaces.filter.HttpFilter.doFilter(HttpFilter.java:77)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:256)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:214)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:316)
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)
Caused by: javax.faces.el.EvaluationException: java.lang.ClassCastException: [Ljava.lang.String; cannot be cast to java.util.List
at javax.faces.component.MethodBindingMethodExpressionAdapter.invoke(MethodBindingMethodExpressionAdapter.java:101)
at com.sun.faces.application.ActionListenerImpl.processAction(ActionListenerImpl.java:102)
... 41 more
Caused by: java.lang.ClassCastException: [Ljava.lang.String; cannot be cast to java.util.List
at de.zulu.zuluvoting.controller.cbtestController.submit(cbtestController.java:71)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:483)
at com.sun.el.parser.AstValue.invoke(AstValue.java:289)
at com.sun.el.MethodExpressionImpl.invoke(MethodExpressionImpl.java:304)
at org.jboss.weld.util.el.ForwardingMethodExpression.invoke(ForwardingMethodExpression.java:40)
at org.jboss.weld.el.WeldMethodExpression.invoke(WeldMethodExpression.java:50)
at com.sun.faces.facelets.el.TagMethodExpression.invoke(TagMethodExpression.java:105)
at javax.faces.component.MethodBindingMethodExpressionAdapter.invoke(MethodBindingMethodExpressionAdapter.java:87)
... 42 more
Controller:
#ManagedBean
#ViewScoped
public class cbtestController implements Serializable, Converter {
private Map<Long, List<SelectItem>> availableItems;
private Map<Long, List<String>> selectedItems;
// ... getters and setters
public List<Long> getIds() {
List<Long> result = new ArrayList<>(availableItems.keySet());
return result;
}
public List<SelectItem> availableItemsById(Long id) {
return availableItems.get(id);
}
#PostConstruct
private void init() {
selectedItems = new HashMap<>();
availableItems = new HashMap<>();
availableItems.put(0L, new ArrayList<SelectItem>());
availableItems.get(0L).add(new SelectItem("option0_1", "Option 0.1"));
availableItems.get(0L).add(new SelectItem("option0_2", "Option 0.2"));
availableItems.put(1L, new ArrayList<SelectItem>());
availableItems.get(1L).add(new SelectItem("option1_1", "Option 1.1"));
availableItems.get(1L).add(new SelectItem("option1_2", "Option 1.2"));
}
public void submit() {
System.out.println("selectedItems = " + selectedItems); // (1)
for (Long id : selectedItems.keySet()) {
System.out.println("selectedItems[" + id + "] = " + selectedItems.get(id)); // (2)
for (String selectedItem : selectedItems
.get(id)) // ClassCastException here
{
System.out.println(" > " + selectedItem);
}
}
}
(1) prints "selectedItems = {0=[Ljava.lang.String;#30185d04, 1=[Ljava.lang.String;#661abe68}"
(2) prints "selectedItems[0] = [Ljava.lang.String;#30185d04"
View:
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE html>
<html xmlns="http://www.w3.org/1999/xhtml"
xmlns:h="http://xmlns.jcp.org/jsf/html"
xmlns:f="http://java.sun.com/jsf/core"
xmlns:ui="http://xmlns.jcp.org/jsf/facelets">
<head>
<title>TODO supply a title</title>
<meta name="viewport" content="width=device-width, initial-scale=1.0"/>
</head>
<body>
<h:form>
<ui:repeat value="#{cbtestController.ids}"
var="id">
<h:selectManyCheckbox value="#{cbtestController.selectedItems[id]}"
layout="pageDirection">
<f:selectItems value="#{cbtestController.availableItemsById(id)}" />
</h:selectManyCheckbox>
</ui:repeat>
<h:commandButton action="#{cbtestController.submit}"
value="Submit"/>
</h:form>
</body>
</html>
I have been trying to get this working for some time now, and this it's getting really frustrating. I have also tried to write a converter, but I still get a ClassCastException (Not sure if this is correct):
#Override
public Object getAsObject(FacesContext context, UIComponent component, String value) {
for (Long id : availableItems.keySet()) {
List<SelectItem> items = availableItems.get(id);
for (SelectItem item : items) {
if (((String)item.getValue()).equals(value)) {
return item;
}
}
}
return null;
}
#Override
public String getAsString(FacesContext context, UIComponent component, Object value) {
return (String)value;
}
Do I even need the converter? What am I doing wrong?

Answer 1

I've experienced a somewhat similar problem. I had a Map with a List of Integers as value. Much like you. And I was using the Map value with a h:selectManyCheckbox inside a ui:repeat as well. But I kept getting ClassCastExceptions because the Map value for some reason was a List of Strings instead, when I submitted my form.
I ended up using a IntegerArray class instead of a List as value in my Map. That class then held the (in my case) array of Integers.
IntegerArray:
public class IntegerArray implements Serializable {
private Integer[] array;
public IntegerArray() {
}
public IntegerArray(Integer[] array) {
this.array = array;
}
public Integer[] getArray() {
return array;
}
public void setArray(Integer[] array) {
this.array = array;
}
}
That worked.