jsf 2 - How do I get selectManyCheckBox to return something other than List<String>?

Question

This is a pattern that I would use over and over again if I get it to work. I have an enum name Log.LogKey that I want to user to pick out instances of. So the facelet has this:

             <h:form id="testForm" >

                <h:selectManyCheckbox value="#{test.selectedKeys}" >
                    <f:selectItems value="#{test.allKeys}"
                                   var="lk"
                                   itemLabel="#{lk.display}"
                                   itemValue="#{lk}" />
                </h:selectManyCheckbox>

                <h:commandButton value="Do It" action="#{test.doNothng}" />

            </h:form>

The enum has a getter called getDisplay(). The selectItems attribute calls that correctly because that's the string that gets rendered to the user. And the backing bean has this:

public class Test implements Serializable {

private List<Log.LogKey> selectedKeys = null;

public List<Log.LogKey> getAllKeys() {
    return Arrays.asList(Log.LogKey.values());
}

public List<Log.LogKey> getSelectedKeys() { return selectedKeys; }

public void setSelectedKeys(List selected) {
    System.out.println("getSelecgedKeus() got " + selected.size());
    int i = 0;
    for (Object obj : selected) {
        System.out.println(i++ + " is " + obj.getClass() + ":" + obj);
    }
}

public String doNothng() { return null; }

}

So on the form submit, the array setSelectedKeys(selected) gets called with a List of Strings, not a List of Log.LogKey. The reference to #{lk} in the selectItems tag is converting the object to a string. What would be the right way to do this?

Answer 1

You need to specify a converter. JSF EL is not aware about the generic List type because that's lost during runtime. When you do not explicitly specify a converter, JSF will not convert the submitted String values and plain fill the list with them.

In your particular case, you can make use of the JSF builtin EnumConverter, you just have to super() the enum type in the constructor:

package com.example;

import javax.faces.convert.EnumConverter;
import javax.faces.convert.FacesConverter;

@FacesConverter(value="logKeyConverter")
public class LogKeyConverter extends EnumConverter {

    public LogKeyConverter() {
        super(Log.LogKey.class);
    }

}

To use it, just declare it as follows:

<h:selectManyCheckbox value="#{test.selectedKeys}" converter="logKeyConverter">
    ...
</h:selectManyCheckbox>

See also:

• Use enum in h:selectManyCheckbox