1public class CustomElement extends ElementBase implements ElementInterface {
 2    @Override
 3    public Setting[] getSettings() throws ElementException {
 4        Setting settingA = new Setting("settingA", "Setting A", "The first setting",
 5                Setting.OPTIONAL, Setting.SINGLE, Setting.SUBSTITUTION_ALLOWED, Setting.STRING);
 6        Setting settingB = new Setting("settingB", "Setting B", "The second setting",
 7                Setting.OPTIONAL, Setting.SINGLE, Setting.SUBSTITUTION_ALLOWED, Setting.STRING);
 8       
 9        // Validate that at least one of Setting A or Setting B has been set
10        settingA.setCustomValidator(new OrValidator(settingB));
11       
12        return new Setting[] {settingA, settingB};
13    }
14    // The rest of the class has been omitted
15}
16class OrValidator implements SettingValidator
17{
18    private Setting otherSetting;
19   
20    public OrValidator(Setting otherSetting)
21    {
22        this.otherSetting = otherSetting;
23    }
24   
25    /**
26     * Validation method for OrValidator.
27     * @param value The setting to validate.
28     * @param setting Contains information about the setting being validated.
29     * @param allSettingParams Contains information about all settings in the custom element, keyed by each setting's real name.
30     * @return A list of error messages to display.
31     */
32    @Override
33    public List<String> validate(String value, SettingParams params,
34            Map<String, SettingParams> allSettingParams)
35    {
36        List<String> errors = new ArrayList<String>();
37       
38        SettingParams otherSettingParams = allSettingParams.get(otherSetting.getRealName());
39        if (otherSettingParams != null &&
40                StringUtils.isEmpty(otherSettingParams.getCurrentValue()) &&
41                StringUtils.isEmpty(value))
42        {
43            errors.add("At least one of " + params.getDisplayName() + " or " +
44                    otherSettingParams.getDisplayName() + " must be set.");
45        }
46       
47        return errors;
48    }