propertyResolver.setPlaceholderPrefix(this.placeholderPrefix);
propertyResolver.setPlaceholderSuffix(this.placeholderSuffix);
propertyResolver.setValueSeparator(this.valueSeparator);
StringValueResolver valueResolver = new StringValueResolver() {
public String resolveStringValue(String strVal) {
String resolved = ignoreUnresolvablePlaceholders ?
propertyResolver.resolvePlaceholders(strVal) :
propertyResolver.resolveRequiredPlaceholders(strVal);
return (resolved.equals(nullValue) ? null : resolved);