liquibase-maven-plugin/src/main/java/org/liquibase/maven/plugins/AbstractLiquibaseMojo.java
private boolean isCurrentFieldValueSpecified(Field f) throws IllegalAccessException {
        Object currentValue = f.get(this);
        if (currentValue == null) {
            return false;
        }

        Object defaultValue = getDefaultValue(f);
        if (defaultValue == null) {
            return currentValue != null;
        } else {
            // There is a default value, check to see if the user has selected something other
            // than the default
            return !defaultValue.equals(f.get(this));
        }
    }
private boolean isCurrentFieldValueSpecified(Field f) throws IllegalAccessException {
        Object currentValue = f.get(this);
        if (currentValue == null) {
            return false;
        }

        Object defaultValue = getDefaultValue(f);
        if (defaultValue == null) {
            return currentValue != null;
        } else {
            // There is a default value, check to see if the user has selected something other
            // than the default
            return !defaultValue.equals(f.get(this));
        }
    }
This method will check to see if the user has specified a value different to that of
the default value. This is not an ideal solution, but should cover most situations in
the use of the plugin.

@param f The Field to check if a user has specified a value for.
@return <code>true</code> if the user has specified a value.