@AssertTrue(message="'propertiesLocation' and 'variables' only apply to script")
	public boolean noScriptOptionsWithExpression() {
		return getScript() == null ^ (getPropertiesLocation() == null && getVariables() == null);
	}
User can't explicitly set both script and expression.
spring-xd-module-spi/src/main/java/org/springframework/xd/module/options/mixins/ExpressionOrScriptMixin.java