@AssertTrue(message = "'script' cannot be null or empty") //Allows subclasses to override 'script' is required.
	public boolean isValid() {
		return StringUtils.hasText(script);
	}
Validates the configuration meets expected conditions. Subclasses may override validation rules.
@return true if configuration is valid.
spring-xd-module-spi/src/main/java/org/springframework/xd/module/options/mixins/ScriptMixin.java