code: public SpringELExpressionParser getSpringExpressionParser() {
          val configuration = new SpelParserConfiguration();
          val spelExpressionParser = new SpelExpressionParser(configuration);
          val parser = new SpringELExpressionParser(spelExpressionParser, this.flowBuilderServices.getConversionService());
          parser.addPropertyAccessor(new ActionPropertyAccessor());
          parser.addPropertyAccessor(new BeanFactoryPropertyAccessor());
          parser.addPropertyAccessor(new FlowVariablePropertyAccessor());
          parser.addPropertyAccessor(new MapAdaptablePropertyAccessor());
          parser.addPropertyAccessor(new MessageSourcePropertyAccessor());
          parser.addPropertyAccessor(new ScopeSearchingPropertyAccessor());
          parser.addPropertyAccessor(new BeanExpressionContextAccessor());
          parser.addPropertyAccessor(new MapAccessor());
          parser.addPropertyAccessor(new MapAdaptablePropertyAccessor());
          parser.addPropertyAccessor(new EnvironmentAccessor());
          parser.addPropertyAccessor(new ReflectivePropertyAccessor());
          return parser;
      }
docs: Gets spring expression parser.
  
  @return the spring expression parser