code: public Expression create(String expression, ExpressionType expressionType, PropertyResolver propertyResolver) {
          if (expressionType == null) {
              expressionType = ExpressionType.MVEL;
          }
          if (propertyResolver == null) {
              propertyResolver = SystemAndTestPropertyResolver.INSTANCE;
          }
          switch (expressionType) {
          case MVEL:
              return new MVELExpression(expression, propertyResolver);
          default:
              throw CommonKnowledgeMessages.MESSAGES.unknownExpressionType(expressionType.toString());
          }
      }
docs: Creates a new Expression.
  
  @param expression the expression string
  @param expressionType the expression type
  @param propertyResolver the property resolver
  @return the Expression