value-object | Value objects | Authorization library

I shared below a simplified version of the problem I'm trying to solve. There must be something wrong in my formulation, perhaps regarding the decision variables. All of the flow is sent to Destination1 by the model, but I am attempting to build a model that would evenly distribute the flow. When I force Destination2 to receive flow with an additional constraint, the objective value improves, so I'm not sure why such a solution is not found instead of the less optimal.

I appreciate your thoughts and am happy to answer any questions about this model.

I don't understand the purpose of the _id field when it refers to a simple nested object, eg it is not used as a root entity in a dedicated collection.

Let's say, we have a simple value-object like Money({currency: String, amount: Number }). Obviously, you are never going to store such a value object by itself in a dedicated collection. It will rather be attached to a Transaction or a Product, which will have their own collection.

But you still might query for specific currencies or amounts that are higher/lower than a given value. And you might programmatically (not on DB level) set the value of a transaction to the same as of a purchased product.

Would you need an _id in this case? What are the cases, where a nested object needs an _id?

I want to keep some data in H2 database by making a CRUD repository, using Hibernate.

I can't get the database to store my entries whatsoever. Currently, I'm trying to achieve that during updating the db by making a sample entry. Entry is looking good in the logs, but table is not created/updated/generated.

Why Hibernate is not unable to create a table in this case? (if the problem lies in structure of my data)

Here's my Entity, Game.java class (I've tried without @Column annotations, no difference. Id is not auto-generated, I need to be able to enter my own ID everytime):

.Net Core 3

By this and this examples I try create validation of domain model with value objects. But I get error.

In a nutshell I am trying for the first time to build a couple of Value Objects (VO's) and cannot resolve the this.name usage in my constructors.

I just discovered the concept of Value Objects from this article ("Convert Guard Clauses to Value Objects") and when trying to implement the sample code ran into a few problems where the author oversimplified the example. I have worked all of them out except for one last bug that is preventing the code from building with the following compiler messages:

I have been using value object in asp.net core 2.0 project, which was running properly on that project.

I updated the project to 2.1 and it is giving me an error as

Invalid object name 'EntityAdress'.

Entity:

I started reading chapter 5 of E. Evans DDD and try to make head or tail of the concepts.

In context of ddd what is and what is not entity and what is value object ?

looking at Value object or entity object in my Hibernate mapping? - but it is about Hibernate, not DDD, I ask about DDD

1. In above sample of hibernate OrderLine is Entity, but is OrderLine still a DDD entity ?
2. And more generally, can we say that any jpa/Hibernate @Entity is DDD entity, or not ?
3. It seems to me, that OrderLine is a good example of Jpa/Hibernate entity that is not a DDD entity, is it ?

If we for instance had used some object database we would possibly store Order togeter with it's OrderLines, wouldn't we ?

1. In terms of relational databases could we say, that Jpa @Entity that is mapped in database as OnDeleteCascade is not a DDD Entity, but it is still a value object ?
2. Is hibernate @Embedded always a DDD value object ? (seems yes, it has no identity)

Ok, and now other case with other doubts. Lets say that we have two different systems one in Java other in Python. One for billing other for marketing. Both of them have a Customer Entity.

1. Do we say that BillingCustomer is the same DDD Entity as MarketingCustomer (assuming both of them represent the same Customer John Doe born 01.01.1980 wiht ssn 12-34-56)? This would imply that in java two different classes, even not having common parent (except from Object) can represent the same DDD entity. If so, how should equals be implemented in above classes ?
2. Should java equals return true for two different java classes representing the same DDD entity ?

It is often written that Entities are mutable and value objects are immutable.

1. How would we implement below with java and hibernate :

   @Entity Person has @Embedded Address, Person class has getters and setters and Address only getters ? And to change address street we would do sth like person.setAddress (Address.builder(person.getAddress()).setStreet("newStreet").build()) ?

On one hand, the invariants should be protected (To make invalid states impossible early and preferably at compile time rather than run time), and on the other hand, passing domain knowledge out of the domain is wrong.

On one hand, the value objects protect our domain invariants at first place, on the other hand using them as commands or as it's properties equals passing domain knowledge around.

The only solution for both protecting the invariants, and avoiding the domain knowledge from leaking the domain boundary (encapsulating the domain model), seems to wrap the aggregates in a command-to-value-object-mapper.

I'm using CQRS along with ES.

Is it ok to have a wrapper as a command-to-value-object-mapper around my aggregate roots? Is there any other solution?

I’m currently having issues with EF core 2.1 and a web api used by a native client to update an object which contains several levels of embedded objects. I’ve already read theses two topics:

Entity Framework Core: Fail to update Entity with nested value objects

https://docs.microsoft.com/en-us/ef/core/saving/disconnected-entities

I’ve learned through this that it is indeed not that obvious for now to update objects in EF Core 2. But I’ve not yet managed to find a solution that works. On each attempt I’m having an exception telling me that a “step” is already tracked by EF.

My model looks like this: