Questions tagged [entity]

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120 views

Clean Architecture, what are objects that does not completely fit as entities?

I'm reading chapter 20, "Business Rules", of clean architecture book, in this chapter Uncle Bob defines entities as: An Entity is an object within our computer system that embodies a small ...
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2answers
95 views

DDD Modeling - Entity with generic and specific data

Suppose I am buying coffee. There are several types of coffee (A1, A2, A3), but sometimes I want to make a reference to all types of coffee (like if I had a coffee "grouped"). Considering ...
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1answer
114 views

Dealing with business logic on DTOs using a DDD

I have a scenario in which an Entity defines an EntityRepresentation that is created from another end. The EntityRepresentation is a value object that implements some logic that should be performed on ...
-2
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1answer
108 views

DDD Best way to preserve integrity of entity

I have an entity that contain the status of data (WaitingForData, ReadyForData, DataUsed). class Batch { int Status { get; } DateTime StartTime { get; } string Code { get; } void ...
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3answers
378 views

When to use entity and when to use DTOs

Hi I am very new to using DTOs, and I am starting to understand it slowly, but there are still some missing puzzles for me. I understand the use of DTOs in the way of decoupling the persistence data ...
-1
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1answer
149 views

Modeling a workout schedule using OOP(DDD specifically)

I am just getting into DDD, and I am trying to model a very basic exercise schedule. I have a Schedule and I have a Slot the slot takes 0 - many Exercise entities. The schedule is composed of Slots ...
15
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4answers
3k views

Should entities contain information about their amount?

Can I get some thoughts on the entity design? Let's say I have an entity called Book. Let's say I create a specific instance of that book. It has a title A and an author B. Since there can be multiple ...
-1
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2answers
74 views

How to change a data model

In my model a user entity has three attributes : ID, name, hasBoyfriend. I want now to change hasBoyfriend to boyFriendsNames which is an array of names . The user entity is used by many services. The ...
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2answers
240 views

Relationship between entities in different aggregates and size of aggregate

I read a lot about DDD but few thing are still unclear. At this moment I have two dilemma The size of aggregates. How small could be an aggregate? For example we have: class Car { String colorId ...
1
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2answers
257 views

Database Design: Storing price date wise, or date range wise?

I must store prices for various items on multiple dates. The table schema would look like this: CREATE TABLE date_wise_price ( item_code varchar, date date, price numeric(19,4) ) An ...
-3
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1answer
42 views

What is proper approach to code first entity relationship design?

I been trying to figure out, what i hoped is a simple problem, but am yet to land with an answer. How do you go about designing an entity relationship diagram when doing code first development? The ...
2
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2answers
309 views

Entity delete validation in a microservice environment

In a microservice environment there are two services: Service A and Service B. Service A manages an entity called x which has one to many relationship with service B's entity called y When a network ...
1
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1answer
76 views

How to decide on abstraction level and entity definitions?

I am working on a hobby project of mine where I want to make an application to doing my personal finances. Just for learning. I am trying to adhere and implement best practices and patterns to learn ...
0
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1answer
110 views

Can I put domain services inside domain entities?

Say I have a domain entity User: class User { constructor (username, email, password) { this.username = username this.email = email this.password = password } } Now, all users need a ...
0
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1answer
4k views

Best practice for references in DTOs and entities in Spring

Given the following architecture and frameworks: Spring Boot Application with Spring Data JPA (Hibernate is used as OR mapper); layered architecture as followed. REST layer Service layer Persistence ...
8
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2answers
534 views

Why can't Entities leave the inner layers in the Clean Architecture?

I was reading about the clean architecture, and I don't get this part: Don't use your Entity objects as data structures to pass around in the outer layers. Make separate data model objects for that. ...
0
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1answer
199 views

Need for a domain model in a service in 3 tier architecture?

I am building an API Rest with Spring Boot and I would like to clarify a concept about my architecture, to see if the community can help me. Imagine that in my database I have a table called Person. ...
0
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0answers
191 views

DDD Value Objects and Entity Without ORM Mapping in PHP

First, as I know, Entity in DDD is almost same with Value Object except Entity has identity. Every article I have read say same thing that entity id has ORM mapping with any ORM tool. But I don’t want ...
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0answers
111 views

Changing entities in Clean Architecture

I'm modeling the "Domain" Layer of "Clean Architecture" for an application that gets its data from an XML file when starts. The XML file looks like: <?xml version="1.0" encoding="UTF-8" ?> <...
1
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2answers
900 views

When to model an aggregate's entities as part of a value object?

I've read a lot about Domain Driven Design including books from Eric Evans and Vaughn Vernon. So I am familiar with the concepts Aggregate Root, Entity, and Value Object. But while I was modeling ...
7
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3answers
4k views

Domain vs Entities model? Domain-Driven-Design (DDD)?

In this github, https://github.com/johnph/simple-transaction, under the Transaction.Framework project, there are entities (located at Data/Entities) AccountSummaryEntity.cs AccountTransactionEntity ...
3
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4answers
384 views

What is optimal number of entity abstraction levels?

Sorry about the vague question, please do suggest different formulations. Anyway here is the kernel of the question: How many classes representing an entity/resource or whatever you want to call it, ...
7
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1answer
641 views

How to prevent concurrency problems when using the repository pattern?

Considering that: when using the repository pattern you deal with entities - those are the atomic units you persist (regardless of Hibernate or "manually") when changing an entity you save it as a ...
1
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1answer
2k views

Aggregate root being created by multiple other aggregate roots

I know the title is confusing, I didn't how to word it. I'm studying the Domain Driven Design (DDD) and I'm reading the book "NET Microservices Architecture for Containerized NET Applications" from ...
2
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1answer
234 views

Can we have a ternary relationship together with a recursive one in E-R diagrams

I am designing an E-R Diagram for a simple system where there are some users and contests. A user can create a contest or invite other users to the contest who can decide to accept or not. I am ...
1
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1answer
802 views

How to determine aggregates when entities are shared?

So I'm trying to figure out exactly what my aggregates/aggregate roots are in my structure, and can't seem to wrap my head around it. Database contains the following tables: SALESGROUP ID ...
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2answers
2k views

Depend on DDD Entities or Interfaces?

My understanding is that the dependency inversion principle does not apply to entities, because entities basically are your application - it generally doesn't make sense to swap out a different ...
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2answers
798 views

What is DDD's concepts mapping to microservice's concepts? [closed]

DDD concepts: Domain, Aggregate, Entity, Value object, Bounded context Should every aggregate be a single microservice and have a single DB ( since every microservice should have a single specific DB)...
0
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1answer
77 views

Do menu option lists (and similar labels) belong in the database?

I am moving in the direction from database-centric design to entity-centric design (say, starting with class definitions instead of starting with a ERD), and am questioning things: Often in a ...
4
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2answers
536 views

Repository pattern usage

I need some advice regarding repository pattern. Let's assume i have UserBal which stands for business logic which uses UserRepositoryDal where all database logic for that entity stands (queries to ...
1
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1answer
232 views

Using the same entity for different use cases

Suppose I have a User entity with name and age attributes. A User can own Boxes. A Box has the name and color attributes. Business rules dictate that one User can own at most 5 boxes. So, in this case,...
1
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2answers
558 views

Domain models vs entity models vs Hibernate lazy loading

In a new Java project I plan to use an extra layer above Hibernate entities. So there would be a CustomerEntity and CustomerDomain. The reason for that is that the CustomerDomain can contain extra ...
0
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1answer
195 views

Modify a property of an aggregate's entity

Suppose I have a house-lending service, like Airbnb. I have a House entity, which can have a name. There's also the Reservation entity, which has a start date, an end date, and a name (which isn't ...
4
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3answers
184 views

ER diagram - feasibility of a requirement

I need to model the following requirement in an Entity-Relationship diagram. "Customers place orders, which contain a list of products with their quantity and prices. A shipment is made when ...
5
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3answers
261 views

Is a repository return a graph of entities violating SRP?

I'm working in this scenario Post entity has many Image entities. I also have repository to both entities: PostRepository ImageRepository Since this entities are tightly related, when I get a Post ...
0
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1answer
66 views

Delete dependent entities

I have a temporary report table which has a foreign key (source_id), e.g. report table: | id | val1 | val2 | source_id | | -- | ---- | ---- | --------- | | 1 | 102 | 0.5 | 1 | | 2 | 99 |...
1
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1answer
154 views

How to set nullable/optional property of database object to NULL in backend?

We are building API which mainly passes database objects back and forth between user and database, so the main flow of information is quite basic: Table (view) <-- ORM --> C#/Java/etc. Objects &...
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2answers
526 views

When converting the ER into the class diagram, what happened to the Weak Entities in the ER diagram

I am trying to convert an ER diagram into a class diagram. Below image is showing that part of my ER diagram and which contains a weak entity call 'Parent'. Therefore when we consider the ER diagram, ...
3
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3answers
4k views

Business Logic Entities and Data Access Layer Entities

I am thinking on how to structure a project. I wonder if it is a good practice to use different entity classes between the BL and DAL in order to decouple these layers. I have worked on projects ...
-1
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1answer
821 views

Updating entity with REST

I'm looking for the "Holy Grail" (best practise) of how to update an entity with REST? There are three main approaches I've found so far: Always send full entity, regardless what has been changed ...
0
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2answers
434 views

Should entity properties be represented by a value object?

I read somewhere that one should be generous in creating value objects for entity properties that are part of the class API. So I did that with my project entity/aggregate, but it still looks weird: ...
1
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1answer
803 views

PHP: Domain model and aggregates

I am building an app that uses a client and a project entity. The clients can extend their profile over various screens in their account, like status, settings, etc. These data sets are saved in ...
0
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1answer
101 views

Best way to handle environment specif fields in Hibernate

We have one microservice that will be deployed on two different environments(A and B). There are some common fields and also some are specific to the environment. Example: SomeEntity for environment ...
0
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2answers
1k views

Should i use an abstract class or an interface for my doctrine model?

In Doctrine, assuming I want to implement different types of vehicles. Maybe a car, a plane, a bicycle and so on ... all these vehicles have many different properties but also very common things like ...
3
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2answers
1k views

DDD - delegate business rule of domain object to external service

Situation: I am implementing DDD in my first project and I would like to clarify how to correctly implement strategy pattern (in my case check if API token is active). This is a business rule of ...
37
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1answer
50k views

What is the use of DTO instead of Entity?

I am working on RCP application, I'm new to this application. Spring beans are used to write business logic to save/fetch entities. But, instead of sending entities directly to client we are ...
4
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1answer
572 views

DDD: How to work with entity variations?

Let's say I have an Entity that represents an employee: Employee First name Last name Birthdate Hair color Eye color Gender .... (and so on) Now, imagine I have a website ...
8
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1answer
11k views

Data Objects for each layer(DTO vs Entity vs Response objects)

Let's say I'm building a Customer web application(in Spring Boot 2), which also exposes rest end points. I'm modeling my application into 3 layers. a) UI - CustomerDTO b) REST - ...
1
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1answer
644 views

Imposing conditional entity relations

While working on an application, I am facing an issue. And I am not sure how to solve this. For explanation I have managed to come up with a simple example below: Consider a Grocery Store ...
4
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5answers
3k views

Why is the ampersand (&) a HTML Entity?

I understand the rationale behind why most of the HTML character Entities were created, but I don't understand the purpose behind the ampersand HTML entity. &amp; contains more bits than a & ...