以角度创建模型类的最佳方法是什么？

Question

I want suggestion on how to create model class in angular for interacting with database Let's say my spring JPA entity is Environment.java

    @Entity
    public class Environment {

        @Id
        @GeneratedValue(strategy=GenerationType.SEQUENCE)
        @Column(name = "ENV_SId", nullable = false)
        private Long envSid;

        @Column(name = "ENV_NAME",nullable = false)
        private String envName;

        public Long getEnvSid() {
            return envSid;
        }

        public void setEnvSid(Long envSid) {
            this.envSid = envSid;
        }

        public String getEnvName() {
            return envName;
        }

        public void setEnvName(String envName) {
            this.envName = envName;
        }
    }

My angular model class is environment.model.ts

    export class Environment {
        envName: string;
    }

Because the primary key is auto-generated I will use my environment.model.ts class to post data to the server. But while getting the data I also need the primary key envSid together with envName in my angular app. Do I need to create two different models for the two cases? One model with only envName while doing POST request and one model with envSid and envName while doing GET request?

Answer 1

That's a question I have been pondering quite a bit, and below is my conclusion. I'm happy to discuss whether it always makes sense or not.

The principle I use is: your model should have all fields that make sense for a complete object.

In your case, it means that id should be part of the model.

The rationale behind that is:

• When you manipulate an object, you want to rely on the fact you have a full object , not a half-formed object that is not yet saved to database or whatever. Otherwise, you have to account for the fact that your object may be incomplete in each operation (update, etc.)
• It makes sense that the data you use to create an object (the POST request you mention) is not yet an object , but just the initialization data. Sometimes, it might not even map to the specific fields of your model, so it is good practice to keep them separate.

In your case, I would indeed have 2 models: EnvironmentInitializeData and EnvironmentModel or whatever name, you get the idea.

By the way, the initialization data does not always need to be expressed as a type since it is often used only once and in a straightforward manner.

Answer 2

The good practice is to create 1 model Interface per Data Transfer Object . So in your case, you should do something like that:

environment.model.ts

export interface Environment {
    envName: string;
    envSid: number;
}

environmentToPost.model.ts

export interface EnvironmentToPost {
    envName: string;
    // ...
}