Directive @primaryKey

The @required directive provides the ability to generate a DSL in such a way that the field marked with this directive is automatically added to the query. The @primaryKey directive does the same, but additionally generates equals and hashCode functions for entities by all fields marked with this directive. You cannot exclude a field marked with this directive from the query. Kobby does not generate __withoutXXX() methods for fields marked with such a directive, and does not allow such fields to be excluded using the __minimize() function. Let define a GraphQL schema:

type Query {
    films: Film!
}

type Film {
    id: ID!
    title: String!
}

This schema allows us to write a query using the generated DSL that looks like this:

val context: ExampleContext = exampleContextOf(createMyAdapter())
val response = context.query {
    films {
        id()
        title()
    }
}

response.films.forEach { film ->
    println("Film ${film.id} ${film.title}")
}

If we want to generate a DSL that will automatically include the id field in the query and to generate the equals and hashCode functions for the Film entity using the id field, we must mark this field with the @primaryKey directive. Let's modify our schema:

directive @primaryKey on FIELD_DEFINITION

type Query {
    films: [Film!]!
}

type Film {
    id: ID! @primaryKey
    title: String!
}

Now we can write our query like this:

val context: ExampleContext = exampleContextOf(createMyAdapter())
val response = context.query {
    films {
        title()
    }
}

response.films.forEach { film ->
    println("Film ${film.id} ${film.title}")
}

The generated DSL will automatically add the id field to the projection of the Film query. In addition, the equals and hashCode functions will be generated for Film entity implementation (file entity/impl/FilmImpl.kt):

internal class FilmImpl(
    internal val __innerContext: ExampleContext,
    internal val __innerProjection: FilmProjectionImpl,
    internal val __innerDto: FilmDto
) : Film {
    // ... skipped

    override fun equals(other: Any?): Boolean {
        if (this === other) {
            return true
        }
        if (javaClass != other?.javaClass) {
            return false
        }

        other as FilmImpl
        return __innerDto.id == other.__innerDto.id
    }

    override fun hashCode(): Int = __innerDto.id?.hashCode() ?: 0

    // ... skipped
}

DTO

By default, the @primaryKey directive does not affect the DTO layer. Kobby will not generate equals and hashCode functions for FilmDto:

data class FilmDto(
    val id: Long? = null,
    val title: String? = null
)

To switch on equals and hashCode functions generation on DTO layer set kotlin.dto.applyPrimaryKeys property to true.

Gradle:

plugins {
    id("io.github.ermadmi78.kobby")
}

kobby {
    kotlin {
        dto {
            applyPrimaryKeys = true
        }
    }
}

Maven:

<plugin>
    <groupId>io.github.ermadmi78</groupId>
    <artifactId>kobby-maven-plugin</artifactId>
    <executions>
        <execution>
            <goals>
                <goal>generate-kotlin</goal>
            </goals>
            <configuration>
                <kotlin>
                    <dto>
                        <applyPrimaryKeys>true</applyPrimaryKeys>
                    </dto>
                </kotlin>
            </configuration>
        </execution>
    </executions>
</plugin>

And Kobby will generate equals and hashCode functions for FilmDto:

data class FilmDto(
    val id: Long? = null,
    val title: String? = null
) {
    override fun equals(other: Any?): Boolean {
        if (this === other) {
            return true
        }
        if (javaClass != other?.javaClass) {
            return false
        }

        other as FilmDto
        return id == other.id
    }

    override fun hashCode(): Int = id?.hashCode() ?: 0
}

Restrictions

• The @primaryKey directive can only be applied to a field with no arguments.
• The @primaryKey directive can only be applied to a field that returns a scalar or enum type.
• The @primaryKey directive cannot be applied to overridden fields. In this case, apply the directive to the base interface field.

In case of violation of any restriction, the directive will be ignored.

In case of a field is marked with several directives at once - @default, @required, @primaryKey, the behavior of the Kobby Plugin is undefined!