association-arguments.md

graphql-provider/Add arguments to associations

GraphQL has a nice feature that not only queries can have arguments, but associations between entities can also have arguments.

Graphql-provider allows you to add arguments to collection fields, i.e. fields mapped by list, connection, mappedList and mappedConnection.

Here, we demonstrate how to add arguments to the association Book.authors.

package com.example.demo.mapper.entity

import com.example.demo.model.Book
import org.babyfish.graphql.provider.EntityMapper
import org.babyfish.graphql.provider.dsl.EntityTypeDSL
import com.example.demo.model.firstName
import com.example.demo.model.lastName
import org.babyfish.kimmer.sql.ast.ilike
import org.springframework.stereotype.Component
import java.util.*

@Component
class BookMapper: EntityMapper<Book, UUID>() {

    override fun EntityTypeDSL<Book, UUID>.config() {

        ... The static mapping configuration we discussed ...
    }

    fun authors(firstName: String?, lastName: String?) = // α
        runtime.filterList(Book::authors) { // β
            db {
                firstName?.let {
                    where { table.firstName ilike it } // γ
                }
                lastName?.let {
                    where { table.lastName ilike it }
                }
            }
        }
}

• α

  Provides a public function.

  • In theory, the function name is arbitrary, but for readability it is recommended to keep the same as the name of Book::authors at β

  • The arguments of this function will be converted to the arguments of the Book.authors association in the GraphQL Schema

  • This function has no return type

• β

  • runtime is a protected property provided by the superclass org.babyfish.graphql.provider.EntityMapper

  • Book::authors represents the association property for which you want to add arguments

• γ

  table represents the generic parameter of the association property type. Here, the generic parameter of type List<Author> is Author, so table represents AUTHOR

Start app, access http://localhost:8080/graphiql, and execute

query {
  books {
    name
    store {
      name
    }
    authors(firstName: "Alex") {
      firstName
      lastName
    }
  }
}

The response is

{
  "data": {
    "books": [
      {
        "name": "Effective TypeScript",
        "store": {
          "name": "O'REILLY"
        },
        "authors": []
      },
      {
        "name": "GraphQL in Action",
        "store": {
          "name": "MANNING"
        },
        "authors": []
      },
      {
        "name": "Learning GraphQL",
        "store": {
          "name": "O'REILLY"
        },
        "authors": [
          {
            "firstName": "Alex",
            "lastName": "Banks"
          }
        ]
      },
      {
        "name": "Programming TypeScript",
        "store": {
          "name": "O'REILLY"
        },
        "authors": []
      }
    ]
  }
}

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