Kotlin-grahpql自定义类型配置

kotlin-graphql默认只支持基本的几个类型，需添加其他类型的支持，只能通过配置Hooks。

异常

若未配置，启动时会报异常。以下代码是因为对象中有LocalDateTime，schema无法进行解析，因此报错。

Invocation of init method failed; nested exception is org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'com.expediagroup.graphql.spring.RoutesConfiguration': Unsatisfied dependency expressed through constructor parameter 1; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'schema' defined in class path resource [com/expediagroup/graphql/spring/SchemaAutoConfiguration.class]: Bean instantiation via factory method failed; nested exception is org.springframework.beans.BeanInstantiationException: Failed to instantiate [graphql.schema.GraphQLSchema]: Factory method 'schema' threw exception; nested exception is com.expediagroup.graphql.exceptions.TypeNotSupportedException: Cannot convert java.time.LocalDateTime since it is not a valid GraphQL type or outside the supported packages "[com.xxxx.xx]"

对此报错，官网也给出了解释。

image.png

解决

• CustomerTypeHooks

import com.expediagroup.graphql.hooks.SchemaGeneratorHooks
import graphql.language.StringValue
import graphql.schema.Coercing
import graphql.schema.GraphQLScalarType
import graphql.schema.GraphQLType
import java.time.LocalDateTime
import java.time.format.DateTimeFormatter
import kotlin.reflect.KType

/**
 * @Author: anson
 * @Date: 2020/8/17 1:18 PM
 */
class CustomerTypeHooks : SchemaGeneratorHooks {
    override fun willGenerateGraphQLType(type: KType): GraphQLType? = when (type.classifier) {
        LocalDateTime::class -> graphqlDateType
        else -> null
    }
}

internal val graphqlDateType = GraphQLScalarType.newScalar()
        .name("Date")
        .description("A type representing a formatted java.time.LocalDateTime")
        .coercing(InstantCoercing)
        .build()

private object InstantCoercing : Coercing<LocalDateTime, String> {
    private val formatter = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss")
    override fun parseValue(input: Any?): LocalDateTime {
        val timeString = formatter.parse(serialize(input))
        return LocalDateTime.from(timeString)
    }

    override fun parseLiteral(input: Any?): LocalDateTime? {
        val timeString = (input as? StringValue)?.value
        return LocalDateTime.from(formatter.parse(timeString))
    }

    override fun serialize(dataFetcherResult: Any?): String = dataFetcherResult.toString()
}

• 配置到Spring启动类

import com.***.CustomerTypeHooks
import org.springframework.boot.autoconfigure.SpringBootApplication
import org.springframework.boot.runApplication
import org.springframework.context.annotation.Bean

@SpringBootApplication
class GrahpqlApplication {
    @Bean
    fun hooks() = CustomerTypeHooks()
}

fun main(args: Array<String>) {
    runApplication<GrahpqlApplication>(*args)
}