R2DBC and enum (PostgreSQL)

问题

Does H2DBC support PostgreSQL enums? I checked they git page but it doesn't mention anything about it. If it does, how enums could be used (INSERT, SELECT)?
Lets say PostgreSQL enum

CREATE TYPE mood AS ENUM ('UNKNOWN', 'HAPPY', 'SAD', ...);

Java class

@Data
public class Person {
    private String name;
    private Mood mood;
    // ...

    enum Mood{ UNKNOWN, HAPPY, SAD, ...}
}

I tried:

        // insert
        var person = ...;
        client.insert()
                .table("people")
                .using(person)
                .then()
                .subscribe(System.out::println);

        // select
        var query = "SELECT * FROM people";
        client.execute(query)
                .as(Person.class)
                .fetch().all()
                .subscribe(System.out::println);

But I'm getting error messages:

# on insert
 WARN [reactor-tcp-epoll-1] (Loggers.java:294) - Error: SEVERITY_LOCALIZED=ERROR, SEVERITY_NON_LOCALIZED=ERROR, CODE=42804, MESSAGE=column "mood" is of type mood but expression is of type character varying, HINT=You will need to rewrite or cast the expression., POSITION=61, FILE=parse_target.c, LINE=591, ROUTINE=transformAssignedExpr
# on select
ERROR [reactor-tcp-epoll-1] (Loggers.java:319) - [id: 0x8581acdb, L:/127.0.0.1:39726 ! R:127.0.0.1/127.0.0.1:5432] Error was received while reading the incoming data. The connection will be closed.
reactor.core.Exceptions$ErrorCallbackNotImplemented: org.springframework.data.mapping.MappingException: Could not read property private ...

I found similar post but without luck to solve my problem.. maybe I was applying it wrong..
Any help or tips are welcome.

回答1:

Tested with org.springframework.data:spring-data-r2dbc:1.0.0.RELEASE and io.r2dbc:r2dbc-postgresql:0.8.1.RELEASE.

Kotlin version.

Define a enum class

enum class Mood {
    UNKNOWN,
    HAPPY,
    SAD
}

Create a custom codec

class MoodCodec(private val allocator: ByteBufAllocator) :  Codec<Mood> {
    override fun canEncodeNull(type: Class<*>): Boolean = false

    override fun canEncode(value: Any): Boolean = value is Mood

    override fun encode(value: Any): Parameter {
        return Parameter(Format.FORMAT_TEXT, oid) {
            ByteBufUtils.encode(allocator, (value as Mood).name)
        }
    }

    override fun canDecode(dataType: Int, format: Format, type: Class<*>): Boolean = dataType == oid

    override fun decode(buffer: ByteBuf?, dataType: Int, format: Format, type: Class<out Mood>): Mood? {
        buffer ?: return null
        return Mood.valueOf(ByteBufUtils.decode(buffer))
    }

    override fun type(): Class<*> = Mood::class.java

    override fun encodeNull(): Parameter =
        Parameter(Format.FORMAT_TEXT, oid, Parameter.NULL_VALUE)

    companion object {
        // Get form `select oid from pg_type where typname = 'mood'`
        private const val oid = YOUR_ENUM_OID
    }
}

Registe the codec

You may need change runtimeOnly("io.r2dbc:r2dbc-postgresql") to implementation("io.r2dbc:r2dbc-postgresql")

@Configuration
@EnableR2dbcRepositories
class AppConfig : AbstractR2dbcConfiguration() {
    override fun connectionFactory(): ConnectionFactory = PostgresqlConnectionConfiguration.builder()
        .port(5432) // Add your config here.
        .codecRegistrar { _, allocator, registry ->
            registry.addFirst(MoodCodec(allocator))
            Mono.empty()
        }.build()
        .let { PostgresqlConnectionFactory(it) }
}

来源：https://stackoverflow.com/questions/60084867/r2dbc-and-enum-postgresql

标签

postgresql

enums

spring-data

spring-data-r2dbc

r2dbc