SpringBoot Bug since v2.7.4: Spring Data R2DBC does not fetch a valid JSON from MySQL via MariaDB driver

• Java 17
• Spring Boot v2.7.4
• MySQL 5.7
• MariaDB R2DBC driver (see why)

MySQL:

CREATE TABLE `some_table`
(
    `id`   BIGINT(20) UNSIGNED NOT NULL AUTO_INCREMENT,
    `json` JSON DEFAULT NULL,
    PRIMARY KEY (`id`)
) ENGINE = InnoDB
  DEFAULT CHARSET = utf8mb4
  COLLATE = utf8mb4_unicode_ci;

INSERT INTO some_table (id, json) VALUE (1, '{}');

Mapping:

@Data
@AllArgsConstructor
@NoArgsConstructor
@Table("some_table")
public class SomeTable {

    @Id
    @Column("id")
    private Long id;

    @Column("json")
    private String json;

}

Repository:

@Repository
public interface SomeTableRepository extends ReactiveCrudRepository<SomeTable, Long> {
}

When calling someTableRepository.findById(1L), the returned SomeTable#json is expected to be "{}" but it actually is "123,125". Not sure where that cryptic 123,125 comes from. According to https://stackoverflow.com/a/21343591/1225328, "123 and 125 is ascii for { and }", but that doesn't explain why it started failing with v2.7.4.

Works fine with Spring Boot v2.7.3.

Probably due to some dependency upgrade but I can't find my way out of the dependency tree of Spring Boot 🙈

Replicated in https://github.com/sp00m/spring-boot-2.7.4-r2dbc-json-issue, see https://github.com/sp00m/spring-boot-2.7.4-r2dbc-json-issue/blob/master/src/test/java/base/SomeTableRepositoryTest.java#L42 which passes with v2.7.3, but fails with v2.7.4:

expected value: SomeTable(id=1, json={}); actual value: SomeTable(id=1, json=123,125)

Comment From: wilkinsona

Thanks for the easy-to-use sample.

This appears to be a regression in R2DBC Borca-SR2. Things work fine with SR1. More specifically, the problem appears to be in 1.1.2 of the MariaDB driver. The problem does not occur with 1.1.1-rc, the version included in Borca-SR1. I think this should be reported here. /cc @mp911de