JHipster 8.6.0 JDL生成应用，枚举字段获取详情抛类型不匹配异常

我使用JHipster 8.6.0基于JDL生成一个单体应用，该应用仅包含一个带枚举值的实体，且启用Elasticsearch搜索引擎。对应的JDL配置如下：

application {
  config {
    applicationType monolith
    authenticationType oauth2
    baseName EnumTest
    buildTool maven
    cacheProvider hazelcast
    clientFramework angular
    clientTheme solar
    clientThemeVariant dark
    databaseType sql
    devDatabaseType postgresql
    enableHibernateCache true
    enableSwaggerCodegen true
    enableTranslation true
    languages [fr, en]
    messageBroker false
    microfrontends []
    nativeLanguage fr
    packageName fr.jhipster.test
    prodDatabaseType postgresql
    reactive false
    searchEngine elasticsearch
    serviceDiscoveryType no
    skipUserManagement true
    testFrameworks [gatling, cucumber, cypress]
    websocket false
    withAdminUi true
  }

  entities *
}

entity Address {
  isoCountryCode IsoCountryCode
}

enum IsoCountryCode {
  FRA,
  ENG,
}

paginate * with pagination
dto * with mapstruct
service all with serviceImpl

当尝试查看某条Address的详情时，出现如下异常：

2024-07-22T09:29:35.569+02:00 ERROR 23384 --- [  XNIO-1 task-5] f.m.l.d.web.rest.AddressResource         : Exception in getAddress() with cause = 'org.hibernate.PropertyAccessException: Could not set value of type [fr.jhipster.test.domain.enumeration.IsoCountryCode]: 'fr.jhipster.test.domain.Address.isoCountryCode' (setter)' and exception = 'Could not set value of type [fr.jhipster.test.domain.enumeration.IsoCountryCode]: 'fr.jhipster.test.domain.Address.isoCountryCode' (setter)' 

org.springframework.orm.jpa.JpaSystemException: Could not set value of type [fr.jhipster.test.domain.enumeration.IsoCountryCode]: 'fr.jhipster.test.domain.Address.isoCountryCode' (setter)
        at org.springframework.orm.jpa.vendor.HibernateJpaDialect.convertHibernateAccessException(HibernateJpaDialect.java:341)
        at org.springframework.orm.jpa.vendor.HibernateJpaDialect.translateExceptionIfPossible(HibernateJpaDialect.java:241)
(...)
Caused by: org.hibernate.PropertyAccessException: Could not set value of type [fr.jhipster.test.domain.enumeration.IsoCountryCode]: 'fr.jhipster.test.domain.Address.isoCountryCode' (setter)
        at org.hibernate.property.access.spi.SetterFieldImpl.set(SetterFieldImpl.java:88)
(...)
Caused by: java.lang.IllegalArgumentException: Can not set fr.jhipster.test.domain.enumeration.IsoCountryCode field fr.jhipster.test.domain.Address.isoCountryCode to fr.jhipster.test.domain.enumeration.IsoCountryCode
        at java.base/jdk.internal.reflect.UnsafeFieldAccessorImpl.throwSetIllegalArgumentException(UnsafeFieldAccessorImpl.java:167)
        at java.base/jdk.internal.reflect.UnsafeFieldAccessorImpl.throwSetIllegalArgumentException(UnsafeFieldAccessorImpl.java:171)
        at java.base/jdk.internal.reflect.UnsafeObjectFieldAccessorImpl.set(UnsafeObjectFieldAccessorImpl.java:81)
        at java.base/java.lang.reflect.Field.set(Field.java:799)
        at org.hibernate.property.access.spi.SetterFieldImpl.set(SetterFieldImpl.java:57)

问题原因与解决方法 #

原因 #

同时使用SQL数据库和Elasticsearch时，JHipster生成的代码会出现枚举类加载冲突：Hibernate从SQL加载的枚举实例，与Elasticsearch处理时使用的枚举类实例来自不同类加载器，JVM会将其视为不同类型，导致反射赋值时抛出类型不匹配异常。

解决方法 #

在JDL中给枚举字段显式指定存储类型，让Hibernate与Elasticsearch使用一致的枚举处理策略。修改后的实体定义如下：

entity Address {
  isoCountryCode IsoCountryCode @Enumerated(STRING)
}

• 使用@Enumerated(STRING)会将枚举以字符串形式存储到SQL数据库，同时Elasticsearch也会映射为字符串类型；
• 若希望以序号存储，可替换为@Enumerated(ORDINAL)。

显式指定枚举存储策略后，JHipster生成的实体类会添加对应的JPA注解，Elasticsearch的文档映射也会同步匹配，从根源避免类加载冲突导致的类型不匹配问题。

内容的提问来源于stack exchange，提问作者Pierre Taquet