mongodb - 在Grails中是否可以加入mongo和mysql域？

Question

我有一个域使用MySQL db，其他域使用MongoDB。我可以加入他们吗？

例如:

上诉(mongo域)

class Appeal {

    static mapWith = "mongo"

    Organization organization <=== MySQL domain
    ...
}

组织(MySQL域)

class Organization {
    ... 
    static hasMany = [ appeals : Appeal ]; <==join to mongo domain
}

异常(exception)是:

Error initializing the application: Error creating bean with name 'transactionManagerPostProcessor': Initialization of bean failed;
nested exception is
org.springframework.beans.factory.BeanCreationException: Error
creating bean with name 'transactionManager': Cannot resolve reference
to bean '$primaryTransactionManager' while setting constructor
argument with key [0]; nested exception is
org.springframework.beans.factory.BeanCreationException: Error
creating bean with name '$primaryTransactionManager': Cannot resolve
reference to bean 'sessionFactory' while setting bean property
'sessionFactory'; nested exception is
org.springframework.beans.factory.BeanCreationException: Error
creating bean with name 'sessionFactory': Invocation of init method
failed; nested exception is org.hibernate.MappingException:
Association references unmapped class: lc.itgroup.education.dao.Appeal
    Message: Error creating bean with name 'transactionManagerPostProcessor': Initialization of bean failed;
nested exception is
org.springframework.beans.factory.BeanCreationException: Error
creating bean with name 'transactionManager': Cannot resolve reference
to bean '$primaryTransactionManager' while setting constructor
argument with key [0]; nested exception is
org.springframework.beans.factory.BeanCreationException: Error
creating bean with name '$primaryTransactionManager': Cannot resolve
reference to bean 'sessionFactory' while setting bean property
'sessionFactory'; nested exception is
org.springframework.beans.factory.BeanCreationException: Error
creating bean with name 'sessionFactory': Invocation of init method
failed; nested exception is org.hibernate.MappingException:
Association references unmapped class: lc.itgroup.education.dao.Appeal

Answer 1

不，但是您可以估算一下。在两个不同的关系数据库中连接两个表会遇到同样的问题-每个表都有自己的SessionFactory，并且Hibernate或GORM中不支持跨数据库或数据存储进行连接。

要进行近似估算，请存储其他表/文档的主键，并使用过渡方法为您检索实例。基本上，这就是Hibernate为您所做的-它存储外键值并按需自动加载实例。

class Appeal {

    static mapWith = "mongo"

    void setOrganization(Organization organization) {
        organizationId = organization.id
    }
    Organization getOrganization() {
        organizationId ? Organization.get(organizationId) : null
    }
    static transients = ['organization']

    Long organizationId
    ...
}

使用这种方法，您的代码将非常类似于两个表都在同一数据库中时的样子。当您访问Organization时，它将使用以前保留的ID从数据库中检索它。

重要的是organization属性是 transient 的，因为具有这样的匹配的get / set对将被视为持久属性，并且如您所见，这将失败。只有ID应该被保留。