OneToMany关系不能保存在具有液态的春季

Question

我正试图在春季建立一个数据模型，这个模型以一对多的关系级联到3层以下，但我无法让它与清算脚本一起工作。

我使用spring引导与Kotlin和液化库与PostgreSQL数据库。

我到目前为止所做的：

• 削减代码，只包含不起作用的部分(见下文)
• 我尝试了@OneToMany和@JoinTable以及@JoinColumn，我也尝试了@ManyToMany，以排除@OneToMany
• 的问题我运行了相同的代码(下面)，没有清算库，让Hibernate/JPA从实际工作的模型
• 中创建表，所以我从这些表中生成了清算脚本，但它们与我自己的完全相同(除了使用这些模型的关键names)
• retrieving数据外(如果我直接通过SQL插入数据)

老实说，我不确定问题是在模型中，在配置中，还是在清算脚本中，所以我只发布所有这些。我缺少配置了吗？我配置的级联正确吗？我的模型定义/液化基脚本出错了吗？

我在保存父母方面的例外是：

Hibernate: insert into parent (name) values (?)
2021-12-15 23:29:16.797  WARN 14115 --- [    Test worker] o.h.engine.jdbc.spi.SqlExceptionHelper   : SQL Error: 0, SQLState: 23502
2021-12-15 23:29:16.798 ERROR 14115 --- [    Test worker] o.h.engine.jdbc.spi.SqlExceptionHelper   : ERROR: null value in column "id" of relation "parent" violates not-null constraint
  Detail: Failing row contains (null, Test 1).
org.springframework.dao.DataIntegrityViolationException: could not execute statement; SQL [n/a]; constraint [id" of relation "parent]; nested exception is org.hibernate.exception.ConstraintViolationException: could not execute statement
...
Caused by: org.hibernate.exception.ConstraintViolationException: could not execute statement
...
Caused by: org.postgresql.util.PSQLException: ERROR: null value in column "id" of relation "parent" violates not-null constraint
  Detail: Failing row contains (null, Test 2).

我试图运行的代码：

val parent = Parent(
    id = 0,
    name = "Test 2"
).apply {
    children = mutableSetOf(
        Child(
            id = 0,
            name = "Test 21",
            parent = this
        ).apply {
            grandchildren =
                mutableSetOf(
                    Grandchild(
                        id = 0,
                        name = "Test 211",
                        child = this
                    )
                )
        },
        Child(
            id = 0,
            name = "Test 22",
            parent = this
        )
    )
}

val saveParent: Parent = parentRepository.save(parent)

模型：

@Entity
class Parent(
    @Id @GeneratedValue(strategy = GenerationType.IDENTITY)
    var id: Long = 0,
    var name: String,
    @OneToMany(mappedBy = "parent", cascade = [CascadeType.ALL])
    var children: MutableSet<Child> = mutableSetOf()
)

@Entity
class Child(
    @Id @GeneratedValue(strategy = GenerationType.IDENTITY)
    var id: Long = 0,
    var name: String,
    @ManyToOne @JoinColumn(name = "child_id")
    var parent: Parent,
    @OneToMany(mappedBy = "child", cascade = [CascadeType.ALL])
    var grandchildren: MutableSet<Grandchild> = mutableSetOf()
)

@Entity
class Grandchild(
    @Id @GeneratedValue(strategy = GenerationType.IDENTITY)
    var id: Long = 0,
    var name: String,
    @ManyToOne @JoinColumn(name = "child_id")
    var child: Child
)

application.yml

spring:
  datasource:
    platform: postgres
    url: jdbc:postgresql://localhost:5432/onetomany?ssl=false
    driver-class-name: org.postgresql.Driver
    initialization-mode: always
  jpa:
    database: postgresql
    database-platform: org.hibernate.dialect.PostgreSQLDialect
    generate-ddl: false
    hibernate:
      ddl-auto: none
  liquibase:
    enabled: true
    change-log: classpath:db/master.xml

清算脚本：

<?xml version="1.1" encoding="UTF-8" standalone="no"?>
<databaseChangeLog xmlns="http://www.liquibase.org/xml/ns/dbchangelog"
  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xsi:schemaLocation="http://www.liquibase.org/xml/ns/dbchangelog http://www.liquibase.org/xml/ns/dbchangelog/dbchangelog-4.1.xsd">
  <changeSet author="bruce (generated)" id="data-1">
    <createTable tableName="parent">
      <column name="id" type="BIGINT">
        <constraints nullable="false" primaryKey="true" primaryKeyName="PK_PARENT"/>
      </column>
      <column name="name" type="VARCHAR(255)">
        <constraints nullable="false"/>
      </column>
    </createTable>
  </changeSet>
  <changeSet author="bruce (generated)" id="data-2">
    <createTable tableName="child">
      <column name="id" type="BIGINT">
        <constraints nullable="false" primaryKey="true" primaryKeyName="PK_CHILD"/>
      </column>
      <column name="name" type="VARCHAR(255)">
        <constraints nullable="false"/>
      </column>
      <column name="parent_id" type="BIGINT">
        <constraints nullable="false"/>
      </column>
    </createTable>
  </changeSet>
  <changeSet author="bruce (generated)" id="data-3">
    <createTable tableName="grandchild">
      <column name="id" type="BIGINT">
        <constraints nullable="false" primaryKey="true" primaryKeyName="PK_GRANDCHILD"/>
      </column>
      <column name="name" type="VARCHAR(255)">
        <constraints nullable="false"/>
      </column>
      <column name="child_id" type="BIGINT">
        <constraints nullable="false"/>
      </column>
    </createTable>
  </changeSet>
  <changeSet author="bruce (generated)" id="data-6">
    <addForeignKeyConstraint baseColumnNames="parent_id" baseTableName="child" constraintName="FK_CHILD_PARENT"
                             deferrable="false" initiallyDeferred="false" onDelete="RESTRICT" onUpdate="RESTRICT"
                             referencedColumnNames="id" referencedTableName="parent" validate="true"/>
  </changeSet>
  <changeSet author="bruce (generated)" id="data-8">
    <addForeignKeyConstraint baseColumnNames="child_id" baseTableName="grandchild" constraintName="FK_CHILD_GRANDCHILD"
                             deferrable="false" initiallyDeferred="false" onDelete="RESTRICT" onUpdate="RESTRICT"
                             referencedColumnNames="id" referencedTableName="child" validate="true"/>
  </changeSet>
</databaseChangeLog>

Answer 1

@GeneratedValue(strategy = GenerationType.IDENTITY)通常通过在数据库中指定一个自动递增的默认值来工作，比如nextval('my_entity_sequence'::regclass)。插入时，DB将生成标识符。

在Postgres中，有serial/bigserial伪类型来指定一个自动增量列(这将在内部创建序列和列默认值)，因此DDL可以例如如下所示：

create table my_entity ( id bigserial not null, primary key (id) )

https://www.postgresql.org/docs/current/datatype-numeric.html

在您的例子中，液化库忽略了所有ID列的类型/默认值(现在只是一个“父”-insert失败了，但是其他实体的插入也会失败)。

这是一个已知的清算基础问题：https://github.com/liquibase/liquibase/issues/1009 --围绕它工作的建议包括手动在变更集中指定autoIncrement="true"。