Java spring Hibernate：尝试实现多对一关系时出错

我试图实现一个多对一的关系，用户可以有很多帖子。使用的数据库是postgresql

我遇到的错误如下所示，是由休眠引起的：alter table post drop约束FKL1P5MT95JNGSGP4VTAW04EGH：

org.hibernate.tool.schema.spi.CommandAcceptanceException: Error executing DDL "alter table post drop constraint FKl1p5mt95jngsghp4vtaw04egh" via JDBC Statement
    at org.hibernate.tool.schema.internal.exec.GenerationTargetToDatabase.accept(GenerationTargetToDatabase.java:67) ~[hibernate-core-5.4.21.Final.jar:5.4.21.Final]
    at org.hibernate.tool.schema.internal.SchemaDropperImpl.applySqlString(SchemaDropperImpl.java:375) ~[hibernate-core-5.4.21.Final.jar:5.4.21.Final]
    at org.hibernate.tool.schema.internal.SchemaDropperImpl.applySqlStrings(SchemaDropperImpl.java:359) ~[hibernate-core-5.4.21.Final.jar:5.4.21.Final]
    at org.hibernate.tool.schema.internal.SchemaDropperImpl.applyConstraintDropping(SchemaDropperImpl.java:331) ~[hibernate-core-5.4.21.Final.jar:5.4.21.Final]
    at org.hibernate.tool.schema.internal.SchemaDropperImpl.dropFromMetadata(SchemaDropperImpl.java:230) ~[hibernate-core-5.4.21.Final.jar:5.4.21.Final]
    at org.hibernate.tool.schema.internal.SchemaDropperImpl.performDrop(SchemaDropperImpl.java:154) ~[hibernate-core-5.4.21.Final.jar:5.4.21.Final]
    at org.hibernate.tool.schema.internal.SchemaDropperImpl.doDrop(SchemaDropperImpl.java:126) ~[hibernate-core-5.4.21.Final.jar:5.4.21.Final]
    at org.hibernate.tool.schema.internal.SchemaDropperImpl.doDrop(SchemaDropperImpl.java:112) ~[hibernate-core-5.4.21.Final.jar:5.4.21.Final]
    at org.hibernate.tool.schema.spi.SchemaManagementToolCoordinator.performDatabaseAction(SchemaManagementToolCoordinator.java:145) ~[hibernate-core-5.4.21.Final.jar:5.4.21.Final]
    at org.hibernate.tool.schema.spi.SchemaManagementToolCoordinator.process(SchemaManagementToolCoordinator.java:73) ~[hibernate-core-5.4.21.Final.jar:5.4.21.Final]
    at org.hibernate.internal.SessionFactoryImpl.<init>(SessionFactoryImpl.java:316) ~[hibernate-core-5.4.21.Final.jar:5.4.21.Final]
    at org.hibernate.boot.internal.SessionFactoryBuilderImpl.build(SessionFactoryBuilderImpl.java:469) ~[hibernate-core-5.4.21.Final.jar:5.4.21.Final]
    at org.hibernate.jpa.boot.internal.EntityManagerFactoryBuilderImpl.build(EntityManagerFactoryBuilderImpl.java:1259) ~[hibernate-core-5.4.21.Final.jar:5.4.21.Final]
    at org.springframework.orm.jpa.vendor.SpringHibernateJpaPersistenceProvider.createContainerEntityManagerFactory(SpringHibernateJpaPersistenceProvider.java:58) ~[spring-orm-5.2.9.RELEASE.jar:5.2.9.RELEASE]
    at org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean.createNativeEntityManagerFactory(LocalContainerEntityManagerFactoryBean.java:365) ~[spring-orm-5.2.9.RELEASE.jar:5.2.9.RELEASE]
    at org.springframework.orm.jpa.AbstractEntityManagerFactoryBean.buildNativeEntityManagerFactory(AbstractEntityManagerFactoryBean.java:391) ~[spring-orm-5.2.9.RELEASE.jar:5.2.9.RELEASE]
    at java.base/java.util.concurrent.FutureTask.run(FutureTask.java:264) ~[na:na]
    at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1130) ~[na:na]
    at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:630) ~[na:na]
    at java.base/java.lang.Thread.run(Thread.java:832) ~[na:na]
Caused by: org.postgresql.util.PSQLException: ERROR: relation "post" does not exist
    at org.postgresql.core.v3.QueryExecutorImpl.receiveErrorResponse(QueryExecutorImpl.java:2553) ~[postgresql-42.2.16.jar:42.2.16]
    at org.postgresql.core.v3.QueryExecutorImpl.processResults(QueryExecutorImpl.java:2285) ~[postgresql-42.2.16.jar:42.2.16]
    at org.postgresql.core.v3.QueryExecutorImpl.execute(QueryExecutorImpl.java:323) ~[postgresql-42.2.16.jar:42.2.16]
    at org.postgresql.jdbc.PgStatement.executeInternal(PgStatement.java:473) ~[postgresql-42.2.16.jar:42.2.16]
    at org.postgresql.jdbc.PgStatement.execute(PgStatement.java:393) ~[postgresql-42.2.16.jar:42.2.16]
    at org.postgresql.jdbc.PgStatement.executeWithFlags(PgStatement.java:322) ~[postgresql-42.2.16.jar:42.2.16]
    at org.postgresql.jdbc.PgStatement.executeCachedSql(PgStatement.java:308) ~[postgresql-42.2.16.jar:42.2.16]
    at org.postgresql.jdbc.PgStatement.executeWithFlags(PgStatement.java:284) ~[postgresql-42.2.16.jar:42.2.16]
    at org.postgresql.jdbc.PgStatement.execute(PgStatement.java:279) ~[postgresql-42.2.16.jar:42.2.16]
    at com.zaxxer.hikari.pool.ProxyStatement.execute(ProxyStatement.java:95) ~[HikariCP-3.4.5.jar:na]
    at com.zaxxer.hikari.pool.HikariProxyStatement.execute(HikariProxyStatement.java) ~[HikariCP-3.4.5.jar:na]
    at org.hibernate.tool.schema.internal.exec.GenerationTargetToDatabase.accept(GenerationTargetToDatabase.java:54) ~[hibernate-core-5.4.21.Final.jar:5.4.21.Final]
    ... 19 common frames omitted

该错误发生在任何类型的请求之前初始化程序时

spring.jpa.hibernate.ddl auto

设置为

create

，因此在我的理解中，前面的表/值不应该有任何干扰

是什么导致了这个错误

我包括一个生成数据库的屏幕，如jetbrains Idea所示，以防万一：

---

您的定义看起来不错，看看错误，我假设它来自

create

设置-否则Hibernate将尝试删除任何约束。是否可以手动删除数据库/表，然后再次尝试运行该程序？

是的，我手动删除了所有表，并得到相同的错误。我注意到在日志中约束的名称有大写字母，但在我的屏幕中没有。我会看看这是否是导致错误的原因（如果我能找到设置）似乎我没有正确删除。我不明白为什么，但当我创建了另一个项目并给它相同的代码时，它没有崩溃。然后我再次运行了我当前的代码（使用相同的代码），它成功了。我的猜测是删除表是不够的，可能有一个值或配置我错过了：）不仅有表，还有序列，有时还有其他东西。真是太好了！我不建议使用create设置，如果这个应用程序要投入生产，你可能需要使用liquibase和createdrop（仅本地）。另见

import lombok.Data;
import javax.persistence.*;
import java.util.Set;

@Entity
@Data
public class WebsiteUser {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;
    private String userName;
    private String password;
    private String email;
    @OneToMany(mappedBy = "user", cascade = CascadeType.REMOVE)
    private Set<Post> posts;
}

import lombok.Data;
import javax.persistence.*;
import java.time.Instant;

@Entity
@Data
public class Post {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;
    private String title;
    private String content;
    private Instant createdOn;
    private Instant updatedOn;
    @ManyToOne
    private WebsiteUser user;
}