java - hibernate : Why is it trying to drop/create database on startup?

Question

我是 Spring 的新手。我终于成功地构建了我的应用程序，没有错误，但是当我查看输出时，我有很多我不理解的信息。

首先每个表都有这个错误，它似乎是一个 Hibernate/Spring 错误:

Hibernate: alter table entity.administrationaction drop constraint FKjaafjywumaavhae5kjyo34gx5
        2016-11-13 12:16:41.475 ERROR 2156 --- [           main] org.hibernate.tool.hbm2ddl.SchemaExport  : HHH000389: Unsuccessful: alter table entity.administrationaction drop constraint FKjaafjywumaavhae5kjyo34gx5
        2016-11-13 12:16:41.475 ERROR 2156 --- [           main] org.hibernate.tool.hbm2ddl.SchemaExport  : ERREUR: la relation « entity.administrationaction » n'existe pas 

然后每个表都是这样:

Hibernate: drop table if exists entity.administrationaction cascade

然后每个表都是这样:

Hibernate: create table entity.administrationaction (id  serial not null, action int4, creation_date timestamp, entity_class varchar(255), entity_id int4, message varchar(255), administrator_id int4, primary key (id))

所以这就像 Spring 试图删除我所有的数据库并重新创建它。为什么 ？这是正常的还是我做错了什么？

Answer 1

放在application.properties/application.yml中

spring.jpa.hibernate.ddl-auto=update

这个属性可以设置值

1. update (Update the schema if necessary)
2. create (create the schema and destroy previous data)
3. create-drop (create and then destroy the schema at the end of the session)
4. none (disable ddl handling)
5. validate (validate the schema , make no changes to the database)