java - Hibernate hbm2ddl.auto配置的可能值是什么，它们做了什么(What are the possible values of the Hibernate hbm2ddl.auto configuration and what do they do)

Question

I really want to know more about the update, export and the values that could be given to hibernate.hbm2ddl.auto

(我真的想知道更多关于更新，导出和可以给hibernate.hbm2ddl.auto的值的更多信息)
I need to know when to use the update and when not?

(我需要知道何时使用更新，何时不知道？)

And what is the alternative?

(还有什么选择？)

These are changes that could happen over DB:

(这些是可能发生在DB上的变化：)

• new tables

  (新表)

• new columns in old tables

  (旧表中的新列)

• columns deleted

  (列已删除)

• data type of a column changed

  (列的数据类型已更改)

• a type of a column changed its attributes

  (列的类型更改了其属性)

• tables dropped

  (桌子掉了)

• values of a column changed

  (列的值已更改)

In each case what is the best solution?

(在每种情况下，最佳解决方案是什么？)

  ask by translate from so

Answer 1

From the community documentation :

(来自社区文档 ：)

hibernate.hbm2ddl.auto Automatically validates or exports schema DDL to the database when the SessionFactory is created.

(hibernate.hbm2ddl.auto创建SessionFactory时，自动验证或将架构DDL导出到数据库。)

With create-drop, the database schema will be dropped when the SessionFactory is closed explicitly.

(使用create-drop，当SessionFactory显式关闭时，将删除数据库模式。)

eg validate |

(例如验证|)

update |

(更新|)

create |

(创建|)

create-drop

(创建降)

So the list of possible options are,

(所以可能的选项列表是，)

• validate : validate the schema, makes no changes to the database.

  (validate ：验证模式，不对数据库进行任何更改。)

• update : update the schema.

  (更新 ：更新架构。)

• create : creates the schema, destroying previous data.

  (create ：创建架构，销毁以前的数据。)

• create-drop : drop the schema when the SessionFactory is closed explicitly, typically when the application is stopped.

  (create-drop ：显式关闭SessionFactory时删除模式，通常是在应用程序停止时。)

These options seem intended to be developers tools and not to facilitate any production level databases, you may want to have a look at the following question;

(这些选项似乎是开发人员工具，而不是为了促进任何生产级数据库，您可能想要查看以下问题;)

Hibernate: hbm2ddl.auto=update in production?

(Hibernate：hbm2ddl.auto =在生产中更新？)