在Java中从JPA批注更改表

Question

I have a definition for a column like that:

@Column
private String my_column;

And by default in Postgres database type for this field is character varying(255) .

Now, I want to change the data type for this column.

How I can do this without entry in database and alter table?

I tried this:

@Lob
@Column
private String my_column;

And

@Column(columnDefinition = "TEXT")
private String my_column;

But, without results.

Answer 1

The thing is, that JPA does not handle Schema changes. JPA maps your existing DB to Java Classes, it does not manage the database it self.

As for schema changes managment. A common practice is to have a schema migration tool to handle that, for example Flyway and Liquibase are a popular solutions.

There you can write a SQL script, to change the DB column type to "text" and it will apply those changes when you run the DB migration process.

Or you can always just access your DB and modify it manually.