Read all table and columns in Jpa/Hibernate

How to get metadata about all table and columns managed by JPA/Hibernate?

There are many ways to get a list of table and columns in your project that uses JPA/Hibernate. Each has pros and cons.

Option A) Direct Query on INFORMATION_SCHEMA.

Simplest way is to do direct query on INFORMATION_SCHEMA  or similar schema that the database internally uses.

For MySQL, H2, MariaDB etc the following would work. We will need specific query for each database.

SELECT * from INFORMATION_SCHEMA.TABLES
SELECT * FROM INFORMATION_SCHEMA.COLUMNS

Option B) DB Independent query using JDBC API

We can do DB independent query by using JDBC API to return the Metadata. It would use DB specific query provided by DB driver to return the metadata.

DataSource ds = ; //create/wire DataSource object
DatabaseMetaData metaData = ds.getConnection().getMetaData();
ResultSet schemasRS = metaData.getSchemas();
ResultSet tablesRS = metaData.getTables(null, null, null, new String[]{"TABLE"});

We can iterate over the ResultSet to get the schema, table and columns. It would return everything that the Database has.

Option C) Use EntityManager MetaModel to read Entity classes

In order to retrieve only the entity/tables that the application uses, we can rely on some Java Reflection magic as following:

EntityManager em; //autowire the bean
MetamodelImplementor metaModelImpl = (MetamodelImplementor) em.getMetamodel();
List<String> tableNames = metaModelImpl
    .entityPersisters()
    .values().stream()
    .map(ep -> ((AbstractEntityPersister) ep).getTableName())
    .toList();

Option D) Use Hibernate Magic

Use hibernate's Metadata class that stores the ORM model determined by provided entity mappings.

org.hibernate.boot.Metadata metadata; //getting the Metadata is tricky though

for (PersistentClass persistentClass : metadata.getEntityBindings()) {
    tableNames.add(persistentClass.getTable().getExportIdentifier());
}