JPA不会使用@Transactional批注保存选择结果

Question

I can't save result of select into database using JPA in Spring Boot application. The code that I use is below:

@Override
@Transactional
public void fetchAndSave() {
    List<TestData> all = testDataRepository.findAllRecords();
    testDataRepository.saveAll(all);
    // let suppose I will save another data here that's why I need @Transactional for roll-back in case of exception
}

@Repository
public interface TestDataRepository extends JpaRepository<TestData, Long> {
    @Query(value = "select raw_values.identificator AS id, raw_values.name as value from test.raw_values", nativeQuery = true)
    List<TestData> findAllRecords();
}

When I call fetchAndSave with a property spring.jpa.show-sql=true I see in logs only select:

Hibernate: select raw_values.identificator AS id, raw_values.name as value from test.raw_values

In a case I don't use @Transactional I can see more requests to database in logs and values are saved:

Hibernate: select raw_values.identificator AS id, raw_values.name as value from test.raw_values
Hibernate: select testdata0_.id as id1_0_0_, testdata0_.value as value2_0_0_ from test.test_data testdata0_ where testdata0_.id=?
Hibernate: select testdata0_.id as id1_0_0_, testdata0_.value as value2_0_0_ from test.test_data testdata0_ where testdata0_.id=?
Hibernate: select testdata0_.id as id1_0_0_, testdata0_.value as value2_0_0_ from test.test_data testdata0_ where testdata0_.id=?
Hibernate: insert into test.test_data (value, id) values (?, ?)
Hibernate: insert into test.test_data (value, id) values (?, ?)
Hibernate: insert into test.test_data (value, id) values (?, ?)

I have a pretty simple table in database, DDL looks like:

create table test_data
(
    id    serial not null
        constraint test_data_pk
            primary key,
    value varchar(256)
);
-- There are 3 records in table raw_values
create table table_name
(
    identificator integer not null
        constraint table_name_pk
            primary key,
    name          varchar(256)
);

Can you help me to identify the reason of such behavior? I expect records to be saved into database when I use @Transactional .

Answer 1

The short answer for "why it does not save" is: because they are already saved.

The longer answer is Hibernate sees that these IDs has already present in DB, and it does not save them.

If you want to inset another three entities to DB, just create duplicates for these objects, with id=null and save them:

List<TestData> all = testDataRepository.findAllRecords();
List<TestData> copies = all.stream()
   .map(testData -> new TestData(...)) //copy all the fields EXCEPT ID
   .collect(toList());
testDataRepository.saveAll(copies);