When testing Java applications that interact with a database, it's important to ensure that the test environment is clean and consistent. One approach to achieving this is to roll back database transactions after each test, so that the database is restored to its original state before each test.

Here are the steps you can follow to roll back transactions in Java for database testing:

1. Set up the database: Before you can test database interactions, you need to have a database set up with the appropriate schema and tables. You can use a tool like Liquibase or Flyway to manage database schema migrations and versioning.

2. Set up the test environment: You can use a tool like JUnit or TestNG to set up the test environment, including creating test data and establishing a connection to the database.

3. Begin a transaction: Before each test, you should begin a new transaction using the connection to the database. This allows you to make changes to the database during the test without affecting the database state for other tests.

4. Perform the database interaction: In each test, you should perform the database interaction that you are testing, such as creating a new record or updating an existing record.

5. Roll back the transaction: After each test, you should roll back the transaction to undo any changes that were made during the test. This ensures that the database is restored to its original state before each test.

Here's an example of a JUnit test that rolls back transactions after each test:

public class UserDaoTest {
    private Connection connection;
    private UserDao userDao;

    @Before
    public void setUp() throws SQLException {
        connection = DriverManager.getConnection("jdbc:mysql://localhost/test", "root", "password");
        userDao = new UserDao(connection);
        connection.setAutoCommit(false);
    }

    @After
    public void tearDown() throws SQLException {
        connection.rollback();
        connection.close();
    }

    @Test
    public void testCreateUser() throws SQLException {
        // Create a new user
        User user = new User();
        user.setName("John Doe");
        user.setEmail("[email protected]");
        user.setPassword("password");
        user.setRole("user");

        // Save the user to the database
        userDao.save(user);

        // Verify that the user was saved successfully
        User savedUser = userDao.findById(user.getId());
        assertNotNull(savedUser);
        assertEquals(user.getName(), savedUser.getName());
        assertEquals(user.getEmail(), savedUser.getEmail());
        assertEquals(user.getPassword(), savedUser.getPassword());
        assertEquals(user.getRole(), savedUser.getRole());
    }
}

By rolling back transactions after each test, you can ensure that the database state is consistent and that each test is run in a clean environment.