JarCastingiter-jdbc
Iterator-focused JDBC wrapper library
This project was inspired by Spring-Jdbc. In particular, named parameter SQL queries and stream-like result processing, without storing the whole result set in memory. But unlike Spring-Jdbc, the goal of this project is to provide and accept iterators wherever possible instead of callbacks and collections.
Add
Using the following Maven coordinates:
<dependency>
<groupId>com.codeborne</groupId>
<artifactId>iter-jdbc</artifactId>
<version>0.2</version>
</dependency>
Use
Create a repository:
public class BooksRepo {
public BooksRepo(DataSource ds) {
this.ds = ds;
}
private final DataSource ds;
private static final Query<Book> allBooksQuery = new Query<>(
"select b.TITLE from BOOKS",
BooksRepo::mapRowToBook
);
private static Book mapRowToBook(ResultSet rs) throws SQLException {
return new Book(rs.getString("TITLE"));
}
public CloseableIterator<Book> allBooks() {
try (Connection conn = ds.getConnection()) {
return allBooksQuery.connect(conn)
.runOnce(emptyMap());
} catch (SQLException e) {
throw new RuntimeException(e);
}
}
}
Create a service:
public class BooksReportService {
public BooksReportService(BooksRepo repo) {
this.repo = repo;
}
private final BooksRepo repo;
public void writeReport(Writer w) {
try (CloseableIterator<Book> books = repo.allBooks()) {
int bookNum = 0;
while (books.hasNext()) {
bookNum++;
Book book = books.next();
w.write(bookNum + ".\t" + book.getTitle() + "\n");
}
} catch (IOException e) {
throw new RuntimeException(e);
}
}
}
Test
Test repositories with integration tests and a real database.
Test service classes using CloseableListIterator. Test that code under test closes resources (prepared queries and iterators):
class BooksReportServiceTest {
BooksRepo repo = mock(BooksRepo.class);
BooksReportService reportService = new BooksReportService(repo);
@Test
void writeReport() {
CloseableListIterator<Book> books = spy(new CloseableListIterator<>(
new Book("A book"),
new Book("Another book"),
new Book("One more book")
));
when(repo.allBooks()).thenReturn(books);
StringWriter w = new StringWriter();
reportService.writeReport(w);
assertThat(w.toString()).isEqualTo(
"1.\tA book\n" +
"2.\tAnother book\n" +
"3.\tOne more book\n"
);
verify(books).close();
}
}