jdbc_team_project

Task description.

import javax.sql.DataSource;
import java.io.Serializable;
import java.time.LocalDate;
import java.util.ArrayList;
import java.util.List;
import java.util.Optional;
import java.util.stream.Stream;

// 1st part
interface ORManager {
    // let it work with ids:
    // - Long (autogenerated at DB side)  (HIGH)
    // - UUID (autogenerated at ORM side) (MEDIUM)
    // - String                           (OPTIONAL)
    // The fields may be of types:
    // - int/Integer                      (HIGH)
    // - long/Long                        (HIGH)
    // - double/Double                    (OPTIONAL)
    // - boolean/Boolean                  (OPTIONAL)
    // - String                           (HIGH)
    // - LocalDate                        (MEDIUM)
    // - LocalTime                        (MEDIUM)
    // - LocalDateTime/Instant            (MEDIUM)
    // - BigDecimal                       (OPTIONAL)
    // - Enum +                           (OPTIONAL)
    //   @Enumerated(EnumType.ORDINAL/EnumType.STRING)

    // initialize connection factory for the DB
    // read the jdbc url, username and password from
    //  the given property file
    static ORManager withPropertiesFrom(String filename) {
        return null; // todo
    }

    // initialize connection factory for the DB based on the DataSource
    static ORManager withDataSource(DataSource dataSource) {
        return null; // todo
    }

    // generate the schema in the DB
    // for given list of entity classes (and all related
    //  by OneToMany/ManyToOne) create a schema in DB
    void register(Class... entityClasses);

    // CREATE
    // save a new object to DB, set id if autogenerated
    // or merge into DB if id is present
    Object save(Object o);
    // save a new object to DB, set id if autogenerated
    // throw if the object has id already set (except for String)
    void persist(Object o);

    // READ
    <T> Optional<T> findById(Serializable id, Class<T> cls);
    // READ ALL
    <T> List<T> findAll(Class<T> cls);
    // READ ALL LAZY
    <T> Iterable<T> findAllAsIterable(Class<T> cls); // (MEDIUM)
    <T> Stream<T> findAllAsStream(Class<T> cls);     // (OPTIONAL)

    // UPDATE
    <T> T merge(T o);  // send o -> DB row (to table)
    <T> T update(T o); // send o <- DB row (from table)

    // DELETE
    // set autogenerated id to null
    // return true if successfully deleted
    boolean delete(Object o);
}
// todo: declare properly the annotations
// 1st part
@interface Entity {} //                          (HIGH)
@interface Id {} //                              (HIGH)
@interface Table {String value() default "";} // (HIGH)
@interface Column {String value() default "";}// (HIGH)
// 2nd part
@interface OneToMany {String mappedBy() default "";}  // (MEDIUM)
@interface ManyToOne {String columnName() default "";} // (MEDIUM)

// 1st part
class Main {
    public static void main(String[] args) {
        String propertiesFilename = "";
        ORManager ormManager = ORManager.withPropertiesFrom(
                propertiesFilename
        );
        ormManager.register(Book.class, Publisher.class);

        var publisher = new Publisher("MyPub");
        ormManager.persist(publisher);

        var book1 = new Book("Solaris", LocalDate.of(1961, 1, 1));
        ormManager.persist(book1);

        book1.setPublisher(publisher);
        ormManager.merge(book1);

        // ...
    }
}

@Entity
@Table("books")
class Book {
    @Id
    private Long id;
    private String title;
    @Column("published_at")
    private LocalDate publishedAt;

    public Book() {
    }

    public Book(String title, LocalDate publishedAt) {
        this.title = title;
        this.publishedAt = publishedAt;
    }

    public Long getId() {
        return id;
    }

    public String getTitle() {
        return title;
    }

    public void setTitle(String title) {
        this.title = title;
    }

    public LocalDate getPublishedAt() {
        return publishedAt;
    }

    public void setPublishedAt(LocalDate publishedAt) {
        this.publishedAt = publishedAt;
    }

    // 2nd stage:
    @ManyToOne(columnName = "publisher_id")
    Publisher publisher = null;

    public Publisher getPublisher() {
        return publisher;
    }

    public void setPublisher(Publisher publisher) {
        this.publisher = publisher;
    }
}

@Entity
class Publisher {
    @Id
    private Long id;
    private String name;

    public Publisher() {
    }

    public Publisher(String name) {
        this.name = name;
    }

    public Long getId() {
        return id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    // 2nd stage
    @OneToMany(mappedBy = "publisher")
    private List<Book> books = new ArrayList<>();

    public List<Book> getBooks() {
        return books;
    }
}