~ refactor database into multiple files

Signed-off-by: Johannes Theiner <j.theiner@live.de>

pom.xml

@@ -147,6 +147,7 @@
         </dependency>
 
 
+        <!--Database-->
         <dependency>
             <groupId>org.mariadb.jdbc</groupId>
             <artifactId>mariadb-java-client</artifactId>

src/main/java/de/hsel/itech/db/AuthorDB.java

@@ -0,0 +1,133 @@
+package de.hsel.itech.db;
+
+import de.hsel.itech.db.pojo.Author;
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
+
+import java.sql.Connection;
+import java.sql.PreparedStatement;
+import java.sql.ResultSet;
+import java.sql.SQLException;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Map;
+
+/**
+ * @author Johannes Theiner
+ * @version 0.1
+ * @since 0.5
+ **/
+public class AuthorDB {
+
+    private Database database;
+
+
+    AuthorDB(Database database) {
+        this.database = database;
+    }
+
+    /**
+     * gets tableAuthor by id.
+     *
+     * @param id ID from database
+     * @return {@link de.hsel.itech.db.pojo.Author}
+     */
+    @Nullable
+    public Author get(long id) {
+        Map.Entry<ResultSet, Connection> entry = database.getResultSetById(database.tableAuthor, id);
+        assert entry != null;
+
+        ResultSet rs = entry.getKey();
+        Author author = null;
+        try {
+            author = new Author(rs.getLong("id"), rs.getString("name"));
+            entry.getValue().close();
+        } catch (SQLException e) {
+            e.printStackTrace();
+        }
+        return author;
+    }
+
+    /**
+     * gets tableAuthor by name.
+     *
+     * @param name tableAuthor name
+     * @return {@link de.hsel.itech.db.pojo.Author}
+     */
+    @Nullable
+    public Author get(@NotNull String name) {
+        Map.Entry<ResultSet, Connection> entry = database.getResultSetsByValue(database.tableAuthor, "name", name);
+        assert entry != null;
+        assert entry.getKey() != null;
+
+        Author author = null;
+        ResultSet rs = entry.getKey();
+        try {
+            if (rs.next())
+                author = new Author(rs.getLong("id"), rs.getString("name"));
+            entry.getValue().close();
+        } catch (SQLException e) {
+            e.printStackTrace();
+        }
+
+        return author;
+    }
+
+    /**
+     * inserts Author.
+     *
+     * @param author Author
+     * @return insert count
+     */
+    public int insert(@NotNull Author author) {
+        Connection connection = database.getConnection();
+        assert connection != null;
+
+        int insertCount = 0;
+        try {
+            PreparedStatement statement = connection.prepareStatement("INSERT INTO author (name) VALUES (?)");
+            statement.setString(1, author.getName());
+
+            insertCount += statement.executeUpdate();
+
+            connection.close();
+        } catch (SQLException ex) {
+            ex.printStackTrace();
+        }
+        return insertCount;
+    }
+
+    /**
+     * deletes tableAuthor from database.
+     *
+     * @param id tableAuthor id
+     * @return deletion count
+     */
+    public int delete(long id) {
+        return database.delete(id, database.tableAuthor);
+    }
+
+    /**
+     * gets list of tableAuthor ids from database.
+     *
+     * @param id tableBook id from database
+     * @return {@link java.util.List}
+     */
+    @Nullable
+    List<Integer> getAll(long id) {
+        Map.Entry<ResultSet, Connection> entry = database.getResultSetsById(database.tableAuthorBook, database.tableBook, id);
+        assert entry != null;
+        try {
+            List<Integer> list = new ArrayList<>();
+            ResultSet rs = entry.getKey();
+            while (rs.next()) {
+                list.add(rs.getInt(database.tableAuthor));
+            }
+            entry.getValue().close();
+            return list;
+        } catch (SQLException e) {
+            e.printStackTrace();
+        }
+        return null;
+    }
+}

src/main/java/de/hsel/itech/db/BookDB.java

@@ -0,0 +1,265 @@
+package de.hsel.itech.db;
+
+import de.hsel.itech.db.pojo.Author;
+import de.hsel.itech.db.pojo.Book;
+import de.hsel.itech.db.pojo.Category;
+import de.hsel.itech.db.pojo.Publisher;
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
+
+import java.sql.*;
+import java.time.Year;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Map;
+
+/**
+ * @author Johannes Theiner
+ * @version 0.1
+ * @since 0.5
+ **/
+public class BookDB {
+    private Database database;
+
+    BookDB(Database database) {
+        this.database = database;
+    }
+
+    /**
+     * gets tableBook by id.
+     *
+     * @param id ID from database
+     * @return {@link de.hsel.itech.db.pojo.Book}
+     */
+    @Nullable
+    public Book get(long id) {
+        Map.Entry<ResultSet, Connection> entry = database.getResultSetById(database.tableBook, id);
+        assert entry != null;
+        return build(entry);
+    }
+
+    /**
+     * builds tableBook from entry.
+     *
+     * @param entry Map.Entry
+     * @return BookDB
+     */
+    @Nullable
+    private Book build(@NotNull Map.Entry<ResultSet, Connection> entry) {
+
+        Book book = null;
+        ResultSet rs = entry.getKey();
+        try {
+            Category category = database.category().get(rs.getLong(database.tableCategory));
+            Publisher publisher = database.publisher().get(rs.getLong(database.tablePublisher));
+            List<Integer> authorIds = database.author().getAll(rs.getLong("id"));
+            assert category != null;
+            assert publisher != null;
+            assert authorIds != null;
+
+            List<Author> authors = new ArrayList<>();
+            for (int i : authorIds) {
+                Author author = database.author().get(i);
+                assert author != null;
+                authors.add(author);
+            }
+            book = new Book(rs.getLong("id"), rs.getLong("isbn"), authors, publisher, category, rs.getString("title"),
+                    Year.of(rs.getInt("year")), rs.getInt("price"), rs.getString("description"),
+                    rs.getString("image"));
+
+            entry.getValue().close();
+        } catch (SQLException e) {
+            e.printStackTrace();
+        }
+        return book;
+    }
+
+    /**
+     * gets all books.
+     *
+     * @return {@link java.util.List}
+     */
+    @Nullable
+    public List<Book> getAll() {
+        List<Long> ids = database.getIds(database.tableBook);
+        List<Book> books = new ArrayList<>();
+        for (long id : ids) {
+            books.add(get(id));
+        }
+        return books;
+    }
+
+    /**
+     * gets books by tableCategory.
+     *
+     * @param category tableCategory id
+     * @return {@link java.util.List}
+     */
+    @Nullable
+    public List<Book> getAll(long category) {
+        Connection connection = database.getConnection();
+        assert connection != null;
+
+        List<Book> books = new ArrayList<>();
+        try {
+            PreparedStatement statement = connection.prepareStatement("SELECT (id) FROM book WHERE category = ?");
+            statement.setLong(1, category);
+
+            ResultSet resultSet = statement.executeQuery();
+
+            while (resultSet.next()) {
+                books.add(get(resultSet.getLong("id")));
+            }
+
+            connection.close();
+        } catch (SQLException e) {
+            e.printStackTrace();
+        }
+        return books;
+    }
+
+    /**
+     * getAll books by tableCategory.
+     *
+     * @param category Category object
+     * @return {@link java.util.List}
+     */
+    @Nullable
+    public List<Book> getAll(@NotNull Category category) {
+        return getAll(category.getId());
+    }
+
+    /**
+     * exists tableBook with isbn ?
+     *
+     * @param isbn isbn
+     * @return true if tableBook with isbn exists
+     */
+    public boolean exists(long isbn) {
+        Map.Entry<ResultSet, Connection> entry = database.getResultSetByValue(database.tableBook, "isbn", isbn);
+        try {
+            if (entry != null && entry.getKey() != null) {
+                entry.getValue().close();
+                return true;
+            }
+        } catch (SQLException ex) {
+            ex.printStackTrace();
+        }
+        return false;
+    }
+
+    /**
+     * deletes tableBook from database.
+     *
+     * @param id tableBook id
+     * @return deletion count
+     */
+    public int delete(long id) {
+        int deleteCount = 0;
+
+        try {
+            Connection connection = database.getConnection();
+            assert connection != null;
+
+            PreparedStatement statement = connection.prepareStatement("DELETE FROM author_book WHERE book = ?");
+            statement.setLong(1, id);
+            deleteCount = +statement.executeUpdate();
+
+            connection.close();
+        } catch (SQLException ex) {
+            ex.printStackTrace();
+        }
+
+        deleteCount += database.delete(id, database.tableBook);
+
+        return deleteCount;
+    }
+
+
+    /**
+     * Inserts tableBook into database.
+     * authors, publishers, and tableCategory have to exist.
+     *
+     * @param book BookDB
+     * @return insert count
+     */
+    public int insert(@NotNull Book book) {
+        Connection connection = database.getConnection();
+        assert connection != null;
+
+        int insertCount = 0;
+
+        //tableAuthor exists ?
+        List<Author> authors = new ArrayList<>();
+        for (Author author : book.getAuthors()) {
+            if (author.getId() == 0) {
+                Author dbAuthor = database.author().get(author.getName());
+                if (dbAuthor == null) {
+                    insertCount += database.author().insert(author);
+                    dbAuthor = database.author().get(author.getName());
+                }
+                authors.add(dbAuthor);
+            } else authors.add(author);
+        }
+
+        //tablePublisher exists ?
+        Publisher publisher;
+        if (book.getPublisher().getId() == 0) {
+            Publisher dbPublisher = database.publisher().get(book.getPublisher().getName());
+            if (dbPublisher != null)
+                publisher = dbPublisher;
+            else {
+                insertCount += database.publisher().insert(new Publisher(book.getPublisher().getName()));
+                publisher = database.publisher().get(book.getPublisher().getName());
+            }
+        } else publisher = book.getPublisher();
+
+        //tableCategory exists ?
+        Category category;
+        if (book.getCategory().getId() == 0) {
+            Category dbCategory = database.category().get(book.getCategory().getName());
+            if (dbCategory != null)
+                category = dbCategory;
+            else {
+                insertCount += database.category().insert(new Category(book.getCategory().getName(), database.getRandomImage()));
+                category = database.category().get(book.getCategory().getName());
+            }
+        } else category = book.getCategory();
+
+        assert publisher != null;
+        assert category != null;
+
+        //insert tableBook
+        try {
+            PreparedStatement statement = connection.prepareStatement("INSERT INTO book(isbn, title, description, " +
+                    "price, year, publisher, category, image) VALUES (?, ?, ?, ?, ?, ?, ?, ?)", Statement.RETURN_GENERATED_KEYS);
+            statement.setLong(1, book.getIsbn());
+            statement.setString(2, book.getTitle());
+            statement.setString(3, book.getDescription());
+            statement.setInt(4, book.getPrice());
+            statement.setInt(5, book.getYear().getValue());
+            statement.setLong(6, publisher.getId());
+            statement.setLong(7, category.getId());
+            statement.setString(8, book.getImage());
+            insertCount += statement.executeUpdate();
+            ResultSet resultSet = statement.getGeneratedKeys();
+            long lastId = -1;
+            while (resultSet.next()) {
+                lastId = resultSet.getLong("id");
+            }
+
+            //add tableBook to tableAuthor
+            for (Author author : authors) {
+                PreparedStatement authorStatement = connection.prepareStatement("INSERT INTO " + database.tableAuthorBook + " (author, book) VALUES (?, ?);");
+                authorStatement.setLong(1, author.getId());
+                authorStatement.setLong(2, lastId);
+                insertCount += authorStatement.executeUpdate();
+            }
+
+            connection.close();
+        } catch (SQLException ex) {
+            ex.printStackTrace();
+        }
+        return insertCount;
+    }
+}

src/main/java/de/hsel/itech/db/CategoryDB.java

@@ -0,0 +1,133 @@
+package de.hsel.itech.db;
+
+import de.hsel.itech.db.pojo.Category;
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
+
+import java.sql.Connection;
+import java.sql.PreparedStatement;
+import java.sql.ResultSet;
+import java.sql.SQLException;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Map;
+
+/**
+ * @author Johannes Theiner
+ * @version 0.1
+ * @since 0.5
+ **/
+public class CategoryDB {
+
+    private Database database;
+
+    CategoryDB(Database database) {
+        this.database = database;
+    }
+
+    /**
+     * gets tableCategory by id.
+     *
+     * @param id ID from database
+     * @return {@link de.hsel.itech.db.pojo.Category}
+     */
+    @Nullable
+    public Category get(long id) {
+        Map.Entry<ResultSet, Connection> entry = database.getResultSetById(database.tableCategory, id);
+        if(entry != null) {
+            ResultSet rs = entry.getKey();
+
+            try {
+                rs.beforeFirst();
+            } catch (SQLException e) {
+                e.printStackTrace();
+            }
+            return get(entry);
+        }
+        return null;
+    }
+
+    /**
+     * getAll tableCategory by name.
+     *
+     * @param name tableCategory name
+     * @return {@link de.hsel.itech.db.pojo.Category}
+     */
+    @Nullable
+    public Category get(@NotNull String name) {
+        Map.Entry<ResultSet, Connection> entry = database.getResultSetsByValue(database.tableCategory, "name", name);
+        assert entry != null;
+
+        return get(entry);
+    }
+
+    /**
+     * getAll Category from database entry.
+     * @param entry entry
+     * @return Category
+     */
+    @Nullable
+    private Category get(@NotNull Map.Entry<ResultSet, Connection> entry) {
+        ResultSet rs = entry.getKey();
+        Category category = null;
+        try {
+            while (rs.next()) {
+                category = new Category(rs.getLong("id"), rs.getString("name"), rs.getString("image"));
+            }
+            entry.getValue().close();
+        } catch (SQLException ex) {
+            ex.printStackTrace();
+        }
+        return category;
+    }
+
+    /**
+     * getAll all categories.
+     *
+     * @return list of categories
+     */
+    @Nullable
+    public List<Category> getAll() {
+        List<Long> ids = database.getIds(database.tableCategory);
+        List<Category> categories = new ArrayList<>();
+        for (long id : ids) {
+            categories.add(get(id));
+        }
+        return categories;
+    }
+
+    /**
+     * deletes tableCategory from database.
+     *
+     * @param id tableCategory count
+     * @return deletion count
+     */
+    public int delete(long id) {
+        return database.delete(id, database.tableCategory);
+    }
+
+    /**
+     * inserts Category into database.
+     *
+     * @param category Category
+     * @return insert count
+     */
+    public int insert(@NotNull Category category) {
+        Connection connection = database.getConnection();
+        assert connection != null;
+
+        int insertCount = 0;
+
+        try {
+            PreparedStatement statement = connection.prepareStatement("INSERT INTO category (name, image) VALUES (?, ?)");
+            statement.setString(1, category.getName());
+            statement.setString(2, category.getImage());
+            insertCount += statement.executeUpdate();
+
+            connection.close();
+        } catch (SQLException ex) {
+            ex.printStackTrace();
+        }
+        return insertCount;
+    }
+}

src/main/java/de/hsel/itech/db/Database.java

@@ -1,10 +1,6 @@
 package de.hsel.itech.db;
 
 import de.hsel.itech.config.Configuration;
-import de.hsel.itech.db.pojo.Author;
-import de.hsel.itech.db.pojo.Book;
-import de.hsel.itech.db.pojo.Category;
-import de.hsel.itech.db.pojo.Publisher;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
 import org.json.JSONObject;
@@ -13,8 +9,10 @@ import org.mariadb.jdbc.MariaDbPoolDataSource;
 import java.io.*;
 import java.net.URL;
 import java.nio.charset.Charset;
-import java.sql.*;
+import java.sql.Connection;
-import java.time.Year;
+import java.sql.PreparedStatement;
+import java.sql.ResultSet;
+import java.sql.SQLException;
 import java.util.AbstractMap;
 import java.util.ArrayList;
 import java.util.List;
@@ -29,11 +27,16 @@ import java.util.Map;
  */
 public class Database {
 
-    private final String book = "book";
+    final String tableBook = "book";
-    private final String author = "author";
+    final String tableAuthor = "author";
-    private final String authorBook = "author_book";
+    final String tableAuthorBook = "author_book";
-    private final String publisher = "publisher";
+    final String tablePublisher = "publisher";
-    private final String category = "category";
+    final String tableCategory = "category";
+
+    private AuthorDB authorDB;
+    private BookDB bookDB;
+    private CategoryDB categoryDB;
+    private PublisherDB publisherDB;
 
     private static Database instance;
 
@@ -88,7 +91,7 @@ public class Database {
      * @return {@link java.sql.Connection}
      */
     @Nullable
-    private Connection getConnection() {
+    Connection getConnection() {
         try {
             return dataSource.getConnection();
         } catch (SQLException e) {
@@ -97,537 +100,30 @@ public class Database {
         return null;
     }
 
-    /**
+    public BookDB book() {
-     * gets author by id.
+        if(bookDB == null)
-     *
+            bookDB = new BookDB(this);
-     * @param id ID from database
+        return bookDB;
-     * @return {@link de.hsel.itech.db.pojo.Author}
-     */
-    @Nullable
-    public Author getAuthor(long id) {
-        Map.Entry<ResultSet, Connection> entry = getResultSetById(author, id);
-        assert entry != null;
-
-        ResultSet rs = entry.getKey();
-        Author author = null;
-        try {
-            author = new Author(rs.getLong("id"), rs.getString("name"));
-            entry.getValue().close();
-        } catch (SQLException e) {
-            e.printStackTrace();
-        }
-        return author;
     }
 
-    /**
+    public AuthorDB author() {
-     * gets author by name.
+        if(authorDB == null)
-     *
+            authorDB = new AuthorDB(this);
-     * @param name author name
+        return authorDB;
-     * @return {@link de.hsel.itech.db.pojo.Author}
-     */
-    @Nullable
-    public Author getAuthor(@NotNull String name) {
-        Map.Entry<ResultSet, Connection> entry = getResultSetsByValue(author, "name", name);
-        assert entry != null;
-        assert entry.getKey() != null;
-
-        Author author = null;
-        ResultSet rs = entry.getKey();
-        try {
-            if (rs.next())
-                author = new Author(rs.getLong("id"), rs.getString("name"));
-            entry.getValue().close();
-        } catch (SQLException e) {
-            e.printStackTrace();
     }
 
-        return author;
+    public CategoryDB category() {
+        if (categoryDB == null)
+            categoryDB = new CategoryDB(this);
+        return categoryDB;
     }
 
-    /**
+    public PublisherDB publisher() {
-     * gets category by id.
+        if(publisherDB == null)
-     *
+            publisherDB = new PublisherDB(this);
-     * @param id ID from database
+        return publisherDB;
-     * @return {@link de.hsel.itech.db.pojo.Category}
-     */
-    @Nullable
-    public Category getCategory(long id) {
-        Map.Entry<ResultSet, Connection> entry = getResultSetById(category, id);
-        if(entry != null) {
-            ResultSet rs = entry.getKey();
-
-            try {
-                rs.beforeFirst();
-            } catch (SQLException e) {
-                e.printStackTrace();
-            }
-            return getCategory(entry);
-        }
-        return null;
     }
 
-    /**
-     * get category by name.
-     *
-     * @param name category name
-     * @return {@link de.hsel.itech.db.pojo.Category}
-     */
-    @Nullable
-    public Category getCategory(@NotNull String name) {
-        Map.Entry<ResultSet, Connection> entry = getResultSetsByValue(category, "name", name);
-        assert entry != null;
-
-        return getCategory(entry);
-    }
-
-    /**
-     * get Category from database entry.
-     * @param entry entry
-     * @return Category
-     */
-    @Nullable
-    private Category getCategory(@NotNull Map.Entry<ResultSet, Connection> entry) {
-        ResultSet rs = entry.getKey();
-        Category category = null;
-        try {
-            while (rs.next()) {
-                category = new Category(rs.getLong("id"), rs.getString("name"), rs.getString("image"));
-            }
-            entry.getValue().close();
-        } catch (SQLException ex) {
-            ex.printStackTrace();
-        }
-        return category;
-    }
-
-    /**
-     * get all categories.
-     *
-     * @return list of categories
-     */
-    @Nullable
-    public List<Category> getCategories() {
-        List<Long> ids = getIds(category);
-        List<Category> categories = new ArrayList<>();
-        for (long id : ids) {
-            categories.add(getCategory(id));
-        }
-        return categories;
-    }
-
-
-    /**
-     * gets publisher by id.
-     *
-     * @param id ID from database
-     * @return {@link de.hsel.itech.db.pojo.Publisher}
-     */
-    @Nullable
-    public Publisher getPublisher(long id) {
-        Map.Entry<ResultSet, Connection> entry = getResultSetById(publisher, id);
-        assert entry != null;
-
-        ResultSet rs = entry.getKey();
-        Publisher publisher = null;
-        try {
-            publisher = new Publisher(rs.getLong("id"), rs.getString("name"));
-            entry.getValue().close();
-        } catch (SQLException e) {
-            e.printStackTrace();
-        }
-        return publisher;
-    }
-
-    /**
-     * get publisher by name.
-     *
-     * @param name publisher name
-     * @return {@link de.hsel.itech.db.pojo.Publisher}
-     */
-    @Nullable
-    public Publisher getPublisher(@NotNull String name) {
-        Map.Entry<ResultSet, Connection> entry = getResultSetsByValue(publisher, "name", name);
-        assert entry != null;
-        assert entry.getKey() != null;
-
-        Publisher publisher = null;
-        ResultSet rs = entry.getKey();
-        try {
-            while (rs.next()) {
-                publisher = new Publisher(rs.getLong("id"), rs.getString("name"));
-            }
-            entry.getValue().close();
-        } catch (SQLException e) {
-            e.printStackTrace();
-        }
-
-        return publisher;
-    }
-
-    /**
-     * gets list of author ids from database.
-     *
-     * @param id book id from database
-     * @return {@link java.util.List}
-     */
-    @Nullable
-    private List<Integer> getAuthors(long id) {
-        Map.Entry<ResultSet, Connection> entry = getResultSetsById(authorBook, book, id);
-        assert entry != null;
-        try {
-            List<Integer> list = new ArrayList<>();
-            ResultSet rs = entry.getKey();
-            while (rs.next()) {
-                list.add(rs.getInt(author));
-            }
-            entry.getValue().close();
-            return list;
-        } catch (SQLException e) {
-            e.printStackTrace();
-        }
-        return null;
-    }
-
-    /**
-     * gets book by id.
-     *
-     * @param id ID from database
-     * @return {@link de.hsel.itech.db.pojo.Book}
-     */
-    @Nullable
-    public Book getBook(long id) {
-        Map.Entry<ResultSet, Connection> entry = getResultSetById(book, id);
-        assert entry != null;
-        return buildBook(entry);
-    }
-
-    /**
-     * builds book from entry.
-     *
-     * @param entry Map.Entry
-     * @return Book
-     */
-    @Nullable
-    private Book buildBook(@NotNull Map.Entry<ResultSet, Connection> entry) {
-
-        Book book = null;
-        ResultSet rs = entry.getKey();
-        try {
-            Category category = getCategory(rs.getLong(this.category));
-            Publisher publisher = getPublisher(rs.getLong(this.publisher));
-            List<Integer> authorIds = getAuthors(rs.getLong("id"));
-            assert category != null;
-            assert publisher != null;
-            assert authorIds != null;
-
-            List<Author> authors = new ArrayList<>();
-            for (int i : authorIds) {
-                Author author = getAuthor(i);
-                assert author != null;
-                authors.add(author);
-            }
-            book = new Book(rs.getLong("id"), rs.getLong("isbn"), authors, publisher, category, rs.getString("title"),
-                    Year.of(rs.getInt("year")), rs.getInt("price"), rs.getString("description"),
-                    rs.getString("image"));
-
-            entry.getValue().close();
-        } catch (SQLException e) {
-            e.printStackTrace();
-        }
-        return book;
-    }
-
-    /**
-     * gets all books.
-     *
-     * @return {@link java.util.List}
-     */
-    @Nullable
-    public List<Book> getBooks() {
-        List<Long> ids = getIds(book);
-        List<Book> books = new ArrayList<>();
-        for (long id : ids) {
-            books.add(getBook(id));
-        }
-        return books;
-    }
-
-    /**
-     * gets books by category.
-     *
-     * @param category category id
-     * @return {@link java.util.List}
-     */
-    @Nullable
-    public List<Book> getBooks(long category) {
-        Connection connection = getConnection();
-        assert connection != null;
-
-        List<Book> books = new ArrayList<>();
-        try {
-            PreparedStatement statement = connection.prepareStatement("SELECT (id) FROM book WHERE category = ?");
-            statement.setLong(1, category);
-
-            ResultSet resultSet = statement.executeQuery();
-
-            while (resultSet.next()) {
-                books.add(getBook(resultSet.getLong("id")));
-            }
-
-            connection.close();
-        } catch (SQLException e) {
-            e.printStackTrace();
-        }
-        return books;
-    }
-
-    /**
-     * get books by category.
-     *
-     * @param category Category object
-     * @return {@link java.util.List}
-     */
-    @Nullable
-    public List<Book> getBooks(@NotNull Category category) {
-        return getBooks(category.getId());
-    }
-
-    /**
-     * exists book with isbn ?
-     *
-     * @param isbn isbn
-     * @return true if book with isbn exists
-     */
-    public boolean existsBook(long isbn) {
-        Map.Entry<ResultSet, Connection> entry = getResultSetByValue(book, "isbn", isbn);
-        try {
-            if (entry != null && entry.getKey() != null) {
-                entry.getValue().close();
-                return true;
-            }
-        } catch (SQLException ex) {
-            ex.printStackTrace();
-        }
-        return false;
-    }
-
-
-    /**
-     * Inserts book into database.
-     * authors, publishers, and category have to exist.
-     *
-     * @param book Book
-     * @return insert count
-     */
-    public int insert(@NotNull Book book) {
-        Connection connection = getConnection();
-        assert connection != null;
-
-        int insertCount = 0;
-
-        //author exists ?
-        List<Author> authors = new ArrayList<>();
-        for (Author author : book.getAuthors()) {
-            if (author.getId() == 0) {
-                Author dbAuthor = getAuthor(author.getName());
-                if (dbAuthor == null) {
-                    insertCount += insert(author);
-                    dbAuthor = getAuthor(author.getName());
-                }
-                authors.add(dbAuthor);
-            } else authors.add(author);
-        }
-
-        //publisher exists ?
-        Publisher publisher;
-        if (book.getPublisher().getId() == 0) {
-            Publisher dbPublisher = getPublisher(book.getPublisher().getName());
-            if (dbPublisher != null)
-                publisher = dbPublisher;
-            else {
-                insertCount += insert(new Publisher(book.getPublisher().getName()));
-                publisher = getPublisher(book.getPublisher().getName());
-            }
-        } else publisher = book.getPublisher();
-
-        //category exists ?
-        Category category;
-        if (book.getCategory().getId() == 0) {
-            Category dbCategory = getCategory(book.getCategory().getName());
-            if (dbCategory != null)
-                category = dbCategory;
-            else {
-                insertCount += insert(new Category(book.getCategory().getName(), getRandomImage()));
-                category = getCategory(book.getCategory().getName());
-            }
-        } else category = book.getCategory();
-
-        assert publisher != null;
-        assert category != null;
-
-        //insert book
-        try {
-            PreparedStatement statement = connection.prepareStatement("INSERT INTO book(isbn, title, description, " +
-                    "price, year, publisher, category, image) VALUES (?, ?, ?, ?, ?, ?, ?, ?)", Statement.RETURN_GENERATED_KEYS);
-            statement.setLong(1, book.getIsbn());
-            statement.setString(2, book.getTitle());
-            statement.setString(3, book.getDescription());
-            statement.setInt(4, book.getPrice());
-            statement.setInt(5, book.getYear().getValue());
-            statement.setLong(6, publisher.getId());
-            statement.setLong(7, category.getId());
-            statement.setString(8, book.getImage());
-            insertCount += statement.executeUpdate();
-            ResultSet resultSet = statement.getGeneratedKeys();
-            long lastId = -1;
-            while (resultSet.next()) {
-                lastId = resultSet.getLong("id");
-            }
-
-            //add book to author
-            for (Author author : authors) {
-                PreparedStatement authorStatement = connection.prepareStatement("INSERT INTO " + authorBook + " (author, book) VALUES (?, ?);");
-                authorStatement.setLong(1, author.getId());
-                authorStatement.setLong(2, lastId);
-                insertCount += authorStatement.executeUpdate();
-            }
-
-            connection.close();
-        } catch (SQLException ex) {
-            ex.printStackTrace();
-        }
-        return insertCount;
-    }
-
-    /**
-     * inserts Category into database.
-     *
-     * @param category Category
-     * @return insert count
-     */
-    public int insert(@NotNull Category category) {
-        Connection connection = getConnection();
-        assert connection != null;
-
-        int insertCount = 0;
-
-        try {
-            PreparedStatement statement = connection.prepareStatement("INSERT INTO category (name, image) VALUES (?, ?)");
-            statement.setString(1, category.getName());
-            statement.setString(2, category.getImage());
-            insertCount += statement.executeUpdate();
-
-            connection.close();
-        } catch (SQLException ex) {
-            ex.printStackTrace();
-        }
-        return insertCount;
-    }
-
-    /**
-     * inserts Author.
-     *
-     * @param author Author
-     * @return insert count
-     */
-    public int insert(@NotNull Author author) {
-        Connection connection = getConnection();
-        assert connection != null;
-
-        int insertCount = 0;
-        try {
-            PreparedStatement statement = connection.prepareStatement("INSERT INTO author (name) VALUES (?)");
-            statement.setString(1, author.getName());
-
-            insertCount += statement.executeUpdate();
-
-            connection.close();
-        } catch (SQLException ex) {
-            ex.printStackTrace();
-        }
-        return insertCount;
-    }
-
-    /**
-     * inserts Publisher.
-     *
-     * @param publisher Publisher
-     * @return insert count
-     */
-    public int insert(@NotNull Publisher publisher) {
-        Connection connection = getConnection();
-        assert connection != null;
-
-        int insertCount = 0;
-        try {
-            PreparedStatement statement = connection.prepareStatement("INSERT INTO publisher (name) VALUES (?)");
-            statement.setString(1, publisher.getName());
-
-            insertCount += statement.executeUpdate();
-
-            connection.close();
-        } catch (SQLException ex) {
-            ex.printStackTrace();
-        }
-        return insertCount;
-    }
-
-    /**
-     * deletes book from database.
-     *
-     * @param id book id
-     * @return deletion count
-     */
-    public int deleteBook(long id) {
-        int deleteCount = 0;
-
-        try {
-            Connection connection = getConnection();
-            assert connection != null;
-
-            PreparedStatement statement = connection.prepareStatement("DELETE FROM author_book WHERE book = ?");
-            statement.setLong(1, id);
-            deleteCount = +statement.executeUpdate();
-
-            connection.close();
-        } catch (SQLException ex) {
-            ex.printStackTrace();
-        }
-
-        deleteCount += delete(id, book);
-
-        return deleteCount;
-    }
-
-    /**
-     * deletes author from database.
-     *
-     * @param id author id
-     * @return deletion count
-     */
-    public int deleteAuthor(long id) {
-        return delete(id, author);
-    }
-
-    /**
-     * deletes publisher from database.
-     *
-     * @param id publisher id
-     * @return deletion count
-     */
-    public int deletePublisher(long id) {
-        return delete(id, publisher);
-    }
-
-    /**
-     * deletes category from database.
-     *
-     * @param id category count
-     * @return deletion count
-     */
-    public int deleteCategory(long id) {
-        return delete(id, category);
-    }
 
 
     /**
@@ -637,7 +133,7 @@ public class Database {
      * @param table table name
      * @return deletion count
      */
-    private int delete(long id, @NotNull String table) {
+    int delete(long id, @NotNull String table) {
         Connection connection = getConnection();
         assert connection != null;
 
@@ -655,12 +151,12 @@ public class Database {
     }
 
     /**
-     * get all ids from specified table.
+     * getAll all ids from specified table.
      *
      * @param table table
      * @return list of ids
      */
-    private List<Long> getIds(@NotNull String table) {
+    List<Long> getIds(@NotNull String table) {
         Map.Entry<ResultSet, Connection> entry = getColumnsFromResultSet(table, "id");
         assert entry != null;
 
@@ -687,12 +183,12 @@ public class Database {
      * @return {@link java.util.Map.Entry}
      */
     @Nullable
-    private Map.Entry<ResultSet, Connection> getResultSetById(@NotNull String table, long id) {
+    Map.Entry<ResultSet, Connection> getResultSetById(@NotNull String table, long id) {
         return getResultSetByValue(table, "id", id);
     }
 
     @Nullable
-    private Map.Entry<ResultSet, Connection> getResultSetByValue(@NotNull String table, @NotNull String column, long value) {
+    Map.Entry<ResultSet, Connection> getResultSetByValue(@NotNull String table, @NotNull String column, long value) {
         Connection connection = getConnection();
         try {
             assert connection != null;
@@ -719,7 +215,7 @@ public class Database {
      * @return {@link java.util.Map.Entry}
      */
     @Nullable
-    private Map.Entry<ResultSet, Connection> getResultSetsById(@NotNull String table, @NotNull String column, long id) {
+    Map.Entry<ResultSet, Connection> getResultSetsById(@NotNull String table, @NotNull String column, long id) {
         Connection connection = getConnection();
         try {
             assert connection != null;
@@ -741,7 +237,7 @@ public class Database {
      * @return {@link java.util.Map.Entry}
      */
     @Nullable
-    private Map.Entry<ResultSet, Connection> getResultSetsByValue(@NotNull String table, @NotNull String column, @NotNull String value) {
+    Map.Entry<ResultSet, Connection> getResultSetsByValue(@NotNull String table, @NotNull String column, @NotNull String value) {
         Connection connection = getConnection();
         try {
             assert connection != null;
@@ -795,10 +291,9 @@ public class Database {
     }
 
     @Nullable
-    private String getRandomImage() {
+    String getRandomImage() {
-        try {
-            InputStream is = new URL("https://api.unsplash.com/photos/random?client_id=" + Configuration.get().getUnsplash().getAccessKey()).openStream();
         try {
+            try (InputStream is = new URL("https://api.unsplash.com/photos/random?client_id=" + Configuration.get().getUnsplash().getAccessKey()).openStream()) {
                 BufferedReader rd = new BufferedReader(new InputStreamReader(is, Charset.forName("UTF-8")));
                 StringBuilder sb = new StringBuilder();
                 int cp;
@@ -807,8 +302,6 @@ public class Database {
                 }
                 JSONObject json = new JSONObject(sb.toString());
                 return json.getString("id");
-            } finally {
-                is.close();
             }
 
 

src/main/java/de/hsel/itech/db/PublisherDB.java

@@ -0,0 +1,110 @@
+package de.hsel.itech.db;
+
+import de.hsel.itech.db.pojo.Publisher;
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
+
+import java.sql.Connection;
+import java.sql.PreparedStatement;
+import java.sql.ResultSet;
+import java.sql.SQLException;
+import java.util.Map;
+
+/**
+ * @author Johannes Theiner
+ * @version 0.1
+ * @since 0.5
+ **/
+public class PublisherDB {
+
+    private Database database;
+
+    PublisherDB(Database database) {
+        this.database = database;
+    }
+
+    /**
+     * gets tablePublisher by id.
+     *
+     * @param id ID from database
+     * @return {@link de.hsel.itech.db.pojo.Publisher}
+     */
+    @Nullable
+    public Publisher get(long id) {
+        Map.Entry<ResultSet, Connection> entry = database.getResultSetById(database.tablePublisher, id);
+        assert entry != null;
+
+        ResultSet rs = entry.getKey();
+        Publisher publisher = null;
+        try {
+            publisher = new Publisher(rs.getLong("id"), rs.getString("name"));
+            entry.getValue().close();
+        } catch (SQLException e) {
+            e.printStackTrace();
+        }
+        return publisher;
+    }
+
+    /**
+     * getAll tablePublisher by name.
+     *
+     * @param name tablePublisher name
+     * @return {@link de.hsel.itech.db.pojo.Publisher}
+     */
+    @Nullable
+    public Publisher get(@NotNull String name) {
+        Map.Entry<ResultSet, Connection> entry = database.getResultSetsByValue(database.tablePublisher, "name", name);
+        assert entry != null;
+        assert entry.getKey() != null;
+
+        Publisher publisher = null;
+        ResultSet rs = entry.getKey();
+        try {
+            while (rs.next()) {
+                publisher = new Publisher(rs.getLong("id"), rs.getString("name"));
+            }
+            entry.getValue().close();
+        } catch (SQLException e) {
+            e.printStackTrace();
+        }
+
+        return publisher;
+    }
+
+
+
+
+    /**
+     * inserts Publisher.
+     *
+     * @param publisher Publisher
+     * @return insert count
+     */
+    public int insert(@NotNull Publisher publisher) {
+        Connection connection = database.getConnection();
+        assert connection != null;
+
+        int insertCount = 0;
+        try {
+            PreparedStatement statement = connection.prepareStatement("INSERT INTO publisher (name) VALUES (?)");
+            statement.setString(1, publisher.getName());
+
+            insertCount += statement.executeUpdate();
+
+            connection.close();
+        } catch (SQLException ex) {
+            ex.printStackTrace();
+        }
+        return insertCount;
+    }
+
+    /**
+     * deletes tablePublisher from database.
+     *
+     * @param id tablePublisher id
+     * @return deletion count
+     */
+    public int delete(long id) {
+        return database.delete(id, database.tablePublisher);
+    }
+}

src/main/java/de/hsel/itech/db/pojo/Book.java

@@ -9,7 +9,7 @@ import java.time.Year;
 import java.util.List;
 
 /**
- * POJO for Book.
+ * POJO for BookDB.
  *
  * @author Johannes Theiner
  * @version 0.1

src/main/java/de/hsel/itech/jsf/CategoryBean.java

@@ -33,10 +33,10 @@ public class CategoryBean implements Serializable {
     }
 
     public List<Category> getCategories() {
-        return Database.getInstance().getCategories();
+        return Database.getInstance().category().getAll();
     }
 
     public List<Book> getBooks() {
-        return Database.getInstance().getBooks(category);
+        return Database.getInstance().book().getAll(category);
     }
 }

src/main/java/de/hsel/itech/jsf/SettingsBean.java

@@ -0,0 +1,24 @@
+package de.hsel.itech.jsf;
+
+import lombok.Getter;
+import lombok.Setter;
+
+import javax.faces.bean.ManagedBean;
+import javax.faces.bean.SessionScoped;
+
+/**
+ * @author Johannes Theiner
+ * @version 0.1
+ * @since 0.5
+ **/
+
+@ManagedBean
+@SessionScoped
+public class SettingsBean {
+
+
+    @Getter
+    @Setter
+    private boolean darkTheme = false;
+
+}

src/main/java/de/hsel/itech/servlet/BookList.java

@@ -38,7 +38,7 @@ public class BookList extends HttpServlet {
     protected void doPost(@NotNull final HttpServletRequest req, @NotNull final HttpServletResponse resp) throws IOException {
         req.setCharacterEncoding(StandardCharsets.UTF_8.name());
 
-        //get database object
+        //getAll database object
         Database db = Database.getInstance();
 
         resp.setCharacterEncoding(StandardCharsets.UTF_8.name());
@@ -51,7 +51,7 @@ public class BookList extends HttpServlet {
         String param = req.getParameter("removeid");
         if (param != null && Long.parseLong(param) != 0) {
             long isbn = Long.parseLong(param);
-            db.deleteBook(isbn);
+            db.book().delete(isbn);
             resp.sendRedirect("booklist");
         }
 
@@ -79,7 +79,7 @@ public class BookList extends HttpServlet {
                 String image = req.getParameter("image");
 
                 //check isbn
-                if (db.existsBook(isbn)) {
+                if (db.book().exists(isbn)) {
                     out.println("<aside class =\"m-note m-danger\">");
                     out.println("<h3>Es gibt bereits ein Buch mit dieser ISBN </h3>");
                     out.println("</aside>");
@@ -96,7 +96,7 @@ public class BookList extends HttpServlet {
                             category,
                             title, Year.of(year), price, description, image
                     );
-                    db.insert(book);
+                    db.book().insert(book);
                     resp.sendRedirect("booklist");
                 }
             } catch (Exception e) {
@@ -110,7 +110,7 @@ public class BookList extends HttpServlet {
 
 
         //list all books
-        List<Book> books = db.getBooks();
+        List<Book> books = db.book().getAll();
         if (books != null) {
 
             //book entries

src/main/webapp/categories.jsp

@@ -12,7 +12,7 @@
     <h1 class="m-text-center">Kategorien</h1>
 <div class="m-row">
 <%
-    for(Category category : Objects.requireNonNull(Database.getInstance().getCategories())) {
+    for(Category category : Objects.requireNonNull(Database.getInstance().category().getAll())) {
         %>
     <div class="m-col-t-4">
         <a href="category.jsp?id=<%= category.getId() %>">

src/main/webapp/category.jsp

@@ -22,7 +22,7 @@
 } else {
     long id = Long.valueOf(idValue);
     Database db = Database.getInstance();
-    category = db.getCategory(id);
+    category = db.category().get(id);
     if (category != null) {
 %>
 <div class="m-container">
@@ -30,7 +30,7 @@
     </h1>
     <div class="m-row">
         <%
-            for (Book book : Objects.requireNonNull(db.getBooks(category))) {
+            for (Book book : db.book().getAll(category)) {
         %>
         <div class="m-col-t-4">
             <figure class="m-figure">

src/main/webapp/index.html

@@ -8,6 +8,7 @@
     <li><a href="preview">Grobspezifikation</a></li>
     <li><a href="booklist">Backend</a></li>
     <li><a href="categories.jsp">Kategorienübersicht</a></li>
+    <li><a href="category.jsf">Warengruppe ausgeben</a></li>
 </ul>
 </body>
 </html>

src/main/webapp/template.xhtml

@@ -14,7 +14,7 @@
 
     <link href="css/custom.css" rel="stylesheet"/>
     <link href="css/slick-theme.css" rel="stylesheet"/>
-    <link rel="stylesheet" type="text/css" href="//cdn.jsdelivr.net/npm/slick-carousel@1.8.1/slick/slick.css"/>
+    <link rel="stylesheet" type="text/css" href="https://cdn.jsdelivr.net/npm/slick-carousel@1.8.1/slick/slick.css"/>
     <link rel="stylesheet" href="https://use.fontawesome.com/releases/v5.8.1/css/all.css"/>
 
     <title>Amazon Light</title>
@@ -37,7 +37,7 @@
                 <div id="m-navbar-collapse" class="m-col-t-12 m-show-m m-col-m-none m-right-m">
                     <div class="m-row">
                         <ol class="m-col-t-6 m-col-m-none">
-                            <li><a href="#">Katalog</a></li>
+                            <li><a href="category.jsf">Katalog</a></li>
                             <li><a href="#">(1) Warenkorb</a></li>
                         </ol>
                         <ol class="m-col-t-6 m-col-m-none" start="4">
@@ -55,14 +55,19 @@
                                 <a href="#"><i class="fas fa-ellipsis-v"/></a>
                                 <ol>
                                     <li>Dark Theme
+                                        <h:form>
                                             <div class="onoffswitch">
-                                            <input type="checkbox" name="onoffswitch" class="onoffswitch-checkbox"
+
-                                                   id="myonoffswitch" onchange="changeTheme()"/>
+                                                <h:selectBooleanCheckbox styleClass="onoffswitch-checkbox"
-                                            <label class="onoffswitch-label" for="myonoffswitch">
+                                                                         id="myonoffswitch"
+                                                                         title="onoffswitch" onchange="changeTheme()"
+                                                                         value="#{settingsBean.darkTheme}"/>
+                                                <h:outputLabel styleClass="onoffswitch-label" for="myonoffswitch">
                                                     <span class="onoffswitch-inner"/>
                                                     <span class="onoffswitch-switch"/>
-                                            </label>
+                                                </h:outputLabel>
                                             </div>
+                                        </h:form>
                                     </li>
                                 </ol>
                             </li>
@@ -132,8 +137,7 @@
 <script type="text/javascript" src="//cdn.jsdelivr.net/npm/slick-carousel@1.8.1/slick/slick.min.js"/>
 <script>
     function changeTheme() {
-
+        if ('#{settingsBean.darkTheme}' === 'true') {
-        if (document.getElementById('myonoffswitch').checked) {
             swapStyleSheet("dark", "#22272e");
         } else {
             swapStyleSheet("light", "#cb4b16");
@@ -151,7 +155,8 @@
             infinite: true,
             slidesToShow: 6,
             slidesToScroll: 3
-        })
+        });
+        changeTheme();
     });
 </script>
 </body>