Home work 4

basics/src/main/java/ru/msu/vmk/NumberSample.java

@@ -3,9 +3,23 @@
 import java.math.BigDecimal;
 
 public class NumberSample {
+
     public static BigDecimal[] split(BigDecimal amount, int n) {
-        // разделить amount на n частей
-        // если остается остаток, прибавить его к первому числу
-        return null;
+        var array = new BigDecimal[n];
+        double temp = amount.doubleValue();
+        int previousSize = n;
+        for (int i = 0; n > 0; i++, n--) {
+            double size = temp / n;
+            if (previousSize > 2) {
+                array[i] = BigDecimal.valueOf((int) size);
+            } else {
+                array[i] = BigDecimal.valueOf(size);
+            }
+            temp -= size;
+        }
+        if (previousSize > 2) {
+            array[0] = BigDecimal.valueOf((int) (amount.doubleValue() / previousSize)).add(BigDecimal.valueOf(amount.doubleValue() % previousSize));
+        }
+        return array;
     }
 }

collections/pom.xml

@@ -23,6 +23,16 @@
             <artifactId>junit-jupiter</artifactId>
             <version>5.9.2</version>
         </dependency>
+        <dependency>
+            <groupId>org.apache.derby</groupId>
+            <artifactId>derby</artifactId>
+            <version>10.14.2.0</version>
+        </dependency>
+        <dependency>
+            <groupId>org.apache.derby</groupId>
+            <artifactId>derbynet</artifactId>
+            <version>10.6.2.1</version>
+        </dependency>
         <dependency>
             <groupId>org.junit.jupiter</groupId>
             <artifactId>junit-jupiter-api</artifactId>

collections/src/main/java/ru/msu/vmk/Book.java

@@ -1,13 +1,55 @@
 package ru.msu.vmk;
 
+import java.util.Objects;
+
 public class Book {
+
+    private int bookId;
     private String title;
 
+    private int isReserved;
+
+    public Book() {
+    }
+
     public Book(String title){
         this.title = title;
     }
 
+    public int getBookId() {
+        return bookId;
+    }
+
+    public void setBookId(int bookId) {
+        this.bookId = bookId;
+    }
+
     public String getTitle(){
         return title;
     }
+
+    public void setTitle(String title) {
+        this.title = title;
+    }
+
+    public int getIsReserved() {
+        return isReserved;
+    }
+
+    public void setIsReserved(int isReserved) {
+        this.isReserved = isReserved;
+    }
+
+    @Override
+    public boolean equals(Object o) {
+        if (this == o) return true;
+        if (o == null || getClass() != o.getClass()) return false;
+        Book book = (Book) o;
+        return bookId == book.bookId && isReserved == book.isReserved && Objects.equals(title, book.title);
+    }
+
+    @Override
+    public int hashCode() {
+        return Objects.hash(bookId, title, isReserved);
+    }
 }

collections/src/main/java/ru/msu/vmk/Library.java

@@ -1,15 +1,41 @@
 package ru.msu.vmk;
 
+import java.sql.Connection;
+import java.sql.SQLException;
 import java.util.List;
 
 /* Институтская библиотека */
 public interface Library {
     /* Регистрация новой книги */
-    void addNewBook(Book book);
+    void addNewBook(Book book) throws SQLException;
+
     /* Студент берет книгу */
-    void borrowBook(Book book, String student);
+    void borrowBook(Book book, String student) throws SQLException;
+
     /* Студент возвращает книгу */
-    void returnBook(Book book, String student);
+    void returnBook(Book book, String student) throws SQLException;
+
     /* Получить список свободных книг */
-    List<Book> findAvailableBooks();
+    List<Book> findAvailableBooks() throws SQLException;
+    /*Инициализация базы данных*/
+    void init() throws SQLException;
+
+    Connection getConnection() throws SQLException;
+
+    Book getBookByTitle(String title) throws SQLException;
+
+    void updateIsReservedFlag(int bookId, int isReserved) throws SQLException;
+
+    Student getStudentByName(String name) throws SQLException;
+
+    List<Relation> getRelationByStudentId(int studentId) throws SQLException;
+
+    void insertNewStudent(String student) throws SQLException;
+
+    void insertNewRelation(int bookId, int studentId) throws SQLException;
+
+    boolean deleteRelation(int relationId) throws SQLException;
+
+
+
 }

collections/src/main/java/ru/msu/vmk/LibraryImpl.java

@@ -1,25 +1,240 @@
 package ru.msu.vmk;
 
+import java.sql.*;
+import java.util.ArrayList;
 import java.util.List;
+import java.util.logging.Logger;
+
+public class LibraryImpl implements Library {
+
+    private final Logger logger = Logger.getLogger(LibraryImpl.class.getName());
+
+    private final String jdbcUrl;
+    private final String user;
+    private final String password;
+
+    public LibraryImpl(String jdbcUrl, String user, String password) {
+        this.jdbcUrl = jdbcUrl;
+        this.user = user;
+        this.password = password;
+    }
 
-public class LibraryImpl implements Library{
     @Override
-    public void addNewBook(Book book) {
+    public void addNewBook(Book book) throws SQLException {
+        Book bookInLibrary = getBookByTitle(book.getTitle());
+        if (bookInLibrary == null) {
+            String sql = "insert into LIBRARY.BOOK (TITLE, IS_RESERVED) values (?,?)";
+            try (Connection connection = getConnection(); PreparedStatement pr = connection.prepareStatement(sql)) {
+                pr.setString(1, book.getTitle());
+                pr.setInt(2, 0);
+                int row = pr.executeUpdate();
+                if (row > 0) {
+                    logger.info("Книга добавлена.");
+                }
+            }
+        } else {
+            logger.info("Книга уже есть в библиотеке!");
+        }
+    }
 
+    @Override
+    public void borrowBook(Book book, String student) throws SQLException {
+        Book bookInLibrary = getBookByTitle(book.getTitle());
+        if (bookInLibrary != null && bookInLibrary.getIsReserved() != 1) {
+            updateIsReservedFlag(bookInLibrary.getBookId(), 1);
+            Student studentInDB = getStudentByName(student);
+            if (studentInDB == null) {
+                insertNewStudent(student);
+                studentInDB = getStudentByName(student);
+            }
+            List<Relation> relations = getRelationByStudentId(studentInDB.getStudentId());
+            if (!relations.isEmpty()) {
+                if (relations.stream().anyMatch(rel -> rel.getBookId() != bookInLibrary.getBookId())) {
+                    insertNewRelation(bookInLibrary.getBookId(), studentInDB.getStudentId());
+                }
+            } else {
+                insertNewRelation(bookInLibrary.getBookId(), studentInDB.getStudentId());
+            }
+            logger.info("Книга выдана.");
+        } else {
+            logger.info("Книги нет в библиотеки.");
+        }
     }
 
     @Override
-    public void borrowBook(Book book, String student) {
+    public void returnBook(Book book, String student) throws SQLException {
+        Student studentInDB = getStudentByName(student);
+        if (studentInDB != null) {
+            List<Relation> relations = getRelationByStudentId(studentInDB.getStudentId());
+            if (!relations.isEmpty()) {
+                relations.stream().filter(rel -> rel.getBookId() == book.getBookId()).forEach(relation -> {
+                    try {
+                        updateIsReservedFlag(relation.getBookId(), 0);
+                        deleteRelation(relation.getRelationId());
+                        logger.info("Книгу вернули.");
+                    } catch (SQLException e) {
+                        logger.severe(e.getMessage());
+                    }
+                });
+            } else {
+                logger.info("За студентом не числится эта книга!");
+            }
+        } else {
+            logger.info("Студент не найден!");
+        }
+    }
 
+    @Override
+    public List<Book> findAvailableBooks() throws SQLException {
+        List<Book> out = new ArrayList<>();
+        String sql = "select * from LIBRARY.BOOK where is_reserved = 0";
+        try (Connection connection = getConnection(); PreparedStatement pr = connection.prepareStatement(sql)) {
+            ResultSet resultSet = pr.executeQuery();
+            while (resultSet.next()) {
+                Book book = new Book();
+                book.setBookId(resultSet.getInt("BOOK_ID"));
+                book.setTitle(resultSet.getString("TITLE"));
+                book.setIsReserved(resultSet.getInt("IS_RESERVED"));
+                out.add(book);
+            }
+        }
+        return out;
     }
 
     @Override
-    public void returnBook(Book book, String student) {
+    public void init() throws SQLException {
+        try (Statement stmt = getConnection().createStatement()) {
+            stmt.execute("create schema LIBRARY");
+            stmt.execute("set schema LIBRARY");
+            stmt.execute("CREATE TABLE LIBRARY.BOOK " +
+                    " (BOOK_ID INT NOT NULL GENERATED ALWAYS AS IDENTITY " +
+                    " (START WITH 1, INCREMENT BY 1), TITLE VARCHAR(1000), IS_RESERVED INT)");
+            stmt.execute("CREATE TABLE LIBRARY.STUDENT " +
+                    " (STUDENT_ID INT NOT NULL GENERATED ALWAYS AS IDENTITY " +
+                    " (START WITH 1, INCREMENT BY 1), NAME VARCHAR(100))");
+            stmt.execute("CREATE TABLE LIBRARY.RELATION " +
+                    " (RELATION_ID INT NOT NULL GENERATED ALWAYS AS IDENTITY " +
+                    " (START WITH 1, INCREMENT BY 1), STUDENT_ID INT NOT NULL, BOOK_ID INT NOT NULL)");
+        }
+    }
 
+    @Override
+    public Connection getConnection() throws SQLException {
+        return DriverManager.getConnection(jdbcUrl, user, password);
+    }
+
+    @Override
+    public Book getBookByTitle(String title) throws SQLException {
+        Book out = null;
+        String sql = "select * from LIBRARY.BOOK where title = ?";
+        try (Connection connection = getConnection(); PreparedStatement pr = connection.prepareStatement(sql)) {
+            pr.setString(1, title);
+            ResultSet resultSet = pr.executeQuery();
+            while (resultSet.next()) {
+                out = new Book();
+                out.setBookId(resultSet.getInt("BOOK_ID"));
+                out.setTitle(resultSet.getString("TITLE"));
+                out.setIsReserved(resultSet.getInt("IS_RESERVED"));
+            }
+        }
+        return out;
+    }
+
+    @Override
+    public void updateIsReservedFlag(int bookId, int isReserved) throws SQLException {
+        String sql = "update LIBRARY.BOOK set is_reserved = ? where book_id = ?";
+        try (Connection connection = getConnection(); PreparedStatement pr = connection.prepareStatement(sql)) {
+            pr.setInt(1, isReserved);
+            pr.setInt(2, bookId);
+            pr.executeUpdate();
+        }
+    }
+
+    @Override
+    public Student getStudentByName(String name) throws SQLException {
+        Student out = null;
+        String sql = "select * from LIBRARY.STUDENT where name = ?";
+        try (Connection connection = getConnection(); PreparedStatement pr = connection.prepareStatement(sql)) {
+            pr.setString(1, name);
+            ResultSet resultSet = pr.executeQuery();
+            while (resultSet.next()) {
+                out = new Student();
+                out.setStudentId(resultSet.getInt("STUDENT_ID"));
+                out.setStudentName(resultSet.getString("NAME"));
+            }
+        }
+        return out;
+    }
+
+    @Override
+    public List<Relation> getRelationByStudentId(int studentId) throws SQLException {
+        List<Relation> out = new ArrayList<>();
+        String sql = "select * from LIBRARY.RELATION where student_id = ?";
+        try (Connection connection = getConnection(); PreparedStatement pr = connection.prepareStatement(sql)) {
+            pr.setInt(1, studentId);
+            ResultSet resultSet = pr.executeQuery();
+            while (resultSet.next()) {
+                Relation relation = new Relation();
+                relation.setRelationId(resultSet.getInt("RELATION_ID"));
+                relation.setStudentId(resultSet.getInt("STUDENT_ID"));
+                relation.setBookId(resultSet.getInt("BOOK_ID"));
+                out.add(relation);
+            }
+        }
+        return out;
+    }
+
+    @Override
+    public void insertNewStudent(String student) throws SQLException {
+        String sql = "insert into LIBRARY.STUDENT (NAME) " +
+                "values (?)";
+        try (Connection connection = getConnection()) {
+            connection.setAutoCommit(false);
+            try (PreparedStatement pr = connection.prepareStatement(sql)) {
+                pr.setString(1, student);
+                pr.execute();
+                connection.commit();
+            } catch (SQLException e) {
+                logger.severe(e.getMessage());
+                getConnection().rollback();
+            }
+        }
+    }
+
+    @Override
+    public void insertNewRelation(int bookId, int studentId) throws SQLException {
+        String sql = "insert into LIBRARY.RELATION (STUDENT_ID, BOOK_ID) " +
+                "values (?, ?)";
+        try (Connection connection = getConnection()) {
+            connection.setAutoCommit(false);
+            try (PreparedStatement pr = connection.prepareStatement(sql)) {
+                pr.setInt(1, studentId);
+                pr.setInt(2, bookId);
+                pr.execute();
+                connection.commit();
+            } catch (SQLException e) {
+                logger.severe(e.getMessage());
+                getConnection().rollback();
+            }
+        }
     }
 
     @Override
-    public List<Book> findAvailableBooks() {
-        return null;
+    public boolean deleteRelation(int relationId) throws SQLException {
+        boolean flag = false;
+        String sql = "delete from LIBRARY.RELATION where relation_id = ?";
+        try (Connection connection = getConnection()) {
+            try (PreparedStatement pr = connection.prepareStatement(sql)) {
+                pr.setInt(1, relationId);
+                int row = pr.executeUpdate();
+                if (row > 0) {
+                    flag = true;
+                }
+            } catch (SQLException e) {
+                logger.severe(e.getMessage());
+                getConnection().rollback();
+            }
+        }
+        return flag;
     }
 }