System Overview

The application provides two primary roles with distinct functionalities:

• Administrator: Manage books (Create, Read, Update, Delete) and manage user accounts.
• Member: Browse available books, borrow books, return books, and view personal borrowing history.

Project Architecture

The project follows a standard layered architecture to separate concerns:

• beans: POJOs representing domain entities (Book, Member, Transaction).
• dao: Data Access Object layer for database interactions.
• service: Business logic layer interfaces.
• service.impl: Concrete implementations of the service interfaces.
• controller: Handles user input and navigation flow.
• util: Utility classes, specifically for JDBC connection managemant.
• test: Entry point for running the application.
• lib: External dependencies (e.g., MySQL JDBC Driver).

Entity Definitions (Beans)

LibraryItem (Book)

package com.library.beans;

public class LibraryItem {
    private int itemId;
    private String title;
    private String writer;
    private int stock;

    public LibraryItem() {}

    public LibraryItem(int itemId, String title, String writer, int stock) {
        this.itemId = itemId;
        this.title = title;
        this.writer = writer;
        this.stock = stock;
    }

    // Getters and Setters
    public int getItemId() { return itemId; }
    public void setItemId(int itemId) { this.itemId = itemId; }
    public String getTitle() { return title; }
    public void setTitle(String title) { this.title = title; }
    public String getWriter() { return writer; }
    public void setWriter(String writer) { this.writer = writer; }
    public int getStock() { return stock; }
    public void setStock(int stock) { this.stock = stock; }

    @Override
    public String toString() {
        return "Item[ID=" + itemId + ", Title='" + title + '\'' + ", Author='" + writer + '\'' + ", Stock=" + stock + ']';
    }
}

BorrowRecord (JieBook)

package com.library.beans;

import java.sql.Timestamp;
import java.util.Date;

public class BorrowRecord {
    private int recordId;
    private int memberId;
    private int itemId;
    private Date borrowDate;
    private Date returnDate;

    public BorrowRecord() {}

    public int getRecordId() { return recordId; }
    public void setRecordId(int recordId) { this.recordId = recordId; }
    public int getMemberId() { return memberId; }
    public void setMemberId(int memberId) { this.memberId = memberId; }
    public int getItemId() { return itemId; }
    public void setItemId(int itemId) { this.itemId = itemId; }
    public Date getBorrowDate() { return borrowDate; }
    public void setBorrowDate(Timestamp borrowDate) { this.borrowDate = borrowDate; }
    public Date getReturnDate() { return returnDate; }
    public void setReturnDate(Timestamp returnDate) { this.returnDate = returnDate; }

    @Override
    public String toString() {
        return "Record[ID=" + recordId + ", Member=" + memberId + ", Item=" + itemId + ", Borrowed=" + borrowDate + ", Returned=" + returnDate + ']';
    }
}

Member (User)

package com.library.beans;

public class Member {
    private int userId;
    private String username;
    private String password;
    private int type; // 1: Admin, 0: User

    public Member() {}

    public int getUserId() { return userId; }
    public void setUserId(int userId) { this.userId = userId; }
    public String getUsername() { return username; }
    public void setUsername(String username) { this.username = username; }
    public String getPassword() { return password; }
    public void setPassword(String password) { this.password = password; }
    public int getType() { return type; }
    public void setType(int type) { this.type = type; }
}

Controller Layer

AdminController

package com.library.controller;

import com.library.beans.BorrowRecord;
import com.library.beans.LibraryItem;
import com.library.beans.Member;
import com.library.service.LibraryService;
import com.library.service.impl.LibraryServiceImpl;

import java.util.List;
import java.util.Scanner;

public class AdminController {
    private Scanner scanner = new Scanner(System.in);
    private LibraryService service = new LibraryServiceImpl();

    public void displayAdminMenu() {
        System.out.println("ADMIN MENU: [1]List Books [2]Add [3]Edit [4]Delete [5]User Mgt [6]Logout");
        int choice = scanner.nextInt();
        switch (choice) {
            case 1 -> listItems();
            case 2 -> addNewItem();
            case 3 -> modifyItem();
            case 4 -> removeItem();
            case 5 -> System.out.println("User management logic here...");
            case 6 -> new AuthController().loginMenu();
        }
    }

    private void listItems() {
        List<LibraryItem> items = service.fetchAllItems();
        items.forEach(System.out::println);
        displayAdminMenu();
    }

    private void addNewItem() {
        LibraryItem item = new LibraryItem();
        System.out.print("Title: "); item.setTitle(scanner.next());
        if (service.checkItemExists(item)) {
            System.out.println("Conflict: Item exists.");
        } else {
            System.out.print("Author: "); item.setWriter(scanner.next());
            System.out.print("Stock: "); item.setStock(scanner.nextInt());
            if (service.saveItem(item) > 0) System.out.println("Added.");
        }
        displayAdminMenu();
    }

    private void modifyItem() {
        System.out.print("Title to edit: ");
        LibraryItem query = new LibraryItem();
        query.setTitle(scanner.next());
        
        if (service.checkItemExists(query)) {
            LibraryItem updatedData = new LibraryItem();
            System.out.print("New Title: "); updatedData.setTitle(scanner.next());
            System.out.print("New Author: "); updatedData.setWriter(scanner.next());
            System.out.print("New Stock: "); updatedData.setStock(scanner.nextInt());
            service.updateItem(query, updatedData);
            System.out.println("Update successful.");
        } else {
            System.out.println("Item not found.");
        }
        displayAdminMenu();
    }

    private void removeItem() {
        System.out.print("ID to delete: ");
        service.deleteItem(scanner.nextInt());
        System.out.println("Deleted.");
        displayAdminMenu();
    }
}

MemberController

package com.library.controller;

import com.library.beans.BorrowRecord;
import com.library.beans.LibraryItem;
import com.library.beans.Member;
import com.library.service.LibraryService;
import com.library.service.impl.LibraryServiceImpl;

import java.util.List;
import java.util.Scanner;

public class MemberController {
    private Scanner scanner = new Scanner(System.in);
    private LibraryService service = new LibraryServiceImpl();
    private Member currentMember;

    public MemberController(Member member) {
        this.currentMember = member;
    }

    public void displayMemberMenu() {
        System.out.println("MEMBER MENU: [1]View Books [2]Borrow [3]Return [4]History [5]Logout");
        int choice = scanner.nextInt();
        switch (choice) {
            case 1 -> browseBooks();
            case 2 -> borrowItem();
            case 3 -> returnItem();
            case 4 -> viewHistory();
            case 5 -> new AuthController().loginMenu();
        }
    }

    private void browseBooks() {
        service.fetchAllItems().forEach(System.out::println);
        displayMemberMenu();
    }

    private void borrowItem() {
        System.out.print("Enter Book ID to borrow: ");
        int itemId = scanner.nextInt();
        
        if (service.findItemById(itemId) == 1) {
            if (service.hasActiveBorrow(currentMember, itemId) > 0) {
                System.out.println("You already have this book borrowed.");
            } else {
                service.processBorrow(currentMember, itemId);
                System.out.println("Borrow successful.");
            }
        } else {
            System.out.println("Book not found.");
        }
        displayMemberMenu();
    }

    private void returnItem() {
        System.out.print("Enter Book ID to return: ");
        int itemId = scanner.nextInt();
        int recordId = service.hasActiveBorrow(currentMember, itemId);
        
        if (recordId > 0) {
            service.processReturn(recordId, itemId);
            System.out.println("Return successful.");
        } else {
            System.out.println("No active borrow record found for this book.");
        }
        displayMemberMenu();
    }

    private void viewHistory() {
        List<BorrowRecord> records = service.getMemberRecords(currentMember);
        records.forEach(System.out::println);
        displayMemberMenu();
    }
}

AuthController

package com.library.controller;

import com.library.beans.Member;
import com.library.service.AuthService;
import com.library.service.impl.AuthServiceImpl;

import java.util.Scanner;

public class AuthController {
    Scanner scanner = new Scanner(System.in);
    AuthService authService = new AuthServiceImpl();

    public void loginMenu() {
        System.out.println("WELCOME: [1]Login [2]Register");
        int choice = scanner.nextInt();
        if (choice == 1) performLogin();
        else performRegistration();
    }

    private void performRegistration() {
        Member m = new Member();
        System.out.print("User: "); m.setUsername(scanner.next());
        System.out.print("Pass: "); m.setPassword(scanner.next());
        
        if (authService.isUsernameTaken(m)) {
            System.out.println("Username taken.");
        } else {
            authService.register(m);
            System.out.println("Registered! Please login.");
        }
        loginMenu();
    }

    private void performLogin() {
        Member m = new Member();
        System.out.print("User: "); m.setUsername(scanner.next());
        System.out.print("Pass: "); m.setPassword(scanner.next());
        
        Member loggedIn = authService.authenticate(m);
        if (loggedIn != null) {
            if (loggedIn.getType() == 1) new AdminController().displayAdminMenu();
            else new MemberController(loggedIn).displayMemberMenu();
        } else {
            System.out.println("Invalid credentials.");
            loginMenu();
        }
    }
}

Service Layer

LibraryService Interface

package com.library.service;

import com.library.beans.BorrowRecord;
import com.library.beans.LibraryItem;
import com.library.beans.Member;
import java.util.List;

public interface LibraryService {
    List<LibraryItem> fetchAllItems();
    int saveItem(LibraryItem item);
    boolean checkItemExists(LibraryItem item);
    void updateItem(LibraryItem oldItem, LibraryItem newItem);
    void deleteItem(int id);
    int findItemById(int id);
    int hasActiveBorrow(Member m, int itemId);
    void processBorrow(Member m, int itemId);
    void processReturn(int recordId, int itemId);
    List<BorrowRecord> getMemberRecords(Member m);
}

AuthService Interface

package com.library.service;

import com.library.beans.Member;

public interface AuthService {
    boolean isUsernameTaken(Member m);
    Member authenticate(Member m);
    void register(Member m);
}

LibraryServiceImpl

package com.library.service.impl;

import com.library.beans.BorrowRecord;
import com.library.beans.LibraryItem;
import com.library.beans.Member;
import com.library.dao.LibraryDao;
import com.library.service.LibraryService;
import java.util.List;

public class LibraryServiceImpl implements LibraryService {
    private LibraryDao dao = new LibraryDao();

    @Override
    public List<LibraryItem> fetchAllItems() { return dao.getAllItems(); }

    @Override
    public int saveItem(LibraryItem item) { return dao.insertItem(item); }

    @Override
    public boolean checkItemExists(LibraryItem item) { return dao.existsByTitle(item); }

    @Override
    public void updateItem(LibraryItem oldItem, LibraryItem newItem) { dao.update(oldItem, newItem); }

    @Override
    public void deleteItem(int id) { dao.remove(id); }

    @Override
    public int findItemById(int id) { return dao.checkId(id); }

    @Override
    public int hasActiveBorrow(Member m, int itemId) { return dao.findActiveBorrow(m, itemId); }

    @Override
    public void processBorrow(Member m, int itemId) {
        dao.createBorrowRecord(m, itemId);
        dao.decrementStock(itemId);
    }

    @Override
    public void processReturn(int recordId, int itemId) {
        dao.markAsReturned(recordId);
        dao.incrementStock(itemId);
    }

    @Override
    public List<BorrowRecord> getMemberRecords(Member m) { return dao.getHistory(m); }
}

Database Utility

package com.library.util;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;

public class DBConnector {
    private static final String DB_URL = "jdbc:mysql://localhost:3306/library_db";
    private static final String DB_USER = "root";
    private static final String DB_PASS = "root";

    static {
        try {
            Class.forName("com.mysql.cj.jdbc.Driver");
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        }
    }

    public static Connection getConnection() {
        try {
            return DriverManager.getConnection(DB_URL, DB_USER, DB_PASS);
        } catch (SQLException e) {
            throw new RuntimeException("Connection failed", e);
        }
    }

    public static void closeAll(Connection c, PreparedStatement ps, ResultSet rs) {
        try { if (rs != null) rs.close(); } catch (SQLException ignored) {}
        try { if (ps != null) ps.close(); } catch (SQLException ignored) {}
        try { if (c != null) c.close(); } catch (SQLException ignored) {}
    }
}

Application Entry Point

package com.library.test;

import com.library.controller.AuthController;

public class Application {
    public static void main(String[] args) {
        System.out.println("--- Library Management System ---");
        new AuthController().loginMenu();
    }
}

Sample Run (Member Flow)

--- Library Management System ---
WELCOME: [1]Login [2]Register
2
User: member01
Pass: pass01
Registered! Please login.
WELCOME: [1]Login [2]Register
1
User: member01
Pass: pass01
MEMBER MENU: [1]View Books [2]Borrow [3]Return [4]History [5]Logout
1
Item[ID=1, Title='The Great Gatsby', Author='Fitzgerald', Stock=5]
Item[ID=2, Title='1984', Author='Orwell', Stock=3]
MEMBER MENU: [1]View Books [2]Borrow [3]Return [4]History [5]Logout
2
Enter Book ID to borrow: 1
Borrow successful.
MEMBER MENU: [1]View Books [2]Borrow [3]Return [4]History [5]Logout
1
Item[ID=1, Title='The Great Gatsby', Author='Fitzgerald', Stock=4]
Item[ID=2, Title='1984', Author='Orwell', Stock=3]
MEMBER MENU: [1]View Books [2]Borrow [3]Return [4]History [5]Logout
3
Enter Book ID to return: 1
Return successful.
MEMBER MENU: [1]View Books [2]Borrow [3]Return [4]History [5]Logout