2、创建jdbc项目，实现数据库连接,使用逻辑三层结构完成如下功能: 1)输入一个员工的信息，完成员工的添加。 2）查询所有员工信息; 3）输入姓名，查询员工信息;

好的，我来为您解答。

首先，我们需要创建一个 Java 项目，并添加 JDBC 驱动包以便连接数据库。这里以 MySQL 数据库为例，以下是代码实现：

1. 创建数据库表

在 MySQL 中创建一个名为 employee 的表，包含 id、name、age、email 四个字段。可以使用如下 SQL 语句：

CREATE TABLE `employee` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `name` varchar(50) NOT NULL,
  `age` int(11) NOT NULL,
  `email` varchar(50) NOT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

2. 创建实体类

创建一个名为 Employee 的实体类，包含 id、name、age、email 四个属性，并提供 getter 和 setter 方法。

public class Employee {
    private int id;
    private String name;
    private int age;
    private String email;

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

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

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }

    public String getEmail() {
        return email;
    }

    public void setEmail(String email) {
        this.email = email;
    }
}

3. 创建 DAO 层

创建一个名为 EmployeeDAO 的类，包含添加员工、查询所有员工、根据姓名查询员工三个方法，并实现数据库连接和 SQL 语句的执行。以下是代码实现：

public class EmployeeDAO {
    // 数据库连接信息
    private static final String DRIVER = "com.mysql.jdbc.Driver";
    private static final String URL = "jdbc:mysql://localhost:3306/test";
    private static final String USERNAME = "root";
    private static final String PASSWORD = "123456";

    // 添加员工
    public void addEmployee(Employee employee) throws SQLException, ClassNotFoundException {
        Class.forName(DRIVER);
        Connection connection = DriverManager.getConnection(URL, USERNAME, PASSWORD);
        PreparedStatement statement = connection.prepareStatement("INSERT INTO employee(name, age, email) VALUES (?, ?, ?)");
        statement.setString(1, employee.getName());
        statement.setInt(2, employee.getAge());
        statement.setString(3, employee.getEmail());
        statement.executeUpdate();
        statement.close();
        connection.close();
    }

    // 查询所有员工
    public List<Employee> getAllEmployees() throws SQLException, ClassNotFoundException {
        Class.forName(DRIVER);
        Connection connection = DriverManager.getConnection(URL, USERNAME, PASSWORD);
        Statement statement = connection.createStatement();
        ResultSet resultSet = statement.executeQuery("SELECT * FROM employee");
        List<Employee> employees = new ArrayList<>();
        while (resultSet.next()) {
            Employee employee = new Employee();
            employee.setId(resultSet.getInt("id"));
            employee.setName(resultSet.getString("name"));
            employee.setAge(resultSet.getInt("age"));
            employee.setEmail(resultSet.getString("email"));
            employees.add(employee);
        }
        resultSet.close();
        statement.close();
        connection.close();
        return employees;
    }

    // 根据姓名查询员工
    public Employee getEmployeeByName(String name) throws SQLException, ClassNotFoundException {
        Class.forName(DRIVER);
        Connection connection = DriverManager.getConnection(URL, USERNAME, PASSWORD);
        PreparedStatement statement = connection.prepareStatement("SELECT * FROM employee WHERE name = ?");
        statement.setString(1, name);
        ResultSet resultSet = statement.executeQuery();
        Employee employee = null;
        if (resultSet.next()) {
            employee = new Employee();
            employee.setId(resultSet.getInt("id"));
            employee.setName(resultSet.getString("name"));
            employee.setAge(resultSet.getInt("age"));
            employee.setEmail(resultSet.getString("email"));
        }
        resultSet.close();
        statement.close();
        connection.close();
        return employee;
    }
}

4. 创建 Service 层

创建一个名为 EmployeeService 的类，包含添加员工、查询所有员工、根据姓名查询员工三个方法，并调用 DAO 层的方法进行数据库操作。以下是代码实现：

public class EmployeeService {
    private EmployeeDAO employeeDAO = new EmployeeDAO();

    // 添加员工
    public void addEmployee(Employee employee) throws SQLException, ClassNotFoundException {
        employeeDAO.addEmployee(employee);
    }

    // 查询所有员工
    public List<Employee> getAllEmployees() throws SQLException, ClassNotFoundException {
        return employeeDAO.getAllEmployees();
    }

    // 根据姓名查询员工
    public Employee getEmployeeByName(String name) throws SQLException, ClassNotFoundException {
        return employeeDAO.getEmployeeByName(name);
    }
}

5. 创建 Presentation 层

创建一个名为 EmployeeUI 的类，包含添加员工、查询所有员工、根据姓名查询员工三个方法的实现，并调用 Service 层的方法进行数据库操作。以下是代码实现：

public class EmployeeUI {
    private EmployeeService employeeService = new EmployeeService();

    // 添加员工
    public void addEmployee() throws SQLException, ClassNotFoundException {
        Scanner scanner = new Scanner(System.in);
        System.out.print("请输入员工姓名：");
        String name = scanner.nextLine();
        System.out.print("请输入员工年龄：");
        int age = scanner.nextInt();
        scanner.nextLine();
        System.out.print("请输入员工邮箱：");
        String email = scanner.nextLine();
        Employee employee = new Employee();
        employee.setName(name);
        employee.setAge(age);
        employee.setEmail(email);
        employeeService.addEmployee(employee);
        System.out.println("员工添加成功！");
    }

    // 查询所有员工
    public void getAllEmployees() throws SQLException, ClassNotFoundException {
        List<Employee> employees = employeeService.getAllEmployees();
        System.out.println("所有员工信息如下：");
        for (Employee employee : employees) {
            System.out.println("id：" + employee.getId() + "，姓名：" + employee.getName() + "，年龄：" + employee.getAge() + "，邮箱：" + employee.getEmail());
        }
    }

    // 根据姓名查询员工
    public void getEmployeeByName() throws SQLException, ClassNotFoundException {
        Scanner scanner = new Scanner(System.in);
        System.out.print("请输入员工姓名：");
        String name = scanner.nextLine();
        Employee employee = employeeService.getEmployeeByName(name);
        if (employee != null) {
            System.out.println("员工信息如下：");
            System.out.println("id：" + employee.getId() + "，姓名：" + employee.getName() + "，年龄：" + employee.getAge() + "，邮箱：" + employee.getEmail());
        } else {
            System.out.println("未找到该员工！");
        }
    }
}

6. 编写主程序

创建一个名为 Main 的主程序，包含添加员工、查询所有员工、根据姓名查询员工三个功能的实现。以下是代码实现：

public class Main {
    public static void main(String[] args) throws SQLException, ClassNotFoundException {
        EmployeeUI employeeUI = new EmployeeUI();
        Scanner scanner = new Scanner(System.in);
        while (true) {
            System.out.println("请选择要进行的操作：");
            System.out.println("1. 添加员工");
            System.out.println("2. 查询所有员工");
            System.out.println("3. 根据姓名查询员工");
            System.out.println("0. 退出程序");
            int choice = scanner.nextInt();
            scanner.nextLine();
            switch (choice) {
                case 1:
                    employeeUI.addEmployee();
                    break;
                case 2:
                    employeeUI.getAllEmployees();
                    break;
                case 3:
                    employeeUI.getEmployeeByName();
                    break;
                case 0:
                    System.out.println("程序已退出！");
                    System.exit(0);
                default:
                    System.out.println("请输入正确的操作！");
            }
        }
    }
}

以上就是使用逻辑三层结构完成输入一个员工的信息，完成员工的添加；查询所有员工信息；输入姓名，查询员工信息的代码实现。