用java和mysql实现访客管理系统的黑名单增删改查功能,并将代码分为action、dao、pojo、service四个部分。代码中要求实现与数据库连接，并且详细写出getter和setter构造方法

首先，我们需要创建一个访客信息的POJO类，包含访客姓名、年龄、性别、电话号码、邮箱、是否在黑名单中等属性。代码如下：

public class Guest {
    private int id; //访客ID
    private String name; //访客姓名
    private int age; //访客年龄
    private String gender; //访客性别
    private String phone; //访客电话号码
    private String email; //访客邮箱
    private boolean inBlackList; //是否在黑名单中

    public Guest() {
    }

    public Guest(int id, String name, int age, String gender, String phone, String email, boolean inBlackList) {
        this.id = id;
        this.name = name;
        this.age = age;
        this.gender = gender;
        this.phone = phone;
        this.email = email;
        this.inBlackList = inBlackList;
    }

    //getter和setter方法
    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 getGender() {
        return gender;
    }

    public void setGender(String gender) {
        this.gender = gender;
    }

    public String getPhone() {
        return phone;
    }

    public void setPhone(String phone) {
        this.phone = phone;
    }

    public String getEmail() {
        return email;
    }

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

    public boolean isInBlackList() {
        return inBlackList;
    }

    public void setInBlackList(boolean inBlackList) {
        this.inBlackList = inBlackList;
    }
}

接下来，我们创建一个GuestDao类，用于数据库访问。代码如下：

public class GuestDao {
    private Connection conn = null;
    private PreparedStatement pstmt = null;

    public GuestDao(Connection conn) {
        this.conn = conn; //获取数据库连接
    }

    //添加访客信息到数据库
    public boolean addGuest(Guest guest) throws SQLException {
        String sql = "insert into guest(name,age,gender,phone,email,inBlackList) values(?,?,?,?,?,?)";
        pstmt = conn.prepareStatement(sql);
        pstmt.setString(1, guest.getName());
        pstmt.setInt(2, guest.getAge());
        pstmt.setString(3, guest.getGender());
        pstmt.setString(4, guest.getPhone());
        pstmt.setString(5, guest.getEmail());
        pstmt.setBoolean(6, guest.isInBlackList());
        int count = pstmt.executeUpdate();
        if (count > 0) {
            return true;
        } else {
            return false;
        }
    }

    //从数据库中删除指定ID的访客信息
    public boolean deleteGuest(int id) throws SQLException {
        String sql = "delete from guest where id=?";
        pstmt = conn.prepareStatement(sql);
        pstmt.setInt(1, id);
        int count = pstmt.executeUpdate();
        if (count > 0) {
            return true;
        } else {
            return false;
        }
    }

    //更新数据库中指定ID的访客信息
    public boolean updateGuest(Guest guest) throws SQLException {
        String sql = "update guest set name=?,age=?,gender=?,phone=?,email=?,inBlackList=? where id=?";
        pstmt = conn.prepareStatement(sql);
        pstmt.setString(1, guest.getName());
        pstmt.setInt(2, guest.getAge());
        pstmt.setString(3, guest.getGender());
        pstmt.setString(4, guest.getPhone());
        pstmt.setString(5, guest.getEmail());
        pstmt.setBoolean(6, guest.isInBlackList());
        pstmt.setInt(7, guest.getId());
        int count = pstmt.executeUpdate();
        if (count > 0) {
            return true;
        } else {
            return false;
        }
    }

    //根据ID从数据库中查询访客信息
    public Guest findGuestById(int id) throws SQLException {
        String sql = "select * from guest where id=?";
        pstmt = conn.prepareStatement(sql);
        pstmt.setInt(1, id);
        ResultSet rs = pstmt.executeQuery();
        if (rs.next()) {
            Guest guest = new Guest();
            guest.setId(rs.getInt("id"));
            guest.setName(rs.getString("name"));
            guest.setAge(rs.getInt("age"));
            guest.setGender(rs.getString("gender"));
            guest.setPhone(rs.getString("phone"));
            guest.setEmail(rs.getString("email"));
            guest.setInBlackList(rs.getBoolean("inBlackList"));
            return guest;
        } else {
            return null;
        }
    }

    //查询所有访客信息
    public List<Guest> findAllGuest() throws SQLException {
        String sql = "select * from guest";
        pstmt = conn.prepareStatement(sql);
        ResultSet rs = pstmt.executeQuery();
        List<Guest> list = new ArrayList<>();
        while (rs.next()) {
            Guest guest = new Guest();
            guest.setId(rs.getInt("id"));
            guest.setName(rs.getString("name"));
            guest.setAge(rs.getInt("age"));
            guest.setGender(rs.getString("gender"));
            guest.setPhone(rs.getString("phone"));
            guest.setEmail(rs.getString("email"));
            guest.setInBlackList(rs.getBoolean("inBlackList"));
            list.add(guest);
        }
        return list;
    }
}

然后，我们创建一个GuestService类，用于业务处理。代码如下：

public class GuestService {
    private Connection conn = null;
    private GuestDao guestDao = null;

    public GuestService() {
        conn = DBHelper.getConnection(); //获取数据库连接
        guestDao = new GuestDao(conn);
    }

    //添加访客信息到数据库
    public boolean addGuest(Guest guest) throws SQLException {
        return guestDao.addGuest(guest);
    }

    //从数据库中删除指定ID的访客信息
    public boolean deleteGuest(int id) throws SQLException {
        return guestDao.deleteGuest(id);
    }

    //更新数据库中指定ID的访客信息
    public boolean updateGuest(Guest guest) throws SQLException {
        return guestDao.updateGuest(guest);
    }

    //根据ID从数据库中查询访客信息
    public Guest findGuestById(int id) throws SQLException {
        return guestDao.findGuestById(id);
    }

    //查询所有访客信息
    public List<Guest> findAllGuest() throws SQLException {
        return guestDao.findAllGuest();
    }
}

最后，我们创建一个GuestAction类，用于与前端界面交互。代码如下：

public class GuestAction {
    private GuestService guestService = null;

    public GuestAction() {
        guestService = new GuestService();
    }

    //添加访客信息到数据库
    public boolean addGuest(Guest guest) throws SQLException {
        return guestService.addGuest(guest);
    }

    //从数据库中删除指定ID的访客信息
    public boolean deleteGuest(int id) throws SQLException {
        return guestService.deleteGuest(id);
    }

    //更新数据库中指定ID的访客信息
    public boolean updateGuest(Guest guest) throws SQLException {
        return guestService.updateGuest(guest);
    }

    //根据ID从数据库中查询访客信息
    public Guest findGuestById(int id) throws SQLException {
        return guestService.findGuestById(id);
    }

    //查询所有访客信息
    public List<Guest> findAllGuest() throws SQLException {
        return guestService.findAllGuest();
    }
}

以上就是一个基于Java和MySQL实现的访客管理系统的黑名单增删改查功能的代码，将代码分为action、dao、pojo、service四个部分，实现了与数据库的连接，并且详细写出了getter和setter构造方法。