三層架構(gòu)

三層結(jié)構(gòu)解釋：

視圖層：主要是用于與用戶進行交互，比如接收用戶輸入的內(nèi)容將返回結(jié)果向用戶展示等。

業(yè)務邏輯層：實現(xiàn)每個功能的特定的邏輯方法。

數(shù)據(jù)訪問層：主要是與數(shù)據(jù)庫進行連接，然后對數(shù)據(jù)庫進行增刪改查工作。

結(jié)構(gòu)一：

包的層級結(jié)構(gòu)：

三層結(jié)構(gòu)目錄架構(gòu)：

命名規(guī)則為公司域名反寫 eg:com.li.xxx

bean：存放JavaBean，一張表對應一個類，一個字段對應一個屬性

dao：存放連接數(shù)據(jù)庫及對數(shù)據(jù)庫進行增刪改查的操作的接口

dao.impl：存放dao接口的實現(xiàn)類

service：存放邏輯層的接口

service.impl：存放邏輯層的接口的實現(xiàn)類

view：用戶交互層的接口

view.impl：用戶交互層的接口的實現(xiàn)類

包內(nèi)的實現(xiàn)類：

在編寫代碼之前先要創(chuàng)建一個數(shù)據(jù)庫：

CREATE TABLE `student` (
  `Sid` int NOT NULL AUTO_INCREMENT,
  `Sname` varchar(10) CHARACTER SET utf8mb4 COLLATE utf8mb4_0900_ai_ci DEFAULT NULL,
  `birthday` datetime DEFAULT NULL,
  `ssex` varchar(10) CHARACTER SET utf8mb4 COLLATE utf8mb4_0900_ai_ci NOT NULL DEFAULT '男',
  `classid` int DEFAULT NULL,
  PRIMARY KEY (`Sid`) USING BTREE
) ENGINE=InnoDB AUTO_INCREMENT=23 DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_0900_ai_ci ROW_FORMAT=DYNAMIC;

以學生類為例下面是實現(xiàn)代碼：

Student的JavaBean：

public class Student {
    //JavaBean實體類
    private int sid;
    private String sname;
    private Date birthday;
    private String ssex;
    private int classid;
    
    public Student(){
    }
    public Student(int sid,String sname,Date birthday,String ssex,int classid){
        this.sid = sid;
        this.sname = sname;
        this.birthday = birthday;
        this.ssex = ssex;
        this.classid = classid;
    }

    public int getSid() {
        return sid;
    }

    public void setSid(int sid) {
        this.sid = sid;
    }

    public String getSname() {
        return sname;
    }

    public void setSname(String sname) {
        this.sname = sname;
    }

    public Date getBirthday() {
        return birthday;
    }

    public void setBirthday(Date birthday) {
        this.birthday = birthday;
    }

    public String getSsex() {
        return ssex;
    }

    public void setSsex(String ssex) {
        this.ssex = ssex;
    }

    public int getClassid() {
        return classid;
    }

    public void setClassid(int classid) {
        this.classid = classid;
    }

    @Override
    public String toString() {
        return "Student{" +
                "sid=" + sid +
                ", sname='" + sname + '\'' +
                ", birthday=" + birthday +
                ", ssex='" + ssex + '\'' +
                ", classid=" + classid +
                '}';
    }

Dao層的接口：

稍作贅述：接口的出現(xiàn)實際上是為了制定規(guī)則，代碼編寫三要素：方法名、參數(shù)、返回值類型；而在接口中定義這三個東西然后讓子類實現(xiàn)，當某一層未開發(fā)時也不影響其他層的開發(fā)。

public interface IStudentDao {
    //增加
    public int addStudent(Student s);
    //刪除
    public int deleteStudent(int sid);
    //修改
    public int updateStudent(Student s);
    //查詢
    public Student findStudentBySid(int sid);
    //全查
    public List<Student> findAllStudent();
}

Dao層接口的實現(xiàn)類：

//增加記錄
    @Override
    public int addStudent(Student s) {
        Connection conn = null;
        PreparedStatement presta = null;
        int update = 0;
        try {
            Class.forName("com.mysql.cj.jdbc.Driver");
            String url = "jdbc:mysql://localhost:3306/myschool?charset=utf8mb4&useSSL=false&useTimezone=true&serverTimezone=GMT%2B8&characterEncoding=utf-8&allowPublicKeyRetrieval=true";
            String user = "root";
            String pwd = "123456";
            conn = DriverManager.getConnection(url, user, pwd);
            String sql = "insert into student(sname,birthday,ssex,classid) values (?,?,?,?)";
            presta = conn.prepareStatement(sql);
//            presta.setObject(1,s.getSid());
            presta.setObject(1,s.getSname());
            presta.setObject(2,s.getBirthday());
            presta.setObject(3,s.getSsex());
            presta.setObject(4,s.getClassid());
            update = presta.executeUpdate();
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        } catch (SQLException throwables) {
            throwables.printStackTrace();
        }finally {
            if (presta != null){
                try {
                    presta.close();
                } catch (SQLException throwables) {
                    throwables.printStackTrace();
                }
            }
            if (conn != null){
                try {
                    conn.close();
                } catch (SQLException throwables) {
                    throwables.printStackTrace();
                }
            }
        }
        return update;
    }

    //刪除記錄
    @Override
    public int deleteStudent(int sid) {
        int update  = 0;
        PreparedStatement presta = null;
        Connection conn = null;
        try {
            Class.forName("com.mysql.cj.jdbc.Driver");
            String url = "jdbc:mysql://localhost:3306/myschool?charset=utf8mb4&useSSL=false&useTimezone=true&serverTimezone=GMT%2B8&characterEncoding=utf-8&allowPublicKeyRetrieval=true";
            String user = "root";
            String pwd = "123456";
            conn = DriverManager.getConnection(url, user, pwd);
            String sql = "delete from student where sid = ?";
            presta = conn.prepareStatement(sql);
            presta.setObject(1,sid);
            update = presta.executeUpdate();
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        } catch (SQLException throwables) {
            throwables.printStackTrace();
        }finally {
            if(presta != null){
                try {
                    presta.close();
                } catch (SQLException throwables) {
                    throwables.printStackTrace();
                }
            }
            if(conn != null){
                try {
                    conn.close();
                } catch (SQLException throwables) {
                    throwables.printStackTrace();
                }
            }
        }
        return update;
    }

    //修改記錄
    @Override
    public int updateStudent(Student s) {
        int update  = 0;
        PreparedStatement presta = null;
        Connection conn = null;
        try {
            Class.forName("com.mysql.cj.jdbc.Driver");
            String url = "jdbc:mysql://localhost:3306/myschool?charset=utf8mb4&useSSL=false&useTimezone=true&serverTimezone=GMT%2B8&characterEncoding=utf-8&allowPublicKeyRetrieval=true";
            String user = "root";
            String pwd = "123456";
            conn = DriverManager.getConnection(url, user, pwd);
            String sql = "update student set sname = ?,birthday = ? ,ssex = ? ,classid = ?  where sid = ?";
            presta = conn.prepareStatement(sql);
            presta.setObject(1,s.getSname());
            presta.setObject(2,s.getBirthday());
            presta.setObject(3,s.getSsex());
            presta.setObject(4,s.getClassid());
            presta.setObject(5,s.getSid());
            update = presta.executeUpdate();
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        } catch (SQLException throwables) {
            throwables.printStackTrace();
        }finally {
            if (presta != null){
                try {
                    presta.close();
                } catch (SQLException throwables) {
                    throwables.printStackTrace();
                }
            }
            if (conn != null){
                try {
                    conn.close();
                } catch (SQLException throwables) {
                    throwables.printStackTrace();
                }
            }
        }
        return update;
    }

    //sid查詢
    @Override
    public Student findStudentBySid(int sid) {
        Connection conn = null;
                Student student = null;
        PreparedStatement statement = null;
        try {
            Class.forName("com.mysql.cj.jdbc.Driver");
            String url = "jdbc:mysql://localhost:3306/myschool?charset=utf8mb4&useSSL=false&useTimezone=true&serverTimezone=GMT%2B8&characterEncoding=utf-8&allowPublicKeyRetrieval=true";
            String user = "root";
            String pwd = "123456";
            conn = DriverManager.getConnection(url, user, pwd);
            String sql = "select * from student where sid = ?";
            statement = conn.prepareStatement(sql);
            statement.setObject(1,sid);
            ResultSet resultSet = statement.executeQuery();
            if(resultSet.next()){
                student = new Student();
                student.setSid(resultSet.getInt("sid"));
                student.setSname(resultSet.getString("sname"));
                student.setBirthday(resultSet.getDate("birthday"));
                student.setSsex(resultSet.getString("ssex"));
                student.setClassid(resultSet.getInt("classid"));
            }
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        } catch (SQLException throwables) {
            throwables.printStackTrace();
        }finally {
            if (statement != null){
                try {
                    statement.close();
                } catch (SQLException throwables) {
                    throwables.printStackTrace();
                }
            }
            if(conn != null){
                try {
                    conn.close();
                } catch (SQLException throwables) {
                    throwables.printStackTrace();
                }
            }
        }

        return student;
    }

    //全查
    @Override
    public List<Student> findAllStudent() {
        Connection conn = null;
        PreparedStatement statement = null;
        List list = new ArrayList();
        try {
            Class.forName("com.mysql.cj.jdbc.Driver");
            String url = "jdbc:mysql://localhost:3306/myschool?charset=utf8mb4&useSSL=false&useTimezone=true&serverTimezone=GMT%2B8&characterEncoding=utf-8&allowPublicKeyRetrieval=true";
            String user = "root";
            String pwd = "123456";
            conn = DriverManager.getConnection(url, user, pwd);
            String sql = "select * from student";
            statement = conn.prepareStatement(sql);
            ResultSet resultSet = statement.executeQuery();
            while (resultSet.next()){
                Student stu = new Student();
                stu.setSid(resultSet.getInt("sid"));
                stu.setSname(resultSet.getString("sname"));
                stu.setBirthday(resultSet.getDate("birthday"));
                stu.setSsex(resultSet.getString("ssex"));
                stu.setClassid(resultSet.getInt("classid"));
                list.add(stu);
            }
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        } catch (SQLException throwables) {
            throwables.printStackTrace();
        }finally {
            if (statement != null){
                try {
                    statement.close();
                } catch (SQLException throwables) {
                    throwables.printStackTrace();
                }
            }
            if(conn != null){
                try {
                    conn.close();
                } catch (SQLException throwables) {
                    throwables.printStackTrace();
                }
            }
        }

        return list;
    }

service層的接口：

public interface IStudentService {

    //注冊（添加字段）
    public boolean register(Student s);

    //刪除學生
    public boolean deleteStu(int sid);

    //修改學生信息
    public boolean modifyStu(Student s);

    //Sid查詢學生
    public Student info(int sid);

    //所有學生列表
    public List<Student> student();

}

service層的接口的實現(xiàn)類：

//添加學生字段
    @Override
    public boolean register(Student s) {
        boolean isok = false;
        IStudentDao isd = new StudentDaoImpl();
        int ret = isd.addStudent(s);
        if (ret > 0) {
            isok = true;
        }
        return isok;
    }

    //刪除學生字段
    @Override
    public boolean deleteStu(int sid) {
        boolean isok = false;
        IStudentDao isd = new StudentDaoImpl();
        int ret = isd.deleteStudent(sid);
        if (ret > 0){
            isok = true;
        }
        return isok;
    }

    //修改學生字段
    @Override
    public boolean modifyStu(Student s) {
        boolean isok = false;
        IStudentDao isd = new StudentDaoImpl();
        int i = isd.updateStudent(s);
        if (i > 0){
            isok = true;
        }
        return isok;
    }

    //Sid查學生字段
    @Override
    public Student info(int sid) {
        IStudentDao isd = new StudentDaoImpl();
        Student studentBySid = isd.findStudentBySid(sid);
        return studentBySid;
    }

    //學生字段全查
    @Override
    public List<Student> student() {
        IStudentDao isd = new StudentDaoImpl();
        List<Student> allStudent = isd.findAllStudent();
        return allStudent;
    }

View的是接口：

public interface IStudentView {
    //學生的注冊
    public void showstuadd();

    //學生的修改
    public void showstumodify();

    //學生的全部查詢
    public void showstuinfo();

    //學生的Sid查詢
    public void showstuinfoSid();

    //學生的刪除
    public void showstudelete();

    //學生的菜單
    public void showstumenu();
}

View的是接口的實現(xiàn)類：

//學生的注冊（添加字段）
    @Override
    public void showstuadd() {

        SimpleDateFormat format = new SimpleDateFormat();
        Scanner input  = new Scanner(System.in);
        System.out.println("添加學生：");
        System.out.println("請輸入學生姓名");
        String sname = input.next();
        System.out.println("請輸入學生生日");
        String bir = input.next();
        System.out.println("請輸入學生性別");
        String sex = input.next();
        System.out.println("請輸入學生班級");
        int classid = input.nextInt();
        Student stu = new Student();
        stu.setSname(sname);
        try {
            stu.setBirthday(format.parse(bir));
        } catch (ParseException e) {
            stu.setBirthday(new Date());
        }
        stu.setSsex(sex);
        stu.setClassid(classid);
        IStudentService iss = new StudentServiceImpI();
        boolean register = iss.register(stu);
        if (register){
            System.out.println("插入成功");
        }else{
            System.out.println("插入失敗");
        }

    }

    //學生的修改
    @Override
    public void showstumodify() {
        SimpleDateFormat format = new SimpleDateFormat();
        Scanner input  = new Scanner(System.in);
        System.out.println("修改學生信息：");
        System.out.println("請輸入需要修改的學生編號");
        int sid = input.nextInt();
        System.out.println("請輸入學生新姓名");
        String sname = input.next();
        System.out.println("請輸入學生新生日");
        String bir = input.next();
        System.out.println("請輸入學生新性別");
        String sex = input.next();
        System.out.println("請輸入學生新班級");
        int classid = input.nextInt();
        Student stu = new Student();
        stu.setSname(sname);
        try {
            stu.setBirthday(format.parse(bir));
        } catch (ParseException e) {
            stu.setBirthday(new Date());
        }
        stu.setSsex(sex);
        stu.setClassid(classid);
        stu.setSid(sid);
        IStudentService iss = new StudentServiceImpI();
        boolean register = iss.modifyStu(stu);
        if (register){
            System.out.println("修改成功");
        }else{
            System.out.println("修改失敗");
        }
    }

    //學生的全部查詢
    @Override
    public void showstuinfo() {
        IStudentService iss = new StudentServiceImpI();
        List<Student> list = iss.student();
        list.forEach(System.out::println);
    }

    //學生的Sid查詢
    @Override
    public void showstuinfoSid() {
        Scanner scan = new Scanner(System.in);
        System.out.println("請輸入需要查詢的ID：");
        int i = scan.nextInt();
        IStudentService iss = new StudentServiceImpI();
        Student info = iss.info(i);
        System.out.println(info);
    }

    //學生的刪除
    @Override
    public void showstudelete() {
        Scanner scan = new Scanner(System.in);
        System.out.println("請輸入要刪除學生的ID：");
        int anInt = scan.nextInt();
        IStudentService iss = new StudentServiceImpI();
        boolean deleteStu = iss.deleteStu(anInt);
        if (deleteStu){
            System.out.println("刪除成功！");
        }else{
            System.out.println("刪除失敗！");
        }
    }

    //學生的菜單
    @Override
    public void showstumenu() {
        Scanner input = new Scanner(System.in);
        System.out.println("歡迎使用校園系統(tǒng)--學生模塊管理");
        int key = -1;
        do {
            System.out.println("輸入:\n1.添加學生\n2.根據(jù)ID查看信息\n3.查看所有學生\n4.修改學生\n5.開除學生\n0.退出程序");
            System.out.println("請輸入：");
            if(input.hasNextInt()) {
                key = input.nextInt();
                switch(key) {
                    case 1:
                    {
                        showstuadd();
                    }
                    break;
                    case 2:
                    {
                        showstuinfoSid();
                    }
                    break;
                    case 3:
                    {
                        showstuinfo();
                    }
                    break;
                    case 4:
                    {
                        showstumodify();
                    }
                    break;
                    case 5:
                    {
                        showstudelete();
                    }
                    break;
                    default:
                        System.out.println("請輸入正確的序號");
                        break;
                }
            }else {
                System.out.println("請輸入菜單中的序號，否則打死你");
                input.next();
            }

        }while(key != 0);
        System.out.println("感謝使用");
    }

測試類：

public static void main(String[] args) {
       IStudentView isv = new IStudentViewImpI();
       isv.showstumenu();
    }

結(jié)構(gòu)二：

結(jié)構(gòu)一中，在DAO層中頻繁的進行數(shù)據(jù)連接創(chuàng)建訪問對象等，結(jié)構(gòu)復雜，代碼重復率高，因此結(jié)構(gòu)二中對DAO層進行了抽象。

創(chuàng)建DaoUtil類：將加載驅(qū)動，獲取連接，流的釋放進行抽象。

public class DaoUtil {
    //加載驅(qū)動
    //驅(qū)動的加載只需加載一次，因此使用靜態(tài)代碼塊，當加載此類時，會隨著類的加載而加載一次
    static {
        try {
            Class.forName("com.mysql.cj.jdbc.Driver");
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        }
    }
    
    //獲取連接
    public static Connection getConn(){
        Connection conn = null;
        try {
            String url = "jdbc:mysql://localhost:3306/myschool?charset=utf8mb4&useSSL=false&useTimezone=true&serverTimezone=GMT%2B8&characterEncoding=utf-8&allowPublicKeyRetrieval=true";
            String user = "root";
            String pwd = "123456";
            conn = DriverManager.getConnection(url, user, pwd);
        } catch (SQLException throwables) {
            throwables.printStackTrace();
        }
        return conn;
    }

    //關(guān)閉連接
    public static void closeResource(Connection conn, PreparedStatement prep, ResultSet res){
        if (res != null){
            try {
                res.close();
            } catch (SQLException throwables) {
                throwables.printStackTrace();
            }
        }
        if (prep != null){
            try {
                prep.close();
            } catch (SQLException throwables) {
                throwables.printStackTrace();
            }
        }
        if (conn != null){
            try {
                conn.close();
            } catch (SQLException throwables) {
                throwables.printStackTrace();
            }
        }
    }
}

創(chuàng)建BaseDao：用來存放增刪改和查的方法；這里需要注意的是，增刪改操作時返回值是int的整數(shù)值，表示數(shù)據(jù)庫中的受影響的行數(shù)。而查詢操作返回的是ResultSet類型的結(jié)果，因此需要分開進行寫。

public class BaseDao {
    protected Connection conn;
    protected PreparedStatement prepstat;
    protected ResultSet rs;

    //增刪改
    protected int update(String sql,Object...args){
        int ret = 0;
        try {
            conn = DaoUtil.getConn();
            prepstat = conn.prepareStatement(sql);
            if (args != null) {
                for (int i = 0; i < args.length; i++) {
                    prepstat.setObject(i + 1,args[i]);
                }
            }
            ret = prepstat.executeUpdate();
        } catch (SQLException throwables) {
            throwables.printStackTrace();
        }finally {
            DaoUtil.closeResource(conn, prepstat, rs);
        }
        return ret;
    }

    //查詢
    protected ResultSet query(String sql,Object...args){
        ResultSet rs = null;
        try {
            conn = DaoUtil.getConn();
            prepstat = conn.prepareStatement(sql);
            if (args != null){
                for (int i = 0; i < args.length; i++) {
                    prepstat.setObject(i + 1,args[i]);
                }
            }
            rs = prepstat.executeQuery();
        } catch (SQLException throwables) {
            throwables.printStackTrace();
        }
        return rs;
    }

}

抽象后的實現(xiàn)類如下：

public class StudentDaoImpl extends BaseDao implements IStudentDao {
    //增加記錄
    @Override
    public int addStudent(Student s) {
        String sql = "insert into student(sname,birthday,ssex,classid) values (?,?,?,?)";
        return update(sql,s.getSname(),s.getBirthday(),s.getSsex(),s.getClass());
    }

    //刪除記錄
    @Override
    public int deleteStudent(int sid) {
        String sql = "delete from student where sid = ?";
        return update(sql,sid);
    }

    //修改記錄
    @Override
    public int updateStudent(Student s) {
        String sql = "update student set sname = ?,birthday = ? ,ssex = ? ,classid = ?  where sid = ?";
        return update(sql,s.getSname(),s.getBirthday(),s.getSsex(),s.getClassid(),s.getSid());
    }

    //sid查詢
    @Override
    public Student findStudentBySid(int sid) {
        Student s = null;
        SimpleDateFormat format = new SimpleDateFormat();
        try {
            String sql = "select * from student where sid = ?";
            rs = query(sql, sid);
            if (rs.next()) {
                s = new Student();
                s.setSid(rs.getInt("sid"));
                s.setSname(rs.getString("sname"));
                try {
                    s.setBirthday(format.parse(rs.getString("birthday")));
                } catch (ParseException e) {
                    e.printStackTrace();
                }
                s.setSsex(rs.getString("ssex"));
                s.setClassid(rs.getInt("classid"));
                s.setSid(rs.getInt("sid"));
            }
        } catch (SQLException throwables) {
            throwables.printStackTrace();
        }finally {
            DaoUtil.closeResource(conn, prepstat, rs);
        }
        return s;
    }
        //全查
    @Override
    public List<Student> findAllStudent() {
        Student s = null;
        List list = new ArrayList();
        SimpleDateFormat format = new SimpleDateFormat();
        try {
            String sql = "select * from student where sid = ?";
            rs = query(sql);
            if (rs.next()) {
                s = new Student();
                s.setSid(rs.getInt("sid"));
                s.setSname(rs.getString("sname"));
                try {
                    s.setBirthday(format.parse(rs.getString("birthday")));
                } catch (ParseException e) {
                    e.printStackTrace();
                }
                s.setSsex(rs.getString("ssex"));
                s.setClassid(rs.getInt("classid"));
                s.setSid(rs.getInt("sid"));
                list.add(s);
            }
        } catch (SQLException throwables) {
            throwables.printStackTrace();
        }finally {
            DaoUtil.closeResource(conn, prepstat, rs);
        }
        return list;
    }
}

不同的分法可能會略微有所區(qū)別，劃分程度不同，劃分的層級可能也不同，但本質(zhì)思想不變，將代碼功能模塊化，實現(xiàn)高內(nèi)聚低耦合，例如Dao用來做數(shù)據(jù)庫連接等操作，就盡量只需調(diào)方法傳參就能執(zhí)行即可，不要在執(zhí)行的過程中還需要其他層數(shù)據(jù)的介入，主要也是為了開發(fā)的高效性，同時便于對代碼進行測試。文章來源地址http://www.zghlxwxcb.cn/news/detail-772111.html

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