JSP（Java Servlet Page）分层架构

秒速五厘米 2022-07-13 10:24 180阅读 0赞

## **JSP（Java Servlet Page）分层架构** ##

## Java ##

也就是前面学习的Java SE学习内容

## Servlet ##

Servlet是运行在Tomcat之中的一个小组件。他可以接受用户的请求以及响应用户。

创建Servlet步骤：

*  第一步：创建类继承与HttpServlet
 *  第二步：实现doGet()/doPost()提交方式、init()方法 service()方法、destroy方法()  
    ）
 *  第三步：配置Web.xml文件

<servlet>
        <servlet-name>mServlet<servlet-name>
        <servlet-class>com.ryan....mServlet<servlet-class>
    <servlet>
    
    <servlet-mapping>
        <servlet-name>mServlet</servlet-name>
        <url-pattern>/mServlet</url-pattern>
    <servlet-mapping>

## Page ##

展示给用户看得页面，类似html页面，只是加入了Java代码,后缀名为“.jsp”的网页界面

## **分层架构** ##

**数据库连接帮助类**

--------------------

public class ConnUtil {
        
        /**
         * 连接数据库方法
         * @return conn
         */
        public static Connection getConnection(){
            Connection conn = null;
            try {
                Class.forName("com.microsoft.sqlserver.jdbc.SQLServerDriver");
                conn = DriverManager.getConnection("jdbc:sqlserver://localhost:1433;databaseName=mytest;","sa","123456");
            } catch (ClassNotFoundException e) {
                e.printStackTrace();
            } catch (SQLException e) {
                e.printStackTrace();
            }
            return conn;
        }
        /**
         * 关闭数据库方法
         * @param conn
         * @param pstate
         * @param rs
         */
        public static void close(Connection conn,PreparedStatement pstate,ResultSet rs){
            try {
                if(rs!=null){
                    rs.close();
                }
                if(pstate!=null){
                    pstate.close();
                }
                if(conn!=null){
                    conn.close();
                }
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
    }

--------------------

1 . Dao层位于数据访问层  
将内存当中的对象保存到数据库当中的过程（持久化）。

public interface UserDao {
    
        public int save(User user);//保存数据
        public List<User> findAllUser();//查询全部数据，保存到list集合中
        public User findSingleUser(String id);//根据用户的id查询
        public int updateNameById(String id);//根据用户的id更新数据
        public int deleteNameById(String id);//根据用户的id删除数据
    }

Dao层实例

public class UserDaoImpl implements UserDao{
        
    
        @Override
        public int save(User user) {
            Connection conn = null;
            PreparedStatement pstate = null;
            ResultSet rs = null;
            int row = 0;
            String sql = "insert into T_user(name,password) values(?,?)";
            conn = ConnUtil.getConnection();
            try {
                pstate = conn.prepareStatement(sql);
                pstate.setString(1, user.getName());
                pstate.setString(2, user.getPassword());
                row = pstate.executeUpdate();
            } catch (SQLException e) {
                e.printStackTrace();
            }
            return row;
        }
    
        @Override
        public List<User> findAllUser() {
            Connection conn = null;
            PreparedStatement pstate = null;
            ResultSet rs = null;
            List<User> users = new ArrayList<User>();
            String sql = "select * from T_user";
            conn = ConnUtil.getConnection();
            try {
                pstate = conn.prepareStatement(sql);
                rs = pstate.executeQuery();
                while(rs.next()){
                    User user = new User();
                    user.setId(rs.getInt(1));
                    user.setName(rs.getString(2));
                    user.setPassword(rs.getString(3));
                    users.add(user);
                }
            } catch (SQLException e) {
                e.printStackTrace();
            }finally{
                ConnUtil.close(conn, pstate, rs);
            }
            return users;
        }
    
        @Override
        public User findSingleUser(int id) {
            Connection conn = null;
            PreparedStatement pstate = null;
            ResultSet rs = null;
            User user = null;
            String sql = "select * from T_user where id =?";
            conn = ConnUtil.getConnection();
            try {
                pstate = conn.prepareStatement(sql);
                pstate.setInt(1, id);
                rs = pstate.executeQuery();
                while(rs.next()){
                    user = new User();
                    user.setId(rs.getInt(1));
                    user.setName(rs.getString(2));
                    user.setPassword(rs.getString(3));
                }
    //          System.out.println(user.getId()+"---"+user.getName()+"---"+user.getPassword());
            } catch (SQLException e) {
                e.printStackTrace();
            }finally{
                ConnUtil.getConnection();
            }
            return user;
        }
    
        @Override
        public int updateNameById(User user) {
            Connection conn = null;
            PreparedStatement pstate = null;
            ResultSet rs = null;
            int row = 0;
            String sql = "update T_user set name = ?,password = ? where id = ?";
            conn = ConnUtil.getConnection();
            try {
                pstate = conn.prepareStatement(sql);
                pstate.setString(1, user.getName());
                pstate.setString(2, user.getPassword());
                pstate.setInt(3, user.getId());
                row = pstate.executeUpdate();
            } catch (SQLException e) {
                e.printStackTrace();
            }finally{
                ConnUtil.close(conn, pstate, rs);
            }
            return row;
        }
    
        @Override
        public int deleteNameById(int id) {
            Connection conn = null;
            PreparedStatement pstate = null;
            ResultSet rs = null;
    
            int row = 0;
            String sql = "delete T_user where id = ?";
            conn = ConnUtil.getConnection();
            try {
                pstate = conn.prepareStatement(sql);
                pstate.setInt(1, id);
                row = pstate.executeUpdate();
            } catch (SQLException e) {
                e.printStackTrace();
            }finally{
                ConnUtil.close(conn, pstate, rs);
            }
            return row;
        }
    
    }

2 . Service 业务逻辑层  
描述：  
该层主要是针对于不同的系统中的特殊业务逻辑功能的处理。  
登录功能和注册的功能

public interface UserService {
    
        //查询所有用户信息
        List<User> findAllUser();
        //注册用户信息
        int registerUser(User user);
        //注销用户
        int remove(int id);
        //修改用户
        int updateUser(String name,String password);
    }

服务层实例：

public class UserServiceiImpl implements UserService {
        
    
        UserDaoImpl daoImpl = new UserDaoImpl();
        @Override
        public List<User> findAllUser() {
            return daoImpl.findAllUser();
        }
    
        @Override
        public int registerUser(User user) {
            //查询这条数据是否存在
            User user2 = daoImpl.findSingleUser(user.getId());
            int row = 0;
            if(user2 == null){
                row = daoImpl.save(user);
            }
            return row;
        }
    
        @Override
        public int remove(int id) {
            return daoImpl.deleteNameById(id);
        }
    
        @Override
        public int updateUser(String name,String password) {
            return daoImpl.updateNameById(new User(name, password));
        }
    
    }

3 . Servlet 请求以及响应层

public class findAllUserServlet extends HttpServlet {
        
    
        UserServiceiImpl impl = new UserServiceiImpl();
        public void doGet(HttpServletRequest request, HttpServletResponse response)
                throws ServletException, IOException {
            request.setCharacterEncoding("utf-8");
            response.setContentType("text/html;utf-8");
    
            List<User>list = impl.findAllUser();
            request.setAttribute("users", list);
            request.getRequestDispatcher("list.jsp").forward(request, response);
        }
    
        public void doPost(HttpServletRequest request, HttpServletResponse response)
                throws ServletException, IOException {
            doGet(request, response);
        }

*目录结构：*  
![这里写图片描述][SouthEast]

[SouthEast]: /images/20220713/f2a8b1b93bed4fa4b5271327ae14605d.png