使用基本MVC2模式创建新闻网站

Posted 2021-12-01 wajp

1.什么是MVC

MVC全名是Model View Controller，是模型(model)－视图(view)－控制器(controller)的缩写，一种软件设计典范，用一种业务逻辑、数据、界面显示分离的方法组织代码，将业务逻辑聚集到一个部件里面，在改进和个性化定制界面及用户交互的同时，不需要重新编写业务逻辑。MVC被独特的发展起来用于映射传统的输入、处理和输出功能在一个逻辑的图形化用户界面的结构中。

（1）Model层：Model指模型部分，一般在应用中Model层包括业务处理层和数据访问层。数据访问层主要是对数据库的一些操作的封装。业务处理层应用JavaBean构建，  JavaBean主要是用作将从View层获取的数据和数据库的数据进行桥接。除却JavaBean以外，若想构建分布式应用系统，可以应用EJB组件进行业务逻辑层的构建。

 

（2）Controller层：Controller指控制部分，一般是对View层提交的请求为其设置对应的Servlet进行特定功能的处理，这里的进行特定功能的处理一般是编写在Model中的业务处理层中的。Controller一般只是在Web应用中充当一个中介者的作用。

 

（3）View层：View指视图部分，这一部分的内容是展示给用户实际进行交互的，通常使用JSP和html进行构建（个人比较喜欢以HTML嵌入JSP的方式来构建网页）。

 

综上来说，一个小型完整的基于MVC设计模式的Web应用程序的处理流程应该如下：

 

 

      由上面的图中我们可以看出，用户在客户端（Web应用的客户端即为浏览器）中发出请求的时候，请求首先由View层的JSP/HTML将HTTP请求传给控制器中对应的Servlet，然后由Servlet负责调用Model层中的业务逻辑处理部分进行要求的处理，处理期间如果设计数据库的操作，则与数据库进行操作，最后全部操作结束之后，由业务逻辑层将结果发给控制层，控制层以HTTP响应的形式将结果发送回客户端。

 

 MVC编程模式

MVC 是一种使用 MVC（Model View Controller 模型-视图-控制器）设计创建 Web 应用程序的模式： ^[1] 

• Model（模型）表示应用程序核心（比如数据库记录列表）。
• View（视图）显示数据（数据库记录）。
• Controller（控制器）处理输入（写入数据库记录）。

MVC 模式同时提供了对 HTML、CSS 和 javascript 的完全控制。

Model（模型）是应用程序中用于处理应用程序数据逻辑的部分。
　　通常模型对象负责在数据库中存取数据。

View（视图）是应用程序中处理数据显示的部分。
　　通常视图是依据模型数据创建的。

Controller（控制器）是应用程序中处理用户交互的部分。
　　通常控制器负责从视图读取数据，控制用户输入，并向模型发送数据。

MVC 分层有助于管理复杂的应用程序，因为您可以在一个时间内专门关注一个方面。例如，您可以在不依赖业务逻辑的情况下专注于视图设计。同时也让应用程序的测试更加容易。

MVC 分层同时也简化了分组开发。不同的开发人员可同时开发视图、控制器逻辑和业务逻辑。

 

实验代码：

package bean;

public class News {
    String title;
    String datetime;
    String content;
    String type;
    int id;
    
    public News(String title,String datetime,String content,String type,int id){
        super();
        this.title = title;
        this.datetime = datetime;
        this.content = content;
        this.type = type;
        this.id = id;
    }
    
    public int getId(){
        return id;
    }
    public void setId(int id){
        this.id = id;
    }
    
    public News(){
        
    }
    
    public String getTitle(){
        return title;
    }
    public void setTitle(String title){
        this.title = title;
    }
    
    public String getDatetime(){
        return datetime;
    }
    public void setDatetime(String datetime){
        this.datetime = datetime;
    }
    
    public String getContent(){
        return content;
    }
    public void setContent(String content){
        this.content = content;
    }
    
    public String getType(){
        return type;
    }
    public void setType(String type){
        this.type = type;
    }
    
    public News(String title,String datetime,String content,String type){
        super();
        this.title = title;
        this.datetime = datetime;
        this.content = content;
        this.type = type;
    }

}

News.java

package bean;

public class User {
    String name;
    String password;
    public User(){
        
    }
    
    public String getName(){
        return name;
    }
    public void setName(String name){
        this.name = name;
    }
    
    public String getPassword(){
        return password;
    }
    public void setPassword(String password){
        this.password = password;
    }
    
    public User(String name,String password){
        super();
        this.name = name;
        this.password = password;
    }
}

User.java

package com.dao;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.ArrayList;
import java.util.List;

import bean.News;

public class Newsdao {
    @SuppressWarnings("unused")
    private static final long serialVersionUID = 1L;
    
    static Connection con = null;
    public static Connection getCon(){
        String driverName = "com.mysql.cj.jdbc.Driver";
        String url = "jdbc:mysql://localhost:3306/newsdata?useSSL=false&serverTimezone=UTC&allowPublicKeyRetrieval=true";
        String name = "root";
        String pwd = "123456";
        try{
            Class.forName(driverName);
            try{
                con = DriverManager.getConnection(url,name,pwd);
            }catch(SQLException e){
                e.printStackTrace();
            }
        }catch(ClassNotFoundException e){
            e.printStackTrace();
        }
        return con;
    }
    
    //添加新闻
    public boolean addNews(News news){
        con = Newsdao.getCon();
        boolean flag = false;
        String sql = "insert news(title,type,datetime,content) values(‘"+news.getTitle()+"‘,‘"+news.getType()+"‘,‘"+news.getDatetime()+"‘,‘"+news.getContent()+"‘)";
        try{
            PreparedStatement ps = con.prepareStatement(sql);
            int i = ps.executeUpdate();
            ps.close();
            con.close();
            if(i>0){
                flag = true;
            }
        }catch(SQLException e){
            System.out.println("添加出错！");
            e.printStackTrace();
        }
        return flag;
    }
    
    public List<News> selectByID(int id){
        con = Newsdao.getCon();
        List<News> list = new ArrayList<>();
        String sql = "select * from news where id="+id+"";
        System.out.println(sql);
        Statement state;
        ResultSet rs;
        try{
            state = con.createStatement();
            rs = state.executeQuery(sql);
            while(rs.next()){
                News news = new News();
                news.setTitle(rs.getString("title"));
                news.setDatetime(rs.getString("content"));
                news.setContent(rs.getString("content"));
                news.setType(rs.getString("type"));
                news.setId(id);
                list.add(news);
            }
            rs.close();
            state.close();
            con.close();
        }catch(SQLException e){
            System.out.println("查询出错！");
            e.printStackTrace();
        }
        return list;
    }
    
    //删除新闻
    public List<News> selectAll(){
        con = Newsdao.getCon();
        List<News> list = new ArrayList<News>();
        String sql = "select * from news";
        Statement state;
        ResultSet rs;
        try{
            state = con.createStatement();
            rs = state.executeQuery(sql);
            while(rs.next()){
                News news = new News();
                news.setId(rs.getInt("id"));
                news.setTitle(rs.getString("title"));
                news.setDatetime(rs.getString("datetime"));
                news.setContent(rs.getString("content"));
                news.setType(rs.getString("type"));
                list.add(news);
            }
            rs.close();
            state.close();
            con.close();
        }catch(SQLException e){
            System.out.println("查询出错！");
            e.printStackTrace();
        }
        return list;
    }
    
    //修改新闻
    public boolean update(News news){
        con = Newsdao.getCon();
        boolean flag = false;
        String sql = "update news set title=‘"+news.getTitle()+"‘,type=‘"+news.getType()+"‘,datetime=‘"+news.getDatetime()+"‘,content=‘"+news.getContent()+"‘ where id = "+news.getId()+"";
        System.out.println(sql);
        Statement state = null;
        try{
            state = con.createStatement();
            int i=state.executeUpdate(sql);
            System.out.println(i);
            if(i>0){
                flag = true;
            }
        }catch(SQLException e){
            System.out.println("更新错误！");
            e.printStackTrace();
        }
        return flag;
    }
    
    //删除新闻
    public boolean delete(int id){
        con = Newsdao.getCon();
        boolean flag = false;
        String sql = "delete from news where id=‘"+id+"‘";
        PreparedStatement ps;
        try{
            ps = con.prepareStatement(sql);
            int i = ps.executeUpdate();
            if(i>0){
                flag = true;
            }
        }catch(SQLException e){
            System.out.println("删除错误！");
            e.printStackTrace();
        }
        return flag;
    }
}

Newsdao.java

package com.dao;

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

import bean.User;

public class Userdao {
    private static final long serialVersionUID = 1L;
    private String driverName="com.mysql.cj.jdbc.Driver";
    private String url="jdbc:mysql://localhost:3306/newsdata?useSSL=false&serverTimezone=UTC&allowPublicKeyRetrieval=true";
    private String name="root";
    private String pwd="123456";
    
    public boolean login(User u) {
        boolean flag=false;
        String sql="select * from user where uname=‘"+u.getName()+"‘ and password=‘"+u.getPassword()+"‘";
        System.out.println(sql);
        Connection connection=null;
        Statement statement=null;
        ResultSet resultSet=null;
                try {
                    //System.out.println("******************");
                    Class.forName(driverName);
                    try {
                        //System.out.println("##################3");
                        connection = DriverManager.getConnection(url, name, pwd);
                        //System.out.println("******************");
                        statement = connection.createStatement();
                        resultSet = statement.executeQuery(sql);
                        flag=resultSet.next();
                        resultSet.close();
                        statement.close();
                        connection.close();
                        //System.out.println(flag+"**********");
                    } catch (SQLException e) {
                        e.printStackTrace();
                    }
                    
                } catch (ClassNotFoundException e) {
                    e.printStackTrace();
                }
                
        return flag;
    }
}

Userdao.java

package servlet;

import java.io.IOException;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import com.dao.Newsdao;

import bean.News;


@WebServlet("/AddServlet")
public class AddServlet extends HttpServlet {

       
    public AddServlet() {
        super();
    }
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doPost(request,response);
    }

    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        request.setCharacterEncoding("utf-8");
        response.setContentType("text/html;charset=UTF-8");
        String title=request.getParameter("title");
        String type=request.getParameter("type");
        String datetime=request.getParameter("datetime");
        String content=request.getParameter("ueditor");
        System.out.println("这是ueditor的内容"+title+content);
        News news=new News();
        news.setTitle(title);
        news.setContent(content);
        news.setDatetime(datetime);
        news.setType(type);
        
        Newsdao nd=new Newsdao();
        
        try{
            nd.addNews(news);
            response.sendRedirect("newslistServlet");
            //request.getRequestDispatcher("/newslist.jsp").forward(request, response);
        }catch(Exception e) {
            System.out.println("添加失败");
        }
    }

}

AddServlet.java

package servlet;

import java.io.IOException;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import com.dao.Newsdao;

@WebServlet("/DeleteServlet")
public class DeleteServlet extends HttpServlet {
    private static final long serialVersionUID = 1L;
       
    public DeleteServlet() {
        super();
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doPost(request,response);
    }
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        request.setCharacterEncoding("utf-8");
        response.setContentType("text/html;charset=utf-8");
        String id=(String)request.getParameter("id");
        System.out.println("被删除的新闻");
        int nid=Integer.parseInt(id);
        Newsdao nd=new Newsdao();
        nd.delete(nid);
        response.sendRedirect("newslistServlet");
    }

}

DeleteServlet.java

package servlet;

import java.io.IOException;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import com.dao.Newsdao;

import bean.News;

@WebServlet("/UpdateServlet")
public class UpdateServlet extends HttpServlet {
    private static final long serialVersionUID = 1L;
   
    public UpdateServlet() {
        super();
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doPost(request,response);
        
    }

    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        response.setContentType("text/html;charset=UTF-8");
        request.setCharacterEncoding("utf-8");
        String id=request.getParameter("id");
        System.out.println("id的值为"+id);
        int nid=Integer.parseInt(id);
        String title=request.getParameter("title");
        String type=request.getParameter("type");
        String datetime=request.getParameter("datetime");
        String content=request.getParameter("editor");
        News news=new News();
        news.setId(nid);
        news.setTitle(title);
        news.setContent(content);
        news.setDatetime(datetime);
        news.setType(type);
        Newsdao nd=new Newsdao();
        try{
            nd.update(news);
            response.sendRedirect("newslistServlet");
        }catch(Exception e) {
            System.out.println("修改失败");
        }
    }

}

UpdataServlet.java

package servlet;

import java.io.IOException;

import java.util.List;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import com.dao.Newsdao;

import bean.News;

@WebServlet("/SelectServlet")
public class SelectServlet extends HttpServlet {
    private static final long serialVersionUID = 1L;
    public SelectServlet() {
        super();
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doPost(request,response);
    }

    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        request.setCharacterEncoding("utf-8");
        response.setContentType("text/html;cahrset=utf-8");
        String id=request.getParameter("id");
        int nid=Integer.parseInt(id);
        Newsdao nd=new Newsdao();
        List<News> list=nd.selectByID(nid);
        request.setAttribute("news", list);
        
        System.out.println(list.size());
        request.getRequestDispatcher("/content.jsp").forward(request, response);
        
        
        
    }

}

SelectServlet.java