Servlet——利用数据库、前后端接口实现一个简单的博客系统

素颜马尾好姑娘i 2023-02-26 10:28 152阅读 0赞

### 简单的博客系统 ###

*  需求分析
 *  数据库设计
 *   *  1、提取需求中的实体
     *  2、实体的属性
     *  3、实体之间关系
     *  数据库建表
 *  Java代码操作
 *   *  a）创建一个类，管理数据库的连接
     *  b）创建实体类
     *  c）实现数据库的基本的增删改查
 *  前后端接口设计并实现
 *   *  1）获取注册页面
     *  2）实现注册功能(注册页面中提交的form表单数据，需要服务器处理)
     *  3）获取登录页面
     *  4）实现登录功能（登陆页面提交的数据，需要服务器来处理
     *  5）获取文章列表
     *  6)获取文章详细内容
     *  7)新增/发布文章
     *  5-7
     *  8)删除文章
 *  成果

# 需求分析 #

1)注册新用户  
2)登陆已有用户  
3)展示博客列表(每项包含了文章的标题,作者)  
点击标题就会跳转到文章详情页.  
分页功能也暂时不考虑  
4)文章详情页中,可以看到文章标题,作者,文章内容  
评论功能，分类功能,推荐相关文章功能等,先不考虑  
5)发布新的博客（不考虑富文本编辑.）  
6)删除自己的博客

# 数据库设计 #

## 1、提取需求中的实体 ##

两张表User Article

## 2、实体的属性 ##

用户： 名字 密码  
文章： 标题 内容

## 3、实体之间关系 ##

一对多  
a）user表中加入一个userId字段，身份标识  
b）Article表中加入一个userId字段，表示该文章是哪个用户发的  
![在这里插入图片描述][20200715130555548.png]

## 数据库建表 ##

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2NoYXJfbQ_size_16_color_FFFFFF_t_70]

drop database if exists myBlog;
    create database myblog;
    
    use myblog;
    
    drop table if exists user;
    create table user (
        userId int primary key auto_increment,
        name varchar(50) unique,
        password varchar(50)
    );
    
    drop table if exists article;
    create table article (
        articleId int primary key auto_increment,
        title varchar(255),
        content text,
        userId int,
        foreign key(userId) references user(userId)
    );

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2NoYXJfbQ_size_16_color_FFFFFF_t_70 1]

# Java代码操作 #

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2NoYXJfbQ_size_16_color_FFFFFF_t_70 2]

## a）创建一个类，管理数据库的连接 ##

import com.mysql.jdbc.jdbc2.optional.MysqlDataSource;
    
    import javax.sql.DataSource;
    import java.sql.Connection;
    import java.sql.PreparedStatement;
    import java.sql.ResultSet;
    import java.sql.SQLException;
    
    public class DButil {
        
        private static String url = "jdbc:mysql://127.0.0.1:3306/blog?characterEncoding=utf-8&useSSL=true";
        private static String username = "root";
        private static String password = "";
    
        private static volatile DataSource DATASOURCE = null;
    
        private static DataSource getDATASOURCE() {
        
            //双层校验锁
    
            if(DATASOURCE == null){
        
                synchronized (DButil.class){
        
                    if(DATASOURCE == null){
        
                        DATASOURCE = new MysqlDataSource();
                        ((MysqlDataSource)DATASOURCE).setUrl(url);
                        ((MysqlDataSource)DATASOURCE).setUser(username);
                        ((MysqlDataSource)DATASOURCE).setPassword(password);
                    }
                }
            }
            return DATASOURCE;
        }
    
        public static Connection getConnect(){
        
            try{
        
                //从池子中获取连接
                Connection connection = getDATASOURCE().getConnection();
                return connection;
            } catch (SQLException e) {
        
                e.printStackTrace();
                throw new RuntimeException("获取数据库连接失败！");
            }
        }
    
        //断开连接
        public static void getClose(Connection connection,
                                    PreparedStatement statement,
                                    ResultSet resultSet){
        
            if(resultSet != null){
        
                try {
        
                    resultSet.close();
                } catch (SQLException e) {
        
                    e.printStackTrace();
                }
            }
            if(statement != null){
        
                try {
        
                    statement.close();
                } catch (SQLException e) {
        
                    e.printStackTrace();
                }
            }
            if(connection != null){
        
                try {
        
                    connection.close();
                } catch (SQLException e) {
        
                    e.printStackTrace();
                }
            }
        }
    }

## b）创建实体类 ##

创建一个User类和Article类  
这俩类的属性,要和数据库表结构,是相关联的  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2NoYXJfbQ_size_16_color_FFFFFF_t_70 3]

public class User {
        
        private int userId;
        private String userName;
        private String password;
    
        public int getUserId() {
        
            return userId;
        }
    
        public void setUserId(int userId) {
        
            this.userId = userId;
        }
    
        public String getUserName() {
        
            return userName;
        }
    
        public void setUserName(String userName) {
        
            this.userName = userName;
        }
    
        public String getPassword() {
        
            return password;
        }
    
        public void setPassword(String password) {
        
            this.password = password;
        }
    
        @Override
        public String toString() {
        
            return "User{" +
                    "userId=" + userId +
                    ", userName='" + userName + '\'' +
                    ", password='" + password + '\'' +
                    '}';
        }
    }

public class Article {
        
        private int articleId;
        private String articleTitle;
        private String articleContent;
        private int userId;
    
        public int getArticleId() {
        
            return articleId;
        }
    
        public void setArticleId(int articleId) {
        
            this.articleId = articleId;
        }
    
        public String getArticleTitle() {
        
            return articleTitle;
        }
    
        public void setArticleTitle(String articleTitle) {
        
            this.articleTitle = articleTitle;
        }
    
        public String getArticleContent() {
        
            return articleContent;
        }
    
        public void setArticleContent(String articleContent) {
        
            this.articleContent = articleContent;
        }
    
        public int getUserId() {
        
            return userId;
        }
    
        public void setUserId(int userId) {
        
            this.userId = userId;
        }
    
        @Override
        public String toString() {
        
            return "Article{" +
                    "articleId=" + articleId +
                    ", articleTitle='" + articleTitle + '\'' +
                    ", articleContent='" + articleContent + '\'' +
                    ", userId=" + userId +
                    '}';
        }
    }

## c）实现数据库的基本的增删改查 ##

**DAO表示数据访问层.  
通过UserDao这个类来完成针对用户的数据库表操作.**

import DButil.DButil;
    import Entity.User;
    
    import java.sql.Connection;
    import java.sql.PreparedStatement;
    import java.sql.ResultSet;
    import java.sql.SQLException;
    
    public class UserDao {
        
    
        //新增用户（注册）
        public void add(User user){
        
            Connection connection = null;
            PreparedStatement preparedStatement = null;
    
            String sql = "insert into user values (null ,?,?)";
    
            try {
        
                connection = DButil.getConnect();
                preparedStatement = connection.prepareStatement(sql);
                preparedStatement.setString(1,user.getUserName());
                preparedStatement.setString(2,user.getPassword());
    
                int ret = preparedStatement.executeUpdate();
                if (ret != 1) {
        
                    System.out.println("插入新用户失败!");
                    return;
                }
                System.out.println("插入新用户成功");
            } catch (SQLException e) {
        
                e.printStackTrace();
            }finally {
        
                DButil.getClose(connection,preparedStatement,null);
            }
        }
    
        //按照名字查找用户（登录）
        public User findUserByName(String name){
        
            Connection connection = null;
            PreparedStatement preparedStatement = null;
            ResultSet resultSet = null;
    
            String sql="select * from user where userName=?";
            try{
        
                assert connection != null;
                connection = DButil.getConnect();
                preparedStatement = connection.prepareStatement(sql);
                preparedStatement.setString(1,name);
                resultSet = preparedStatement.executeQuery();
                if (resultSet.next()){
        
                    User user = new User();
                    user.setUserId(resultSet.getInt("userId"));
                    user.setUserName(resultSet.getString("userName"));
                    user.setPassword(resultSet.getString("password"));
                    return user;
    
    
                }
            } catch (SQLException e) {
        
                e.printStackTrace();
            }finally {
        
                DButil.getClose(connection,preparedStatement,resultSet);
            }
            return null;
        }
    
        //通过id查找用户
        public User findUserById(int id){
        
            Connection connection = null;
            PreparedStatement preparedStatement = null;
            ResultSet resultSet = null;
    
            String sql = "select * from user where userId = ?";
            try{
        
                connection = DButil.getConnect();
                preparedStatement = connection.prepareStatement(sql);
                preparedStatement.setInt(1,id);
                resultSet = preparedStatement.executeQuery();
                if (resultSet.next()){
        
                    User user = new User();
                    user.setUserId(resultSet.getInt("userId"));
                    user.setUserName(resultSet.getString("userName"));
                    user.setPassword(resultSet.getString("password"));
                    return user;
    
                }
    
            } catch (SQLException e) {
        
                e.printStackTrace();
            }finally {
        
                DButil.getClose(connection,preparedStatement,resultSet);
            }
            return null;
    
        }
    
       /* public static void main(String[] args) {
            UserDao userDao = new UserDao();
            User user = new User();
            user.setUserName("hhh");
            user.setPassword("123");
    
            userDao.add(user);
    
            System.out.println(findUserByName("hhh"));
            System.out.println(findUserById(1));
        }*/
    
    }

通过ArticleDao这个类完成针对文章的数据库表操作.

import DButil.DButil;
    import Entity.Article;
    
    import java.sql.Connection;
    import java.sql.PreparedStatement;
    import java.sql.ResultSet;
    import java.sql.SQLException;
    import java.util.ArrayList;
    import java.util.List;
    
    public class ArticleDao {
        
        //1、新增文章（发布博客）
        public static void add(Article article){
        
            Connection connection = null;
            PreparedStatement preparedStatement = null;
    
    
            String sql = "insert into article values (null,?,?,?)";
            try{
        
                connection = DButil.getConnect();
                preparedStatement = connection.prepareStatement(sql);
                preparedStatement.setString(1,article.getArticleTitle());
                preparedStatement.setString(2,article.getArticleContent());
                preparedStatement.setInt(3,article.getUserId());
    
                int ret = preparedStatement.executeUpdate();
                if(ret != 1){
        
                    System.out.println("文章添加失败！");
                    return;
                }else {
        
                    System.out.println("文章添加成功！");
                }
    
            } catch (SQLException e) {
        
                e.printStackTrace();
            }finally {
        
                DButil.getClose(connection,preparedStatement,null);
            }
        }
        //2、查看文章列表（把所有文章信息都查出来，不查正文）\
        public List<Article> findArticleList(){
        
            Connection connection = null;
            PreparedStatement preparedStatement = null;
            ResultSet resultSet = null;
            List<Article> articleList = new ArrayList<>();
    
    
            String sql = "select articleId,articleTitle,userId from article";
            try{
        
                connection = DButil.getConnect();
                preparedStatement = connection.prepareStatement(sql);
                resultSet = preparedStatement.executeQuery();
    
                while (resultSet.next()){
        
                 Article article = new Article();
                 article.setArticleId(resultSet.getInt("articleId"));
                 article.setArticleTitle(resultSet.getString("articleTitle"));
                 article.setUserId(resultSet.getInt("userId"));
    
                 articleList.add(article);
    
                }
                return articleList;
    
            } catch (SQLException e) {
        
                e.printStackTrace();
            }finally {
        
                DButil.getClose(connection,preparedStatement,resultSet);
            }
            return null;
        }
        //3、根据文章id查看指定文章详情(查看正文)
        public Article findArticleByArticleId(int articleId){
        
            Connection connection = null;
            PreparedStatement preparedStatement = null;
            ResultSet resultSet = null;
    
    
            String sql = "select * from article where articleId=?";
            try{
        
                connection = DButil.getConnect();
                preparedStatement = connection.prepareStatement(sql);
                preparedStatement.setInt(1,articleId);
                resultSet = preparedStatement.executeQuery();
    
                if (resultSet.next()){
        
                    Article article = new Article();
                    article.setArticleId(resultSet.getInt("articleId"));
                    article.setArticleTitle(resultSet.getString("articleTitle"));
                    article.setArticleContent(resultSet.getString("articleContent"));
                    article.setUserId(resultSet.getInt("userId"));
                    return article;
                }
    
            } catch (SQLException e) {
        
                e.printStackTrace();
            }finally {
        
                DButil.getClose(connection,preparedStatement,resultSet);
            }
            return null;
    
        }
    
        //4、删除指定文章（给定文章ID删除）
        public void  deleteArticle(int articleId){
        
            Connection connection = null;
            PreparedStatement preparedStatement = null;
    
            String sql ="delete from article where articleId =?";
            try{
        
                connection = DButil.getConnect();
                preparedStatement = connection.prepareStatement(sql);
                preparedStatement.setInt(1,articleId);
                int ret = preparedStatement.executeUpdate();
                if(ret != 1){
        
                    System.out.println("删除文章失败！");
                    return;
                }else {
        
                    System.out.println("删除文章成功！");
                }
            } catch (SQLException e) {
        
                e.printStackTrace();
            }finally {
        
                DButil.getClose(connection,preparedStatement,null);
            }
        }
    
       /*public static void main(String[] args) {
            ArticleDao articleDao = new ArticleDao();
            Article article = new Article();
            article.setArticleTitle("爱你就像爱生命");
            article.setArticleContent("一想到你我这张丑脸就泛起微笑！");
            article.setUserId(1);
            articleDao.add(article);
           *//* System.out.println(findArticleList());
            System.out.println(findArticleByArticleId(4));*//*
        }
    */
    }

# 前后端接口设计并实现 #

约定,服务器都能接收啥样的请求,每个请求具体的格式如何,对应的响应结果又如何.（自定制协议，基于http的基础上进行拓展）  
![在这里插入图片描述][20200718180645607.png]

## 1）获取注册页面 ##

GET/register.html（GET /signup.html）  
前后端按照同一种方式开发

<!DOCTYPE html>
    <html lang="zxx">
    
    <head>
        <title>注册</title>
        
        <meta charset="UTF-8">
        <meta name="viewport" content="width=device-width, initial-scale=1.0">
        <meta http-equiv="X-UA-Compatible" content="ie=edge">
        
        <link rel="stylesheet" href="css/style.css" type="text/css" media="all" />
    </head>
    
    <body>
    <section class="w3l-coming-soon">
        <div class="bgimg text-center">
            <div class="topleft">
                <a class="brand-logo" href="#index.html">Adventure</a>
            </div>
            <div class="middle">
                <h2>Stay Tuned</h2>
                <h1>We ARE COMING SOON</h1>
    
                <p id="demo"></p>
    
                <div class="form-right-inf">
                    <form action="register" method="post" >
                        <div class="forms-gds">
                            <input type="text" name="userName" placeholder="请输入用户名" >
                            <br/>
                            <input type="text" name="password" placeholder="请输入密码" >
                            <br/>
                            <button class="btn theme-button">注册</button>
                        </div>
                    </form>
    
                </div>
            </div>
            
            
        </div>
    
    </section>
    
    </body>
    </html>

响应：  
注册页面，页面上带有两个输入框（输入用户名密码）一个提交按钮

## 2）实现注册功能(注册页面中提交的form表单数据，需要服务器处理) ##

请求：  
POST/register  
name = XXX&password=XXX

import Dao.UserDao;
    import Entity.User;
    import View.HtmlGenerator;
    
    import javax.servlet.ServletException;
    import javax.servlet.http.HttpServlet;
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpServletResponse;
    import java.io.IOException;
    
    public class RegisterServlet extends HttpServlet {
        
        @Override
        protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        
            req.setCharacterEncoding("utf-8");
            resp.setContentType("text/html; charset=utf-8");
            String name = req.getParameter("userName");
            String password = req.getParameter("password");
            // 1. 获取到前端提交的数据(用户名, 密码), 校验是否合法.
            if(name == null|| "".equals(name) || password == null|| "".equals(password)){
        
                String html = HtmlGenerator.getMessagePage("用户名或者密码为空！",
                        "register.html");
                resp.getWriter().write(html);
                return;
            }
    
            // 2. 拿着用户名在数据库中查一下, 看看当前用户名是否已经存在. 如果存在, 认为注册失败(用户名不能重复)
            UserDao userDao = new UserDao();
            User existUser = userDao.findUserByName(name);
    
            if(existUser != null){
        
                String html = HtmlGenerator.getMessagePage("用户名重复！","register.html");
                resp.getWriter().write(html);
                return;
            }
            // 3. 根据前端提交的数据, 构造 User 对象并插入到数据库中.
            User user = new User();
            user.setUserName(name);
            user.setPassword(password);
            userDao.add(user);
    
            // 4. 返回一个结果页面, 提示当前注册成功.
            String html = HtmlGenerator.getMessagePage("注册成功！",
                    "login.html");
            resp.getWriter().write(html);
    
        }
    }

响应：  
返回一个提示页面，告诉用户注册成功还是失败，并且能跳转到登录页面

## 3）获取登录页面 ##

请求  
GET/login.html

<!DOCTYPE html>
    <html lang="zxx">
    
    <head>
        <title>登录</title>
        
        <meta charset="UTF-8">
        <meta name="viewport" content="width=device-width, initial-scale=1.0">
        <meta http-equiv="X-UA-Compatible" content="ie=edge">
        
        <link rel="stylesheet" href="css/style.css" type="text/css" media="all" />
    </head>
    
    <body>
    <section class="w3l-coming-soon">
        <div class="bgimg text-center">
            <div class="topleft">
                <a class="brand-logo" href="#index.html">Adventure</a>
            </div>
            <div class="middle">
                <h2>Stay Tuned</h2>
                <h1>We ARE COMING SOON</h1>
    
                <p id="demo"></p>
    
                <div class="form-right-inf">
                    <form action="login" method="post" >
                        <div class="forms-gds">
                            <input type="text" name="userName" placeholder="请输入用户名" >
                            <br/>
                            <input type="text" name="password" placeholder="请输入密码" >
                            <br/>
                            <button class="btn theme-button">登录</button>
                        </div>
                    </form>
    
                </div>
            </div>
            
            
        </div>
    
    </section>
    
    </body>
    </html>

在这里插入代码片

响应：  
返回一个登陆页面，包含两个输入框和一个登录按钮

## 4）实现登录功能（登陆页面提交的数据，需要服务器来处理 ##

请求：  
POST/login  
name = XXX&password=XXX

import Dao.UserDao;
    import Entity.User;
    import View.HtmlGenerator;
    
    import javax.servlet.ServletException;
    import javax.servlet.http.HttpServlet;
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpServletResponse;
    import javax.servlet.http.HttpSession;
    import java.io.IOException;
    
    public class LoginServlet extends HttpServlet {
        
    
        @Override
        protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        
            req.setCharacterEncoding("utf-8");
            resp.setContentType("text/html; charset=utf-8");
            String name = req.getParameter("userName");
            String password = req.getParameter("password");
            // 1. 获取到用户名和密码. 并进行简单校验
            if(name == null || "".equals(name) || password == null || "".equals(password)){
        
                String html = HtmlGenerator.getMessagePage("用户名或者密码为空！","login.html");
                resp.getWriter().write(html);
                return;
            }
            // 2. 数据库中查找, 看用户是否存在.
            // 3. 对比密码是否匹配
    
            UserDao userDao = new UserDao();
            User user = userDao.findUserByName(name);
            if(user == null || !password.equals(user.getPassword())){
        
                String html = HtmlGenerator.getMessagePage("用户名或者密码错误！","login.html");
                resp.getWriter().write(html);
                return;
            }
            // 4. 匹配成功则认为登陆成功, 创建一个 Session
            HttpSession httpSession = req.getSession(true);
            httpSession.setAttribute("user",user);
            // 5. 返回一个登陆成功的提示页面
            String html = HtmlGenerator.getMessagePage("登陆成功!",
                    "article");
            resp.getWriter().write(html);
    
        }
    }

响应：  
返回一个提示页面，告诉用户登录成功还是失败

## 5）获取文章列表 ##

请求：  
GET/article

响应：  
返回文章的列表页面（包含一些文章的标题，点击标题进入到详情页）

## 6)获取文章详细内容 ##

请求:  
GET /article?articleld= 1

响应:  
返回文章的详情页(包含文章的内容)

## 7)新增/发布文章 ##

请求:  
POST /article  
title=xxx&content= xXXX  
响应:  
返回一一个提示页面,告诉用户发布成功还是失败.

## 5-7 ##

import Dao.ArticleDao;
    import Dao.UserDao;
    import Entity.Article;
    import Entity.User;
    
    
    import View.HtmlGenerator;
    
    import javax.servlet.ServletException;
    import javax.servlet.http.HttpServlet;
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpServletResponse;
    import javax.servlet.http.HttpSession;
    import java.io.IOException;
    import java.util.List;
    
    public class ArticleServlet extends HttpServlet {
        
    
        //获取文章列表 获取文章详细内容
        @Override
        protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        
            req.setCharacterEncoding("utf-8");
            resp.setContentType("text/html; charset=utf-8");
            // 1. 判定用户的登陆状态. 如果用户尚未登陆, 就要提示用户来登陆.
            HttpSession httpSession = req.getSession(false);
            if (httpSession == null) {
        
                String html = HtmlGenerator.getMessagePage("您尚未登陆",
                        "login.html");
                resp.getWriter().write(html);
                return;
            }
            User user = (User) httpSession.getAttribute("user");
            // 2. 判断请求中是否存在 articleId 参数.
            String articleIdStr = req.getParameter("articleId");
            if (articleIdStr == null) {
        
                //  a) 没有这个参数就去执行获取文章列表操作articleDao中查找文章列表不需要id
                getAllArticleList(user, resp);
    
            } else {
        
                //  b) 有这个参数就去执行获取文章详情操作.
                getOneArticle(Integer.parseInt(articleIdStr), user, resp);
    
            }
        }
            private void getAllArticleList(User user, HttpServletResponse resp) throws IOException  {
        
                // 1. 查找数据库
                ArticleDao articleDao = new ArticleDao();
                List<Article> articleList = articleDao.findArticleList();
                // 2. 构造页面
                String html = HtmlGenerator.getArticleListPage(articleList, user);
                resp.getWriter().write(html);
    
    
            }
            private void getOneArticle(int articleId, User user, HttpServletResponse resp) throws IOException {
        
                // 1. 查找数据库
                ArticleDao articleDao = new ArticleDao();
                Article article = articleDao.findArticleByArticleId(articleId);
                if (article == null) {
        
                    //文章未找到
                    String html = HtmlGenerator.getMessagePage("文章不存在",
                            "article");
                    resp.getWriter().write(html);
                    return;
                }
                // 2. 根据作者id 找到作者信息, 进一步得到作者姓名
                UserDao userDao = new UserDao();
                User author = userDao.findUserById(article.getUserId());
                // 3. 构造页面
                String html = HtmlGenerator.getArticleDetailPage(article, user, author);
                resp.getWriter().write(html);
    
            }
    
        //实现新增文章
        @Override
        protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        
            req.setCharacterEncoding("utf-8");
            resp.setContentType("text/html; charset=utf-8");
            // 1. 判定用户的登陆状态. 如果用户尚未登陆, 就要提示用户来登陆.
            HttpSession httpSession = req.getSession(false);
            if (httpSession == null) {
        
                String html = HtmlGenerator.getMessagePage("您尚未登陆",
                        "login.html");
                resp.getWriter().write(html);
                return;
            }
            User user = (User) httpSession.getAttribute("user");
    
            // 2. 从请求中读取浏览器提交的数据(title, content), 并进行简单校验
            String title = req.getParameter("articleTitle");
            String content = req.getParameter("articleContent");
            if (title == null || "".equals(title)
                    || content == null || "".equals(content)) {
        
                String html = HtmlGenerator.getMessagePage("提交的标题或者正文为空!",
                        "article");
                resp.getWriter().write(html);
                return;
            }
            // 3. 把数据插入到数据库中.
            ArticleDao articleDao = new ArticleDao();
            Article article = new Article();
            article.setArticleTitle(title);
            article.setArticleContent(content);
            article.setUserId(user.getUserId());
            articleDao.add(article);
            // 4. 返回一个插入成功的页面.
            String html = HtmlGenerator.getMessagePage("发布成功！","article");
            resp.getWriter().write(html);
            return;
        }
    }

## 8)删除文章 ##

请求:  
GET /deleteArticle?articleld= 1

import Dao.ArticleDao;
    import Entity.Article;
    import Entity.User;
    import View.HtmlGenerator;
    
    import javax.servlet.ServletException;
    import javax.servlet.http.HttpServlet;
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpServletResponse;
    import javax.servlet.http.HttpSession;
    import java.io.IOException;
    
    public class DeleteArticleServlet extends HttpServlet {
        
        @Override
        protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        
            req.setCharacterEncoding("utf-8");
            resp.setContentType("text/html;charset=utf-8");
            // 1. 验证用户的登陆状态, 如果未登陆, 肯定不能删除.
            HttpSession httpSession = req.getSession(false);
            if(httpSession == null){
        
                String html = HtmlGenerator.getMessagePage("您尚未登录！","login.html");
                resp.getWriter().write(html);
                return;
            }
            User user = (User) httpSession.getAttribute("user");
    
            // 2. 读取请求内容, 获取到要删除的文章 id
            String articleIdStr = req.getParameter("articleId");
            if (articleIdStr == null || "".equals(articleIdStr)) {
        
                String html = HtmlGenerator.getMessagePage("要删除的文章 id 有误!",
                        "article");
                resp.getWriter().write(html);
                return;
            }
            // 3. 根据文章 id 查找到该文章的作者. 当前用户如果就是作者, 才能删除, 否则删除失败.
            ArticleDao articleDao = new ArticleDao();
            Article article = articleDao.findArticleByArticleId(Integer.parseInt(articleIdStr));
            if(article.getUserId() != user.getUserId()){
        
                String html = HtmlGenerator.getMessagePage("您只能删除自己的文章!",
                        "article");
                resp.getWriter().write(html);
                return;
            }
            // 4. 真正执行数据库删除操作
            articleDao.deleteArticle(Integer.parseInt(articleIdStr));
            // 5. 返回一个 "删除成功" 的页面.
            String html = HtmlGenerator.getMessagePage("删除成功!",
                    "article");
            resp.getWriter().write(html);
    
        }
    }

响应:  
返回一个提示页面,告诉用户删除成功还是失败.

import Entity.Article;
    import Entity.User;
    
    import java.util.List;
    
    public class HtmlGenerator {
        
        public static String getMessagePage(String message, String nextUrl) {
        
            StringBuilder stringBuilder = new StringBuilder();
            stringBuilder.append("<html>");
            stringBuilder.append("<head>");
            stringBuilder.append("<meta charset=\"utf-8\">");
            stringBuilder.append("<title>提示页面</title>");
            stringBuilder.append("</head>");
            stringBuilder.append("<body>");
    
            stringBuilder.append("<h3 style=\"clear:both;text-align:center;\">");
            stringBuilder.append(message);
            stringBuilder.append("</h3>");
    
            stringBuilder.append(String.format("<a href=\"%s\" style=\"clear:both;text-align:center;\"> 点击这里进行跳转 </a>",
                    nextUrl));
    
            stringBuilder.append("</body>");
            stringBuilder.append("</html>");
    
            return stringBuilder.toString();
    
        }
        // 按照字符串拼装的方式, 生成 html
        public static String getArticleListPage(List<Article> articles, User user) {
        
            StringBuilder stringBuilder = new StringBuilder();
            stringBuilder.append("<html>");
            stringBuilder.append("<head>");
            stringBuilder.append("<meta charset=\"utf-8\">");
            stringBuilder.append("<title>提示页面</title>");
            stringBuilder.append("<style>");
            // style 标签内部就是写 CSS 的逻辑
            stringBuilder.append(".article {" +
                    "color: #333;" +
                    "text-decoration: none;" +
    //                "display: inline-block;" +
                    "width: 200px;" +
                    "height: 50px;" +
                    "}");
            stringBuilder.append(".article:hover {" +
                    "color: white;" +
                    "background-color: orange;" +
                    "}");
            stringBuilder.append("body {" +
                    "background-repeat: none;" +
                    "background-position: 0 center;" +
                    "}");
            stringBuilder.append("</style>");
            stringBuilder.append("</head>");
            stringBuilder.append("<body>");
    
            stringBuilder.append("<h3  style=\"clear:both;text-align:center; \"> 欢迎您!    " + user.getUserName() + "</h3>");
            stringBuilder.append("<hr>");
            // 要有一个文章列表. 显示每个文章的标题.
            for (Article article : articles) {
        
                stringBuilder.append(String.format("<div style=\"width: 200px; height: 50px; line-height: 50px\"> <a class=\"article\" href=\"article?articleId=%d\"> %s </a>" +
                                "<a href=\"deleteArticle?articleId=%d\"> 删除 </a></div>",
                        article.getArticleId(), article.getArticleTitle(), article.getArticleId()));
            }
            stringBuilder.append("<hr>");
            stringBuilder.append(String.format("<div>当前共有博客 %d 篇</div>", articles.size()));
    
            // 在这里新增发布文章的区域
            stringBuilder.append("<div> 发布文章 </div>");
            stringBuilder.append("<div>");
            stringBuilder.append("<form method=\"post\" action=\"article\">");
            stringBuilder.append("<input type=\"text\" style=\"width: 500px; margin-bottom: 10px;\" name=\"articleTitle\" placeholder=\"请输入标题\">");
            stringBuilder.append("<br>");
            stringBuilder.append("<textarea name=\"articleContent\" style=\"width: 500px; height: 300px;\"></textarea>");
            stringBuilder.append("<br>");
            stringBuilder.append("<input style=\"background-color: #FFA500;\" type=\"submit\" value=\"发布文章\">");
            stringBuilder.append("</form>");
            stringBuilder.append("</div>");
    
            stringBuilder.append("</body>");
            stringBuilder.append("</html>");
            return stringBuilder.toString();
        }
    
    
        public static String getArticleDetailPage(Article article, User user, User author) {
        
            StringBuilder stringBuilder = new StringBuilder();
            stringBuilder.append("<html>");
            stringBuilder.append("<head>");
            stringBuilder.append("<meta charset=\"utf-8\">");
            stringBuilder.append("<title>提示页面</title>");
            stringBuilder.append("<style>");
            // style 标签内部就是写 CSS 的逻辑
            stringBuilder.append("a {" +
                    "color: #333;" +
                    "text-decoration: none;" +
                    "display: inline-block;" +
                    "width: 200px;" +
                    "height: 50px;" +
                    "}");
            stringBuilder.append("a:hover {" +
                    "color: white;" +
                    "background-color: orange;" +
                    "}");
            stringBuilder.append("body {" +
                    "background-repeat: none;" +
                    "background-position: 0 center;" +
                    "}");
            stringBuilder.append("</style>");
            stringBuilder.append("</head>");
            stringBuilder.append("<body>");
            stringBuilder.append("<h3 style=\"clear:both;text-align:center;\"> 欢迎您! " + user.getUserName() + "</h3>");
            stringBuilder.append("<hr>");
    
            stringBuilder.append(String.format("<h1>%s</h1>", article.getArticleTitle()));
            stringBuilder.append(String.format("<h4>作者: %s</h4>", author.getUserName()));
            // 构造正文的地方.
            // HTML 中本来就不是用 \n 表示换行的.
            stringBuilder.append(String.format("<div>%s</div>", article.getArticleContent()
                    .replace("\n", "<br>")));
    
            stringBuilder.append("</body>");
            stringBuilder.append("</html>");
            return stringBuilder.toString();
        }
    }

# 成果 #

关于前端大家可以自己套模板就好啦  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2NoYXJfbQ_size_16_color_FFFFFF_t_70 4]  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2NoYXJfbQ_size_16_color_FFFFFF_t_70 5]  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2NoYXJfbQ_size_16_color_FFFFFF_t_70 6]

[20200715130555548.png]: /images/20230209/cc46d1b84d33470d8aa283717382fad7.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2NoYXJfbQ_size_16_color_FFFFFF_t_70]: /images/20230209/44a15c3965534990a2cd759a895ed9e6.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2NoYXJfbQ_size_16_color_FFFFFF_t_70 1]: /images/20230209/82d3b795ae6b4946a06b81b1460db90a.png
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[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2NoYXJfbQ_size_16_color_FFFFFF_t_70 3]: /images/20230209/996d6d5307304406b18e7826d2f02c1b.png
[20200718180645607.png]: /images/20230209/e7da9f32d82e48d2b24defac03e83c62.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2NoYXJfbQ_size_16_color_FFFFFF_t_70 4]: /images/20230209/828d705e848540ccbd6e699f30d1755f.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2NoYXJfbQ_size_16_color_FFFFFF_t_70 5]: /images/20230209/281c2eb42531446f94604be4ac805568.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2NoYXJfbQ_size_16_color_FFFFFF_t_70 6]: /images/20230209/39c5db01879246c592f4d032a9dcb46b.png