利用Servlet做一套增删改查

╰半夏微凉° 2021-12-04 05:47 202阅读 0赞

真的，稳住，考上研，利用两年逆袭。一步一步来，实在不行，最后最差也不过就是就回家种地，想想也不错。

# 前期准备配置 #

### 建一个动态web项目 ###

新建Dynamic Web Project  
File->New->Other->Web->Dynamic Web Project

### 新建web.xml文件并新建几个包 ###

![1648300-20190522173737069-1957604576.png][]![1648300-20190522173803795-293049283.png][]

# 开始写代码 #

### 在entity在新建两个类，User（用来登录）和Hero（用来增删改查） ###

user表和用户表，代建。

### 数据库连接放util中包中 ###

package util;
    
    import java.sql.Connection;
    import java.sql.DriverManager;
    
    import javax.sound.midi.Soundbank;
    
    public class DbUtil {
    
        private String dbUrl="jdbc:mysql://localhost:3306/how2java";
        private String dbUserName="root";
        private String dbPassword="123456";
        private String jdbcName="com.mysql.jdbc.Driver";
        
        /**
         * 获取数据库连接
         * @return
         * @throws Exception
         */
        public Connection getCon() throws Exception{
            Class.forName(jdbcName);
            Connection con=DriverManager.getConnection(dbUrl,dbUserName,dbPassword);
            System.out.println("数据库连接成功！");
            return con;
        }
        
        /**
         * 关闭数据库连接
         * @param con
         * @throws Exception
         */
        public void closeCon(Connection con) throws Exception{
            if(con!=null){
                con.close();
            }
        }
        
    }

### hero的增删查改的方法实现放在dao包下 ###

package dao;
    
    import java.util.ArrayList;
    import java.util.List;
    
    import com.mysql.jdbc.Connection;
    import com.mysql.jdbc.PreparedStatement;
    import com.mysql.jdbc.ResultSet;
    import com.mysql.jdbc.Statement;
    
    import entity.Hero;
    import util.DbUtil;
    
    public class HeroDAO {
        DbUtil dbutil = new DbUtil();
    //添加新英雄
        public void add(Hero hero) {
            String sql = "insert into hero values(null,?,?,?)";
            try {
                Connection c = (Connection) dbutil.getCon();
                PreparedStatement ps = (PreparedStatement) c.prepareStatement(sql);
                ps.setString(1, hero.name);
                ps.setFloat(2, hero.hp);
                ps.setInt(3, hero.damage);
    
                ps.execute();
    
                ResultSet rs = (ResultSet) ps.getGeneratedKeys();
                if (rs.next()) {
                    int id = rs.getInt(1);
                    hero.id = id;
                }
            } catch (Exception e) {
    
                e.printStackTrace();
            }
        }
    //更新英雄
        public void update(Hero hero) {
    
            String sql = "update hero set name= ?, hp = ? , damage = ? where id = ?";
            try (Connection c = (Connection) dbutil.getCon();
                    PreparedStatement ps = (PreparedStatement) c.prepareStatement(sql);) {
    
                ps.setString(1, hero.name);
                ps.setFloat(2, hero.hp);
                ps.setInt(3, hero.damage);
                ps.setInt(4, hero.id);
    
                ps.execute();
    
            } catch (Exception e) {
    
                e.printStackTrace();
            }
    
        }
    //删除英雄
        public void delete(int id) {
    
            try (Connection c = (Connection) dbutil.getCon();
    
                    Statement s = (Statement) c.createStatement();) {
    
                String sql = "delete from hero where id = " + id;
    
                s.execute(sql);
    
            } catch (Exception e) {
    
                e.printStackTrace();
            }
        }
    //根据id号获得英雄
        public Hero get(int id) {
            Hero hero = null;
    
            try (Connection c = (Connection) dbutil.getCon(); Statement s = (Statement) c.createStatement();) {
    
                String sql = "select * from hero where id = " + id;
    
                ResultSet rs = (ResultSet) s.executeQuery(sql);
    
                if (rs.next()) {
                    hero = new Hero();
                    String name = rs.getString(2);
                    float hp = rs.getFloat("hp");
                    int damage = rs.getInt(4);
                    hero.name = name;
                    hero.hp = hp;
                    hero.damage = damage;
                    hero.id = id;
                }
    
            } catch (Exception e) {
    
                e.printStackTrace();
            }
            return hero;
        }
    
        public List<Hero> list() {
            return list(0, Short.MAX_VALUE);
        }
    
        public List<Hero> list(int start, int count) {
            List<Hero> heros = new ArrayList<Hero>();
    
            String sql = "select * from hero order by id asc limit ?,? ";
    
            try (Connection c = (Connection) dbutil.getCon();
                    PreparedStatement ps = (PreparedStatement) c.prepareStatement(sql);) {
    
                ps.setInt(1, start);
                ps.setInt(2, count);
    
                ResultSet rs = (ResultSet) ps.executeQuery();
    
                while (rs.next()) {
                    Hero hero = new Hero();
                    int id = rs.getInt(1);
                    String name = rs.getString(2);
                    float hp = rs.getFloat("hp");
                    int damage = rs.getInt(4);
                    hero.id = id;
                    hero.name = name;
                    hero.hp = hp;
                    hero.damage = damage;
                    heros.add(hero);
                }
            } catch (Exception e) {
    
                e.printStackTrace();
            }
            return heros;
        }
    }

### 登录模块 ###

<!DOCTYPE html>
    <html>
    <head>
    <meta charset="UTF-8">
    <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
    <title>登录页面</title>
    </head>
    <body>
      
    <form action="login" method="POST">
    账号: <input type="text" name="name"> <br>
    密码: <input type="password" name="password"> <br>
    <input type="submit" value="登录">
    </form>
      
    </body>
    </html>

从<form action="login" method="POST">可以看出，action为login,method为post
    现在需要在web.xml中配置映射

<?xml version="1.0" encoding="UTF-8"?>
    <web-app>
        <servlet>
            <servlet-name>LoginServlet</servlet-name>
            <servlet-class>servlet.LoginServlet</servlet-class>
        </servlet>
     
        <servlet-mapping>
            <servlet-name>LoginServlet</servlet-name>
            <url-pattern>/login</url-pattern>
        </servlet-mapping>  
    </web-app>

**现在编写LoginServlet类**

package servlet;
    
    import javax.servlet.http.HttpServlet;
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpServletResponse;
    
    import com.mysql.jdbc.Connection;
    import com.mysql.jdbc.ResultSet;
    import com.mysql.jdbc.Statement;
    
    import util.DbUtil;
    
    public class LoginServlet extends HttpServlet {
        protected void doPost(HttpServletRequest request, HttpServletResponse response) {
            String name = request.getParameter("name");
            String password = request.getParameter("password");
            System.out.println(name + "  " + password);
            String sql = "select * from user where name = '" + name +"' and password = '" + password+"'";
            DbUtil dbConnect = new DbUtil();
            try {
                Connection con = (Connection) dbConnect.getCon();
                Statement s = (Statement) con.createStatement();
                ResultSet set = (ResultSet) s.executeQuery(sql);
                if (set.next()) {
                    System.out.println("账号密码正确");
                    request.getSession().setAttribute("userName", name);
                    request.getRequestDispatcher("/listHero").forward(request, response);//服务器跳转
                } else {
                    response.sendRedirect("fail.html");// 客户端跳转
                    System.out.println("账号密码错误");
                }
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
    }

### **客户端跳转我设置了登录信息错误跳转到的页面** ###

<!DOCTYPE html>
    <html>
    <head>
    <meta charset="UTF-8">
    <title>Insert title here</title>
    </head>
    <body>
    <h1>密码或账号错误</h1>
    <a href="login.html">回到登陆界面重新登陆</a>
    </body>
    </html>

### 服务器跳转是在web.xml中映射一个路径，然后在相应的servlet中执行操作 ###

<servlet>
            <servlet-name>HeroListServlet</servlet-name>
            <servlet-class>servlet.HeroListServlet</servlet-class>
        </servlet>
     
        <servlet-mapping>
            <servlet-name>HeroListServlet</servlet-name>
            <url-pattern>/listHero</url-pattern>
        </servlet-mapping>

#### **编写**HeroListServlet，以html形式展示出英雄列表 ####

package servlet;
    
    import java.io.IOException;
    import java.util.List;
    
    import javax.servlet.ServletException;
    import javax.servlet.http.HttpServlet;
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpServletResponse;
    
    import dao.HeroDAO;
    import entity.Hero;
    
    public class HeroListServlet extends HttpServlet{
        protected void service(HttpServletRequest request, HttpServletResponse response)
                throws ServletException, IOException {
             String userName = (String) request.getSession().getAttribute("userName");
             System.out.println("欢迎"+userName);
            if (null == userName) {
                response.sendRedirect("login.html");
                return;
            }
            response.setContentType("text/html; charset=UTF-8");
            
            
            List<Hero> heros = new HeroDAO().list();
    
            StringBuffer sb = new StringBuffer();
            
            sb.append("<h1 align='center'>Welcome:</h1>");
            String ps = ("<h2 align='center'>%s</h2>");
            String ps1 = String.format(ps, userName);
            sb.append(ps1);
            
            ps1 = ("<div align='center'><a href='addHero.html'>增加成员</a></div>");//增加添加新成员的连接
            sb.append(ps1);
            
            
            sb.append("<table align='center' border='1' cellspacing='0'>\r\n");
            sb.append("<tr><td>id</td><td>name</td><td>hp</td><td>damage</td><td>delete</td><td>edit</td></tr>\r\n");
    
            String trFormat = "<tr><td>%d</td><td>%s</td><td>%f</td><td>%d</td>"
                    + "<td><a href='deleteHero?id=%d'>delete</a></td>"//添加删除连接
                    + "<td><a href='editHero?id=%d'>edit</a></td></tr>\r\n";//添加修改连接
    
            for (Hero hero : heros) {
                //System.out.println(hero);
                String tr = String.format(trFormat, hero.getId(), hero.getName(), hero.getHp(),
                        hero.getDamage(),hero.getId(),hero.getId());//设置删除和修改连接下的id就是相对应英雄的id
                sb.append(tr);
            }
            sb.append("</table>");
            response.getWriter().write(sb.toString());
        }
    }

#### 增加新成员链接下的操作 ####

转到添加页面addHero.html

<!DOCTYPE html>
     
    <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
     
    <form action="addHero" method="post">
         名字 ： <input type="text" name="name"> <br>
    血量 ： <input type="text" name="hp"> <br>
    伤害： <input type="text" name="damage"> <br>
             <input type="submit" value="增加 ">
    </form>

添加英雄

package servlet;
    
    import java.io.IOException;
    
    import javax.servlet.ServletException;
    import javax.servlet.http.HttpServlet;
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpServletResponse;
    
    import dao.HeroDAO;
    import entity.Hero;
    import net.sf.json.JSONObject;
    
    public class HeroAddServlet extends HttpServlet{
        protected void doPost(HttpServletRequest request, HttpServletResponse response)
                 throws ServletException, IOException{
            
            request.setCharacterEncoding("UTF-8");
            
            String name = request.getParameter("name");
            String hp = request.getParameter("hp");
            String damage = request.getParameter("damage");
            
            Hero hero = new Hero();
            hero.setName(name);
            hero.setHp(Float.parseFloat(hp));
            hero.setDamage(Integer.parseInt(damage));
            
            new HeroDAO().add(hero);
            System.out.println("添加成功"+hero.toString());
            
            request.getRequestDispatcher("/listHero").forward(request, response);
        }
    }

配置web.xml（添加编辑删除的）

<servlet-mapping>
            <servlet-name>HeroAddServlet</servlet-name>
            <url-pattern>/addHero</url-pattern>
        </servlet-mapping>  
        
        <servlet>
            <servlet-name>HeroDeleteServlet</servlet-name>
            <servlet-class>servlet.HeroDeleteServlet</servlet-class>
        </servlet>
     
        <servlet-mapping>
            <servlet-name>HeroDeleteServlet</servlet-name>
            <url-pattern>/deleteHero</url-pattern>
        </servlet-mapping>
        
        <servlet>
            <servlet-name>HeroEditServlet</servlet-name>
            <servlet-class>servlet.HeroEditServlet</servlet-class>
        </servlet>
     
        <servlet-mapping>
            <servlet-name>HeroEditServlet</servlet-name>
            <url-pattern>/editHero</url-pattern>
        </servlet-mapping>

#### 删除操作 ####

**编辑操作**

package servlet;
    
    import java.io.IOException;
    
    import javax.servlet.http.HttpServlet;
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpServletResponse;
    
    import dao.HeroDAO;
    import entity.Hero;
    
    public class HeroEditServlet extends HttpServlet {
        public void service(HttpServletRequest request, HttpServletResponse response) throws IOException {
            
            int id = Integer.parseInt(request.getParameter("id"));
            Hero hero = new HeroDAO().get(id);
            StringBuffer format = new StringBuffer();
            response.setContentType("text/html; charset=UTF-8");
    
            format.append("<!DOCTYPE html>");
    
            format.append("<form action='updateHero' method='post'>");
            format.append("名字 ： <input type='text' name='name' value='%s' > <br>");
            format.append("血量 ： <input type='text' name='hp'  value='%f' > <br>");
            format.append("伤害： <input type='text' name='damage'  value='%d' > <br>");
            format.append("<input type='hidden' name='id' value='%d'>");
            format.append("<input type='submit' value='更新'>");
            format.append("</form>");
    
            String html = String.format(format.toString(), hero.getName(), hero.getHp(), hero.getDamage(), hero.getId());
    
            response.getWriter().write(html);
        }
    }

<form action='updateHero' method='post'>添加更新
    更新操作

package servlet;
     
    import java.io.IOException;
     
    import javax.servlet.ServletException;
    import javax.servlet.http.HttpServlet;
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpServletResponse;
     
    import dao.HeroDAO;
    import entity.Hero;
     
    public class HeroUpdateServlet extends HttpServlet {
     
        protected void service(HttpServletRequest request, HttpServletResponse response)
                throws ServletException, IOException {
     
            request.setCharacterEncoding("UTF-8");
     
            Hero hero = new Hero();
            hero.setId(Integer.parseInt(request.getParameter("id")));
            hero.setName(request.getParameter("name"));
            hero.setHp(Float.parseFloat(request.getParameter("hp")));
            hero.setDamage(Integer.parseInt(request.getParameter("damage")));
     
            new HeroDAO().update(hero);
     
            request.getRequestDispatcher("/listHero").forward(request, response);
     
        }
    }

# 小结： #

*  前端的数据可以在服务端通过其name属性，利用**request.getParameter("xxx")**;来获取
 *  设置session，**request.getSession().setAttribute("userName", name);**这样在服务端就可以通过 **request.getSession().getAttribute("userName");**获取存入session的username
 *  服务端跳转 **request.getRequestDispatcher("success.html").forward(request, response);**服务端跳转可以看到浏览器的地址依然是之前的路径路径，并不会变成success.html
 *  客户端跳转 **response.sendRedirect("fail.html");**

转载于:https://www.cnblogs.com/dong973711/p/10907733.html

[1648300-20190522173737069-1957604576.png]: https://img2018.cnblogs.com/blog/1648300/201905/1648300-20190522173737069-1957604576.png
[1648300-20190522173803795-293049283.png]: /images/20211204/479ebfd349d24e2bbc57ee9435d171ab.png