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

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

login.html

<!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

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;

public class HeroDeleteServlet extends HttpServlet {

    public void service(HttpServletRequest request, HttpServletResponse response) throws IOException, ServletException {

        int id = Integer.parseInt(request.getParameter("id"));//获得要删除的id

        new HeroDAO().delete(id);//调用删除英雄方法

        request.getRequestDispatcher("/listHero").forward(request, response);//跳转到展示hero页面

    }

}

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");

巴特西

利用Servlet做一套增删改查

前期准备配置

建一个动态web项目

新建web.xml文件并新建几个包

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）

数据库连接放util中包中

hero的增删查改的方法实现放在dao包下

登录模块

客户端跳转我设置了登录信息错误跳转到的页面

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

编写HeroListServlet，以html形式展示出英雄列表

增加新成员链接下的操作

删除操作

小结：

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