package bean;
 
public class Hero {
 
    public int id;
    public String name;
    public float hp;
    public int damage;
	public int getId() {
		return id;
	}
	public void setId(int id) {
		this.id = id;
	}
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
	public float getHp() {
		return hp;
	}
	public void setHp(float hp) {
		this.hp = hp;
	}
	public int getDamage() {
		return damage;
	}
	public void setDamage(int damage) {
		this.damage = damage;
	}
     
}

package 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.Hero;
  
public class HeroDAO {
  
    public HeroDAO() {
        try {
            Class.forName("com.mysql.jdbc.Driver");
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        }
    }
  
    public Connection getConnection() throws SQLException {
        return DriverManager.getConnection("jdbc:mysql://127.0.0.1:3306/how2java?characterEncoding=UTF-8", "root",
                "admin");
    }
  
    public int getTotal() {
        int total = 0;
        try (Connection c = getConnection(); Statement s = c.createStatement();) {
  
            String sql = "select count(*) from hero";
  
            ResultSet rs = s.executeQuery(sql);
            while (rs.next()) {
                total = rs.getInt(1);
            }
  
            System.out.println("total:" + total);
  
        } catch (SQLException e) {
  
            e.printStackTrace();
        }
        return total;
    }
  
    public void add(Hero hero) {
  
        String sql = "insert into hero values(null,?,?,?)";
        try (Connection c = getConnection(); PreparedStatement ps = c.prepareStatement(sql);) {
  
            ps.setString(1, hero.name);
            ps.setFloat(2, hero.hp);
            ps.setInt(3, hero.damage);
  
            ps.execute();
  
            ResultSet rs = ps.getGeneratedKeys();
            if (rs.next()) {
                int id = rs.getInt(1);
                hero.id = id;
            }
        } catch (SQLException e) {
  
            e.printStackTrace();
        }
    }
  
    public void update(Hero hero) {
  
        String sql = "update hero set name= ?, hp = ? , damage = ? where id = ?";
        try (Connection c = getConnection(); PreparedStatement ps = 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 (SQLException e) {
  
            e.printStackTrace();
        }
  
    }
  
    public void delete(int id) {
  
        try (Connection c = getConnection(); Statement s = c.createStatement();) {
  
            String sql = "delete from hero where id = " + id;
  
            s.execute(sql);
  
        } catch (SQLException e) {
  
            e.printStackTrace();
        }
    }
  
    public Hero get(int id) {
        Hero hero = null;
  
        try (Connection c = getConnection(); Statement s = c.createStatement();) {
  
            String sql = "select * from hero where id = " + id;
  
            ResultSet rs = 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 (SQLException 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 desc limit ?,? ";
  
        try (Connection c = getConnection(); PreparedStatement ps = c.prepareStatement(sql);) {
  
            ps.setInt(1, start);
            ps.setInt(2, count);
  
            ResultSet rs = 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 (SQLException e) {
  
            e.printStackTrace();
        }
        return heros;
    }
  
}

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 bean.Hero;
import dao.HeroDAO;

public class HeroListServlet extends HttpServlet {

	protected void service(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
	List<Hero> heros = new HeroDAO().list();
        request.setAttribute("heros", heros);
        request.getRequestDispatcher("listHero.jsp").forward(request, response);

	}
}

<web-app>
    <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>
</web-app>

<%@ page language="java" contentType="text/html; charset=UTF-8"
	pageEncoding="UTF-8" import="java.util.*"%>

<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c"%>

<table align='center' border='1' cellspacing='0'>
	<tr>
		<td>id</td>
		<td>name</td>
		<td>hp</td>
		<td>damage</td>
		<td>edit</td>
		<td>delete</td>
	</tr>
	<c:forEach items="${heros}" var="hero" varStatus="st">
		<tr>
			<td>${hero.id}</td>
			<td>${hero.name}</td>
			<td>${hero.hp}</td>
			<td>${hero.damage}</td>
			<td><a href="editHero?id=${hero.id}">edit</a></td>
			<td><a href="deleteHero?id=${hero.id}">delete</a></td>
		</tr>
	</c:forEach>
</table>