为web应用导入mysql-jdbc的jar包

放在WEB-INF/lib 下指的是能够web应用中找到对应的class
如果要在eclipse中做调试，还是需要为项目添加该jar才可以

编写HeroListServlet

命名规范：[表][行为]Servlet这样一种命名规范
增加：HeroAddServlet

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 {
    @Override
    protected void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        response.setContentType("text/html; charset=UTF-8");
        
        List<Hero> heros = new HeroDAO().list();
        
        StringBuffer sb = new StringBuffer();
        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></tr>\r\n");
        String trFormat = "<tr><td>%d</td><td>%s</td><td>%f</td><td>%d</td></tr>\r\n";
        
        for (Hero hero : heros) {
            String tr = String.format(trFormat, hero.getId(), hero.getName(), hero.getHp(), hero.getDamage());
            sb.append(tr);
        }
 
        sb.append("</table>");
        
        response.getWriter().write(sb.toString());
    }
}

配置web.xml

把路径listHero映射到HeroListServlet上
加上包名

        <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>