Servlet系列教材 （二十三）- CRUD

 

步骤1:先运行，看到效果，再学习
步骤2:模仿和排错
步骤3:编写 HeroUpdateServlet
步骤4:配置web.xml

步骤 1 : 先运行，看到效果，再学习

老规矩，先下载下载区(点击进入)的可运行项目，配置运行起来，确认可用之后，再学习做了哪些步骤以达到这样的效果。

步骤 2 : 模仿和排错

在确保可运行项目能够正确无误地运行之后，再严格照着教程的步骤，对代码模仿一遍。 
模仿过程难免代码有出入，导致无法得到期望的运行结果，此时此刻通过比较正确答案 ( 可运行项目 ) 和自己的代码，来定位问题所在。 
采用这种方式，学习有效果，排错有效率，可以较为明显地提升学习速度，跨过学习路上的各个槛。 

推荐使用diffmerge软件，进行文件夹比较。把你自己做的项目文件夹，和我的可运行项目文件夹进行比较。 
这个软件很牛逼的，可以知道文件夹里哪两个文件不对，并且很明显地标记出来 
这里提供了绿色安装和使用教程：diffmerge 下载和使用教程

步骤 3 : 编写 HeroUpdateServlet

HeroUpdateServlet
根据浏览器提交的id name hp damage创建一个Hero对象
然后调用HeroDAO的update，进行更新

更新结束后，客户端跳转到 /listHero

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 bean.Hero;

import dao.HeroDAO;

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);

        response.sendRedirect("/listHero");

    }

}

步骤 4 : 配置web.xml

新增对路径 /updateHero的映射

<?xml version="1.0" encoding="UTF-8"?>

<web-app>

    <servlet>

        <servlet-name>HelloServlet</servlet-name>

        <servlet-class>HelloServlet</servlet-class>

        <load-on-startup>10</load-on-startup>

    </servlet>

    <servlet-mapping>

        <servlet-name>HelloServlet</servlet-name>

        <url-pattern>/hello</url-pattern>

    </servlet-mapping>

    <servlet>

        <servlet-name>LoginServlet</servlet-name>

        <servlet-class>LoginServlet</servlet-class>

    </servlet>

    <servlet-mapping>

        <servlet-name>LoginServlet</servlet-name>

        <url-pattern>/login</url-pattern>

    </servlet-mapping>

    <servlet>

        <servlet-name>RegisterServlet</servlet-name>

        <servlet-class>RegisterServlet</servlet-class>

    </servlet>

    <servlet-mapping>

        <servlet-name>RegisterServlet</servlet-name>

        <url-pattern>/register</url-pattern>

    </servlet-mapping>

    <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>

    <servlet>

        <servlet-name>HeroAddServlet</servlet-name>

        <servlet-class>servlet.HeroAddServlet</servlet-class>

    </servlet>

    <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>

    <servlet>

        <servlet-name>HeroUpdateServlet</servlet-name>

        <servlet-class>servlet.HeroUpdateServlet</servlet-class>

    </servlet>

    <servlet-mapping>

        <servlet-name>HeroUpdateServlet</servlet-name>

        <url-pattern>/updateHero</url-pattern>

    </servlet-mapping>

</web-app>

更多内容，点击了解： https://how2j.cn/k/servlet/servlet-update/567.html