（二十七）分类信息的curd-分类信息修改

    修改分类步骤分析:

        1.在list.jsp页面上点击修改(编辑)

            /store/adminCategory?method=getById&cid=???

        2.在getById方法中

            获取cid

            调用service 通过id获取一个分类,

            将category放入request域中

            请求转发 edit.jsp

        3.eidt页面是一个表单

            添加action属性

                /store/adminCategory?method=update

            修改内容 点击提交

            添加隐藏域 cid

        4.在update方法中

            获取cid和cname

            封装成category

            调用service的update方法

            重定向/store/adminCategory?method=findAll

        5.在service的update方法中

            调用dao更新

            清空缓存

        6.dao中更新数据

/store/WebContent/admin/category/list.jsp

/store/src/com/louis/web/servlet/AdminCategoryServlet.java

/**

     * 通过id获取分类信息

     * @param request

     * @param response

     * @return

     * @throws Exception

     */

    public String getById(HttpServletRequest request, HttpServletResponse response) throws Exception {

        //1.接受cid

        String cid = request.getParameter("cid");

        //2 调用service完成 查询操作 返回值:category

        CategoryService cs=(CategoryService) BeanFactory.getBean("CategoryService");

        Category c=cs.getById(cid);

        //3.将category放入request域中, 请求转发  /admin/category/edit.jsp

        request.setAttribute("bean", c);

        return "/admin/category/edit.jsp";

    }

/store/src/com/louis/service/impl/CategoryServiceImpl.java

/*

     * 通过cid获取一个分类对象

     */

    @Override

    public Category getById(String cid) throws Exception {

        CategoryDao cd = (CategoryDao) BeanFactory.getBean("CategoryDao");

        return cd.getById(cid);

    }

/store/src/com/louis/dao/impl/CategoryDaoImpl.java

    /**

     * 通过id获取一个分类

     */

    @Override

    public Category getById(String cid) throws Exception {

        QueryRunner qr = new QueryRunner(DataSourceUtils.getDataSource());

        String sql="select * from category where cid = ? limit 1";

        return qr.query(sql, new BeanHandler<>(Category.class), cid);

    }

/store/WebContent/admin/category/edit.jsp

<%@ page language="java" pageEncoding="UTF-8"%>

<HTML>

    <HEAD>

        <meta http-equiv="Content-Language" content="zh-cn">

        <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">

        <LINK href="${pageContext.request.contextPath}/css/Style1.css" type="text/css" rel="stylesheet">

    </HEAD>

    <body>

        <form id="userAction_save_do" name="Form1" action="${pageContext.request.contextPath}/adminCategory?method=update" method="post">

            <!-- 隐藏域 存放cid -->

            <input type="hidden" name="cid" value="${bean.cid }">

            &nbsp;

            <table cellSpacing="1" cellPadding="5" width="100%" align="center" bgColor="#eeeeee" style="border: 1px solid #8ba7e3" border="0">

                <tr>

                    <td class="ta_01" align="center" bgColor="#afd1f3" colSpan="4"

                        height="26">

                        <strong><STRONG>编辑分类</STRONG>

                        </strong>

                    </td>

                </tr>

                <tr>

                    <td width="18%" align="center" bgColor="#f5fafe" class="ta_01">

                        分类名称：

                    </td>

                    <td class="ta_01" bgColor="#ffffff" colspan="3">

                        <input type="text" name="cname" id="userAction_save_do_logonName" value="${bean.cname }" class="bg"/>

                    </td>

                </tr>

                <tr>

                    <td class="ta_01" style="WIDTH: 100%" align="center"

                        bgColor="#f5fafe" colSpan="4">

                        <button type="submit" id="userAction_save_do_submit" value="确定" class="button_ok">

                            确&#23450;

                        </button>

                        <FONT face="宋体">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</FONT>

                        <button type="reset" value="重置" class="button_cancel">重置</button>

                        <FONT face="宋体">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</FONT>

                        <INPUT class="button_ok" type="button" onclick="history.go(-1)" value="返回"/>

                        <span id="Label1"></span>

                    </td>

                </tr>

            </table>

        </form>

    </body>

</HTML>

/store/WebContent/admin/category/edit.jsp

/store/src/com/louis/web/servlet/AdminCategoryServlet.java

/**

     * 更新分类信息方法

     * @param request

     * @param response

     * @return

     * @throws Exception

     */

    public String update(HttpServletRequest request, HttpServletResponse response) throws Exception {

        //1.获取cid cname

        //2.封装参数

        Category c=new Category();

        c.setCid(request.getParameter("cid"));

        c.setCname(request.getParameter("cname"));

        //3.调用service 完成更新操作

        CategoryService cs=(CategoryService) BeanFactory.getBean("CategoryService");

        cs.update(c);

        //4.重定向 查询所有

        response.sendRedirect(request.getContextPath()+"/adminCategory?method=findAll");

        return null;

    }

/store/src/com/louis/service/impl/CategoryServiceImpl.java

/**

     * 更新分类

     */

    @Override

    public void update(Category c) throws Exception {

        //1.调用dao更新

        CategoryDao cd = (CategoryDao) BeanFactory.getBean("CategoryDao");

        cd.update(c);

        //2.清空缓存

        CacheManager cm = CacheManager.create(CategoryServiceImpl.class.getClassLoader().getResourceAsStream("ehcache.xml"));

        Cache cache = cm.getCache("categoryCache");

        cache.remove("clist");

    }

/store/src/com/louis/dao/impl/CategoryDaoImpl.java

/**

     * 更新

     */

    @Override

    public void update(Category c) throws Exception {

        QueryRunner qr = new QueryRunner(DataSourceUtils.getDataSource());

        String sql="update category set cname = ? where cid = ?";

        qr.update(sql, c.getCname(),c.getCid());

    }

问题

1、为什么要使用隐藏域

答：因为是cid

巴特西

（二十七）分类信息的curd-分类信息修改

/store/WebContent/admin/category/list.jsp

/store/src/com/louis/web/servlet/AdminCategoryServlet.java

/store/src/com/louis/service/impl/CategoryServiceImpl.java

/store/src/com/louis/dao/impl/CategoryDaoImpl.java

/store/WebContent/admin/category/edit.jsp

/store/WebContent/admin/category/edit.jsp

/store/src/com/louis/web/servlet/AdminCategoryServlet.java

/store/src/com/louis/service/impl/CategoryServiceImpl.java

/store/src/com/louis/dao/impl/CategoryDaoImpl.java

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