JavaWeb--MVC案例1-------（6）修改

修改：
　　先显示（SELECT 操作）修改的页面，再进行修改（update）
　　显示修改页面
　　　　Update 的超链接：<a href="edit.do?id=<%= customer.getId() %>">UPDATE</a>
　　edit 方法：参考注释
　　JSP 页面：
　　　　获取请求域中的 Customer 对象，调用对应的字段的 get 方法来显示值。
　　　　使用隐藏域来保存要修改的 Customer 对象的 id：<input type="hidden" name="id" value=“<%= customer.getId() %>"/>
　　　　使用隐藏域来保存 oldName：<input type="hidden" name=“oldName" value=“<%= customer.getName() %>"/>
　　关于隐藏域：和其他的表单域一样可以被提交到服务器，只不过在页面上不显示
　　提交到 update.do

edit方法

 private void edit(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException{

        String id = req.getParameter("id");

        String forwardPath = "error.jsp";
        //调用customerDAO的get(int id)获取和id对应的Customer对象customer
        Customer customer = customerDAO.get(Integer.parseInt(id));
        if(customer != null){
            forwardPath = "/updateCustomer.jsp";
            req.setAttribute("customer", customer);
        }

        req.getRequestDispatcher(forwardPath).forward(req, resp);

    }

　　然后到updateCustomer.jsp中

<%@ page import="mvccases.Customer" %><%--
  Created by IntelliJ IDEA.
  User: Skye
  Date: 2017/12/11
  Time: 15:30
  To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>Title</title>
</head>


<body>
<%
    Object message = request.getAttribute("message");
    if(message != null){
%>
        <br>
        <font color="red"><%= message%></font>
        <br>
        <br>
<%
    }
    String id = null;
    String name = null;
    String address = null;
    String phone = null;
    String oldName = null;
    Customer customer = (Customer)request.getAttribute("customer");

    if(customer != null){
        id = customer.getId() + "";
        name = customer.getName();
        oldName = customer.getName();
        address = customer.getAddress();
        phone = customer.getPhone();
    } else{
        id = request.getParameter("id");
        name = request.getParameter("name");
        oldName = request.getParameter("oldName");
        address = request.getParameter("address");
        phone = request.getParameter("phone");
    }
%>

<form action="update.do" method="post">

    <%--隐藏域 --%>
    <input type="hidden" name="id" value="<%= id%>"/>
    <input type="hidden" name="oldName" value="<%= oldName%>"/>

    <table>
        <tr>
            <td>Name:</td>
            <td><input type="text" name="name" value="<%= name%>"/></td>
        </tr>

        <tr>
            <td>Address:</td>
            <td><input type="text" name="address" value="<%= address%>"/></td>
        </tr>

        <tr>
            <td>Phone:</td>
            <td><input type="text" name="phone" value="<%= phone%>"/></td>
        </tr>

        <tr>
            <td><input type="submit" name="Submit"/></td>

        </tr>
        <%-- <form>
             <tr>
                 <th>ID</th>
                 <th>Name</th>
                 <th>Address</th>
                 <th>Phone</th>
             </tr>

             <tr>
                 <td><%=customer.getId()%></td>
                 <td><%=customer.getName()%></td>
                 <td><%=customer.getAddress()%></td>
                 <td><%=customer.getPhone()%></td>
             </tr>
         </form>--%>
    </table>
</form>
</body>
</html>

　　然后使用update()方法更新

private void update(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException{
        String idStr = req.getParameter("id");
        String name = req.getParameter("name");
        String address = req.getParameter("address");
        String phone = req.getParameter("phone");
        String oldName = req.getParameter("oldName");

        if(!oldName.equalsIgnoreCase(name)){
            long count = customerDAO.getCountWithName(name);
            //当名字被占用时
            if(count>0) {
                req.setAttribute("message", "用户名：" + name + "已被占用，请重新选择");

                req.getRequestDispatcher("/updateCustomer.jsp").forward(req, resp);
                return;
            }
        }
        Customer customer = new Customer(name, address, phone);
        customer.setId(Integer.parseInt(idStr));

        customerDAO.update(customer);

        resp.sendRedirect("query.do");

    }