MVC案例——修改用户

男娘i 2021-12-16 15:07 284阅读 0赞

## 修改： ##

——先显示(SELECT操作）修改的页面，在进行修改(update)

——显示修改页面

*  **Update的超链接：<a href="edit.do?id=<%=customer.getId()%>">**
 *  **edit方法：获取id，调用CustomerDAO的方法获取id对应的Customer对象**
 *  **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

## 步骤： ##

1.query.jsp中的修改链接

![1642540-20190705164233694-2133429163.png][]

2.edit.do

private void edit(HttpServletRequest req,HttpServletResponse resp){
            String forwardPath="error.jsp";
    
            //1.获取请求参数id
            String idStr = req.getParameter("id");
    
            //2.调用CustomerDAO的customerDAO.get(id)获取和id对应的Customer对象customer
    
            try {
                Customer customer = customerDAO.get(Integer.parseInt(idStr));
                if (customer!=null){
                    forwardPath = "update.jsp";
                    //3.将customer放入request中
                    req.setAttribute("customer",customer);
                }
            }catch (NumberFormatException e){
    
            }
    
            //4.响应updatecustomer.jsp页面：转发
            try {
                req.getRequestDispatcher(forwardPath).forward(req,resp);
            } catch (ServletException e) {
                e.printStackTrace();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }

3.update.jsp

<%@ page import="com.mvcapp.entity.Customer" %><%--
      Created by IntelliJ IDEA.
      User: dell
      Date: 2019/7/5
      Time: 15:32
      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 meg = request.getAttribute("message");
        if (meg!=null){
    %>
    <br>
    <b style="color: red"><%=meg%></b>
    <br><br>
    <%
        }
        Integer id= null;
        String oldName = null;
    
        String name = null;
        String password = null;
    
        Customer customer = (Customer) request.getAttribute("customer");
        if (customer!=null){
            id = customer.getId();
            oldName = customer.getName();
            name = customer.getName();
            password = customer.getPassword();
        }else {
            id = Integer.parseInt(request.getParameter("id")) ;
            oldName = request.getParameter("oldName");
            name = request.getParameter("oldName");
            password = request.getParameter("password");
        }
    %>
    
    <form action="update.do" method="post">
        <input type="hidden" name="id" value="<%=id%>">
        <input type="hidden" name="oldName" value=<%= oldName%>>
        <table>
            <tr>
                <td>CustomerName:</td>
                <td><input type="text" name="name"  value="<%=name%>"></td>
            </tr>
            <tr>
                <td>CustomerPassword:</td>
                <td><input type="text" name="password" value="<%=password%>"></td>
            </tr>
            <tr>
                <td colspan="2"><input type="submit" value="修改" ></td>
            </tr>
        </table>
    </form>
    </body>
    </html>

4.update.do

private void update(HttpServletRequest req, HttpServletResponse resp) {
            //1.获取表单参数：id,name,password
            String id = req.getParameter("id");
            String name = req.getParameter("name");
            String password = req.getParameter("password");
            String oldName = req.getParameter("oldName");
            System.out.println(name);
            System.out.println(password);
            //2.检验name是否已经被占用
            //2.1比较name和oldName是否相同，若相同说明name可用
            if (!oldName.equalsIgnoreCase(name)){
                long count = customerDAO.getCountWithName(name);
                //2.2若返回值大于0，则响应update.jsp页面：通过转发的方式来响应=add.jsp
                if (count>0){
                    //2.2.1在update.jsp页面显示一个错误信息：用户名name已经被占用，请重新选择！
                    //在request中放入一个属性message：用户名name已经被占用，请重新选择，
                    //在页面通过request.getAttribute("message")的方式来显示
                    req.setAttribute("message","用户名"+name+"已经被占用，请重新选择！");
    
                    //2.2.2add.jsp的表单值可以回显，
                    //显示提交表单的新的值，而name显示oldName，而不是新提交的name
                    try {
                        req.getRequestDispatcher("update.jsp").forward(req,resp);
                    } catch (ServletException e) {
                        e.printStackTrace();
                    } catch (IOException e) {
                        e.printStackTrace();
                    }
                    //2.2.3结束方法：return
                    return;
                }
            }
            //3.若验证通过，则把表单参数封装为一个Customer对象customer
            Customer customer = new Customer(name,password);
    
            customer.setId(Integer.parseInt(id));
            //4.调用CustomerDAO的update(Customer customer)执行更新操作
               customerDAO.update(customer);
            //5.重定向到query.do
            try {
                resp.sendRedirect("query.do");
            } catch (IOException e) {
                e.printStackTrace();
            }
        }

实验效果：

![1642540-20190705164711530-98070253.png][]

转载于:https://www.cnblogs.com/yangHS/p/11139310.html

[1642540-20190705164233694-2133429163.png]: /images/20211214/8e923b16fd7a4e6c8dc67d8cb244eb14.png
[1642540-20190705164711530-98070253.png]: /images/20211214/5ab8eecc42bf41f299fabc609b84038f.png