代码实例--请求的转发：RequestDispatcher对象处理请求的两个方法--forward和include

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最新推荐文章于 2023-01-14 08:58:37 发布

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本文详细介绍了如何在Java Servlet中使用forward()和include()方法，从indextest.jsp获取用户输入，通过ValidateServlet进行验证。成功则通过forward跳转到welcomeva.jsp，失败时利用include返回并显示错误提示。

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验证requset的forward()、include()跳转

indextest.jsp ：接受用户输入的用户名和密码
ValidateServlet.java: 验证用户的数据是否正确
- 正确，则用 forward 方法跳转到 welcomeva.jsp（显示欢迎信息的页面）
- 错误，则调用 include 方法跳转到 indextest.jsp，并给出错误提示

首页面–indextest.jsp

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<head>
    <meta charset="UTF-8">
    <title>登录</title>
    <link rel="stylesheet" href="https://cdn.staticfile.org/twitter-bootstrap/3.3.7/css/bootstrap.min.css">
    <script src="https://cdn.staticfile.org/jquery/2.1.1/jquery.min.js"></script>
    <script src="https://cdn.staticfile.org/twitter-bootstrap/3.3.7/js/bootstrap.min.js"></script>
</head>
<body>
<div class="form-group">
<form  action="${pageContext.request.contextPath}/chap3validatefi" method="post" class="form-horizontal" role="form">
    <table class="table table hover">
        <tr>
            <td> <label for="username" class="col-sm-2 control-label">用户名</label></td>
            <td><input type="text" class="form-control" id="username" name="username" placeholder="请输入密码"></td>
        </tr>
        <tr>
            <td><label for="userpass" class="col-sm-2 control-label">密码</label></td>
            <td><input type="password" class="form-control" id="userpass" name="userpass" placeholder="请输入密码"></td>
        </tr>
        <tr>
            <td><input type="submit" class="btn btn-success" align="center" ></td>
        </tr>
    </table>
</form>
</div>
</body>
</html>

数据处理及验证–ValidateServlet.java

@WebServlet(name = "ValidateServlet", urlPatterns = "/chap3validatefi")
public class ValidateServlet extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    	// 设置响应的文本类型、编码方式
        response.setContentType("text/html;charset=utf-8");
        response.setCharacterEncoding("utf-8");
        PrintWriter out = response.getWriter();
		
        String userName = request.getParameter("username");
        String userPass = request.getParameter("userpass");
		
        System.out.println(userName + ";" + userPass);

        if ("admin".equals(userName) && "123".equals(userPass)) {
            out.print("成功登录，正在用forward方法跳转新的资源");
           	// 创建request范围的变量userName-admin
            request.setAttribute("userName ", "admin");
			// 创建RequestDispatcher对象
            RequestDispatcher rd = request.getRequestDispatcher("/chapter3jsp/welcomeva.jsp");
            // 转发请求
            rd.forward(request, response);
        } else {
            out.print("登录失败，正在用include方法跳转新的资源");
            out.print("用户名或者密码错误，请重新输入!");
            RequestDispatcher rd = request.getRequestDispatcher("/chapter3jsp/indextest.jsp");
            rd.include(request, response);
        }
    }
}

欢迎界面–welcomeva.jsp

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>登录成功</title>
</head>
<body>
<%=request.getParameter("username")%>欢迎你，登录成功！
</body>
</html>