JSP jsp:useBean介绍

2024-04-28 19:18

文章标签 介绍 jsp usebean

本文主要是介绍JSP jsp:useBean介绍，希望对大家解决编程问题提供一定的参考价值，需要的开发者们随着小编来一起学习吧！

创建JavaBean实例：

<jsp:useBean id=”name” class=”” scope=”page/session/request/application”/>

id为类的另一个名字，class指定具体的类，scope表示范围，在scope的范围内查找是否有指定的属性存在

赋值

指定参数和值
<jsp:setProperty name="user" property="password" value="123" />
将指定参数的值赋值给JavaBean的属性
<jsp:setProperty name="user" param="pwd" property="password" />
通过自省机制自动匹配
<jsp:setProperty name="user" property="*" />

使用jsp:useBean的目的是减少Script的使用
一个典型的javabean: JavaBean.java

package Bean;
import java.io.Serializable;
public class JavaBean implements Serializable {private String name ;private String password;public JavaBean(String name, String password) {super();this.name = name;this.password = password;}public JavaBean() {super();}public String getName() {return name;}public void setName(String name) {this.name = name;}public String getPassword() {return password;}public void setPassword(String password) {this.password = password;} public boolean isValid(){if(name.equals("tom") && password.equals("123")){return true;}return false;}
}

使用jsp:Bean标签

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<jsp:useBean id="user" class="Bean.JavaBean" scope="page" />
<jsp:setProperty name="user" property="*" /><html><body><font color='red'><jsp:getProperty property="name" name="user"/></font></body>
</html>

web容器翻译后的Java代码

      Bean.JavaBean user = null;user = (Bean.JavaBean) _jspx_page_context.getAttribute("user", javax.servlet.jsp.PageContext.PAGE_SCOPE);if (user == null){user = new Bean.JavaBean();_jspx_page_context.setAttribute("user", user, javax.servlet.jsp.PageContext.PAGE_SCOPE);}

采用传统方式的做法：

<%@ page language="java" import="java.util.*,Bean.JavaBean" pageEncoding="UTF-8"%>
<html><body><%JavaBean user = (JavaBean)request.getAttribute("user");if(user == null){user = new JavaBean();}user.setName(request.getParameter("name"));user.setPassword(request.getParameter("pwd"));if(user.isValid()){out.println("登录成功");}else{out.println("登录失败");}%></body>
</html