JavaBean是符合某种规范的Java组件，也就是Java类。 它必须满足如下规范：
1）必须有一个零参数的默认构造函数
2）必须有get和set方法，类的字段必须通过get和set 方法来访问。 （get方法无参，set方法有参）
我们下面就来看一个JavaBean的例子。
一般网页登陆都需要用户名和密码，我们可以把用户名和密码存放在JavaBean中。
代码如下：
Java代码 
- package mytrain.formbean;
- public class userBean {
- private String name;
- private String password;
- 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;
- }
- }
package mytrain.formbean;
public class userBean {
private String name;
private String password;
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;
}
}
有了JavaBean以后，我们怎么在JSP页面中访问它呢？
方法有2种： 直接访问和JSP标签访问 （不过我们推荐通过标签来访问） 1）直接访问 a) 声明bean 在页面顶部导入JavaBean类： <%@ page import="mytrain.formbean.userBean" %> 在JSP段实例化类： <% userBean user = new userBean(); %> b) 访问bean <% user.setXXX(aa); %> <%=user.getXXX();%>
2）标签访问 （推荐） a) 声明bean 使用userBean标签： <jsp:useBean id="user" class="mytrain.formbean.userBean"/> b) 访问bean 通过setProperty标签来设置： <jsp:setProperty name="user" property="name" param="mUserName"/> 通过getProperty标签来取得： <jsp:getProperty name="user" property="name"/>
下面我们来看一下完整的代码。
标签访问法：
Html代码
- <%@ page language="java" pageEncoding="GBK"%>
- <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
- <html>
- <head>
- <title>表单Bean例子2</title>
- <link rel="StyleSheet" href="../../CSS/style.css" type="text/css" />
- </head>
- <body>
- <form action="" method="post">
- <table>
- <tr>
- <td>
- <span class="blue10">用户名:</span>
- </td>
- <td>
- <input type="text" name="mUserName" size="20"><br>
- </td>
- </tr>
- <tr>
- <td>
- <span class="blue10">密 码:</span>
- </td>
- <td>
- <input type="password" name="mPassword" size="20"><br>
- </td>
- </tr>
- <tr>
- <td>
- </td>
- <td>
-
- <input type=submit value="submit"/>
- </td>
- </tr>
- </table>
- </form>
- <jsp:useBean id="user" class="mytrain.formbean.userBean"/>
- <jsp:setProperty name="user" property="name" param="mUserName"/>
- <jsp:setProperty name="user" property="password" param="mPassword"/>
- <hr/>
- 用户名：<jsp:getProperty name="user" property="name"/>
- <br>
- 密 码：<jsp:getProperty name="user" property="password"/>
- </body>
- </html>
<%@ page language="java" pageEncoding="GBK"%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<title>表单Bean例子2</title>
<link rel="StyleSheet" href="../../CSS/style.css" type="text/css" />
</head>
<body>
<form action="" method="post">
<table>
<tr>
<td>
<span class="blue10">用户名:</span>
</td>
<td>
<input type="text" name="mUserName" size="20"><br>
</td>
</tr>
<tr>
<td>
<span class="blue10">密 码:</span>
</td>
<td>
<input type="password" name="mPassword" size="20"><br>
</td>
</tr>
<tr>
<td>
</td>
<td>
<input type=submit value="submit"/>
</td>
</tr>
</table>
</form>
<jsp:useBean id="user" class="mytrain.formbean.userBean"/>
<jsp:setProperty name="user" property="name" param="mUserName"/>
<jsp:setProperty name="user" property="password" param="mPassword"/>
<hr/>
用户名：<jsp:getProperty name="user" property="name"/>
<br>
密 码：<jsp:getProperty name="user" property="password"/>
</body>
</html>
直接访问法：
Html代码
- <%@ page language="java" pageEncoding="GBK"%>
- <%@ page import="mytrain.formbean.userBean" %>
- <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
- <html>
- <head>
- <title>表单Bean例子3</title>
- <link rel="StyleSheet" href="../../CSS/style.css" type="text/css" />
- </head>
- <body>
- <form action="" method="post">
- <table>
- <tr>
- <td>
- <span class="blue10">用户名:</span>
- </td>
- <td>
- <input type="text" name="mUserName" size="20"><br>
- </td>
- </tr>
- <tr>
- <td>
- <span class="blue10">密 码:</span>
- </td>
- <td>
- <input type="password" name="mPassword" size="20"><br>
- </td>
- </tr>
- <tr>
- <td>
- </td>
- <td>
-
- <input type=submit value="submit"/>
- </td>
- </tr>
- </table>
- </form>
- <%
- userBean user = new userBean();
- user.setName(request.getParameter("mUserName"));
- user.setPassword(request.getParameter("mPassword"));
- %>
- <hr/>
- 用户名：<%=user.getName()%>
- <br>
- 密 码：<%=user.getPassword()%>
- </body>
- </html>
<%@ page language="java" pageEncoding="GBK"%>
<%@ page import="mytrain.formbean.userBean" %>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<title>表单Bean例子3</title>
<link rel="StyleSheet" href="../../CSS/style.css" type="text/css" />
</head>
<body>
<form action="" method="post">
<table>
<tr>
<td>
<span class="blue10">用户名:</span>
</td>
<td>
<input type="text" name="mUserName" size="20"><br>
</td>
</tr>
<tr>
<td>
<span class="blue10">密 码:</span>
</td>
<td>
<input type="password" name="mPassword" size="20"><br>
</td>
</tr>
<tr>
<td>
</td>
<td>
<input type=submit value="submit"/>
</td>
</tr>
</table>
</form>
<%
userBean user = new userBean();
user.setName(request.getParameter("mUserName"));
user.setPassword(request.getParameter("mPassword"));
%>
<hr/>
用户名：<%=user.getName()%>
<br>
密 码：<%=user.getPassword()%>
</body>
</html>