Jsp:useBean使用详解

<jsp:useBean>标签用来在jsp页面中创建一个Bean实例,定义语法如下:

一:<jsp:useBean>语法

<jsp:useBean id="id" scope="page|request|session|application" typeSpec/>

二:<jsp:setProperty>语法

<jsp:setProperty name="beanName" propertyDetail />其中,propertyDetail可以是以下中的一个:

1,property="*"

2,property="propertyName" param="parameterName"

3,property="propertyName"

4,property="propertyName" value="property value"

三:<jsp:getProperty>语法

<jsp:getProperty name="beanName" property="propertyName"/>

程序例子:

一共有三个文件:TestBean.java,register.jsp,register.html

TestBean.java

package com.jsp.ch3;

public class TestBean ... {
private String userName;
private String password;
privateint age;
public String getUserName() ...{
return userName;
}
publicvoid setUserName(String userName) ...{
this.userName = userName;
}
public String getPassword() ...{
return password;
}
publicvoid setPassword(String password) ...{
this.password = password;
}
publicint getAge() ...{
return age;
}
publicvoid setAge(int age) ...{
this.age = age;
}
}

register.html

< html >
< body >
< form action ="register.jsp" method ="post" >
< table >
< tr >
< td >
姓名: < input type ="text" name ="userName" >
</ td >
</ tr >
< tr >
< td >
密码: < input type ="text" name ="password" >
</ td >
</ tr >
< tr >
< td >
年龄: < input type ="text" name ="age" >
</ td >
</ tr >
< tr >
< td >
< input type ="submit" >
</ td >
</ tr >
</ table >
</ form >
</ body >
</ html >

register.jsp

<% ... @ page language="java" pageEncoding="gb2312" %>
< jsp:useBean id ="user" scope ="page" class ="com.jsp.ch3.TestBean" />
< jsp:setProperty name ="user" property ="*" />
或者用以下,param可以不填写,其中param对应的是提交页面的表单name
< jsp:setProperty property ="userName" name ="user" param ="userName" />
< jsp:setProperty property ="password" name ="user" param ="password" />
< jsp:setProperty property ="age" name ="user" param ="age" />
< html >
< body >
注册成功: < br >
< hr >
使用Bean的属性方法 < br >
用户名: <% = user.getUserName() %> < br >
密码: <% = user.getPassword() %> < br >
年龄: <% = user.getAge() %> < br >
< hr >
使用getProperty < br >
用户名: < jsp:getProperty name ="user" property ="userName" />< br >
密码: < jsp:getProperty name ="user" property ="password" />< br >
年龄: < jsp:getProperty name ="user" property ="age" />
客户端名称: <% = request.getRemoteAddr() %>
</ body >
</ html >

 

useBean 你没写class属性
<jsp:useBean id="list" scope="request" type="java.util.List" class="java.util.ArrayList" />
type是引用的类型 class是实例实际上的类型 id是变量名
你没写class就没new出实例来 List是一个接口 class里面要写实现了这个接口的类
我以ArrayList为列的 你也可以用实现了List接口的其他类
<jsp:useBean id="list" scope="request" type="java.util.List" class="java.util.ArrayList" />
这句话的意思翻译成Java代码就是
<%
java.uti.List list = (java.util.List)request.getAttribute("list");
if(list == null) {
list = new java.util.ArrayList();
request.setAttribute("list", list);
}
%>