JavaBean.
JavaBean :軟件組件,主要用於事務處理
規範要求(反射):是一個公共(public)類
不帶參數的構造方法
通過setXXX方法設置屬性,getXXX方法獲取屬性
1. JSP訪問javaBean 的語法
導入JavaBean 類
聲明JavaBean對象
訪問JavaBean屬性
例:<%@ import = “mypack.CounterBean”%>
<jsp:useBeanid=”myBean” class=”mypack.CounterBean” scope=”session”/>
<jsp:getPropertyname=”myBean” property=”count”/>
<jsp:setPropertyname=”myBean” property=”count” value=”0”/>
2. 可以在<jsp:setProperty>中通過param參數來爲bean的屬性動態賦值
<jsp;setProperty property=”age” name=”person”value=”helloworld”/>
對應的Servlet代碼是:
org.apache.jasper.runtime.JspRuntimeLibrary.introspecthelper(_jspx_page_context.findAttribute("person"),"age", request.getParameter("helloworld"), request,"helloworld", false);
3. JavaBean
的存活範圍
---page (默認值)
---request
---session
---application
4 . 當javaBean放在session範圍內時,放在application也不一樣
<jsp:useBeanid=”student” scope=”session” class=”javaBean.Stdent”/>
生成的servlet源代碼是:
javaBean.Student student = null;
synchronized (session) {
student = (javaBean.Student)_jspx_page_context.getAttribute("student",javax.servlet.jsp.PageContext.SESSION_SCOPE);
if (student == null){
student = new javaBean.Student();
_jspx_page_context.setAttribute("student", student, javax.servlet.jsp.PageContext.SESSION_SCOPE);
}
}