在很多时候,action mapping中的attribute 和 name 这两个属性一直困扰我,今天我觉得是该痛下决心拔掉这颗钉子的时候了。
翻看一些资料。。。。。
在《Programming Jakarta Struts》这本书中的第四章“Configuring the Struts Application”中这样一段说明来分别阐述这两
个属性:(102页)
++++++++
atribute:
++++++++
The name of the request or session scope attribute under which the form bean for this action can be accessed.
A value is only allowed here if there is a form bean specified in the name attribute. This attribute is
optional and has no default value.
++++++++
name:
++++++++
The name of the form bean, if any, that is associated with this action. This value must be the name attribute
from one of the form-bean elements defined earlier. This attribute is optional and has no default value.
最初看这些真的还是不好区分这两者。 不过在仔细看过struts的源代码以后,豁然开朗。。。
下面主要对attribute进行解释,应为没有人会对name属性不了解的(呵呵。。。)
解释:在struts实例化actionform的时候,有两种情况:如果已经存在,那么从内存中取回;如果第一次实例化,那么创建,并放入内存。
这样就有一个问题了,struts是根据什么来取回并创建actionform的呢,答案就是attribute的值。让我们进入struts的源代码:
/**
*创建或者取回formbean方法
*该方法在:org.apache.struts.util.RequestUtils中
*/
public static Actionform createActionform(
HttpServletRequest request,
ActionMapping mapping,
ModuleConfig moduleConfig,
ActionServlet servlet) {
。。。。
。。。
// Is there a form bean associated with this mapping?
//得到action mapping中attribute的值
String attribute = mapping.getAttribute();
。。。。
。。。。
Actionform instance = null;
HttpSession session = null;
//yes!!就在这里了,把创建以后的actionform放在request或者session里,看到放入的名字了么,就是mapping.getAttribute();
if ("request".equals(mapping.getScope())) {
instance = (Actionform) request.getAttribute(attribute);
} else {
session = request.getSession();
instance = (Actionform) session.getAttribute(attribute);
}
。。。
。。。
}
下面又有一个问题浮出水面:如果我没有在action mapping中指定attribute呢,那struts 是如何解决的?
答案很简单,如果单从结果上看,此时struts使用的name的值,为什么呢,看struts源代码:
/**
* The request-scope or session-scope attribute name under which our
* form bean is accessed, if it is different from the form bean's
* specified <code>name</code>.
*该代码在:org.apache.struts.config.ActionConfig中
*/
protected String attribute = null;
public String getAttribute() {
//yes!!!!就在这里,看到了吧,如果你没有设定attribute,那么struts 会把name的值拿过来用。呵呵。。。
if (this.attribute == null) {
return (this.name);
} else {
return (this.attribute);
}
}
public void setAttribute(String attribute) {
if (configured) {
throw new IllegalStateException("Configuration is frozen");
}
this.attribute = attribute;
}
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