struts tags 学习

property


value 的类型是  object
则<s:property value="username" />   -----------------------------------------------------------1                          

这里的username被当做ognl表达式

如果我们想要显示字符串只能这样写<s:property value="'username'" />

如果是ognl表达式，则上面1式中就会调用当前action中的getUserName的方法来获取username的值。

Set

The set tag assigns a value to a variable in a specified scope. It is useful when you wish to assign a variable to a complex expression and then simply reference that variable each time rather than the complex expression. This is useful in both cases: when the complex expression takes time (performance improvement) or is hard to read (code readability improvement).

set标签主要是用来将一个复杂的表达式用一个简单的变量进行替换，以后只需读取这个变量就可以读取复杂表达式的值。

<s:set name="personName" value="person.name"/>
Hello, <s:property value="#personName"/>. How are you?

这里将person.name在action context里面设定一个变量personName，之后我们通过property标签将这个值读取出来

The scopes available are as follows :-

application - the value will be set in application scope according to servlet spec. using the name as its key
session - the value will be set in session scope according to servlet spec. using the name as key
request - the value will be set in request scope according to servlet spec. using the name as key
page - the value will be set in page scope according to servlet sepc. using the name as key
action - the value will be set in the request scope and Struts' action context using the name as key



If no scope is specified, it will default to action scope.(request 和 ActionContext)

Include

<s:set var="incPage" value="%{'/_include1.html'}" />

<s:include value="%{#incPage}"></s:include>

include标签的value的类型是string，所以这里就会产生一个问题：如何在include里面使用ognl表达式，这里就引出了%的用法