OGNL中的#,%,$ 三种符号
?OGNL的用法
OGNL是通常要结合Struts 2的标志一起使用，如<s:property value="xx" />等。大家经常遇到的问题是#、%和$这三个符号的使用。下面我想通过例子讲述这个问题：
“#”主要有三种用途：
?名称
作用
例子
parameters
包含当前HTTP请求参数的Map
#parameters.id[0]作用相当于request.getParameter("id")
request
包含当前HttpServletRequest的属性（attribute)的Map
#request.userName相当于request.getAttribute("userName")
session
包含当前HttpSession的属性（attribute）的Map
#session.userName相当于session.getAttribute("userName")
application
包含当前应用的ServletContext的属性（attribute）的Map
#application.userName相当于application.getAttribute("userName")
attr
用于按request > session > application顺序访问其属性（attribute）
#attr.userName相当于按顺序在以上三个范围（scope）内读取userName属性，直到找到为止
package tutorial.action;import java.util.LinkedList;import java.util.List;import java.util.Map;import javax.servlet.ServletContext;import javax.servlet.http.HttpServletRequest;import org.apache.struts2.interceptor.ServletRequestAware;import org.apache.struts2.interceptor.SessionAware;import org.apache.struts2.util.ServletContextAware;import tutorial.model.Book;import com.opensymphony.xwork2.ActionSupport;public class OgnlAction extends ActionSupport implements ServletRequestAware, SessionAware, ServletContextAware { private static final long serialVersionUID = 1L; private HttpServletRequest request; private Map<String, String> session; private ServletContext application; private List<Book> books; public void setServletRequest(HttpServletRequest request) { this.request = request; } @SuppressWarnings("unchecked") public void setSession(Map session) { this.session = session; } public void setServletContext(ServletContext application) { this.application = application; } public List<Book> getBooks() { return books; } @Override public String execute() { request.setAttribute("userName", "Max From request"); session.put("userName", "Max From session"); application.setAttribute("userName", "Max From application"); books = new LinkedList<Book>(); books.add(new Book("978-0735619678", "Code Complete, Second Edition", 32.99)); books.add(new Book("978-0596007867", "The Art of Project Management", 35.96)); books.add(new Book("978-0201633610", "Design Patterns: Elements of Reusable Object-Oriented Software", 43.19)); books.add(new Book("978-0596527341", "Information Architecture for the World Wide Web: Designing Large-Scale Web Sites", 25.19)); books.add(new Book("978-0735605350", "Software Estimation: Demystifying the Black Art", 25.19)); return SUCCESS; }}
<s:set name="myMap" value="#{'key1':'value1','key2':'value2'}"/> <s:property value="#myMap['key1']"/> <s:url value="#myMap['key1']" />
??????????? <result type="redirect">ListPhotos.action?albumId=${albumId}</result>
</action>
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