struts2中的OGNL表达式语言

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不适用任何框架时编写的JSP页面，在JSP页面中通过EL表达式只能访问page/request/session/aaplication范围的属性；

而使用struts框架可以通过EL表达式访问Action中的属性，这是由于：

案例：

struts.xml:

<?xml version="1.0" encoding="UTF-8" ?><!DOCTYPE struts PUBLIC    "-//Apache Software Foundation//DTD Struts Configuration 2.0//EN"    "http://struts.apache.org/dtds/struts-2.0.dtd"><struts><package name="book" extends="struts-default" namespace="/person"><action name="book" class="blog.action.PersonAction"><result name="input">/index.jsp</result><result name="success">/index.jsp</result></action></package></struts>

PersonAction.xml:

package blog.action;import java.util.ArrayList;import java.util.List;import blog.bean.Book;import com.opensymphony.xwork2.ActionSupport;public class PersonAction extends ActionSupport {private String name;private List<Book> books;public String getName() {return name;}public void setName(String name) {this.name = name;}public List<Book> getBooks() {return books;}public void setBooks(List<Book> books) {this.books = books;}public String execute(){this.books = new ArrayList<Book>();this.books.add(new Book(1, "spring", 100));this.books.add(new Book(2, "ejb3.0", 120));this.books.add(new Book(3, "struts2.0", 78));this.name = "李大仁";return "success";}}

Book.java:

package blog.bean;public class Book {private int id;private String name;private double price;public int getId() {return id;}public void setId(int id) {this.id = id;}public String getName() {return name;}public void setName(String name) {this.name = name;}public double getPrice() {return price;}public void setPrice(double price) {this.price = price;}public Book(int id,String name,double price){this.id = id;this.name = name;this.price = price;}}

index.jsp:

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%><%@ taglib uri="/struts-tags" prefix="s"%><%String path = request.getContextPath();String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";%><%     request.setAttribute("user1","lisi");    session.setAttribute("user2","zhangsan"); %><!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"><html>  <head>    <base href="<%=basePath%>">        <title>My JSP 'index.jsp' starting page</title>    <meta http-equiv="pragma" content="no-cache">    <meta http-equiv="cache-control" content="no-cache">    <meta http-equiv="expires" content="0">   </head>    <body>      --通过EL表达式直接访问Action的属性--<br/>      ${name }<br/>        -- 通过OGNL表达式访问request和session范围的数据 --<br/>    <s:property value="#request.user1"/><br/>    <s:property value="#session.user2"/><br/>        <s:set var="list" value="{'user1','user2','user3'}"></s:set>    <br/>-- s:iterator在迭代集合时有个特点：会把当前迭代的对象放在值栈的栈顶 --<br/>    <s:iterator value="#list">        <s:property/><br/>    </s:iterator>       <br/> -- 采用OGNL表达式创建集合 --<br/>    <s:set var="maps" value="#{'key1':11,'key2':22,'key3':33}"></s:set>    <s:iterator value="#maps">        <s:property value="key"/> = <s:property value="value"/> <br/>    </s:iterator>          <br/>-- 采用OGNL表达式判断对象是否存在于集合中 --<br/>    <s:if test="'foo' in {'foo','abc'}">        在    </s:if>    <s:else>        不在    </s:else>        <br/>    <s:if test="'foo' not in {'xxxx','abc'}">        不在    </s:if>    <s:else>        在    </s:else>       <br/><br/> -- OGNL表达式的投影功能 --<br/>    <s:iterator value="books.{?#this.price>80}">        <s:property value="name"/> : 价格      <s:property value="price"/> <br/>    </s:iterator>  </body></html>

结果：