（四）值栈与OGNL

所有的学习我们必须先搭建好Struts2的环境（1、导入对应的jar包，2、web.xml，3、struts.xml）

第一节：值栈简介

值栈是对应每个请求对象的一套内存数据的封装，Struts2 会给每个请求创建一个新的值栈。

值栈能够线程安全地为每个请求提供公共的数据存取服务。

第二节：OGNL 引入

OGNL 是对象图导航语言Object-Graph Navigation Language 的缩写，它是一种功能强大的表达式语言。

OGNL 访问ValueStack 数据

　　<s:property value=”account” />

　　注：这里要添加<%@taglib prefix="s" uri="/struts-tags" %>struts的标签库

OGNL 访问ActionContext 数据

　　访问某个范围下的数据要用#

　　　　#parameters 请求参数request.getParameter(...)；

　　　　#request 请求作用域中的数据request.getAttribute(...)；

　　　　#session 会话作用域中的数据session.getAttribute(...)；

　　　　#application 应用程序作用域中的数据application.getAttribute(...)；

　　　　#attr 按照page request session application 顺序查找值

例子：

 struts.xml
 1 <?xml version="1.0" encoding="UTF-8" ?>
 2 <!DOCTYPE struts PUBLIC
 3     "-//Apache Software Foundation//DTD Struts Configuration 2.0//EN"
 4     "http://struts.apache.org/dtds/struts-2.0.dtd">
 5 
 6 <struts>
 7 
 8   <package name="manage" namespace="/" extends="struts-default">
 9       
10       <action name="hello" class="com.wishwzp.action.HelloAction">
11           <result name="success" >success.jsp</result>
12       </action>
13   </package>
14 
15 </struts>

 HelloAction.java
 1 package com.wishwzp.action;
 2 
 3 import java.util.Map;
 4 
 5 import com.opensymphony.xwork2.ActionContext;
 6 import com.opensymphony.xwork2.ActionSupport;
 7 import com.opensymphony.xwork2.util.ValueStack;
 8 
 9 public class HelloAction extends ActionSupport{
10 
11     /**
12      * 
13      */
14     private static final long serialVersionUID = 1L;
15     
16 
17 
18     @Override
19     public String execute() throws Exception {
20         // 获取ActionContext
21         ActionContext actionContext=ActionContext.getContext();
22         // 获取狭义上的值栈
23         // 值栈是用来存储数据的
24         ValueStack valueStack=actionContext.getValueStack();
25         valueStack.set("name", "张三(valueStack)");
26         valueStack.set("age", 11);
27         
28         Map<String, Object> session=actionContext.getSession();
29         session.put("name", "王五(session)");
30         session.put("age", 13);
31         
32         Map<String, Object> application=actionContext.getApplication();
33         application.put("name", "赵六(application)");
34         application.put("age", 14);
35         return SUCCESS;
36     }    
37 }

 success.jsp
 1 <%@ page language="java" contentType="text/html; charset=UTF-8"
 2     pageEncoding="UTF-8"%>
 3 <%@taglib prefix="s" uri="/struts-tags" %>
 4 <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
 5 <html>
 6 <head>
 7 <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
 8 <title>Insert title here</title>
 9 <%
10     request.setAttribute("name", "李四(request)");
11     request.setAttribute("age", "12");
12 %>
13 </head>
14 <body>
15 获取狭义上的值栈数据：<s:property value="name"/>
16                 <s:property value="age"/><br/>
17 请求参数：<s:property value="#parameters.name"/>
18        <s:property value="#parameters.age"/><br/>
19 request：<s:property value="#request.name"/>
20         <s:property value="#request.age"/><br/>
21 session：<s:property value="#session.name"/>
22         <s:property value="#session.age"/><br/>
23 application：<s:property value="#application.name"/>
24             <s:property value="#application.age"/><br/>
25 attr取值：<s:property value="#attr.name"/>
26         <s:property value="#attr.age"/><br/>
27 </body>
28 </html>

url:http://localhost:8080/Struts2Chap04/hello?name=ssss&age=23

结果：

第三节：OGNL 访问复杂对象

1，访问javaBean 对象；

2，访问集合对象；

3，访问Map 对象；

例子：

 struts.xml
 1 <?xml version="1.0" encoding="UTF-8" ?>
 2 <!DOCTYPE struts PUBLIC
 3     "-//Apache Software Foundation//DTD Struts Configuration 2.0//EN"
 4     "http://struts.apache.org/dtds/struts-2.0.dtd">
 5 
 6 <struts>
 7 
 8   <package name="manage" namespace="/" extends="struts-default">
 9       
10       <action name="hello" class="com.wishwzp.action.HelloAction">
11           <result name="success" >success.jsp</result>
12       </action>
13   </package>
14 
15 </struts>

 Student.java
 1 package com.wishwzp.model;
 2 
 3 public class Student {
 4 
 5     private String name;
 6     private int age;
 7     
 8     public Student() {
 9         super();
10         // TODO Auto-generated constructor stub
11     }
12     public Student(String name, int age) {
13         super();
14         this.name = name;
15         this.age = age;
16     }
17 
18     public String getName() {
19         return name;
20     }
21     public void setName(String name) {
22         this.name = name;
23     }
24     public int getAge() {
25         return age;
26     }
27     public void setAge(int age) {
28         this.age = age;
29     }
30     
31     
32 }

 HelloAction.java
 1 package com.wishwzp.action;
 2 
 3 import java.util.ArrayList;
 4 import java.util.HashMap;
 5 import java.util.List;
 6 import java.util.Map;
 7 
 8 import com.wishwzp.model.Student;
 9 import com.opensymphony.xwork2.ActionContext;
10 import com.opensymphony.xwork2.ActionSupport;
11 import com.opensymphony.xwork2.util.ValueStack;
12 
13 public class HelloAction extends ActionSupport{
14 
15     /**
16      * 
17      */
18     private static final long serialVersionUID = 1L;
19     
20     //访问javaBean对象,并get...和set...
21     private Student student;
22     
23     //访问集合对象,并get...和set...
24     private List<Student> students;
25     
26     //访问Map对象,并get...和set...
27     private Map<String,Student> studentMap;
28     
29     public Map<String, Student> getStudentMap() {
30         return studentMap;
31     }
32 
33     public void setStudentMap(Map<String, Student> studentMap) {
34         this.studentMap = studentMap;
35     }
36 
37     public List<Student> getStudents() {
38         return students;
39     }
40 
41     public void setStudents(List<Student> students) {
42         this.students = students;
43     }
44 
45     public Student getStudent() {
46         return student;
47     }
48 
49     public void setStudent(Student student) {
50         this.student = student;
51     }
52 
53     @Override
54     public String execute() throws Exception {
55         
56         //javaBean对象
57         student=new Student("小扒", 12);
58         
59         //集合对象
60         students=new ArrayList<Student>();
61         students.add(new Student("老九",13));
62         students.add(new Student("老十",14));
63         
64         //Map对象
65         studentMap=new HashMap<String,Student>();
66         studentMap.put("goodStudent", new Student("学霸",20));
67         studentMap.put("badStudent", new Student("学渣",19));
68         return SUCCESS;
69     }
70 
71 }

 success.jsp
 1 <%@ page language="java" contentType="text/html; charset=UTF-8"
 2     pageEncoding="UTF-8"%>
 3 <%@taglib prefix="s" uri="/struts-tags" %>
 4 <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
 5 <html>
 6 <head>
 7 <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
 8 <title>Insert title here</title>
 9 </head>
10 <body>
11 ognl访问javaBean对象：<s:property value="student.name"/>
12                     <s:property value="student.age"/><br/>
13                     
14 ognl访问List集合：<s:property value="students[0].name"/>
15                 <s:property value="students[0].age"/><br/>
16                 <s:property value="students[1].name"/>
17                 <s:property value="students[1].age"/><br/>
18                 
19 ognl访问Map：<s:property value="studentMap['goodStudent'].name"/>
20             <s:property value="studentMap['goodStudent'].age"/><br/>
21             <s:property value="studentMap['badStudent'].name"/>
22             <s:property value="studentMap['badStudent'].age"/><br/>
23 </body>
24 </html>

url访问：http://localhost:8080/Struts2Chap04/hello

结果：

第四节：OGNL 访问静态方法和属性

1，访问静态属性；

2，访问静态方法；需要在struts.xml加上<constant name="struts.ognl.allowStaticMethodAccess" value="true"></constant>

例子：

 struts.xml
 1 <?xml version="1.0" encoding="UTF-8" ?>
 2 <!DOCTYPE struts PUBLIC
 3     "-//Apache Software Foundation//DTD Struts Configuration 2.0//EN"
 4     "http://struts.apache.org/dtds/struts-2.0.dtd">
 5 
 6 <struts>
 7 
 8     <constant name="struts.ognl.allowStaticMethodAccess" value="true"></constant>
 9 
10   <package name="manage" namespace="/" extends="struts-default">
11       
12   </package>
13 
14 </struts>

 MyStatic.java
 1 package com.wishwzp.common;
 2 
 3 public class MyStatic {
 4 
 5     //静态属性
 6     public static final String str="Struts2开心学习";
 7     
 8     //静态方法
 9     public static String printUrl(){
10         System.out.println("http://www.baidu.com");
11         return "http://www.baidu.com";
12     }
13 }

 ognl_static.jsp
 1 <%@ page language="java" contentType="text/html; charset=UTF-8"
 2     pageEncoding="UTF-8"%>
 3 <%@taglib prefix="s" uri="/struts-tags" %>
 4 <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
 5 <html>
 6 <head>
 7 <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
 8 <title>Insert title here</title>
 9 </head>
10 <body>
11 访问静态属性： <s:property value="@com.wishwzp.common.MyStatic@str"/><br/>
12 访问静态方法：<s:property value="@com.wishwzp.common.MyStatic@printUrl()"/>
13 </body>
14 </html>

url:http://localhost:8080/Struts2Chap04/ognl_static.jsp

结果：