Struts2 值栈和OGNL 的使用

一、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。

二、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” />
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

om.cy.action.HelloAction.java:

package com.cy.action;

import java.util.Map;

import com.opensymphony.xwork2.ActionContext;
import com.opensymphony.xwork2.ActionSupport;
import com.opensymphony.xwork2.util.ValueStack;

public class HelloAction extends ActionSupport{
    private static final long serialVersionUID = 1L;

    @Override
    public String execute() throws Exception {
        ActionContext actionContext = ActionContext.getContext();
        ValueStack valueStack = actionContext.getValueStack();
        valueStack.set("name", "张三(valueStack)");
        valueStack.set("age", 11);
        
        Map<String, Object> session = actionContext.getSession();
        session.put("name", "王五(session)");
        session.put("age", 13);
        
        Map<String, Object> application = actionContext.getApplication();
        application.put("name", "赵六(application)");
        application.put("age", 14);
        
        return SUCCESS;
    }
    
}

struts.xml:

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<struts>
    
    <package name="manage" namespace="/" extends="struts-default">
        <action name="hello" class="com.cy.action.HelloAction">
            <result name="success">success.jsp</result>
        </action>
                    
    </package>
    
</struts>

success.jsp:

<%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8"%>
<%@taglib prefix="s" uri="/struts-tags" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title here</title>
<%
    request.setAttribute("name", "李四(request)");
    request.setAttribute("age", 12);
    

   // pageContext.setAttribute("name", "小沛(page)");
    //pageContext.setAttribute("age", "18");
%>
</head>
<body>
    获取狭义上的值栈数据：<s:property value="name"/>
    <s:property value="age"/><br>    
    请求参数：<s:property value="#parameters.name"/>
    <s:property value="#parameters.age"/><br>
    request：<s:property value="#request.name"/>
    <s:property value="#request.age"/><br>
    session：<s:property value="#session.name"/>
    <s:property value="#session.age"/><br>
    application：<s:property value="#application.name"/>
    <s:property value="#application.age"/><br>
    attr取值：<s:property value="#attr.name"/>
    <s:property value="#attr.age"/><br>
</body>
</html>

测试结果：

说明如果不注释掉

ActionContext actionContext = ActionContext.getContext(); ValueStack valueStack = actionContext.getValueStack();

valueStack.set("name", "张三(valueStack)");

valueStack.set("age", 11);这段代码的attr取值为张三(valueStack)，11

然后不注释掉

pageContext.setAttribute("name", "小沛(page)");

pageContext.setAttribute("age", "18");这段代码的话attr取值位小沛(page)，18

三、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

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；<constant name="struts.ognl.allowStaticMethodAccess" value="true"></constant>

success.jsp

<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<%@taglib prefix="s" uri="/struts-tags" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title here</title>
<%
request.setAttribute("name", "李四(request)");
request.setAttribute("age", "12");
%>
</head>
<body>
获取狭义上的值栈数据：<s:property value="name"/>
<s:property value="age"/> 
请求参数：<s:property value="#parameters.name"/>
<s:property value="#parameters.age"/> 
request：<s:property value="#request.name"/>
<s:property value="#request.age"/> 
session：<s:property value="#session.name"/>
<s:property value="#session.age"/> 
application：<s:property value="#application.name"/>
<s:property value="#application.age"/> 
attr取值：<s:property value="#attr.name"/>
<s:property value="#attr.age"/> 
ognl访问javaBean对象：<s:property value="student.name"/>
<s:property value="student.age"/> 
ognl访问List集合：<s:property value="students[0].name"/>
<s:property value="students[0].age"/> 
<s:property value="students[1].name"/>
<s:property value="students[1].age"/> 
ognl访问Map：<s:property value="studentMap['goodStudent'].name"/>
<s:property value="studentMap['goodStudent'].age"/> 
<s:property value="studentMap['badStudent'].name"/>
<s:property value="studentMap['badStudent'].age"/> 
</body>
</html>

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>

<constant name="struts.ognl.allowStaticMethodAccess" value="true"></constant>

<package name="manage" namespace="/" extends="struts-default">

 <action name="hello" class="com.java1234.action.HelloAction">
 <result name="success" >success.jsp</result>
 </action>
</package>

</struts>

Student.java

package com.java1234.model;

public class Student {

   private String name;
   private int age;



   public Student() {
       super();
       // TODO Auto-generated constructor stub
   }


   public Student(String name, int age) {
       super();
       this.name = name;
       this.age = age;
   }

   public String getName() {
       return name;
   }
   public void setName(String name) {
       this.name = name;
   }
   public int getAge() {
       return age;
   }
   public void setAge(int age) {
       this.age = age;
   }


}

HelloAction.java

package com.java1234.action;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

import com.java1234.model.Student;
import com.opensymphony.xwork2.ActionContext;
import com.opensymphony.xwork2.ActionSupport;
import com.opensymphony.xwork2.util.ValueStack;

public class HelloAction extends ActionSupport{

/**
 *
 */
 private static final long serialVersionUID = 1L;

 private Student student;

 private List<Student> students;

 private Map<String,Student> studentMap;

public Map<String, Student> getStudentMap() {
 return studentMap;
 }

public void setStudentMap(Map<String, Student> studentMap) {
 this.studentMap = studentMap;
 }

public List<Student> getStudents() {
 return students;
 }

public void setStudents(List<Student> students) {
 this.students = students;
 }

   public Student getStudent() {
       return student;
   }

   public void setStudent(Student student) {
       this.student = student;
   }

@Override
 public String execute() throws Exception {
 ActionContext actionContext=ActionContext.getContext();
 // 获取狭义上的值栈
 ValueStack valueStack=actionContext.getValueStack();
 valueStack.set("name", "张三(valueStack)");
 valueStack.set("age", 11);

 Map<String, Object> session=actionContext.getSession();
 session.put("name", "王五(session)");
 session.put("age", 13);

 Map<String, Object> application=actionContext.getApplication();
 application.put("name", "赵六(application)");
 application.put("age", 14);

 student=new Student("小扒", 12);

 students=new ArrayList<Student>();
 students.add(new Student("老九",13));
 students.add(new Student("老十",14));

 studentMap=new HashMap<String,Student>();
 studentMap.put("goodStudent", new Student("学霸",20));
 studentMap.put("badStudent", new Student("学渣",19));
 return SUCCESS;
 }

}

输出结果

struts.xml配置，开启ognl允许访问静态方法：

 <constant name="struts.ognl.allowStaticMethodAccess" value="true"></constant>

package com.java1234.common;

public class MyStatic {

   public static final String str="Java知识分享网";

   public static String printUrl(){
       System.out.println("http://www.java1234.com");
       return "http://www.java1234.com";
   }
}

ognl_static.jsp

直接在下面的网址中输入下面的url

Struts2 值栈和OGNL 的使用

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