ActinoProxy的全名是com.opensymphony.xwork2.ActionProxy，
ActionProxy = Action + Proxy，从字面意思来解释：Action的代理。
在Struts中，ActionContext、ActionInvocation、ActionProxy、ActionConfig联系的很紧密。
ActionContext<-->ActionInvocation<-->ActionProxy-->ActionConfig
（1.1）从ActionContext对象可以得到ActionInvocation对象
（1.2）从ActionInvocation对象可以得到ActionContext对象
（2.1）从ActionInvocation对象可以得到ActionProxy对象
（2.2）从ActionProxy对象可以得到ActionInvocation对象
（3.1）从ActionProxy对象可以得到ActionConfig对象
在搜索的时候 ，遇到一句描述ActionInvocation和ActionProxy关系的话，感觉非常切中要害：
Essentially, ActionProxy encapsulates how an Action can be obtained. ActionInvocation encapsulates how the Action is executed when a request is invoked.
本质上来，ActionProxy对如何获取Action对象进行了封装，而ActionInvocation对如何执行Action进行了封装。
原话地址：https://struts.apache.org/docs/action-proxy-actionproxy-factory.html
Typically, an ActionProxy will utilize the ActionInvocation to encapsulate the execution of a particular request.
The ActionInvocation determines how an Action is handled: Is it being intercepted? Is there a PreResultListener acting on it?
在上面图中，
ActionConfig，负责从struts.xml文件中读取配置；
ActionSupport，我们自己实现的Action类一般都继承ActionSupport类；
ActionContext，是Action运行的环境，为Action类提供一些信息；
ActionProxy，是如何获取Action；
ActionInvocation是如何执行Action。
上面标的（1）至（4），都能通过ActionProxy来获得：
（1）表示当前Action类在struts.xml文件中对应的<action>标签所在的<package>标签的namespace属性
（2）表示<action>标签的name属性
（3）表示真实的Action类的实例，不是字符串类型，而<action>标签的class属性对应的类的实例化。
（4）<action>标签的method属性
从我个人理解的角度来说（可能理解是不对的），ActionProxy实现了URL和真正Action类之间的映射。
1、如何获取ActionProxy对象
ActionProxy proxy = invocation.getProxy();
2、如何获取ActionProxy中的值
（1）获取当前<action>所在的命名空间
String namespace = proxy.getNamespace();
（2）获取<action>的名字
String actionName = proxy.getActionName();
（3）获取Action类的实例
Object action = proxy.getAction();
（4）获取<action>执行的方法
String method = proxy.getMethod();
（5）得到ActionInvocation和ActionConfig对象
ActionConfig config = proxy.getConfig(); ActionInvocation invocation2 = proxy.getInvocation();
3、ActionProxy的源代码
package com.opensymphony.xwork2;
import com.opensymphony.xwork2.config.entities.ActionConfig;
/**
* ActionProxy is an extra layer between XWork and the action so that different proxies are possible.
* <p/>
* An example of this would be a remote proxy, where the layer between XWork and the action might be RMI or SOAP.
*
* @author Jason Carreira
*/
public interface ActionProxy {
/**
* Gets the Action instance for this Proxy.
*
* @return the Action instance
*/
Object getAction();
/**
* Gets the alias name this ActionProxy is mapped to.
*
* @return the alias name
*/
String getActionName();
/**
* Gets the ActionConfig this ActionProxy is built from.
*
* @return the ActionConfig
*/
ActionConfig getConfig();
/**
* Sets whether this ActionProxy should also execute the Result after executing the Action.
*
* @param executeResult <tt>true</tt> to also execute the Result.
*/
void setExecuteResult(boolean executeResult);
/**
* Gets the status of whether the ActionProxy is set to execute the Result after the Action is executed.
*
* @return the status
*/
boolean getExecuteResult();
/**
* Gets the ActionInvocation associated with this ActionProxy.
*
* @return the ActionInvocation
*/
ActionInvocation getInvocation();
/**
* Gets the namespace the ActionConfig for this ActionProxy is mapped to.
*
* @return the namespace
*/
String getNamespace();
/**
* Execute this ActionProxy. This will set the ActionContext from the ActionInvocation into the ActionContext
* ThreadLocal before invoking the ActionInvocation, then set the old ActionContext back into the ThreadLocal.
*
* @return the result code returned from executing the ActionInvocation
* @throws Exception can be thrown.
* @see ActionInvocation
*/
String execute() throws Exception;
/**
* Gets the method name to execute, or <tt>null</tt> if no method has been specified (meaning <code>execute</code> will be invoked).
*
* @return the method to execute
*/
String getMethod();
/**
* Gets status of the method value‘s initialization.
*
* @return true if the method returned by getMethod() is not a default initializer value.
*/
boolean isMethodSpecified();
}