1.struts作为控制器，正常很多时候要访问到servlet的API，常用功能:
  (1).获取请求参数,控制界面跳转
  (2).把共享数据存储于request,session,servletContext中,获取作用域中的数据

宏观的来说，应该有三种访问方式。

2.第一种:实现接口，访问Action时完成注入
ServletContextAware
void setServletContext(javax.servlet.ServletContext context)

ServletRequestAware
void setServletRequest(javax.servlet.http.HttpServletRequest request)

ServletResponseAware
void setServletResponse(javax.servlet.http.HttpServletResponse response)

上述方式:Action和ServletAPI耦合太深了.

简单的示例代码：

package cn.wwh.www.web.servletapi;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.apache.struts2.interceptor.ServletRequestAware;
import org.apache.struts2.interceptor.ServletResponseAware;

import com.opensymphony.xwork2.Action;
import com.opensymphony.xwork2.ActionSupport;

/**
 *类的作用：
 * 
 * 
 *@author 一叶扁舟
 *@version 1.0
 *@创建时间： 2014-8-16 上午07:54:05
 */
public class ParamAction1 extends ActionSupport implements ServletRequestAware,
		ServletResponseAware {

	private static final long serialVersionUID = 1L;
	private HttpServletRequest request;
	private HttpServletResponse response;

	@Override
	public String execute() throws Exception {
		String name = request.getParameter("name");
		String age = request.getParameter("age");
		System.out.println("name:" + name);
		System.out.println("age:" + age);
		response.getWriter().write(name + "<br/>");
		response.getWriter().write(age);
		// 没有起到效果，很奇怪
		request.getRequestDispatcher("/views/servletapi/result.jsp").forward(
				request, response);
		return Action.NONE;
	}

	public void setServletRequest(HttpServletRequest request) {
		this.request = request;
	}

	public void setServletResponse(HttpServletResponse response) {
		this.response = response;

	}

}

3.第二种:使用ServletActionContext(开发中使用的很多,因为简单,直观)ServletActionContext: 通过该类提供了ServletAPI的环境,可以获取到Servlet的API信息static PageContext getPageContext()static HttpServletRequest getRequest()static HttpServletResponse getResponse()static ServletContext getServletContext()

该方案可避免Action类实现XxxAware接口，但Action依然与Servlet API直接耦合但是该方式和ServletApi也有耦合.

简单的实例代码：

package cn.wwh.www.web.servletapi;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;

import org.apache.struts2.ServletActionContext;

import com.opensymphony.xwork2.ActionSupport;

/**
 *类的作用：
 * 
 * 
 *@author 一叶扁舟
 *@version 1.0
 *@创建时间： 2014-8-16 上午09:09:02
 */
public class ParamAction2 extends ActionSupport {

	private static final long serialVersionUID = 1L;
	public String execute() throws Exception {

		HttpServletRequest req = ServletActionContext.getRequest();
		String name = ServletActionContext.getRequest().getParameter("name");
		String age = ServletActionContext.getRequest().getParameter("age");
		HttpSession session = req.getSession();
		session.getServletContext();
		System.out.println(name);
		System.out.println(age);
		HttpServletResponse resp = ServletActionContext.getResponse();
		return NONE;
	}

}

   ActionContext
   getContext() 返回ActionContext实例对象
   get(key) 相当于 HttpServletRequest的getAttribute(String name)方法
   put(String,Object) 相当于HttpServletRequest的setAttribute方法
   getApplication() 返回一个Map对象，存取ServletContext属性
   getSession() 返回一个Map对象，存取HttpSession属性
   getParameters() 类似调用HttpServletRequest的getParameterMap()方法 
   setApplication(Map) 将该Map实例里key-value保存为ServletContext的属性名、属性值
   setSession(Map) 将该Map实例里key-value保持为HttpSession的属性名、属性值
   获取ActionContext对象:  ActionContext context = ActionContext.getContext();

简单的示例代码：

package cn.wwh.www.web.servletapi;



import java.lang.reflect.Array;
import java.util.Map;

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

/**
 *类的作用：
 *
 *
 *@author 一叶扁舟
 *@version 1.0
 *@创建时间： 2014-8-16   上午09:31:42
 */
public class ParamAction3 extends ActionSupport {

	private static final long serialVersionUID = 1L;

	public String execute() throws Exception {
		ActionContext ctx = ActionContext.getContext();
		Map<String,Object> paramMap = ctx.getParameters();
		System.out.println(paramMap);
		
		//去paramMap.get("name")数组中索引为0的元素值
		System.out.println(Array.get(paramMap.get("name"), 0));
		
		//往request设置共享数据
		ctx.put("name", "一叶扁舟");//request.setAttribute(key,Object)
		Object requestValue  = http://www.mamicode.com/ctx.get("name");>注意在jsp中读取数据为：
        ${requestScope.name}<br />
        ${sessionScope.sessionKey}<br />
        ${appKey}


 5.通过ActionContext获取request、session、application解耦Map
(1) 对request域的操作
actionContext.put("name", "一叶扁舟") --> 相等与request.setAttribute("name", "一叶扁舟");
Object o = actionContext.get("name"); --> 等同与Object o = request.getAttribute("name");
(2).对session域的操作
Map<String,Object> sessionMap = ActionContext.getContext().getSession();
sessionMap.put("name", "一叶扁舟") --> 等同与session.setAttribute("name", "一叶扁舟");
Object o = sessionMap.get("name") --> 等同与Object o = session.getAttribute("name");
(3).对application域的操作
Map<String,Object> appMap = ActionContext.getContext().getApplication();
appMap.put("name", "一叶扁舟") --> 等同与servletContext.setAttribute("name", "一叶扁舟");
Object o = appMap.get("name") --> 等同与Object o = servletContext.getAttribute("name");
(4). 对请求参数的操作
Map<String,Object> paramMap = ActionContext.getContext().getParameters();
Object o = paramMap.get("username");
String[] values = (String[])o;
String username = values[0];