ActionContext

转载：http://miseryboy.javaeye.com/blog/311363

1、struts2的Action可以通过ActionContext来访问ServletAPI。下面是ActionContext类中包含的几个常用方法：
 
Object get(Object key):该方法类似于调用HttpServletRequest的getAttribute(String name)方法； 
Map getApplication():返回一个Map对象，该对象模拟了该应用的ServletContext实例；
static ActionContext getContext():静态方法，获取系统的ActionContext实例； 
Map getParameters():获取所有的请求参数。类似于调用HttpServletRequest对象的getParameterMap方法； 
Map getSession():返回一个Map对象，该Map对象模拟了HttpSession实例； 
void setApplication(Map application):直接传入一个Map实例，将该Map实例里的key-value对转换成application的属性名，属性值； 
void setSession(Map session):直接传入一个Map实例，将该Map实例里的key-value对转换成session的属性名，属性值

public class LoginAction1 extends ActionSupport {
 
 private Map request;
 private Map session;
 private Map application;
 
 public LoginAction1() {
  request = (Map)ActionContext.getContext().get("request");
  session = ActionContext.getContext().getSession();
  application = ActionContext.getContext().getApplication();
 }
 
 public String execute() {
  request.put("r1", "r1");
  session.put("s1", "s1");
  application.put("a1", "a1");
  return SUCCESS; 
 }
 
 
}
2、Action直接访问ServletAPI，Struts2的Action可以实现下列接口，直接来访问ServletAPI：
ServletContextAware:实现该接口的Action可以直接访问Web应用的ServletContext实例
ServletRequestAware:实现该接口的Action可以直接访问用户请求的HttpServletRequest实例 
ServletResponseAware:实现该接口的Action可以直接访问服务器响应的HttpServletResponse实例

例子：

 public class LoginAction2 extends ActionSupport implements RequestAware,SessionAware, ApplicationAware {
 
 private Map request;
 private Map session;
 private Map application;
 
 //DI dependency injection
 //IoC inverse of control
 public String execute() {
  request.put("r1", "r1");
  session.put("s1", "s1");
  application.put("a1", "a1");
  return SUCCESS; 
 }

 @Override
 public void setRequest(Map request) {
  this.request = request;
 }

 @Override
 public void setSession(Map session) {
  this.session = session;
 }

 @Override
 public void setApplication(Map application) {
  this.application = application;
 }
}

3、struts2还提供了一个ServletActionContext，这个类包含了如下一些静态方法：
static PageContext getPageContext():取得Web应用的PageContext对象； 
static HttpServletRequest getRequest():取得web应用的HttpServletRequest对象； 
static HttpServletResponse getResponse():取得web应用的HttpServletResponse对象；
static ServletContext getServletContext():取得web应用的ServletContext对象；

例子：

public class LoginAction extends ActionSupport {
 
 private HttpServletRequest request;
 private HttpSession session;
 private ServletContext application;
 
 public LoginAction() {
  request = ServletActionContext.getRequest();
  session = request.getSession();
  application = session.getServletContext();
 }
 
 public String execute() {
  request.setAttribute("r1", "r1");
  session.setAttribute("s1", "s1");
  application.setAttribute("a1", "a1");
  return SUCCESS; 
 }

}

4.实现ServletRequestAware

public class LoginAction4 extends ActionSupport implements ServletRequestAware{
 
 private HttpServletRequest request;
 private HttpSession session;
 private ServletContext application;

 public String execute() {
  request.setAttribute("r1", "r1");
  session.setAttribute("s1", "s1");
  application.setAttribute("a1", "a1");
  return SUCCESS; 
 }

 @Override
 public void setServletRequest(HttpServletRequest request) {
  this.request = request;
  this.session = request.getSession();
  this.application = session.getServletContext();
 }
 
}