Struts2 Action访问Web对象的四种方式

1.创建Request，Session，Application的Map对象

action：

Map<String,Object> request;
Map<String,Object> session;
Map<String,Object> application;

public UserAction1(){
System.out.println("UserAction1...");
request = (Map<String, Object>) ActionContext.getContext().get("request");
session = ActionContext.getContext().getSession();
application = ActionContext.getContext().getApplication();
}

jsp：

Request:<s:property value="#request.msg"/>
Session:<s:property value="#session.msg"/>
Application:<s:property value="#application.msg"/>
Attribute:<s:property value="#attr.msg"/>

2.实现RequestAware，SessionAware，ApplicationAware接口（IOC）

public class UserAction2 extends ActionSupport implements RequestAware,SessionAware,ApplicationAware{

public UserAction2(){
System.out.println("UserAction2...");
}

private static final long serialVersionUID = 1L;

private Map<String,Object> request;
private Map<String,Object> session;
private Map<String,Object> application;

UsersDao uDao = new UsersDao();
Users users;

public String execute(){
request.put("msg", "北京欢迎你！");
session.put("msg", "北京欢迎你！");
application.put("msg", "北京欢迎你！");
String str = "failure";
this.addFieldError("loginErr", "用户名或密码不正确。");
if(uDao.queryUsers(users)){
str = "success";
this.addFieldError("loginErr", "");
}
return str;
}

3.创建传统的HttpServletRequest，HttpSession，ServletContext对象

private HttpServletRequest request;
private HttpSession session;
private ServletContext application;

public String execute(){
request = ServletActionContext.getRequest();
session = request.getSession();
application = session.getServletContext();
request.setAttribute("msg", "北京欢迎你！");
session.setAttribute("msg", "北京欢迎你！");
application.setAttribute("msg", "北京欢迎你！");

4.实现ServletRequestAware，ServletContextAware接口(IOC)

private HttpServletRequest request;
private HttpSession session;
private ServletContext application;

public String execute(){
request = ServletActionContext.getRequest();
session = request.getSession();
application = session.getServletContext();
request.setAttribute("msg", "北京欢迎你！");
session.setAttribute("msg", "北京欢迎你！");
application.setAttribute("msg", "北京欢迎你！");