Struts2访问web元素(包括：request，session，application和HttpServletRequest，HttpServletSession， HttpServletContext)的4种方法

说明：
1.常用的是第二中方法取到，Map类型的request，session，application的引用
2.request，session，application是jsp的内置对象，HttpServletRequest，HttpServletSession， HttpServletContext是servlet中与之对应的元素。

一．取得Map类型的request，session，application的引用
1.  直接取得
通过ActionContext中取出相关的web元素。值栈中Stack Context实际就是ActionContext，事实上值栈也放在request里面。
 
package com.xie.action.validate;
 
import java.util.Map;
 
import com.opensymphony.xwork2.ActionContext;
import com.opensymphony.xwork2.ActionSupport;
 
@SuppressWarnings("serial")
public class ActionCheck1 extends ActionSupport {
private Map<String, Object> req;
private Map<String, Object> ses;
private Map<String, Object> app;

public ActionCheck1(){
    req=(Map<String, Object>) ActionContext.getContext().get("request");
    ses=ActionContext.getContext().getSession();
    app=ActionContext.getContext().getApplication();
}

public String execute(){
    req.put("xie", "UC num is 1596144767");
    ses.put("wang", "don't know");
    app.put("liu", "try to don't know");
    return SUCCESS;
}
 
}
页面访问：    
 <s:debug></s:debug><br>
      <s:property value="#request.xie"/>|<%=request.getAttribute("xie") %><br/>
      <s:property value="#session.wang"/>|<%=session.getAttribute("wang") %><br/>
      <s:property value="#application.liu"/>|<%=application.getAttribute("liu") %><br/>
2.  通过IoC方式取得
自己定义的Action应该实现RequestAware,SessionAware,ApplicationAware接口。
 
取得web元素的代码如下：
package com.xie.action.validate;
 
import java.util.Map;
 
import org.apache.struts2.interceptor.ApplicationAware;
import org.apache.struts2.interceptor.RequestAware;
import org.apache.struts2.interceptor.SessionAware;
 
import com.opensymphony.xwork2.ActionSupport;
 
@SuppressWarnings("serial")
public class ActionCheck2 extends ActionSupport implements RequestAware,SessionAware,ApplicationAware {

private Map<String, Object> req;
private Map<String, Object> ses;
private Map<String, Object> app;
 
public void setRequest(Map<String, Object> request) {
                  req=request;
}
 
public void setSession(Map<String, Object> session) {
    ses=session;
}
 
public void setApplication(Map<String, Object> application) {
    app=application;
}

public String execute(){
    req.put("xie", "UC num is 1596144767");
    ses.put("wang", "don't know");
    app.put("liu", "try to don't know");
    return SUCCESS;
}
    
}
三．取得真实类型的HttpServletRequest，HttpServletSession， HttpServletContext的引用
3.直接取得
代码如下：
package com.xie.action.validate;
 
import javax.servlet.ServletContext;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpSession;
 
import org.apache.struts2.ServletActionContext;
 
import com.opensymphony.xwork2.ActionSupport;
 
@SuppressWarnings("serial")
public class ActionCheck3 extends ActionSupport {
        private HttpServletRequest req;
        private HttpSession ses;
        private ServletContext app;
        public ActionCheck3(){
          req=ServletActionContext.getRequest();
          ses=req.getSession();
          app=ses.getServletContext();
        }
    public String execute(){
         req.setAttribute("xie", "UC num is 1596144767");
         ses.setAttribute("wang", "don't know");
         app.setAttribute("liu", "try to don't know");
         return SUCCESS;
    }
}
4.通过IoC取得，需实现ServletRequestAware
取得代码如下：
package com.xie.action.validate;
 
import javax.servlet.ServletContext;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpSession;
 
import org.apache.struts2.interceptor.ServletRequestAware;
 
import com.opensymphony.xwork2.ActionSupport;
 
@SuppressWarnings("serial")
public class ActionCheck4 extends ActionSupport implements ServletRequestAware {

    private HttpServletRequest req;
    private HttpSession ses;
    private ServletContext app;
 
public void setServletRequest(HttpServletRequest request) {
    req=request;
    ses=req.getSession();
    app=ses.getServletContext();
}

public String execute(){
    req.setAttribute("xie", "UC num is 1596144767");
    ses.setAttribute("wang", "don't know");
    app.setAttribute("liu", "try to don't know");
    return SUCCESS;
}
 
}