我们经常需要在 Action 中传入一些参数到 JSP 页面，可以用 来获取参数，但是这些参数都仅限于特定的数据，如果我们想要像 JSP 中使用 request、Session 和 application ，我们怎么办呢?
一、
我们可以通过 ActionContext 对象得到 Request 等的 Map 类型对象进行赋值和参数的传递，代码参考如下：
1: public String execute(){ 2: 3: ((Map)ActionContext.getContext().get("request")).put("r1", "r1");//Request 的 Map 对象 4: ActionContext.getContext().getSession().put("s1", "s1");// Session 的 Map 对象 5: ActionContext.getContext().getApplication().put("a1", "a1");//Application 的 Map 对象 6: return SUCCESS; 7: } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; }通过上面这种方式定义 Action 就可以传递参数了，对此，我们在前台 JSP 页面获取参数的方法有两种：
一种是通过 标签来访问参数：
1: value= "#request.r1"/> 2: value= "#session.s1"/> 3: value= "#application.a1"/> .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; }这种访问方式和在 value 的参数前面加了一个 # ，因为这些都是 Stack Context 里面的 key。
另一种访问参数的方法是我们熟悉的：
1: <%=request.getAttribute("r1") %> 2: <%=session.getAttribute("s1") %> 3: <%=application.getAttribute("a1") %> .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; }或许有些不能理解，Map 型的 Request、Session、Application 可以这样访问？！是的，Struts2 做到了，应该是在内部做了一些转化的，将 Map 转型为 HttpServletRequest、HttpSession 和 ServletContext 。
这种方式是依赖 Struts2 环境的，因为使用了 ActionContext 类。
二、
这种方法是通过依赖注入( DI, Dependency Injection )，或者叫控制反转 ( IoC, Inverse of Control ) 实现的。这种方式最常用。
原理是定义 Action 实现 RequestAware、SessionAware、ApplicationAware 接口，实现里面定义的 setXxxxx( Map xxx ) 方法，之后等待 Struts2 Context 给我们定义的 Action 注入 request、 session 、 application 等等。（控制反转的理解可以认为本来 request、session、application 这些变量是由 Action 自己控制的，实现这些 Aware 接口后控制权就移交给 Struts2 Context 了）
Action 代码如下，其他代码如上所示：
1: package com.cdp.struts2; 2: 3: import java.util.Map; 4: 5: import org.apache.struts2.interceptor.ApplicationAware; 6: import org.apache.struts2.interceptor.RequestAware; 7: import org.apache.struts2.interceptor.SessionAware; 8: 9: import com.opensymphony.xwork2.ActionSupport; 10: 11: public class Action2 extends ActionSupport implements RequestAware, 12: SessionAware, ApplicationAware { 13: 14: private Map request; 15: private Map session; 16: private Map application; 17: 18: public String execute() { 19: 20: request.put("r1", "r1"); 21: session.put("s1", "s1"); 22: application.put("a1", "a1"); 23: return SUCCESS; 24: } 25: 26: public void setRequest(Map request) { 27: this.request = request; 28: 29: } 30: 31: public void setSession(Map session) { 32: this.session = session; 33: 34: } 35: 36: public void setApplication(Map application) { 37: this.application = application; 38: 39: } 40: 41: } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; }需要注意的是，这种方式是最常用的。
三、
第三种方式是直接创建真实的而非 Map 类型的 request 、 session 、 application 对象，方法如下：
1: package com.cdp.struts2; 2: 3: import javax.faces.application.Application; 4: import javax.servlet.ServletContext; 5: import javax.servlet.http.HttpServletRequest; 6: import javax.servlet.http.HttpSession; 7: 8: import org.apache.struts2.ServletActionContext; 9: 10: import com.opensymphony.xwork2.ActionSupport; 11: 12: public class Action3 extends ActionSupport{ 13: 14: private HttpServletRequest request; 15: private HttpSession session; 16: private ServletContext application; 17: 18: public String execute(){ 19: request=ServletActionContext.getRequest(); 20: session=request.getSession(); 21: application=session.getServletContext(); 22: request.setAttribute("r1", "r1"); 23: session.setAttribute("s1", "s1"); 24: application.setAttribute("a1", "a1"); 25: return SUCCESS; 26: } 27: 28: } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; }四、
最后一种也是依赖注入实现的，Action 实现的是 ServletRequestAware 接口，让后通过 request 得到 session，通过 session 得到 application：
1: package com.cdp.struts2; 2: 3: import javax.faces.application.Application; 4: import javax.servlet.ServletContext; 5: import javax.servlet.http.HttpServletRequest; 6: import javax.servlet.http.HttpSession; 7: 8: import org.apache.struts2.ServletActionContext; 9: import org.apache.struts2.interceptor.ServletRequestAware; 10: 11: import com.opensymphony.xwork2.ActionSupport; 12: 13: public class Action4 extends ActionSupport implements ServletRequestAware{ 14: 15: private HttpServletRequest request; 16: private HttpSession session; 17: private ServletContext application; 18: 19: public String execute(){ 20: request.setAttribute("r1", "r1"); 21: session.setAttribute("s1", "s1"); 22: application.setAttribute("a1", "a1"); 23: return SUCCESS; 24: } 25: 26: public void setServletRequest(HttpServletRequest request) { 27: this.request=request; 28: this.session=request.getSession(); 29: this.application=session.getServletContext(); 30: } 31: 32: } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; }