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在 Struts2 中访问 Request、Session 和 Application

2011-02-04 09:43 363 查看

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:  }

1:  value="#request.r1"/>

2:  value="#session.s1"/>

3:  value="#application.a1"/>

1:  <%=request.getAttribute("r1") %>

2:  <%=session.getAttribute("s1") %>

3:  <%=application.getAttribute("a1") %>

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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:  }

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:  }

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:  }

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