struts中servletAPI获得Map类型的方式

（一）通过ActionContext

为了避免与Servlet API耦合在一起，方便Action类做单元测试，Struts 2对HttpServletRequest、HttpSession和ServletContext进行了封装，构造了三个Map对象来替代这三种对象，在Action中，直接使用HttpServletRequest、HttpSession和ServletContext对应的Map对象来保存和读取 数据。可以通过com.opensymphony.xwork2.ActionContext类来得到这三个对象。ActionContext是Action执行的上下文，保存了很多对象如parameters、request、session、application和locale等。通过ActionContext类获取Map对象的方法为：

public class TestAction1 extends ActionSupport{
 
 private Map<String,Object> request;
 private Map<String, Object> session;
 private Map<String, Object> application;
 
 public TestAction1() {
  // TODO Auto-generated constructor stub
  this.request = (Map)ActionContext.getContext().get("request");
  this.session = ActionContext.getContext().getSession();
  this.application = ActionContext.getContext().getApplication();
 }

}

（二）控制反转

 Action类还有另一种获得ServletAPI的解耦方式，这就是我们可以让他实现某些特定的接口，让Struts2框架在运行时向Action实例注入request、session和application对象。这种方式也就是控制反转方式，与之对应的三个接口和它们的方法如下所示：

public class TestAction2 extends ActionSupport implements RequestAware, SessionAware,ApplicationAware{

 private static final long serialVersionUID = 1L;

 private Map<String,Object> request;  

private Map<String, Object> session;

 private Map<String, Object> application;  

 @Override

 public void setApplication(Map<String, Object> application) {   

// TODO Auto-generated method stub   this.application = application;

 }

 @Override

 public void setSession(Map<String, Object> session) {

  // TODO Auto-generated method stub  

 this.session = session;  

}

 @Override  

public void setRequest(Map<String, Object> request) {   

// TODO Auto-generated method stub  

 this.request = request;   

 }

 public TestAction2() {   // TODO Auto-generated constructor stub     }  

 @Override

 public String execute() throws Exception {   

// TODO Auto-generated method stub   

System.out.println("TestAction2 execute...");  

 this.request.put("reqAttr", "reqDirect");  

 this.session.put("sessionAttr", "sessionDirect");  

 this.application.put("applicationAttr", "applicationDirect");   

return SUCCESS;  }

}