刨根問底--struts--得到request-繼承ServletRequestAware

《刨根問底--struts--得到request過程詳解》詳細分析了經過ServletActionContext.getRequest()獲取request的詳細過程，還能夠經過action類繼承ServletRequestAware獲取rquest。ServletRequestAware接口前面的註釋：All Actions that want to have access to the servlet request object must implement this interface.<p>

public interface ServletRequestAware {

    /**
     * Sets the HTTP request object in implementing classes.
     *
     * @param request the HTTP request.
     */
    public void setServletRequest(HttpServletRequest request);
}

具體action中的操做

public class Action extends ActionSupport implements SessionAware,ServletRequestAware{

protected Map session = null;

protected HttpServletRequest request = null;

@Override
public void setServletRequest(HttpServletRequest request) {
	this.request = request;
}

@Override
public void setSession(Map map) {
	this.session = map;
}
}

這樣，就得到了request對象。

具體怎麼何時執行setServletRequest（），如今看看ServletConfigInterceptor攔截器。

public class ServletConfigInterceptor extends AbstractInterceptor implements StrutsStatics {
public String intercept(ActionInvocation invocation) throws Exception {
        final Object action = invocation.getAction();
        final ActionContext context = invocation.getInvocationContext();

        if (action instanceof ServletRequestAware) {
            HttpServletRequest request = (HttpServletRequest) context.get(HTTP_REQUEST);
            ((ServletRequestAware) action).setServletRequest(request);
        }

        if (action instanceof ServletResponseAware) {
            HttpServletResponse response = (HttpServletResponse) context.get(HTTP_RESPONSE);
            ((ServletResponseAware) action).setServletResponse(response);
        }

        if (action instanceof ParameterAware) {
            ((ParameterAware) action).setParameters((Map)context.getParameters());
        }

        if (action instanceof ApplicationAware) {
            ((ApplicationAware) action).setApplication(context.getApplication());
        }
        
        if (action instanceof SessionAware) {
            ((SessionAware) action).setSession(context.getSession());
        }
        
        if (action instanceof RequestAware) {
            ((RequestAware) action).setRequest((Map) context.get("request"));
        }

        if (action instanceof PrincipalAware) {
            HttpServletRequest request = (HttpServletRequest) context.get(HTTP_REQUEST);
            if(request != null) {
                // We are in servtlet environment, so principal information resides in HttpServletRequest
                ((PrincipalAware) action).setPrincipalProxy(new ServletPrincipalProxy(request));
            }
        }
        if (action instanceof ServletContextAware) {
            ServletContext servletContext = (ServletContext) context.get(SERVLET_CONTEXT);
            ((ServletContextAware) action).setServletContext(servletContext);
        }
        return invocation.invoke();
    }
}

註釋：invocation.getAction()獲取action對象， instanceof 判斷action對象是不是默認特定的對象。若是是的話就是執行相應的代碼。

具體何時執行攔截器的intercept（）方法，請看《刨根問底-struts-serviceAction（）建立並執行action
》