Flex Remote Object中直接使用HttpSession的方法.doc

Flex Remote Object中直接使用HttpSession的方法Flex Remote Object可以是POJO,JavaBean或是EJB。在面向服务的架构中(Service Oriented Architecture),我们可以用Remote Object来作为Service Facade，利用应用服务器提供的persistent service来储存状态信息。 Flex既可以提供stateful或stateless的remote object, 另外还有session servlet让mxml获取/和储存session中的内容。这一切听上去都很完美，但是有一个问题，Flex Remote Object本身是无法获得任何有关Running Context的信息，也就是说，你无法从你的 Remote Object 中获得 HttpSession, HttpRequest 和 ServletContext。 所谓的 Flex Session servlet只是让MXML获得session的内容，而不是直接让Remote Object获得session。 Remote Object为什么需要获得HttpRequest, HttpSession? 既然Flex提供了stateful的remote object为什么还要让remote object获得Running Context呢？问题在于Flex中的stateful是基于应用服务器的http session，而且你无法控制AMFGateway建立remote object的过程。打个简单的比方，我们知道一般的应用服务器中，session的时限只有20分钟，而在很多系统的登陆过程中却有选择保持登陆几个月的选项。 其具体实现上就是利用cookie来储存id和password hash，通过控制cookie的存活时间来实现的。而在服务器端，一旦session过期了，则可以从cookie中获得id和password hash重新登陆一遍，从而达到自动认证用户的目的。 如果你的Remote Object无法获得 HttpServletRequest, HttpSession，你就无法实现上述的情况。另外，对于小型的应用来说，直接在Remote object中获得servlet context并利用它来储存/获得共享的资源，可以大大降低开发的复杂程度。 解决方案 要让Remote Object获得HttpSession,HttpRequest和ServletContext并不是一件容易的事情。这里提供了我的一种方法，供大家参考。希望能抛砖引玉，让大家提出更好，更有效的方案。 这个方法的基本思路是利用JAVA提供的 ThreadLocal Object。当服务器接收到一个HTTP请求后，这个请求的整个处理过程是运行在同一个线程中的。 每个HTTP请求的处理会都运行在各自独立的线程中。而在Flex中，所有AMF Remote Object 的请求都需要通过 AMF Gateway Servlet，而Remote Object 的建立和调用恰恰就是运行在这个HTTP请求的线程中。 有了这个原则，我们就可以建立一个Context Object,每当请求建立的时候，就可以把这个请求放入 Context 的 ThreadLocal 中，而当 Remote Object 被AMF Gateway Servlet调用的时候，就可以通过访问 Context 的ThreadLoca l来获得其所对应的那个请求。 而截获发送到AMF Gateway的请求则可以通过Servlet Filter来实现。废话不说了，看代码吧！ 1. 添加以下内容到WEB-INF/web.xml中 AMFSessionFilter op.forum.servlets.AMFSessionFilter AMFSessionFilter AMFGatewayServlet 2. AMFSessionFilter的代码 /* * Created on 1/07/2004 */ package op.forum.servlets; import java.io.IOException; import javax.servlet.Filter; import javax.servlet.FilterChain; import javax.servlet.FilterConfig; import javax.servlet.ServletException; import javax.servlet.ServletRequest; import javax.servlet.ServletResponse; import javax.servlet.http.*; import mons.logging.Log; import mons.logging.LogFactory; /* * author Zombie * version 0.5 */ public class AMFSessionFilter implements Filter private static Log log = LogFactory.getLog(AMFSessionFilter.class); public void init(FilterConfig config) (Init AMFSessionFilter filter); public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws ServletException,IOException AMFContext.setCurrentContext(HttpServletRequest)request, (HttpServletResponse)response); chain.doFilter(request,response); public void destroy() (Destory AMFSessionFilter filter); 3. AMFContext的代码 /* * Created on 1/07/2004 */ package op.forum.servlets; import javax.servlet.*; import javax.servlet.http.*; import op.forum.business.*; import mons.logging.Log; import mons.logging.LogFactory; /* * author Zombie * version 0.5 */ public class AMFContext /* * Context Attribute key for the connection the factory */ public final static String CONNECTION_FACTORY_KEY = sqlMapFactory; /* * The log */ private static Log log = LogFactory.getLog(AMFContext.class); /* * ThreadLocal object for storing object in current thread. */ private static ThreadLocal tl = new ThreadLocal(); /* * Set current context * * param request The HttpRequest object * param response The HttpResponses object */ static public void setCurrentContext(HttpServletRequest request, HttpServletResponse response) AMFContext c = getCurrentContext(); if (c = null) c = new AMFContext(request,response); tl.set(c); else c.setRequest(request); c.setResponse(response); /* * Get current context value * return The current context */ static public AMFContext getCurrentContext() return (AMFContext)tl.get(); /- / / Class members / /- /* * The http request object. The lifecycle of the request object is defined as the request * scope. It may be reused in another incoming connection, so dont use it in another thread. */ private HttpServletRequest request; /* * The http response object. The lifecycle of the response object is defined as the request * scope. Dont use it in another thread. Also dont write output to the response when it is * used in the context, but you may get or set some response header when it is safe. */ private HttpServletResponse response; /* * The constructor is private, to get an instance of the AMFContext, please use * getCurrentContext() method. * * param request * param response */ private AMFContext (HttpServletRequest request, HttpServletResponse response) this.request = request; this.response = response; /* * Get request object * * return Http request object */ public HttpServletRequest getRequest() return request; /* * Set request object * * param Http request object */ public void setRequest(HttpServletRequest request) this.request = request; /* * Get response object * * return Http response object */ public HttpServletResponse getResponse() return response; /* * Set response object * * param response Http response object */ public void setResponse(HttpServletResponse response) this.response = response; /* * Get the servlet context * return */ public ServletContext getServletContext() HttpSession session = this.getSession(); return session.getServletContext(); /* * Get the current running session * return */ public HttpSession getSession() return request.getSession(); /* * Get an object stored in the session. * * param attr Attribute Name * return The value stored under the attribute name. */ public Object getSessionAttribute(String attr) HttpSession session = this.getSession(); return session.getAttribute(attr); /* * Store an object in the session. * * param attr Attribute Name * param value The value. */ public void setSessionAttribute(String attr, Object value) HttpSession session = this.getSession(); session.setAttribute(attr, value); /* * Get an object stored in the servlet context. * * param attr Attribute Name * return The value stored under the attribute name. */ public Object getContextAttribute(String attr) ServletContext sc = this.getServletContext(); return sc.getAttribute(attr); /* * Store an object in the servlet context. * * param attr Attribute Name * param value The value. */ public void setContextAttribute(String attr, Object value) ServletContext sc = this.getServletContext(); sc.setAttribute(attr,value); /* * Get an object stored in the current request. * * param attr Attribute Name * return The value stored under the attribute name. */ public Object getRequestAttribute(String attr) return request.getAttribute(attr); /* * Store an object in the current request. * * param attr Attribute Name * param value The value. */ public void setRequestAttribute(String attr, Object value) request.setAttribute(attr,value); /* * Get the connection factory from the servlet context. The connection factory is in the * application scope. * * return The connection factory for creating sqlMap objects. */ public ConnectionFactory getConnectionFactory() ConnectionFactory factory =(ConnectionFacto