Flex中session的实现

tomcat中的session实现类是StandardSession，
其中Manager 这个接口在StandardSession中有被用到。

1.5jdk中用到了ConcurrentHashMap。
但是flex中本身是没有提供session接口的，那么该如何实现呢？参考别人的文章后总结如下：

1、在web.xml增加

<filter>
   <filter-name>AMFContextFilter</filter-name>
   <filter-class>soft.flex.context.AMFContextFilter</filter-class>
</filter>
<filter-mapping>
   <filter-name>AMFContextFilter</filter-name>
   <servlet-name>MessageBrokerServlet</servlet-name>
</filter-mapping>

2、增加AMFContextFilter文件

package soft.flex.context;

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.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class AMFContextFilter implements 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 init(FilterConfig arg0) throws ServletException {
   // TODO Auto-generated method stub

}

public void destroy() {
   // TODO Auto-generated method stub

}

}

3、增加AMFContext文件

package soft.flex.context;

import javax.servlet.ServletContext;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;

public class AMFContext {

/**
* ThreadLocal object for storing object in current thread.
*/
@SuppressWarnings("unchecked")
private static ThreadLocal tl = new ThreadLocal();

/**
* Set current context
* 
* @param request
*            The HttpRequest object
* @param response
*            The HttpResponses object
*/
@SuppressWarnings("unchecked")
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);
}

}

4、增加FlexSessionInterceptor文件

package soft.flex.context;

import javax.servlet.http.HttpServletRequest;

import org.aopalliance.intercept.MethodInterceptor;
import org.aopalliance.intercept.MethodInvocation;

import soft.common.util.Constants;

public class FlexSessionInterceptor implements MethodInterceptor {

public Object invoke(MethodInvocation invocation) throws Throwable {

   AMFContext context = AMFContext.getCurrentContext();
   HttpServletRequest request = context.getRequest();
   if (request.getSession().getAttribute(Constants.LOGIN_USER_INFO) == null) {
    throw new Exception("Session超时，请您重新登陆！");
   }
   return invocation.proceed();
}
}

5、在applicationContext.xml增加以下内容

<!-- 配置SessionAdvice -->
<bean id="sessionAdvice" class="soft.flex.context.FlexSessionInterceptor" />

    <!-- 配置自动代理 -->
    <bean id="beanNameAutoProxyCreator"
    class="org.springframework.aop.framework.autoproxy.BeanNameAutoProxyCreator">
    <property name="beanNames">
       <list>
        <value>formDesignerService</value>
       </list>
    </property>
    <property name="interceptorNames">
       <value>sessionAdvice</value>
    </property>
    </bean>

这样子的话，在所有的flex请求中都会先执行FlexSessionInterceptor类中的invoke方法如果要在任何java类中获取sessionr的话，使用AMFContext.getCurrentContext().getSession()即可。
其实就是用ThreadLocal这个jdk1.5中的本地线程类完成的。