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在使用flex/as java做项目时 appserver中没有使用到httpSession, 应用服务器提供的httpSession是在用到的时候才会创建, 而blazeds中是不管你需要不需要每一个请求来的时候都会拿到httpSession  新建一个httpFlexSession对象放到threadLocal中去

引发的问题: 在使用集群分发(没有保持会话/session)的时候, 会创建大量并且无用的httpSession对像, 而且httpSession会保持对象(tomcat默认30分钟)很长一段时间,导致appServier内存泄漏

解决方案:

① 缩短httpSession对象保持的时间, 在用户量到一定数量的时候不再起做用

②关闭blazeds的httpFlexSession的创建, 不过blazeds本身并没有提供关闭session的支持 这个时候就需要自己去更改blazeds的源码, 或者自己创建一个messageBrokerServlet. 下面附上修改过后的messgeBrokerServlet(包名必须用flex.messaging, 这里边有用到一个flex.messaging下面另外一个类的一个protected方法)

package flex.messaging;

import java.io.IOException;

import java.io.InputStream;

import java.security.Principal;

import javax.servlet.ServletConfig;

import javax.servlet.ServletException;

import javax.servlet.UnavailableException;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

import edu.emory.mathcs.backport.java.util.concurrent.ConcurrentHashMap;

import flex.messaging.config.ChannelSettings;

import flex.messaging.config.ConfigMap;

import flex.messaging.config.ConfigurationManager;

import flex.messaging.config.FlexConfigurationManager;

import flex.messaging.config.MessagingConfiguration;

import flex.messaging.endpoints.Endpoint;

import flex.messaging.log.Log;

import flex.messaging.log.LogCategories;

import flex.messaging.log.Logger;

import flex.messaging.log.ServletLogTarget;

import flex.messaging.services.AuthenticationService;

import flex.messaging.util.ClassUtil;

import flex.messaging.util.ExceptionUtil;

import flex.messaging.util.Trace;

public class MessageBrokerServlet4Self extends MessageBrokerServlet {

private static final long serialVersionUID = -2509928967558653217L;

private MessageBroker broker;

private static String FLEXDIR = "/WEB-INF/flex/";

private boolean enableFlexSession = false;//关闭httpFlexSession的标志(增加的代码)

//由于继承了messageBrokerServlet 没有办法在init的时候使用super(servletConfig)所以增加了一个属性

//当然也可以不用继承messageBrokerServlet 那样必须把blazeds中messageBrokerServlet中的代码都copy过来

//在这里我只copy了init和service方法 并增加对httpFlexSession的关闭代码

private transient ServletConfig config;

public ServletConfig getConfig() {

return config;

}

/**

* Initializes the servlet in its web container, then creates

* the MessageBroker and adds Endpoints and Services to that broker.

* This servlet may keep a reference to an endpoint if it needs to

* delegate to it in the service method.

*/

public void init(ServletConfig servletConfig) throws ServletException, UnavailableException{

config = servletConfig;//super.init(servletConfig)改为自己的属性

// allocate thread local variables

createThreadLocals();

// Set the servlet config as thread local

FlexContext.setThreadLocalObjects(null, null, null, null, null, servletConfig);

ServletLogTarget.setServletContext(servletConfig.getServletContext());

ClassLoader loader = getClassLoader();

String useCCLoader;

if ((useCCLoader = servletConfig.getInitParameter("useContextClassLoader")) != null &&

useCCLoader.equalsIgnoreCase("true"))

loader = Thread.currentThread().getContextClassLoader();

// Start the broker

try{

// Get the configuration manager

ConfigurationManager configManager = loadMessagingConfiguration(servletConfig);

// Load configuration

MessagingConfiguration config = configManager.getMessagingConfiguration(servletConfig);

// Set up logging system ahead of everything else.

config.createLogAndTargets();

// Create broker.

broker = config.createBroker(servletConfig.getInitParameter("messageBrokerId"), loader);

// Set the servlet config as thread local

FlexContext.setThreadLocalObjects(null, null, broker, null, null, servletConfig);

setupInternalPathResolver();

// Set initial servlet context on broker

broker.setInitServletContext(servletConfig.getServletContext());

Logger logger = Log.getLogger(ConfigurationManager.LOG_CATEGORY);

if (Log.isInfo()) {

logger.info(VersionInfo.buildMessage());

}

// Create endpoints, services, security, and logger on the broker based on configuration

config.configureBroker(broker);

long timeBeforeStartup = 0;

if (Log.isDebug()) {

timeBeforeStartup = System.currentTimeMillis();

Log.getLogger(LOG_CATEGORY_STARTUP_BROKER).debug("MessageBroker with id '{0}' is starting.", new Object[] { broker.getId() });

}

//initialize the httpSessionToFlexSessionMap

synchronized (HttpFlexSession.mapLock) {

if (servletConfig.getServletContext().getAttribute(HttpFlexSession.SESSION_MAP) == null)

servletConfig.getServletContext().setAttribute(HttpFlexSession.SESSION_MAP, new ConcurrentHashMap());

}

broker.start();

if (Log.isDebug()) {

long timeAfterStartup = System.currentTimeMillis();

Long diffMillis = new Long(timeAfterStartup - timeBeforeStartup);

Log.getLogger(LOG_CATEGORY_STARTUP_BROKER).debug("MessageBroker with id '{0}' is ready (startup time: '{1}' ms)",

new Object[] { broker.getId(), diffMillis });

}

//以下是从service-config.xml中取得是否需要开启httpFlexSession的配置

//配置的标签为flexSession-enabled

//channel-amf为配置该标签地方的id属性的值(channle-amf是配置文件中提供的一个默认的id)

//读取到了该配置就可以在service方法中控制httpFlexSession是否关闭了

ChannelSettings channelSettings = config.getChannelSettings("channel-amf");

ConfigMap properties = channelSettings.getProperties();

String str = (String) properties.get("flexSession-enabled");

if(str != null){

enableFlexSession = Boolean.valueOf(str);

}

// Report replaced tokens

configManager.reportTokens();

// Report any unused properties.

config.reportUnusedProperties();

// clear the broker and servlet config as this thread is done

FlexContext.clearThreadLocalObjects();

}

catch (Throwable t) {

// On any unhandled exception destroy the broker, log it and

// rethrow.

System.err.println("**** MessageBrokerServlet failed to initialize due to runtime exception: "

+ ExceptionUtil.exceptionFollowedByRootCausesToString(t));

destroy();

throw new UnavailableException(t.getMessage());

}

}

private void setupInternalPathResolver() {

broker.setInternalPathResolver(new MessageBroker.InternalPathResolver() {

public InputStream resolve(String filename) {

InputStream is = getServletContext().getResourceAsStream(FLEXDIR + filename);

return is;

}

});

}

@SuppressWarnings("unchecked")

private ConfigurationManager loadMessagingConfiguration(ServletConfig servletConfig) {

ConfigurationManager manager = null;

Class managerClass = null;

String className = null;

// Check for Custom Configuration Manager Specification

if (servletConfig != null) {

String p = servletConfig.getInitParameter("services.configuration.manager");

if (p != null) {

className = p.trim();

try {

managerClass = ClassUtil.createClass(className);

manager = (ConfigurationManager) managerClass.newInstance();

} catch (Throwable t) {

if (Trace.config) // Log is not initialized yet.

Trace.trace("Could not load configuration manager as: " + className);

}

}

}

if (manager == null) {

manager = (ConfigurationManager) new FlexConfigurationManager();

}

return manager;

}

/**

* Handle an incoming request, and delegate to an endpoint based on

* content type, if appropriate. The content type mappings for endpoints

* are not externally configurable, and currently the AmfEndpoint

* is the only delegate.

*/

public void service(HttpServletRequest req, HttpServletResponse res) {

try {

// Update thread locals

broker.initThreadLocals();

// Set this first so it is in place for the session creation event. The

// current session is set by the FlexSession stuff right when it is available.

// The threadlocal FlexClient is set up during message deserialization in the

// MessageBrokerFilter.

FlexContext.setThreadLocalObjects(null, null, broker, req, res, getServletConfig());

Principal principal = null;

//下面的这段代码是改动了源码的地方

if (FlexContext.isPerClientAuthentication()) {

principal = FlexContext.getUserPrincipal();

} else {

//判断是否需要httpFlexSession如果不需要则不创建httpFlexSession

if (enableFlexSession) {

HttpFlexSession fs = HttpFlexSession.getFlexSession(req);

principal = fs.getUserPrincipal();

}

}

if (principal == null && req.getHeader("Authorization") != null) {

String encoded = req.getHeader("Authorization");

if (encoded.indexOf("Basic") > -1) {

encoded = encoded.substring(6); // Basic.length()+1

try {

AuthenticationService.decodeAndLogin(encoded, broker.getLoginManager());

} catch (Exception e) {

if (Log.isDebug())

Log.getLogger(LogCategories.SECURITY).info("Authentication service could not decode and login: " + e.getMessage());

}

}

}

String contextPath = req.getContextPath();

String pathInfo = req.getPathInfo();

String endpointPath = req.getServletPath();

if (pathInfo != null)

endpointPath = endpointPath + pathInfo;

Endpoint endpoint = null;

try {

endpoint = broker.getEndpoint(endpointPath, contextPath);

} catch (MessageException me) {

if (Log.isInfo())

Log.getLogger(LogCategories.ENDPOINT_GENERAL).info("Received invalid request for endpoint path '{0}'.",

new Object[] { endpointPath });

if (!res.isCommitted()) {

try {

res.sendError(HttpServletResponse.SC_NOT_FOUND);

} catch (IOException ignore) {

}

}

return;

}

try {

if (Log.isInfo()) {

Log.getLogger(LogCategories.ENDPOINT_GENERAL).info("Channel endpoint {0} received request.", new Object[] { endpoint.getId() });

}

endpoint.service(req, res);

} catch (UnsupportedOperationException ue) {

if (Log.isInfo()) {

Log.getLogger(LogCategories.ENDPOINT_GENERAL).info("Channel endpoint {0} received request for an unsupported operation.",

new Object[] { endpoint.getId() }, ue);

}

if (!res.isCommitted()) {

try {

res.sendError(HttpServletResponse.SC_METHOD_NOT_ALLOWED);

} catch (IOException ignore) {

}

}

}

} finally {

FlexContext.clearThreadLocalObjects();

}

}

}

以下是services-config.xml中的配置(当然也可以不配置, 不配置就会使用在代码中设置的默认值)

url="http://{server.name}:{server.port}/{context.root}/messagebroker/amf"

class="flex.messaging.endpoints.AMFEndpoint"/>

false

false

true

这里改动的代码需要把配置写在channel-definition标签并且ID是channel-amf的properties节点下面

当然也改动代码把使用配置可以更灵活

改动到目前就可开启或关闭httpFlexSession了

当然在appservice中的web.xml中启动的servlet就要换成改动之后的servlet了

MessageBrokerServlet

flex.messaging.MessageBrokerServlet4Self

services.configuration.file

/WEB-INF/flex/services-config.xml

flex.write.path

/WEB-INF/flex

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2011-01-15 17:14

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