淺談Tomcat Session管理分析

protected Session doGetSession(boolean create) {
 
  // There cannot be a session if no context has been assigned yet
  Context context = getContext();
  if (context == null) {
    return (null);
  }
 
  // Return the current session if it exists and is valid
  if ((session != null) && !session.isValid()) {
    session = null;
  }
  if (session != null) {
    return (session);
  }
 
  // Return the requested session if it exists and is valid
  Manager manager = context.getManager();
  if (manager == null) {
    return null;    // Sessions are not supported
  }
  if (requestedSessionId != null) {
    try {
      session = manager.findSession(requestedSessionId);
    } catch (IOException e) {
      session = null;
    }
    if ((session != null) && !session.isValid()) {
      session = null;
    }
    if (session != null) {
      session.access();
      return (session);
    }
  }
 
  // Create a new session if requested and the response is not committed
  if (!create) {
    return (null);
  }
  if ((response != null) &&
      context.getServletContext().getEffectiveSessionTrackingModes().
      contains(SessionTrackingMode.COOKIE) &&
      response.getResponse().isCommitted()) {
    throw new IllegalStateException
    (sm.getString("coyoteRequest.sessionCreateCommitted"));
  }
 
  // Re-use session IDs provided by the client in very limited
  // circumstances.
  String sessionId = getRequestedSessionId();
  if (requestedSessionSSL) {
    // If the session ID has been obtained from the SSL handshake then
    // use it.
  } else if (("/".equals(context.getSessionCookiePath())
      && isRequestedSessionIdFromCookie())) {
    /* This is the common(ish) use case: using the same session ID with
     * multiple web applications on the same host. Typically this is
     * used by Portlet implementations. It only works if sessions are
     * tracked via cookies. The cookie must have a path of "/" else it
     * won't be provided for requests to all web applications.
     *
     * Any session ID provided by the client should be for a session
     * that already exists somewhere on the host. Check if the context
     * is configured for this to be confirmed.
     */
    if (context.getValidateClientProvidedNewSessionId()) {
      boolean found = false;
      for (Container container : getHost().findChildren()) {
        Manager m = ((Context) container).getManager();
        if (m != null) {
          try {
            if (m.findSession(sessionId) != null) {
              found = true;
              break;
            }
          } catch (IOException e) {
            // Ignore. Problems with this manager will be
            // handled elsewhere.
          }
        }
      }
      if (!found) {
        sessionId = null;
      }
    }
  } else {
    sessionId = null;
  }
  session = manager.createSession(sessionId);
 
  // Creating a new session cookie based on that session
  if ((session != null) && (getContext() != null)
      && getContext().getServletContext().
      getEffectiveSessionTrackingModes().contains(
          SessionTrackingMode.COOKIE)) {
    Cookie cookie =
        ApplicationSessionCookieConfig.createSessionCookie(
            context, session.getIdInternal(), isSecure());
 
    response.addSessionCookieInternal(cookie);
  }
 
  if (session == null) {
    return null;
  }
 
  session.access();
  return session;
}

String sessionID;
if (request.getServletContext().getEffectiveSessionTrackingModes()
    .contains(SessionTrackingMode.URL)) {
 
  // Get the session ID if there was one
  sessionID = request.getPathParameter(
      SessionConfig.getSessionUriParamName(
          request.getContext()));
  if (sessionID != null) {
    request.setRequestedSessionId(sessionID);
    request.setRequestedSessionURL(true);
  }
}
 
// Look for session ID in cookies and SSL session
parseSessionCookiesId(req, request);

String sessionCookieName = SessionConfig.getSessionCookieName(context);
 
for (int i = 0; i < count; i++) {
  ServerCookie scookie = serverCookies.getCookie(i);
  if (scookie.getName().equals(sessionCookieName)) {
    // Override anything requested in the URL
    if (!request.isRequestedSessionIdFromCookie()) {
      // Accept only the first session id cookie
      convertMB(scookie.getValue());
      request.setRequestedSessionId
        (scookie.getValue().toString());
      request.setRequestedSessionCookie(true);
      request.setRequestedSessionURL(false);
      if (log.isDebugEnabled()) {
        log.debug(" Requested cookie session id is " +
          request.getRequestedSessionId());
      }
    } else {
      if (!request.isRequestedSessionIdValid()) {
        // Replace the session id until one is valid
        convertMB(scookie.getValue());
        request.setRequestedSessionId
          (scookie.getValue().toString());
      }
    }
  }
}

protected Map<String, Session> sessions = new ConcurrentHashMap<String, Session>();
 
public Session findSession(String id) throws IOException {
  if (id == null) {
    return null;
  }
  return sessions.get(id);
}

public Session createSession(String sessionId) {
   
  if ((maxActiveSessions >= 0) &&
      (getActiveSessions() >= maxActiveSessions)) {
    rejectedSessions++;
    throw new TooManyActiveSessionsException(
        sm.getString("managerBase.createSession.ise"),
        maxActiveSessions);
  }
   
  // Recycle or create a Session instance
  Session session = createEmptySession();
 
  // Initialize the properties of the new session and return it
  session.setNew(true);
  session.setValid(true);
  session.setCreationTime(System.currentTimeMillis());
  session.setMaxInactiveInterval(((Context) getContainer()).getSessionTimeout() * 60);
  String id = sessionId;
  if (id == null) {
    id = generateSessionId();
  }
  session.setId(id);
  sessionCounter++;
 
  SessionTiming timing = new SessionTiming(session.getCreationTime(), 0);
  synchronized (sessionCreationTiming) {
    sessionCreationTiming.add(timing);
    sessionCreationTiming.poll();
  }
  return (session);
 
}

public void setId(String id, boolean notify) {
 
  if ((this.id != null) && (manager != null))
    manager.remove(this);
 
  this.id = id;
 
  if (manager != null)
    manager.add(this);
 
  if (notify) {
    tellNew();
  }
}

protected class ContainerBackgroundProcessor implements Runnable {
 
   @Override
   public void run() {
     Throwable t = null;
     String unexpectedDeathMessage = sm.getString(
         "containerBase.backgroundProcess.unexpectedThreadDeath",
         Thread.currentThread().getName());
     try {
       while (!threadDone) {
         try {
           Thread.sleep(backgroundProcessorDelay * 1000L);
         } catch (InterruptedException e) {
           // Ignore
         }
         if (!threadDone) {
           Container parent = (Container) getMappingObject();
           ClassLoader cl =
             Thread.currentThread().getContextClassLoader();
           if (parent.getLoader() != null) {
             cl = parent.getLoader().getClassLoader();
           }
           processChildren(parent, cl);
         }
       }
     } catch (RuntimeException e) {
       t = e;
       throw e;
     } catch (Error e) {
       t = e;
       throw e;
     } finally {
       if (!threadDone) {
         log.error(unexpectedDeathMessage, t);
       }
     }
   }
 
   protected void processChildren(Container container, ClassLoader cl) {
     try {
       if (container.getLoader() != null) {
         Thread.currentThread().setContextClassLoader
           (container.getLoader().getClassLoader());
       }
       container.backgroundProcess();
     } catch (Throwable t) {
       ExceptionUtils.handleThrowable(t);
       log.error("Exception invoking periodic operation: ", t);
     } finally {
       Thread.currentThread().setContextClassLoader(cl);
     }
     Container[] children = container.findChildren();
     for (int i = 0; i < children.length; i++) {
       if (children[i].getBackgroundProcessorDelay() <= 0) {
         processChildren(children[i], cl);
       }
     }
   }
 }

public void backgroundProcess() {
  count = (count + 1) % processExpiresFrequency;
  if (count == 0)
    processExpires();
}
 
/**
 * Invalidate all sessions that have expired.
 */
public void processExpires() {
 
  long timeNow = System.currentTimeMillis();
  Session sessions[] = findSessions();
  int expireHere = 0 ;
   
  if(log.isDebugEnabled())
    log.debug("Start expire sessions " + getName() + " at " + timeNow + " sessioncount " + sessions.length);
  for (int i = 0; i < sessions.length; i++) {
    if (sessions[i]!=null && !sessions[i].isValid()) {
      expireHere++;
    }
  }
  long timeEnd = System.currentTimeMillis();
  if(log.isDebugEnabled())
     log.debug("End expire sessions " + getName() + " processingTime " + (timeEnd - timeNow) + " expired sessions: " + expireHere);
  processingTime += ( timeEnd - timeNow );
 
}

public boolean isValid() {
 
  if (!this.isValid) {
    return false;
  }
 
  if (this.expiring) {
    return true;
  }
 
  if (ACTIVITY_CHECK && accessCount.get() > 0) {
    return true;
  }
 
  if (maxInactiveInterval > 0) {
    long timeNow = System.currentTimeMillis();
    int timeIdle;
    if (LAST_ACCESS_AT_START) {
      timeIdle = (int) ((timeNow - lastAccessedTime) / 1000L);
    } else {
      timeIdle = (int) ((timeNow - thisAccessedTime) / 1000L);
    }
    if (timeIdle >= maxInactiveInterval) {
      expire(true);
    }
  }
 
  return this.isValid;
}

public Session findSession(String id) throws IOException {
  RedisSession session = null;
 
  if (null == id) {
   currentSessionIsPersisted.set(false);
   currentSession.set(null);
   currentSessionSerializationMetadata.set(null);
   currentSessionId.set(null);
  } else if (id.equals(currentSessionId.get())) {
   session = currentSession.get();
  } else {
   byte[] data = loadSessionDataFromRedis(id);
   if (data != null) {
    DeserializedSessionContainer container = sessionFromSerializedData(id, data);
    session = container.session;
    currentSession.set(session);
    currentSessionSerializationMetadata.set(container.metadata);
    currentSessionIsPersisted.set(true);
    currentSessionId.set(id);
   } else {
    currentSessionIsPersisted.set(false);
    currentSession.set(null);
    currentSessionSerializationMetadata.set(null);
    currentSessionId.set(null);
   }
  }

public void deserializeInto(byte[] data, RedisSession session, SessionSerializationMetadata metadata)
    throws IOException, ClassNotFoundException {
  BufferedInputStream bis = new BufferedInputStream(new ByteArrayInputStream(data));
  Throwable arg4 = null;
 
  try {
    CustomObjectInputStream x2 = new CustomObjectInputStream(bis, this.loader);
    Throwable arg6 = null;
 
    try {
      SessionSerializationMetadata x21 = (SessionSerializationMetadata) x2.readObject();
      metadata.copyFieldsFrom(x21);
      session.readObjectData(x2);
    } catch (Throwable arg29) {
  ......
}

// Ensure generation of a unique session identifier.
if (null != requestedSessionId) {
 sessionId = sessionIdWithJvmRoute(requestedSessionId, jvmRoute);
 if (jedis.setnx(sessionId.getBytes(), NULL_SESSION) == 0L) {
  sessionId = null;
 }
} else {
 do {
  sessionId = sessionIdWithJvmRoute(generateSessionId(), jvmRoute);
 } while (jedis.setnx(sessionId.getBytes(), NULL_SESSION) == 0L); // 1 = key set; 0 = key already existed
}

protected boolean saveInternal(Jedis jedis, Session session, boolean forceSave) throws IOException {
  Boolean error = true;
 
  try {
   log.trace("Saving session " + session + " into Redis");
 
   RedisSession redisSession = (RedisSession)session;
 
   if (log.isTraceEnabled()) {
    log.trace("Session Contents [" + redisSession.getId() + "]:");
    Enumeration en = redisSession.getAttributeNames();
    while(en.hasMoreElements()) {
     log.trace(" " + en.nextElement());
    }
   }
 
   byte[] binaryId = redisSession.getId().getBytes();
 
   Boolean isCurrentSessionPersisted;
   SessionSerializationMetadata sessionSerializationMetadata = currentSessionSerializationMetadata.get();
   byte[] originalSessionAttributesHash = sessionSerializationMetadata.getSessionAttributesHash();
   byte[] sessionAttributesHash = null;
   if (
      forceSave
      || redisSession.isDirty()
      || null == (isCurrentSessionPersisted = this.currentSessionIsPersisted.get())
      || !isCurrentSessionPersisted
      || !Arrays.equals(originalSessionAttributesHash, (sessionAttributesHash = serializer.attributesHashFrom(redisSession)))
     ) {
 
    log.trace("Save was determined to be necessary");
 
    if (null == sessionAttributesHash) {
     sessionAttributesHash = serializer.attributesHashFrom(redisSession);
    }
 
    SessionSerializationMetadata updatedSerializationMetadata = new SessionSerializationMetadata();
    updatedSerializationMetadata.setSessionAttributesHash(sessionAttributesHash);
 
    jedis.set(binaryId, serializer.serializeFrom(redisSession, updatedSerializationMetadata));
 
    redisSession.resetDirtyTracking();
    currentSessionSerializationMetadata.set(updatedSerializationMetadata);
    currentSessionIsPersisted.set(true);
   } else {
    log.trace("Save was determined to be unnecessary");
   }
 
   log.trace("Setting expire timeout on session [" + redisSession.getId() + "] to " + getMaxInactiveInterval());
   jedis.expire(binaryId, getMaxInactiveInterval());
 
   error = false;
 
   return error;
  } catch (IOException e) {
   log.error(e.getMessage());
 
   throw e;
  } finally {
   return error;
  }
 }

public Boolean isDirty() {
  return Boolean.valueOf(this.dirty.booleanValue() || !this.changedAttributes.isEmpty());
}

public void processExpires() {
}

jedis.expire(binaryId, getMaxInactiveInterval());