深入浅析TomCat Session管理分析

@Override
  protected synchronized void startInternal() throws LifecycleException {
    // 省略与Session管理无关的代码
        // Acquire clustered manager
        Manager contextManager = null;
        if (manager == null) {
          if ( (getCluster() != null) && distributable) {
            try {
              contextManager = getCluster().createManager(getName());
            } catch (Exception ex) {
              log.error("standardContext.clusterFail", ex);
              ok = false;
            }
          } else {
            contextManager = new StandardManager();
          }
        } 
        // Configure default manager if none was specified
        if (contextManager != null) {
          setManager(contextManager);
        }
        if (manager!=null && (getCluster() != null) && distributable) {
          //let the cluster know that there is a context that is distributable
          //and that it has its own manager
          getCluster().registerManager(manager);
        }
 　　　　// 省略与Session管理无关的代码
      try {
        // Start manager
        if ((manager != null) && (manager instanceof Lifecycle)) {
          ((Lifecycle) getManager()).start();
        }
        // Start ContainerBackgroundProcessor thread
        super.threadStart();
      } catch(Exception e) {
        log.error("Error manager.start()", e);
        ok = false;
      }
 　　　　// 省略与Session管理无关的代码
  }

@Override
  public synchronized final void start() throws LifecycleException {
    //省略状态校验的代码if (state.equals(LifecycleState.NEW)) {
      init();
    } else if (!state.equals(LifecycleState.INITIALIZED) &&
        !state.equals(LifecycleState.STOPPED)) {
      invalidTransition(Lifecycle.BEFORE_START_EVENT);
    }
    setState(LifecycleState.STARTING_PREP);
    try {
      startInternal();
    } catch (LifecycleException e) {
      setState(LifecycleState.FAILED);
      throw e;
    }
    if (state.equals(LifecycleState.FAILED) ||
        state.equals(LifecycleState.MUST_STOP)) {
      stop();
    } else {
      // Shouldn't be necessary but acts as a check that sub-classes are
      // doing what they are supposed to.
      if (!state.equals(LifecycleState.STARTING)) {
        invalidTransition(Lifecycle.AFTER_START_EVENT);
      }
      setState(LifecycleState.STARTED);
    }
  }

 @Override
  protected void initInternal() throws LifecycleException {
    super.initInternal();
    setDistributable(((Context) getContainer()).getDistributable());
    // Initialize random number generation
    getRandomBytes(new byte[16]);
  }

 protected void getRandomBytes(byte bytes[]) {
    // Generate a byte array containing a session identifier
    if (devRandomSource != null && randomIS == null) {
      setRandomFile(devRandomSource);
    }
    if (randomIS != null) {
      try {
        int len = randomIS.read(bytes);
        if (len == bytes.length) {
          return;
        }
        if(log.isDebugEnabled())
          log.debug("Got " + len + " " + bytes.length );
      } catch (Exception ex) {
        // Ignore
      }
      devRandomSource = null;
      try {
        randomIS.close();
      } catch (Exception e) {
        log.warn("Failed to close randomIS.");
      }
      randomIS = null;
    }
    getRandom().nextBytes(bytes);
  }

public void setRandomFile( String s ) {
    // as a hack, you can use a static file - and generate the same
    // session ids ( good for strange debugging )
    if (Globals.IS_SECURITY_ENABLED){
      randomIS = AccessController.doPrivileged(new PrivilegedSetRandomFile(s));
    } else {
      try{
        devRandomSource=s;
        File f=new File( devRandomSource );
        if( ! f.exists() ) return;
        randomIS= new DataInputStream( new FileInputStream(f));
        randomIS.readLong();
        if( log.isDebugEnabled() )
          log.debug( "Opening " + devRandomSource );
      } catch( IOException ex ) {
        log.warn("Error reading " + devRandomSource, ex);
        if (randomIS != null) {
          try {
            randomIS.close();
          } catch (Exception e) {
            log.warn("Failed to close randomIS.");
          }
        }
        devRandomSource = null;
        randomIS=null;
      }
    }
  }

public Random getRandom() {
    if (this.random == null) {
      // Calculate the new random number generator seed
      long seed = System.currentTimeMillis();
      long t1 = seed;
      char entropy[] = getEntropy().toCharArray();
      for (int i = 0; i < entropy.length; i++) {
        long update = ((byte) entropy[i]) << ((i % 8) * 8);
        seed ^= update;
      }
      try {
        // Construct and seed a new random number generator
        Class<?> clazz = Class.forName(randomClass);
        this.random = (Random) clazz.newInstance();
        this.random.setSeed(seed);
      } catch (Exception e) {
        // Fall back to the simple case
        log.error(sm.getString("managerBase.random", randomClass),
            e);
        this.random = new java.util.Random();
        this.random.setSeed(seed);
      }
      if(log.isDebugEnabled()) {
        long t2=System.currentTimeMillis();
        if( (t2-t1) > 100 )
          log.debug(sm.getString("managerBase.seeding", randomClass) + " " + (t2-t1));
      }
    }
    return (this.random);
  }

 @Override
  protected synchronized void startInternal() throws LifecycleException {
    // Force initialization of the random number generator
    if (log.isDebugEnabled())
      log.debug("Force random number initialization starting");
    generateSessionId();
    if (log.isDebugEnabled())
      log.debug("Force random number initialization completed");
    // Load unloaded sessions, if any
    try {
      load();
    } catch (Throwable t) {
      log.error(sm.getString("standardManager.managerLoad"), t);
    }
    setState(LifecycleState.STARTING);
  }

protected synchronized String generateSessionId() {
    byte random[] = new byte[16];
    String jvmRoute = getJvmRoute();
    String result = null;
    // Render the result as a String of hexadecimal digits
    StringBuilder buffer = new StringBuilder();
    do {
      int resultLenBytes = 0;
      if (result != null) {
        buffer = new StringBuilder();
        duplicates++;
      }
      while (resultLenBytes < this.sessionIdLength) {
        getRandomBytes(random);
        random = getDigest().digest(random);
        for (int j = 0;
        j < random.length && resultLenBytes < this.sessionIdLength;
        j++) {
          byte b1 = (byte) ((random[j] & 0xf0) >> 4);
          byte b2 = (byte) (random[j] & 0x0f);
          if (b1 < 10)
            buffer.append((char) ('0' + b1));
          else
            buffer.append((char) ('A' + (b1 - 10)));
          if (b2 < 10)
            buffer.append((char) ('0' + b2));
          else
            buffer.append((char) ('A' + (b2 - 10)));
          resultLenBytes++;
        }
      }
      if (jvmRoute != null) {
        buffer.append('.').append(jvmRoute);
      }
      result = buffer.toString();
    } while (sessions.containsKey(result));
    return (result);
  }

 public void load() throws ClassNotFoundException, IOException {
    if (SecurityUtil.isPackageProtectionEnabled()){
      try{
        AccessController.doPrivileged( new PrivilegedDoLoad() );
      } catch (PrivilegedActionException ex){
        Exception exception = ex.getException();
        if (exception instanceof ClassNotFoundException){
          throw (ClassNotFoundException)exception;
        } else if (exception instanceof IOException){
          throw (IOException)exception;
        }
        if (log.isDebugEnabled())
          log.debug("Unreported exception in load() "
            + exception);
      }
    } else {
      doLoad();
    }
  }

 private class PrivilegedDoLoad
    implements PrivilegedExceptionAction<Void> {
    PrivilegedDoLoad() {
      // NOOP
    }
    public Void run() throws Exception{
      doLoad();
      return null;
    }
  }

 protected void doLoad() throws ClassNotFoundException, IOException {
    if (log.isDebugEnabled())
      log.debug("Start: Loading persisted sessions");
    // Initialize our internal data structures
    sessions.clear();
    // Open an input stream to the specified pathname, if any
    File file = file();
    if (file == null)
      return;
    if (log.isDebugEnabled())
      log.debug(sm.getString("standardManager.loading", pathname));
    FileInputStream fis = null;
    BufferedInputStream bis = null;
    ObjectInputStream ois = null;
    Loader loader = null;
    ClassLoader classLoader = null;
    try {
      fis = new FileInputStream(file.getAbsolutePath());
      bis = new BufferedInputStream(fis);
      if (container != null)
        loader = container.getLoader();
      if (loader != null)
        classLoader = loader.getClassLoader();
      if (classLoader != null) {
        if (log.isDebugEnabled())
          log.debug("Creating custom object input stream for class loader ");
        ois = new CustomObjectInputStream(bis, classLoader);
      } else {
        if (log.isDebugEnabled())
          log.debug("Creating standard object input stream");
        ois = new ObjectInputStream(bis);
      }
    } catch (FileNotFoundException e) {
      if (log.isDebugEnabled())
        log.debug("No persisted data file found");
      return;
    } catch (IOException e) {
      log.error(sm.getString("standardManager.loading.ioe", e), e);
      if (fis != null) {
        try {
          fis.close();
        } catch (IOException f) {
          // Ignore
        }
      }
      if (bis != null) {
        try {
          bis.close();
        } catch (IOException f) {
          // Ignore
        }
      }
      throw e;
    }
    // Load the previously unloaded active sessions
    synchronized (sessions) {
      try {
        Integer count = (Integer) ois.readObject();
        int n = count.intValue();
        if (log.isDebugEnabled())
          log.debug("Loading " + n + " persisted sessions");
        for (int i = 0; i < n; i++) {
          StandardSession session = getNewSession();
          session.readObjectData(ois);
          session.setManager(this);
          sessions.put(session.getIdInternal(), session);
          session.activate();
          if (!session.isValidInternal()) {
            // If session is already invalid,
            // expire session to prevent memory leak.
            session.setValid(true);
            session.expire();
          }
          sessionCounter++;
        }
      } catch (ClassNotFoundException e) {
        log.error(sm.getString("standardManager.loading.cnfe", e), e);
        try {
          ois.close();
        } catch (IOException f) {
          // Ignore
        }
        throw e;
      } catch (IOException e) {
        log.error(sm.getString("standardManager.loading.ioe", e), e);
        try {
          ois.close();
        } catch (IOException f) {
          // Ignore
        }
        throw e;
      } finally {
        // Close the input stream
        try {
          ois.close();
        } catch (IOException f) {
          // ignored
        }
        // Delete the persistent storage file
        if (file.exists() )
          file.delete();
      }
    }
    if (log.isDebugEnabled())
      log.debug("Finish: Loading persisted sessions");
  }