red5源码分析—服务器处理createStream命令

服务器接到createStream命令后，经过过滤器层层处理，最后会调用BaseRTMPHandler的messageReceived函数，

    public void messageReceived(RTMPConnection conn, Packet packet) throws Exception {
        if (conn != null) {
            IRTMPEvent message = null;
            try {
                message = packet.getMessage();
                final Header header = packet.getHeader();
                final Number streamId = header.getStreamId();
                final Channel channel = conn.getChannel(header.getChannelId());
                final IClientStream stream = conn.getStreamById(streamId);
                conn.setStreamId(streamId);
                conn.messageReceived();
                message.setSource(conn);
                final byte headerDataType = header.getDataType();
                switch (headerDataType) {
                    ...
                    case TYPE_INVOKE:
                    case TYPE_FLEX_MESSAGE:
                        onCommand(conn, channel, header, (Invoke) message);
                        IPendingServiceCall call = ((Invoke) message).getCall();
                        if (message.getHeader().getStreamId().intValue() != 0 && call.getServiceName() == null && StreamAction.PUBLISH.equals(call.getServiceMethodName())) {
                            if (stream != null) {
                                ((IEventDispatcher) stream).dispatchEvent(message);
                            }
                        }
                        break;
                    ...
                    default:
                }
                if (message instanceof Unknown) {

                }
            } catch (Throwable t) {

            }
            ...
        }
    }

createStream命令的消息属于TYPE_INVOKE消息，最后会调用onCommand函数，onCommand定义在RTMPHandler中，在《red5源码分析—5》中已经介绍了一部分OnCommand的代码，现在看另一部分，

    protected void onCommand(RTMPConnection conn, Channel channel, Header source, ICommand command) {
        final IServiceCall call = command.getCall();
        final String action = call.getServiceMethodName();
        if ("_result".equals(action) || "_error".equals(action)) {
            handlePendingCallResult(conn, (Invoke) command);
            return;
        }
        boolean disconnectOnReturn = false;
        boolean connected = conn.isConnected();
        if (connected) {
            if (call.getServiceName() == null) {
                StreamAction streamAction = StreamAction.getEnum(action);
                if (dispatchStreamActions) {
                    try {
                        conn.getScope().getHandler().handleEvent(new StreamActionEvent(streamAction));
                    } catch (Exception ex) {

                    }
                }
                switch (streamAction) {
                    case DISCONNECT:
                        conn.close();
                        break;
                    case CREATE_STREAM:
                    case INIT_STREAM:
                    case CLOSE_STREAM:
                    case RELEASE_STREAM:
                    case DELETE_STREAM:
                    case PUBLISH:
                    case PLAY:
                    case PLAY2:
                    case SEEK:
                    case PAUSE:
                    case PAUSE_RAW:
                    case RECEIVE_VIDEO:
                    case RECEIVE_AUDIO:
                        IStreamService streamService = (IStreamService) ScopeUtils.getScopeService(conn.getScope(), IStreamService.class, StreamService.class);
                        try {
                            if (invokeCall(conn, call, streamService)) {

                            } else {

                            }
                        } catch (Throwable err) {
                            ...
                        }
                        break;
                    default:
                        invokeCall(conn, call);
                }
            } else {
                invokeCall(conn, call);
            }
        } else {
             ...
        }
        if (command instanceof Invoke) {
            if ((source.getStreamId().intValue() != 0) && (call.getStatus() == Call.STATUS_SUCCESS_VOID || call.getStatus() == Call.STATUS_SUCCESS_NULL)) {
                return;
            }
            boolean sendResult = true;
            if (call instanceof IPendingServiceCall) {
                IPendingServiceCall psc = (IPendingServiceCall) call;
                Object result = psc.getResult();
                if (result instanceof DeferredResult) {
                    DeferredResult dr = (DeferredResult) result;
                    dr.setServiceCall(psc);
                    dr.setChannel(channel);
                    dr.setTransactionId(command.getTransactionId());
                    conn.registerDeferredResult(dr);
                    sendResult = false;
                }
            }
            if (sendResult) {
                Invoke reply = new Invoke();
                reply.setCall(call);
                reply.setTransactionId(command.getTransactionId());
                channel.write(reply);
                if (disconnectOnReturn) {
                    conn.close();
                }
            }
        }
    }

OnCommand的前后两部分代码都在《red5源码分析—5》中看过了，不同之处是这里已经与某个服务器的Scope连接了，因此isConnected返回true。再往下就是调用ScopeUtils的getScopeService获得StreamService，getScopeService的定义如下

    public static Object getScopeService(IScope scope, Class<?> intf, Class<?> defaultClass, boolean checkHandler) {

        String attr = IPersistable.TRANSIENT_PREFIX + SERVICE_CACHE_PREFIX + intf.getCanonicalName();
        if (scope.hasAttribute(attr)) {
            return scope.getAttribute(attr);
        }

        Object handler = null;
        if (checkHandler) {
            IScope current = scope;
            while (current != null) {
                IScopeHandler scopeHandler = current.getHandler();
                if (intf.isInstance(scopeHandler)) {
                    handler = scopeHandler;
                    break;
                }
                if (!current.hasParent()) {
                    break;
                }
                current = current.getParent();
            }
        }

        if (handler == null && IScopeService.class.isAssignableFrom(intf)) {
            Field key = null;
            Object serviceName = null;
            try {
                key = intf.getField("BEAN_NAME");
                serviceName = key.get(null);
                if (serviceName instanceof String) {
                    handler = getScopeService(scope, (String) serviceName, defaultClass);
                }
            } catch (Exception e) {

            }
        }
        if (handler == null && defaultClass != null) {
            try {
                handler = defaultClass.newInstance();
            } catch (Exception e) {

            }
        }
        scope.setAttribute(attr, handler);
        return handler;
    }

首先这里会尝试从Scope的缓存中获取已经实例化的StreamService，如果不行就从该Scope开始一直向其父类寻找其中的handler是不是(根据以前的章节可知道，这时这里基本获得的handler是CoreHandler)，再往下就是查看BEAN_NAME，并尝试通过Spring获得或初始化该类，如果还不行，最后就直接通过Java实例化了。
回到onCommand中，假设获得了StreamService，下面就通过invokeCall开始处理了，

    private boolean invokeCall(RTMPConnection conn, IServiceCall call, Object service) {
        final IScope scope = conn.getScope();
        final IContext context = scope.getContext();
        return context.getServiceInvoker().invoke(call, service);
    }

根据前面几章的分析，这里获得的context为org.red5.server.Context，根据red5-default.xml的配置，getServiceInvoker返回org.red5.server.service.ServiceInvoker，因此下面来看它的invoke函数，

    public boolean invoke(IServiceCall call, Object service) {
        IConnection conn = Red5.getConnectionLocal();
        String methodName = call.getServiceMethodName();
        if (methodName.charAt(0) == ‘@‘) {
            methodName = methodName.substring(1);
        }
        Object[] args = call.getArguments();
        Object[] argsWithConnection;
        if (args != null) {
            argsWithConnection = new Object[args.length + 1];
            argsWithConnection[0] = conn;
            for (int i = 0; i < args.length; i++) {
                argsWithConnection[i + 1] = args[i];
            }
        } else {
            argsWithConnection = new Object[] { conn };
        }
        Object[] methodResult = null;
        methodResult = ReflectionUtils.findMethodWithExactParameters(service, methodName, argsWithConnection);
        if (methodResult.length == 0 || methodResult[0] == null) {
            methodResult = ReflectionUtils.findMethodWithExactParameters(service, methodName, args);
            if (methodResult.length == 0 || methodResult[0] == null) {
                methodResult = ReflectionUtils.findMethodWithListParameters(service, methodName, argsWithConnection);
                if (methodResult.length == 0 || methodResult[0] == null) {
                    methodResult = ReflectionUtils.findMethodWithListParameters(service, methodName, args);
                    if (methodResult.length == 0 || methodResult[0] == null) {
                        call.setStatus(Call.STATUS_METHOD_NOT_FOUND);
                        if (args != null && args.length > 0) {
                            call.setException(new MethodNotFoundException(methodName, args));
                        } else {
                            call.setException(new MethodNotFoundException(methodName));
                        }
                        return false;
                    }
                }
            }
        }
        Object result = null;
        Method method = (Method) methodResult[0];
        Object[] params = (Object[]) methodResult[1];
        try {
            if (method.isAnnotationPresent(DeclarePrivate.class)) {
                throw new NotAllowedException("Access denied, method is private");
            }
            final DeclareProtected annotation = method.getAnnotation(DeclareProtected.class);
            if (annotation != null) {
                if (!conn.getClient().hasPermission(conn, annotation.permission())) {
                    throw new NotAllowedException("Access denied, method is protected");
                }
            }
            if (method.getReturnType().equals(Void.TYPE)) {
                method.invoke(service, params);
                call.setStatus(Call.STATUS_SUCCESS_VOID);
            } else {
                result = method.invoke(service, params);
                call.setStatus(result == null ? Call.STATUS_SUCCESS_NULL : Call.STATUS_SUCCESS_RESULT);
            }
            if (call instanceof IPendingServiceCall) {
                ((IPendingServiceCall) call).setResult(result);
            }
        } catch (Exception e) {
            ...
            return false;
        }
        return true;
    }

这里为方便阅读，对异常部分作了改写。这段代码虽然稍微长点，但是其实做的事情很简单，就是从StreamService中获取方法，并调用该方法，具体的代码可以自己分析了，因为不是只找一次，是一次一次放宽了条件来找，找到方法后，就调用其invoke执行方法，并处理返回值。接下来就是调用StreamService的createStream方法，

    public Number createStream() {
        IConnection conn = Red5.getConnectionLocal();
        if (conn instanceof IStreamCapableConnection) {
            try {
                Number streamId = ((IStreamCapableConnection) conn).reserveStreamId();
                }
                return streamId;
            } catch (IndexOutOfBoundsException e) {
                return -1;
            }
        }
        return -1;
    }

这里会简单调用reserveStreamId获得一个随机的streamId并返回，

    public Number reserveStreamId() {
        double d = 1.0d;
        for (; d < MAX_RESERVED_STREAMS; d++) {
            if (reservedStreams.add(d)) {
                break;
            }
        }
        if (d == MAX_RESERVED_STREAMS) {
            throw new IndexOutOfBoundsException("Unable to reserve new stream");
        }
        return d;
    }

回到前面invoke方法中，最后Call的result里保存了刚刚分配的流的ID，并且状态为STATUS_SUCCESS_RESULT，然后返回给客户端。从这里也可以看出，createStream只负责分配一个ID，没有任何文件的创建、Socket的创建等等的功能。