com.lightstreamer.client

Class LightstreamerClient

java.lang.Object

com.lightstreamer.client.LightstreamerClient

public class LightstreamerClient
extends java.lang.Object

Facade class for the management of the communication to Lightstreamer Server. Used to provide configuration settings, event handlers, operations for the control of the connection lifecycle, Subscription handling and to send messages.
// An instance of LightstreamerClient handles the communication with Lightstreamer Server on a specified endpoint. Hence, it hosts one "Session"; or, more precisely, a sequence of Sessions, since any Session may fail and be recovered, or it can be interrupted on purpose. So, normally, a single instance of LightstreamerClient is needed.
However, multiple instances of LightstreamerClient can be used, toward the same or multiple endpoints. By default, all instances will share the same thread for their internal operations, but can be instructed to use dedicated threads by setting the custom "com.lightstreamer.client.session.thread" system property as "dedicated".

Field Summary

Fields

Modifier and Type	Field and Description
ConnectionDetails	connectionDetails Data object that contains the details needed to open a connection to a Lightstreamer Server.
ConnectionOptions	connectionOptions Data object that contains options and policies for the connection to the server.
static java.lang.String	LIB_NAME A constant string representing the name of the library.
static java.lang.String	LIB_VERSION A constant string representing the version of the library.

Constructor Summary

Constructors

Constructor and Description
LightstreamerClient(java.lang.String serverAddress, java.lang.String adapterSet) Creates an object to be configured to connect to a Lightstreamer server and to handle all the communications with it.

Method Summary

Modifier and Type	Method and Description
static void	addCookies(java.net.URI uri, java.util.List<java.net.HttpCookie> cookies) Static method that can be used to share cookies between connections to the Server (performed by this library) and connections to other sites that are performed by the application.
void	addListener(ClientListener listener) Adds a listener that will receive events from the LightstreamerClient instance.
void	connect() Operation method that requests to open a Session against the configured Lightstreamer Server.
void	disconnect() Operation method that requests to close the Session opened against the configured Lightstreamer Server (if any).
java.util.concurrent.Future<java.lang.Void>	disconnectFuture() Works just like disconnect(), but also returns a Future which is notified when all involved threads started by all LightstreamerClient instances living in the JVM have been terminated, because no more activities need to be managed and hence event dispatching is no longer necessary.
static java.util.List<java.net.HttpCookie>	getCookies(java.net.URI uri) Static inquiry method that can be used to share cookies between connections to the Server (performed by this library) and connections to other sites that are performed by the application.
java.util.List<ClientListener>	getListeners() Returns a list containing the ClientListener instances that were added to this client.
java.lang.String	getStatus() Inquiry method that gets the current client status and transport (when applicable).
java.util.List<Subscription>	getSubscriptions() Inquiry method that returns a list containing all the Subscription instances that are currently "active" on this LightstreamerClient.
void	removeListener(ClientListener listener) Removes a listener from the LightstreamerClient instance so that it will not receive events anymore.
void	sendMessage(java.lang.String message) A simplified version of the sendMessage(String,String,int,ClientMessageListener,boolean).
void	sendMessage(java.lang.String message, java.lang.String sequence, int delayTimeout, ClientMessageListener listener, boolean enqueueWhileDisconnected) Operation method that sends a message to the Server.
static void	setLoggerProvider(com.lightstreamer.log.LoggerProvider provider) Static method that permits to configure the logging system used by the library.
static void	setTrustManagerFactory(javax.net.ssl.TrustManagerFactory factory) Provides a mean to control the way TLS certificates are evaluated, with the possibility to accept untrusted ones.
void	subscribe(Subscription subscription) Operation method that adds a Subscription to the list of "active" Subscriptions.
void	unsubscribe(Subscription subscription) Operation method that removes a Subscription that is currently in the "active" state.

Methods inherited from class java.lang.Object

equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

LIB_NAME

@Nonnull
public static final java.lang.String LIB_NAME

A constant string representing the name of the library.

See Also:

Constant Field Values

LIB_VERSION

@Nonnull
public static final java.lang.String LIB_VERSION

A constant string representing the version of the library.

connectionOptions

@Nonnull
public final ConnectionOptions connectionOptions

Data object that contains options and policies for the connection to the server. This instance is set up by the LightstreamerClient object at its own creation.
Properties of this object can be overwritten by values received from a Lightstreamer Server.

connectionDetails

@Nonnull
public final ConnectionDetails connectionDetails

Data object that contains the details needed to open a connection to a Lightstreamer Server. This instance is set up by the LightstreamerClient object at its own creation.
Properties of this object can be overwritten by values received from a Lightstreamer Server.

Constructor Detail

LightstreamerClient

public LightstreamerClient(@Nullable
                           java.lang.String serverAddress,
                           @Nullable
                           java.lang.String adapterSet)

Creates an object to be configured to connect to a Lightstreamer server and to handle all the communications with it. Each LightstreamerClient is the entry point to connect to a Lightstreamer server, subscribe to as many items as needed and to send messages.

Parameters:

serverAddress - the address of the Lightstreamer Server to which this LightstreamerClient will connect to. It is possible to specify it later by using null here. See ConnectionDetails.setServerAddress(String) for details.

adapterSet - the name of the Adapter Set mounted on Lightstreamer Server to be used to handle all requests in the Session associated with this LightstreamerClient. It is possible not to specify it at all or to specify it later by using null here. See ConnectionDetails.setAdapterSet(String) for details.

Throws:

java.lang.IllegalArgumentException - if a not valid address is passed. See ConnectionDetails.setServerAddress(String) for details.

Method Detail

setLoggerProvider

public static void setLoggerProvider(@Nullable
                                     com.lightstreamer.log.LoggerProvider provider)

Static method that permits to configure the logging system used by the library. The logging system must respect the LoggerProvider interface. A custom class can be used to wrap any third-party Java logging system.
If no logging system is specified, all the generated log is discarded.
The following categories are available to be consumed:

• lightstreamer.stream:
  logs socket activity on Lightstreamer Server connections;
  at INFO level, socket operations are logged;
  at DEBUG level, read/write data exchange is logged.
• lightstreamer.protocol:
  logs requests to Lightstreamer Server and Server answers;
  at INFO level, requests are logged;
  at DEBUG level, request details and events from the Server are logged.
• lightstreamer.session:
  logs Server Session lifecycle events;
  at INFO level, lifecycle events are logged;
  at DEBUG level, lifecycle event details are logged.
• lightstreamer.subscriptions:
  logs subscription requests received by the clients and the related updates;
  at WARN level, alert events from the Server are logged;
  at INFO level, subscriptions and unsubscriptions are logged;
  at DEBUG level, requests batching and update details are logged.
• lightstreamer.actions:
  logs settings / API calls.

Parameters:

provider - A LoggerProvider instance that will be used to generate log messages by the library classes.

addListener

public void addListener(@Nonnull
                        ClientListener listener)

Adds a listener that will receive events from the LightstreamerClient instance.
The same listener can be added to several different LightstreamerClient instances.

Parameters:

listener - An object that will receive the events as documented in the ClientListener interface.

See Also:

removeListener(ClientListener)

Lifecycle:

A listener can be added at any time. A call to add a listener already present will be ignored.

removeListener

public void removeListener(@Nonnull
                           ClientListener listener)

Removes a listener from the LightstreamerClient instance so that it will not receive events anymore.

Parameters:

listener - The listener to be removed.

See Also:

addListener(ClientListener)

Lifecycle:

a listener can be removed at any time.

getListeners

@Nonnull
public java.util.List<ClientListener> getListeners()

Returns a list containing the ClientListener instances that were added to this client.

Returns:

a list containing the listeners that were added to this client.

See Also:

addListener(ClientListener)

connect

public void connect()

Operation method that requests to open a Session against the configured Lightstreamer Server.
When connect() is called, unless a single transport was forced through ConnectionOptions.setForcedTransport(String), the so called "Stream-Sense" mechanism is started: if the client does not receive any answer for some seconds from the streaming connection, then it will automatically open a polling connection.
A polling connection may also be opened if the environment is not suitable for a streaming connection.
Note that as "polling connection" we mean a loop of polling requests, each of which requires opening a synchronous (i.e. not streaming) connection to Lightstreamer Server.

Throws:

java.lang.IllegalStateException - if no server address was configured.

See Also:

getStatus(), disconnect(), ClientListener.onStatusChange(String), ConnectionDetails.setServerAddress(String)

Lifecycle:

Note that the request to connect is accomplished by the client in a separate thread; this means that an invocation to getStatus() right after connect() might not reflect the change yet.
When the request to connect is finally being executed, if the current status of the client is not DISCONNECTED, then nothing will be done.

disconnect

public void disconnect()

Operation method that requests to close the Session opened against the configured Lightstreamer Server (if any).
When disconnect() is called, the "Stream-Sense" mechanism is stopped.
Note that active Subscription instances, associated with this LightstreamerClient instance, are preserved to be re-subscribed to on future Sessions.

See Also:

connect()

Lifecycle:

Note that the request to disconnect is accomplished by the client in a separate thread; this means that an invocation to getStatus() right after disconnect() might not reflect the change yet.
When the request to disconnect is finally being executed, if the status of the client is "DISCONNECTED", then nothing will be done.

disconnectFuture

@Nonnull
public java.util.concurrent.Future<java.lang.Void> disconnectFuture()

Works just like disconnect(), but also returns a Future which is notified when all involved threads started by all LightstreamerClient instances living in the JVM have been terminated, because no more activities need to be managed and hence event dispatching is no longer necessary.

Such method is especially useful in those environments which require an appropriate resource management, like "full" Java EE application servers or even the simpler Servlet Containers. The method should be used in replacement of disconnect() in all those circumstances where it is indispensable to guarantee a complete shutdown of all user threads, in order to avoid potential memory leaks and waste resources.

For example, in a web application, it might be possible to leverage a hook like ServletContextListener.contextDestroyed(javax.servlet.ServletContextEvent) to trigger the await of threads termination, before the ServletContext will be shut down.

 
 public void contextDestroyed(ServletContext sce) {
     // client is already instantiated elsewhere and a connection to LightstreamerServer is in place.
     Future disconnected = client.disconnectFuture();
     
     // Blocks until all threads have been terminated.
     disconnected.get()
 }
 
 

Returns:

a Future object representing pending completion of the disconnection task.

See Also:

disconnect(), connect()

getStatus

@Nonnull
public java.lang.String getStatus()

Inquiry method that gets the current client status and transport (when applicable).

Returns:

The current client status. It can be one of the following values:

• "CONNECTING" the client is waiting for a Server's response in order to establish a connection;
• "CONNECTED:STREAM-SENSING" the client has received a preliminary response from the server and is currently verifying if a streaming connection is possible;
• "CONNECTED:WS-STREAMING" a streaming connection over WebSocket is active;
• "CONNECTED:HTTP-STREAMING" a streaming connection over HTTP is active;
• "CONNECTED:WS-POLLING" a polling connection over WebSocket is in progress;
• "CONNECTED:HTTP-POLLING" a polling connection over HTTP is in progress;
• "STALLED" the Server has not been sending data on an active streaming connection for longer than a configured time;
• "DISCONNECTED:WILL-RETRY" no connection is currently active but one will be opened (possibly after a timeout);
• "DISCONNECTED:TRYING-RECOVERY" no connection is currently active, but one will be opened as soon as possible, as an attempt to recover the current session after a connection issue;
• "DISCONNECTED" no connection is currently active.

See Also:

ClientListener.onStatusChange(String)

subscribe

public void subscribe(@Nonnull
                      Subscription subscription)

Operation method that adds a Subscription to the list of "active" Subscriptions. The Subscription cannot already be in the "active" state.
Active subscriptions are subscribed to through the server as soon as possible (i.e. as soon as there is a session available). Active Subscription are automatically persisted across different sessions as long as a related unsubscribe call is not issued.

Parameters:

subscription - A Subscription object, carrying all the information needed to process real-time values.

See Also:

unsubscribe(Subscription)

Lifecycle:

Subscriptions can be given to the LightstreamerClient at any time. Once done the Subscription immediately enters the "active" state.
Once "active", a Subscription instance cannot be provided again to a LightstreamerClient unless it is first removed from the "active" state through a call to unsubscribe(Subscription).
Also note that forwarding of the subscription to the server is made in a separate thread.
A successful subscription to the server will be notified through a SubscriptionListener.onSubscription() event.

unsubscribe

public void unsubscribe(@Nonnull
                        Subscription subscription)

Operation method that removes a Subscription that is currently in the "active" state.
By bringing back a Subscription to the "inactive" state, the unsubscription from all its items is requested to Lightstreamer Server.

Parameters:

subscription - An "active" Subscription object that was activated by this LightstreamerClient instance.

Lifecycle:

Subscription can be unsubscribed from at any time. Once done the Subscription immediately exits the "active" state.
Note that forwarding of the unsubscription to the server is made in a separate thread.
The unsubscription will be notified through a SubscriptionListener.onUnsubscription() event.

getSubscriptions

@Nonnull
public java.util.List<Subscription> getSubscriptions()

Inquiry method that returns a list containing all the Subscription instances that are currently "active" on this LightstreamerClient.
Internal second-level Subscription are not included.

Returns:

A list, containing all the Subscription currently "active" on this LightstreamerClient.
The list can be empty.

See Also:

subscribe(Subscription)

sendMessage

public void sendMessage(@Nonnull
                        java.lang.String message)

A simplified version of the sendMessage(String,String,int,ClientMessageListener,boolean). The internal implementation will call sendMessage(message,null,-1,null,false); Note that this invocation involves no sequence and no listener, hence an optimized fire-and-forget behavior will be applied.

Parameters:

message - a text message, whose interpretation is entirely demanded to the Metadata Adapter associated to the current connection.

sendMessage

public void sendMessage(@Nonnull
                        java.lang.String message,
                        @Nullable
                        java.lang.String sequence,
                        int delayTimeout,
                        @Nullable
                        ClientMessageListener listener,
                        boolean enqueueWhileDisconnected)

Operation method that sends a message to the Server. The message is interpreted and handled by the Metadata Adapter associated to the current Session. This operation supports in-order guaranteed message delivery with automatic batching. In other words, messages are guaranteed to arrive exactly once and respecting the original order, whatever is the underlying transport (HTTP or WebSockets). Furthermore, high frequency messages are automatically batched, if necessary, to reduce network round trips.
Upon subsequent calls to the method, the sequential management of the involved messages is guaranteed. The ordering is determined by the order in which the calls to sendMessage are issued.
If a message, for any reason, doesn't reach the Server (this is possible with the HTTP transport), it will be resent; however, this may cause the subsequent messages to be delayed. For this reason, each message can specify a "delayTimeout", which is the longest time the message, after reaching the Server, can be kept waiting if one of more preceding messages haven't been received yet. If the "delayTimeout" expires, these preceding messages will be discarded; any discarded message will be notified to the listener through ClientMessageListener.onDiscarded(String). Note that, because of the parallel transport of the messages, if a zero or very low timeout is set for a message and the previous message was sent immediately before, it is possible that the latter gets discarded even if no communication issues occur. The Server may also enforce its own timeout on missing messages, to prevent keeping the subsequent messages for long time.
Sequence identifiers can also be associated with the messages. In this case, the sequential management is restricted to all subsets of messages with the same sequence identifier associated.
Notifications of the operation outcome can be received by supplying a suitable listener. The supplied listener is guaranteed to be eventually invoked; listeners associated with a sequence are guaranteed to be invoked sequentially.
The "UNORDERED_MESSAGES" sequence name has a special meaning. For such a sequence, immediate processing is guaranteed, while strict ordering and even sequentialization of the processing is not enforced. Likewise, strict ordering of the notifications is not enforced. However, messages that, for any reason, should fail to reach the Server whereas subsequent messages had succeeded, might still be discarded after a server-side timeout, in order to ensure that the listener eventually gets a notification.
Moreover, if "UNORDERED_MESSAGES" is used and no listener is supplied, a "fire and forget" scenario is assumed. In this case, no checks on missing, duplicated or overtaken messages are performed at all, so as to optimize the processing and allow the highest possible throughput.

Parameters:

message - a text message, whose interpretation is entirely demanded to the Metadata Adapter associated to the current connection.

sequence - an alphanumeric identifier, used to identify a subset of messages to be managed in sequence; underscore characters are also allowed. If the "UNORDERED_MESSAGES" identifier is supplied, the message will be processed in the special way described above. The parameter is optional; if set to null, "UNORDERED_MESSAGES" is used as the sequence name.

delayTimeout - a timeout, expressed in milliseconds. If higher than the Server configured timeout on missing messages, the latter will be used instead.
The parameter is optional; if a negative value is supplied, the Server configured timeout on missing messages will be applied.
This timeout is ignored for the special "UNORDERED_MESSAGES" sequence, although a server-side timeout on missing messages still applies.

listener - an object suitable for receiving notifications about the processing outcome. The parameter is optional; if not supplied, no notification will be available.

enqueueWhileDisconnected - if this flag is set to true, and the client is in a disconnected status when the provided message is handled, then the message is not aborted right away but is queued waiting for a new session. Note that the message can still be aborted later when a new session is established.

Lifecycle:

Since a message is handled by the Metadata Adapter associated to the current connection, a message can be sent only if a connection is currently active. If the special enqueueWhileDisconnected flag is specified it is possible to call the method at any time and the client will take care of sending the message as soon as a connection is available, otherwise, if the current status is "DISCONNECTED*", the message will be abandoned and the ClientMessageListener.onAbort(java.lang.String, boolean) event will be fired.
Note that, in any case, as soon as the status switches again to "DISCONNECTED*", any message still pending is aborted, including messages that were queued with the enqueueWhileDisconnected flag set to true.
Also note that forwarding of the message to the server is made in a separate thread, hence, if a message is sent while the connection is active, it could be aborted because of a subsequent disconnection. In the same way a message sent while the connection is not active might be sent because of a subsequent connection.

addCookies

public static void addCookies(@Nonnull
                              java.net.URI uri,
                              @Nonnull
                              java.util.List<java.net.HttpCookie> cookies)

Static method that can be used to share cookies between connections to the Server (performed by this library) and connections to other sites that are performed by the application. With this method, cookies received by the application can be added (or replaced if already present) to the cookie set used by the library to access the Server. Obviously, only cookies whose domain is compatible with the Server domain will be used internally.
More precisely, this explicit sharing is only needed when the library uses its own cookie storage. This depends on the availability of a default global storage.

• In fact, the library will setup its own local cookie storage only if, upon the first usage of the cookies, a default CookieHandler is not available; then it will always stick to the internal storage.
• On the other hand, if a default CookieHandler is available upon the first usage of the cookies, the library, from then on, will always stick to the default it finds upon each request; in this case, the cookie storage will be already shared with the rest of the application. However, whenever a default CookieHandler of type different from CookieManager is found, the library will not be able to use it and will skip cookie handling .

Parameters:

uri - the URI from which the supplied cookies were received. It cannot be null.

cookies - a list of cookies, represented in the JDK-provided type.

See Also:

getCookies(java.net.URI)

Lifecycle:

This method should be invoked before calling the connect() method. However it can be invoked at any time; it will affect the internal cookie set immediately and the sending of cookies on the next HTTP request or WebSocket establishment.

getCookies

@Nonnull
public static java.util.List<java.net.HttpCookie> getCookies(@Nullable
                                                                       java.net.URI uri)

Static inquiry method that can be used to share cookies between connections to the Server (performed by this library) and connections to other sites that are performed by the application. With this method, cookies received from the Server can be extracted for sending through other connections, according with the URI to be accessed.
See addCookies(java.net.URI, java.util.List<java.net.HttpCookie>) for clarifications on when cookies are directly stored by the library and when not.

Parameters:

uri - the URI to which the cookies should be sent, or null.

Returns:

an immutable list with the various cookies that can be sent in a HTTP request for the specified URI. If a null URI was supplied, all available non-expired cookies will be returned. The cookies are represented in the JDK-provided type.

setTrustManagerFactory

public static void setTrustManagerFactory(@Nonnull
                                          javax.net.ssl.TrustManagerFactory factory)

Provides a mean to control the way TLS certificates are evaluated, with the possibility to accept untrusted ones.

Parameters:

factory - trust manager factory

Throws:

java.lang.NullPointerException - if the factory is null

java.lang.IllegalStateException - if a factory is already installed

Lifecycle:

May be called only once before creating any LightstreamerClient instance.