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.

Field Summary

Fields

Modifier and Type	Field and Description
ConnectionDetails	connectionDetails Bean object that contains the details needed to open a connection to a Lightstreamer Server.
ConnectionOptions	connectionOptions Bean 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
void	addListener(ClientListener listener) Adds a listener that will receive events from the LightstreamerClient instance. The same listener can be added to several different LightstreamerClient instances.
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.
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.
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. Internal second-level Subscription are not included.
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.
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. By bringing back a Subscription to the "inactive" state, the unsubscription from all its items is requested to Lightstreamer Server.

Methods inherited from class java.lang.Object

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

Field Detail

LIB_NAME

public static final java.lang.String LIB_NAME

A constant string representing the name of the library.

See Also:

Constant Field Values

LIB_VERSION

public static final java.lang.String LIB_VERSION

A constant string representing the version of the library.

connectionOptions

public final ConnectionOptions connectionOptions

Bean 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 bean can be overwritten by values received from a Lightstreamer Server.

connectionDetails

public final ConnectionDetails connectionDetails

Bean 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 bean can be overwritten by values received from a Lightstreamer Server.

Constructor Detail

LightstreamerClient

public 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. 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(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(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(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

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 CONNECTING, CONNECTED:* or STALLED, 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.

getStatus

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" no connection is currently active;
• "DISCONNECTED:WILL-RETRY" no connection is currently active but one will be open after a timeout.

See Also:

ClientListener.onStatusChange(String)

subscribe

public void subscribe(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 its pushed 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(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

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(java.lang.String message)

A simplified version of the sendMessage(String,String,int,ClientMessageListener,boolean). The internal implementation will call sendMessage(message,null,0,null,false);

Parameters:

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

sendMessage

public 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. 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. However, any message that, for any reason, doesn't reach the Server can be discarded by the Server if this causes the subsequent message to be kept waiting for longer than a configurable timeout. Note that, because of the asynchronous transport of the requests, if a zero or very low timeout is set for a message, it is not guaranteed that the previous message can be processed, even if no communication issues occur.
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.

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 default timeout, the latter will be used instead.
The parameter is optional; if 0 is supplied, the Server default timeout will be applied.
This timeout is ignored for the special "UNORDERED_MESSAGES" sequence, for which a custom server-side timeout 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.