Package org.transitime.avl

Contains the classes associated with AVL feeds including reading data from an AVL feed and providing it to the main application usually via JMS for live feeds but also by reading data and then directly calling AvlProcessor.processAvlReport(avlReport) for other feeds, especially batch feeds used for debugging or testing.

See: Description

Class Summary

Class	Description
AmigoCloudAvlModule	AVL module for websocket based feed from AmigoCloud.
AvlClient	Receives AVL data from the AvlExecutor or JMS, determines if AVL should be filtered, and processes data that doesn't need to be filtered.
AvlCsvReader	For reading in AVL data from a CSV file.
AvlCsvRecord	Represents a single record in a CSV file containing AVL data.
AvlCsvWriter	For writing a CSV file containing AVL reports.
AvlExecutor	A singleton thread executor for executing AVL reports.
AvlJmsClientModule	Reads AVL data from JMS topic and processes it.
AvlModule	Low-level abstract AVL module class that handles the processing of the data.
AvlQueue	A queue of AvlClient runnables that can be used with a ThreadPoolExecutor.
BatchCsvAvlFeedModule	For reading in a batch of AVL data in CSV format and processing it.
BatchGtfsRealtimeModule	For reading in a batch of GTFS-realtime data and processing it.
GtfsRealtimeModule	For reading in feed of GTFS-realtime AVL data.
NextBusAvlModule	Reads AVL data from a NextBus AVL feed and processes each AVL report.
NmeaGpsLocation	For parsing a NMEA command into a GPS location.
PlaybackModule	For running the system in "playback mode" where AVL data is read from the database instead of from a realtime AVL feed.
PollUrlAvlModule	Subclass of AvlModule to be used when reading AVL data from a feed.
TaipGpsLocation	For parsing Trimble TAIP format GPS commands into a Java object.
TranslocAvlModule	Reads AVL data from a Transloc JSON AVL feed and processes each AVL report.
XmlPollingAvlModule	Polls XML feed for AVL data.
ZonarAvlModule	Reads AVL data from Zonar XML AVL feed.

Package org.transitime.avl Description

Contains the classes associated with AVL feeds including reading data from an AVL feed and providing it to the main application usually via JMS for live feeds but also by reading data and then directly calling AvlProcessor.processAvlReport(avlReport) for other feeds, especially batch feeds used for debugging or testing.

Goal for the AVL module software was to be able to easily handle many different types of live feeds. This includes XML pull feeds where a thread pulls data from XML feed on regular interval, XML push feed where the client writes XML data to a website, and more. Also wanted test projects to easily be able to read from the same feed without having to poll again. Also, for large systems want to be able to use multiple threads for processing the data so get more throughput per machine.

To satisfy these goals for the live feeds JMS can be used so that the feed and the AVL clients can reside on different servers. This allows for multiple subscribers so can easily have test projects using the same AVL data. Also allows components of the feed to reside on different servers so can easily have a pull feed on the predictor machine or a push feed on a separate web server machine. Since JMS is a queue the client can use multiple threads to read and process the AVL data. But JMS doesn't need to be used if the feed is polled, such that the feed polling and the AVL client can reside on the same server, and you don't want to run JMS server.

The JMS topic name used for the AVL feed is the same of the projectId. The topic names are dynamically configured in JMS so that one doesn't need to update a configuration file when a new agency is dealt with. This makes maintaining JMS much simpler.

An AVL feed inherits from the org.transitime.modules.Module class. This means it is very easy to start. Also means that the Module.getProjectId() method is used specify which database the data is to be written to and the name of the JMS topic for the feed. This also means that the command line param -Dtransitime.modules.optionalModulesList=XXX is used to start up the desired AVL modules.

Configuration parameters for AVL modules are listed in the AvlConfig.java class. Important params include -Dtransitime.db.storeDataInDatabase=false if the generated data such as arrivals/departures should not be stored in the database. This is important for when in playback mode for debugging or such. Another important parameter is -Dtransitime.avl.shouldUseJms=true if you want to use JMS. In that case you also need to specify both an AVL feed module and a JMS client module, such as -Dtransitime.modules.optionalModulesList=org.transitime.avl.MuniNextBusAvlModule;org.transitime.avl.AvlJmsClientModule