org.ka2ddo.yaac.filter

Class FilterExpressionParser

java.lang.Object

org.ka2ddo.yaac.filter.FilterExpressionParser

public class FilterExpressionParser
extends java.lang.Object

This class takes a string expression in the format used for APRS-IS feed filters, and converts it into a hierarchy of Filter objects that will provide that filtering. This currently supports the following filters:

Parameter	Filter Type	Description
r/lat/lon/dist	Range filter	Pass posits and objects within dist km from lat/lon. lat and lon are signed decimal degrees, i.e. negative for West/South and positive for East/North.
p/aa/bb/cc...	Prefix filter	Pass traffic with fromCall that starts with aa or bb or cc. Same as b/aa* /bb* /cc*
b/call1/call2...	Buddy list filter	Pass all traffic from exact call: call1, call2, ... (* wild card allowed)
o/obj1/obj2...	Object filter	Pass all objects with the exact name of obj1, obj2, ... (* wild card allowed) (spaces not allowed) (| => / and ~ => *)
t/poimqstunw	Type filter	Pass all traffic based on packet type. One or more types can be defined at the same time, t/otq is a valid definition. p = Position packets o = Objects i = Items m = Message q = Query s = Status t = Telemetry u = User-defined n = NWS format messages and objects w = Weather
s/pri/alt/over	Symbol filter	pri = symbols in primary table (| => /) alt = symbols in alternate table (| => /) over = overlay character (case sensitive) Filter examples s/-> This will pass all House and Car symbols (primary table) s//# This will pass all Digi with or without overlay s//#/T This will pass all Digi with overlay of capital "T"
g/call1/call1/...	Group Message filter	This filter passes all text message packets with the specified callsign-SSID(s) as the addressee of the message. Supports * wildcard.
u/unproto1/unproto2/...	Unproto filter	This filter passes all packets with the specified destination callsign-SSID(s) (also known as the To call or unproto call). Supports * wildcard.
m/dist	My Range filter	This is the same as the range filter except that the center is defined as the current position of this YAAC station. This will change dynamically if this is a mobile station using GPS coordinates.
f/call/dist	Friend Range filter	This is the same as the range filter except that the center is defined as the current known position of call. If the friend station or object moves, future filtering will be based on the new position. If the station is purged from the YAAC station records (either manually or due to inactivity timeout), this filter will cease to affect traffic, but will start working again as soon as the friend station comes on the air again and transmits its position.
a/latN/lonW/latS/lonE	Area filter	Pass positions and objects within the specified axis-aligned bounding box. lat and lon are signed decimal degrees, i.e. negative for West/South and positive for East/North.
e/call1/call2/...	APRS-IS backbone entry I-gate filter	pass all packets that were introduced into the APRS-IS backbone by the specified I-gate stations. '*' wildcards may be used.

Author:

Andrew Pavlin, KA2DDO

Method Summary

Modifier and Type	Method and Description
static Filter	produceFiltersForExpression(java.lang.String filterExpr) Convert the specified string into a hierarchy of Filter objects that will execute the specified filtering.

Methods inherited from class java.lang.Object

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

Method Detail

produceFiltersForExpression

public static Filter produceFiltersForExpression(java.lang.String filterExpr)
                                          throws java.text.ParseException

Convert the specified string into a hierarchy of Filter objects that will execute the specified filtering.

Parameters:

filterExpr - String of APRS-IS server filter expressions

Returns:

a Filter instance that will implement the requested filter expression

Throws:

java.text.ParseException - if filter expression string could not be evaluated