net.sf.eBus.feed

Class EventPattern

java.lang.Object

net.sf.eBus.feed.EventPattern

public final class EventPattern
extends Object

EventPattern provides the two pieces of information needed to do pattern matching: 1) the notification feeds providing the events used in the match and 2) the pattern itself. Patterns come in two types:

• Ordered: events must arrive in the event pattern order to effect a match.
• Unordered: specifies the number of each event type which must be collected to effect a match where the events may arrive in any order.

Once an event series is received matching the pattern, those events are tested against the pattern condition. Only if that condition is satisfied is a MatchEvent generated and forwarded to the subscriber.

Event patterns are constructed via EventPattern.Builder. See that class for detailed instructions on building event patterns.

Author:

Charles W. Rapp

See Also:

EventPattern.Builder

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	EventPattern.Builder Builder is the only way to create an EventFeed instance.
static class	EventPattern.FeedInfo This class provides the information needed by EPatternFeed to open and subscribe to a notification message feed.
static class	EventPattern.PatternType eBus patterns come in two varieties: ordered and unordered.

Field Summary

Fields

Modifier and Type	Field and Description
static String	ALL_EVENTS The group "__ALL_EVENTS__" contains all matched events in received order.
static Predicate<MatchEvent>	DEFAULT_CONDITION Default match event which always returns true.
static int	DEFAULT_MATCH_COUNT The default minimum and maximum match count is 1.
static MatchCondition	DEFAULT_PREDICATE Default event match predicate returns true.
static BiPredicate<List<ENotificationMessage>,ENotificationMessage>	DEFAULT_UNTIL The default until predicate always returns true.
protected String	mPatternName Pattern name used as the MatchEvent subject.

Method Summary

Modifier and Type	Method and Description
static EventPattern.Builder	builder(String pName, EventPattern.PatternType pType) Returns a named, ordered or unordered event pattern builder which has no pre-defined parameters.
static EventPattern.Builder	builder(String pName, EventPattern.PatternType pType, Map<String,EventPattern.FeedInfo> parameters) Returns a named, ordered or unordered event pattern builder using the given parameters.
EventPattern.FeedInfo	feedInfo(String feedName) Returns EventPattern.FeedInfo for the given feed name.
boolean	isExclusive() Returns true if the events matching this pattern are used in one match only.
EMessageKey	messageKey(String feedName) Returns the message key associated with the given feed name.
Map<String,EventPattern.FeedInfo>	parameters() Returns the read-only event pattern parameters map.
String	patternName() Returns the user-assigned pattern name.
EventPattern.PatternType	patternType() Returns the pattern type.

Methods inherited from class java.lang.Object

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

Field Detail

ALL_EVENTS

public static final String ALL_EVENTS

The group "__ALL_EVENTS__" contains all matched events in received order. This means the order may not be chronological according to the event timestamp.

See Also:

Constant Field Values

DEFAULT_UNTIL

public static final BiPredicate<List<ENotificationMessage>,ENotificationMessage> DEFAULT_UNTIL

The default until predicate always returns true.

DEFAULT_MATCH_COUNT

public static final int DEFAULT_MATCH_COUNT

The default minimum and maximum match count is 1.

See Also:

Constant Field Values

DEFAULT_PREDICATE

public static final MatchCondition DEFAULT_PREDICATE

Default event match predicate returns true.

DEFAULT_CONDITION

public static final Predicate<MatchEvent> DEFAULT_CONDITION

Default match event which always returns true. This condition should be used when subscriber wants all match events returned.

mPatternName

protected final String mPatternName

Pattern name used as the MatchEvent subject.

Method Detail

patternName

public String patternName()

Returns the user-assigned pattern name.

Returns:

pattern name.

patternType

public EventPattern.PatternType patternType()

Returns the pattern type.

Returns:

pattern type.

parameters

public Map<String,EventPattern.FeedInfo> parameters()

Returns the read-only event pattern parameters map.

Returns:

event pattern parameters map.

isExclusive

public boolean isExclusive()

Returns true if the events matching this pattern are used in one match only. This means that if an event could be used in two separate matches of the same pattern, it will be used for only the the first completed match. The second match will be dropped as a result.

Exclusive is only within a single pattern. Exclusion does not work between two separate pattern instances.

Returns:

true if events are used in a single match only.

feedInfo

public EventPattern.FeedInfo feedInfo(String feedName)

Returns EventPattern.FeedInfo for the given feed name.

Parameters:

feedName - a known feed name from parameters map.

Returns:

feed information.

Throws:

IllegalArgumentException - if parameter is not a known feed name.

messageKey

public EMessageKey messageKey(String feedName)

Returns the message key associated with the given feed name.

Parameters:

feedName - feed name in parameters map.

Returns:

message key.

Throws:

IllegalArgumentException - if parameter is not a known feed name.

builder

public static EventPattern.Builder builder(String pName,
                                           EventPattern.PatternType pType)

Returns a named, ordered or unordered event pattern builder which has no pre-defined parameters. These parameters must be defined using EventPattern.Builder.beginParameterMap()/ EventPattern.Builder.endParameterMap() before adding components to the event pattern.

Parameters:

pName - user-assigned pattern name. Used for logging purposes only.

pType - specifies whether the pattern is ordered or unordered.

Returns:

event pattern builder.

Throws:

NullPointerException - if pName or pType is null.

IllegalArgumentException - if pName is an empty string.

See Also:

builder(String, PatternType, Map)

builder

public static EventPattern.Builder builder(String pName,
                                           EventPattern.PatternType pType,
                                           Map<String,EventPattern.FeedInfo> parameters)

Returns a named, ordered or unordered event pattern builder using the given parameters. parameters maps a unique name to a notification feed. The map keys are used in the event pattern regular expression to reference a particular notification feed.

This map may not be null, empty, or contain null values.

Parameters:

pName - user-assigned pattern name. Used as the subject for posted match events. purposes only. May not be null or empty.

pType - specifies whether the pattern is ordered or unordered.

parameters - event pattern parameters.

Returns:

event pattern builder.

Throws:

NullPointerException - if pName, pType, or parameters is null.

IllegalArgumentException - if pName is an empty string or parameters is either empty or contains a null value.

See Also:

builder(String, PatternType)