com.pushtechnology.diffusion.client.topics

Interface TopicSelectors

public interface TopicSelectors

Convert strings to TopicSelectors.

Selectors are evaluated against topic paths. A topic path is a '/' separated string of parts, which map to the topic tree. Each part is formed of one or more UTF characters, except '/'. Topic paths are absolute, and evaluated from the root of the topic tree.

An instance of this may be obtained as follows:

 
 TopicSelectors selectors = Diffusion.topicSelectors();
 
 

Since:

5.0

Method Summary

Modifier and Type	Method and Description
TopicSelector	anyOf(String... expressions) Convenient wrapper of anyOf(TopicSelector...) that first parses the supplied expressions to create selectors.
TopicSelector	anyOf(TopicSelector... selectors) Create a SELECTOR_SET selector that matches if any of the provided selectors match.
TopicSelector	parse(String expression) Parse an expression to create a selector.

Method Detail

parse

TopicSelector parse(String expression)
             throws IllegalArgumentException

Parse an expression to create a selector.

The following types of expression are supported. The type is determined by the first character of the expression.

Path

Path expressions begin with the character >. The remainder of the expression must be a valid topic path. A topic path is a '/' separated string of parts. Each part is formed of one or more UTF characters, except '/'.

A PATH selector is returned that only selects the topic with the given path.

The initial > can be omitted if the path begins with a character other than one of #, ?, >, *, $, %, &, or <. This abbreviated syntax allows most topic paths to be used directly as selector expressions which appears more natural. Abbreviated path expressions are converted to standard path expressions by prepending the > character. Thus a/b is interpreted as >a/b.

Diffusion.topicSelectors().parse("a/b").getExpression() will return ">a/b".

Split-path pattern

Split-path pattern expressions begin with the character ?. The remainder of the expression is split into a list of regular expressions using the / character as a separator.

A SPLIT_PATH_PATTERN selector is returned that selects topics for which each regular expression matches each part of the topic path at the corresponding level.

Full-path pattern

Full-path pattern expressions begin with the character *. The remainder of the pattern is a regular expression.

A FULL_PATH_PATTERN selector is returned that selects topics for which the regular expression matches the complete topic path.

Full-path patterns provide a lot of expressive power but should be used sparingly since the server can evaluate split-path patterns more efficiently.

Selector sets are the preferred way to combine expressions. anyOf("a", "b") is equivalent to the full-path expression " */a|/b", but can be evaluated more efficiently by the server.

Selector set

Selector set expressions begin with the character #. The remainder of the expression is a list of contained selectors, formatted as described below.

A SELECTOR_SET selector is returned that selects topics that match any of the contained selectors.

The selector set expression format is complex, The anyOf(String...) convenience method should be preferred over calling this method with a selector set expression. The contained selectors are formatted as follows. First, any selector sets are expanded to produce a full list of non-selector set expressions. Then the selector expressions are concatenated, separated by the separator ////. This separator has been chosen as it is not valid in a path, and is not a useful sequence in a pattern.

Descendant pattern qualifiers

Split-path and full-path pattern expressions can be further modified by appending / or //. These control the behavior of the selector with respect to the descendants of the topics that match the pattern.

• If the expression does not end with / or //, it selects only the topics that match the pattern.
• If the expression ends with /, it selects only the descendants of the matching topics, excluding the matching topics.
• If the expression ends with //, it selects the matching topics and all of their descendants.

Regular expressions

Any Java-style regular expression can be used in split-path and full-path patterns, with the following restrictions:

• A regular expression may not be empty.
• A regular expression used in split-path patterns may not contain the path separator /.
• A regular expression used in full-path patterns may not contain the selector set separator //// .

Regular expressions that break any of these restrictions would never match a topic path, so they make no practical difference.

Examples

Path expressions

	Matches alpha/beta?	Matches alpha/beta/gamma?
>alpha/beta	yes	no
alpha/beta	yes	no
>alpha/beta/gamma	no	yes
alpha/beta/gamma	no	yes
>beta	no	no
beta	no	no
>.*/.*	no	no
>/alpha/beta/	yes	no
/alpha/beta/	yes	no

Split-path pattern expressions

	Matches alpha/beta?	Matches alpha/beta/gamma?
?alpha/beta	yes	no
?alpha/beta/gamma	no	yes
?beta	no	no
?.*	no	no
?.*/.*	yes	no
?alpha/beta/	no	yes
?alpha/beta//	yes	yes
?alpha/.*//	yes	yes

Full-path pattern expressions

	Matches alpha/beta?	Matches alpha/beta/gamma?
*alpha/beta	yes	no
*alpha/beta/gamma	no	yes
*beta	no	no
*.*beta	yes	no
*.*	yes	yes
*alpha/beta/	no	yes
*alpha/beta//	yes	yes

Parameters:

expression - The topic selector expression.

Returns:

The topic selector.

Throws:

IllegalArgumentException - If expression is not valid.

IllegalArgumentException - If expression is not one of the supported types.

anyOf

TopicSelector anyOf(String... expressions)
             throws IllegalArgumentException

Convenient wrapper of anyOf(TopicSelector...) that first parses the supplied expressions to create selectors.

Parameters:

expressions - The expressions.

Returns:

A selector which matches any of expressions.

Throws:

IllegalArgumentException - If one of expressions cannot be parsed.

anyOf

TopicSelector anyOf(TopicSelector... selectors)

Create a SELECTOR_SET selector that matches if any of the provided selectors match.

Parameters:

selectors - The selectors.

Returns:

A selector which matches if any of selectors do.