Foglight for Java EE Technologies 5.9.13 - Application Servers User Guide

If a regular expression contains “|” operators, the left most matching sub-expression is chosen. Example: if the regular expression is ‘(cat|dog)’ and the target string is ‘cats and dogs’, the match succeeds with ‘cat’ after the first three letters have been scanned.

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The longest match wins

In “*”, “+”, and “?” constructs, longer matches are chosen in preference to shorter ones. Example: if the regular expression is ‘^He’s ba*’ and the target string is ‘He’s baaaaack!’, the match succeeds with ‘He’s baaaaa’ after the full list of contiguous a’s have been scanned.

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In sequences of expression components, the components are considered from left to right

Related topics:

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Typical regular expression patterns

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Matching with character classes

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Matching any character: the dot

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Alternation in regular expressions

Typical regular expression patterns

The caret and dollar represent the start and end, respectively, of a string. They do not represent characters, but simply the abstract notion of begin and end. They are useful as anchors for the rest of the regular expression.

Table 87. Regular expression match patterns
Regular Expression	Matches
^www[.]quest[.]com$	www.quest.com but not http://www.quest.com or www.quest.com/index.html
^com[.]quest[.].*	com.quest.performasure, but not homedir.com.quest.performasure
rmi$	java.rmi, but not java.rmi.activation


	NOTE: The meaning of the caret is different if it is the first entry in a character class. In this case, it means ‘anything but’ the characters following it. For example, [^abc] in a regular expression means that some single character must be matched at the position of the character class within the regular expression, but it can’t be ‘a’ or ‘b’ or ‘c’. If a caret (^) appears anywhere else but the first position in a character class, it simply stands for itself. The same is true for a dollar sign ($) in a character class: it is just a dollar sign, not a metacharacter.

Related topics:

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How regular expressions are scanned

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Matching with character classes

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Matching any character: the dot

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Alternation in regular expressions

Matching with character classes

Using character classes provides a range of possibilities and enables you to give a specific list. The first example in the table shows the use of a regular expression to match the American or British spelling of the word ‘analyze.’

Table 88. Regular Expression match patterns with character classes
Regular Expression	Matches
Analy[sz]e this	Analyze this, and Analyse this
www[0-9][0-9]?[.]example	www0.example, www01.example, but not www001.example The regular expression matches ‘www’ followed by a numeral, followed by no more than one more numeral, followed by ‘.example’. Thus, 001 fails the match.
www[^a-zA-Z]?\.example	www.example, www1.example, but not wwwx.example
www[.]quest[.]com www.quest.com	This is the recommended way of matching the dot separator in Java package names and fully qualified names.


	CAUTION: The dash (-) is a metacharacter only when it occurs between two characters in a character class. Otherwise, it is just an ordinary character. The exception to the rule of interpreting a dash as a range operator when it is between two characters is the following: the regular expression [^-*] means ‘exclude dashes and asterisks from a match.’

Related topics:

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How regular expressions are scanned

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Typical regular expression patterns

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Matching any character: the dot

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Alternation in regular expressions

Matching any character: the dot

You use the dot (.) metacharacter when you want to indicate that any character is allowed at this position. Combined with parentheses, dot metacharacters can be used to indicate the number of arbitrary characters to be allowed after another pattern. See the second entry in the table below for an example of this case. The first entry in the table is an illustration of the commonly seen ‘dot-star’ combination, which matches any number of arbitrary characters. Also, it’s important to remember that dots are not metacharacters when they occur within a character class.


	CAUTION: Because the dot is a metacharacter, real periods in package names and URLs must be enclosed in square brackets or preceded by backslashes when they are part of a regular expression.

Table 89. Regular expression match patterns with the dot
Regular Expression	Matches
com\.quest\..*	com.quest.the rest of the string, commas, spaces, periods, and all. As long as the test string contains ‘com.quest.’ followed by any number of additional characters, the match succeeds.
[ ]co(.\|..\|...\|....)[ ]	The ‘words’ cod, coal, codes, collar, and even co13 The character classes at both ends of the regular expression contain the space character, which limits the match to space-separated words. The matched word must begin with ‘co’, followed by one, two, three, or four characters.
594[-./]1026	594-1026, 594.1026, 594/1026 A dot inside a character class is not a metacharacter.


	CAUTION: A forward slash (/) marks regular expression boundaries in the configuration files for Foglight for Java EE Technologies. It is used to start and end regular expressions. You can escape with a backslash (\) if you are using a forward slash in a regular expression in a Foglight for Java EE Technologies configuration file. The forward slash is a regular character when it is used outside of the configuration files for Foglight for Java EE Technologies. A dot in a character class is not a metacharacter. A dash is not a metacharacter if it is the first or last character in a character class, or if it follows a leading caret.

Related topics:

•

How regular expressions are scanned

•

Typical regular expression patterns

•

Matching with character classes

•

Alternation in regular expressions