Perl5Substitution implements a Substitution consisting of a
literal string, but allowing Perl5 variable interpolation referencing
saved groups in a match. This class is intended for use with
Util.substitute.
The substitution string may contain variable interpolations referring
to the saved parenthesized groups of the search pattern.
A variable interpolation is denoted by $1, or $2,
or $3, etc. If you want such expressions to be
interpreted literally, you should set the numInterpolations
parameter to INTERPOLATE_NONE . It is easiest to explain
what an interpolated variable does by giving an example:
Suppose you have the pattern b\d+: and you want to substitute
the b's for a's and the colon for a dash in parts of
your input matching the pattern. You can do this by changing the
pattern to b(\d+): and using the substitution expression
a$1-. When a substitution is made, the $1 means
"Substitute whatever was matched by the first saved group of the
matching pattern." An input of b123: after substitution
would yield a result of a123-. But there's a little more
to be aware of. If you set the numInterpolations parameter to
INTERPOLATE_ALL, then every time a match is found, the
interpolation variables are computed relative to that match.
But if numInterpolations is set to some positive integer, then
only the interpolation variables for the first numInterpolations
matches are computed relative to the most recent match. After that,
the remaining substitutions have their variable interpolations performed
relative to the numInterpolations 'th match. So using the
previously mentioned pattern and substitution expression, if you have
an input of
Tank b123: 85 Tank b256: 32 Tank b78: 22
and use a numInterpolations value of INTERPOLATE_ALL and
numSubs value (see
Util.substitute)
of SUBSTITUTE_ALL, then your result will be:
Tank a123- 85 Tank a256- 32 Tank a78- 22
But if you set numInterpolations to 2 and keep
numSubs with a value of SUBSTITUTE_ALL, your result is:
Tank a123- 85 Tank a256- 32 Tank a256- 22
Notice how the last substitution uses the same value for $1
as the second substitution.
A final thing to keep in mind is that if you use an interpolation variable
that corresponds to a group not contained in the match, then it is
interpreted as the empty string. So given the regular expression from the
example, and a substitution expression of a$2-, the result
of the last sample input would be:
Tank a- 85 Tank a- 32 Tank a- 22
The special substitution $& will interpolate the entire portion
of the input matched by the regular expression. $0 will
do the same, but it is recommended that it be avoided because the
latest versions of Perl use $0 to store the program name rather
than duplicate the behavior of $&.
Also, the result of substituting $ followed by a non-positive integer
is undefined. In order to include a $ in a substitution, it should
be escaped with a backslash (e.g., "\\$0").
Perl5 double-quoted string case modification is also supported in
the substitution. The following escape sequences are supported:
\\U
make substitution uppercase until end of substitution or \\E
\\u
make next character uppercase
\\L
make substitution uppercase until end of substitution or \\E
\\l
make next character uppercase
\\E
mark the end of the case modification
The double backslashes are shown to remind you that to make a
backslash get past Java's string handling and appear as a backslash
to the substitution, you must escape the backslash.
INTERPOLATE_ALL
A constant used when creating a Perl5Substitution indicating that
interpolation variables should be computed relative to the most
recent pattern match.
static int
INTERPOLATE_NONE
A constant used when creating a Perl5Substitution indicating that
interpolation variables should be interpreted literally, effectively
disabling interpolation.
Constructor Summary
Perl5Substitution()
Default constructor initializing substitution to a zero length
String and the number of interpolations to
INTERPOLATE_ALL.
Perl5Substitution(java.lang.String substitution)
Creates a Perl5Substitution using the specified substitution
and setting the number of interpolations to
INTERPOLATE_ALL.
Perl5Substitution(java.lang.String substitution,
int numInterpolations)
Creates a Perl5Substitution using the specified substitution
and setting the number of interpolations to the specified value.
Method Summary
void
appendSubstitution(java.lang.StringBuffer appendBuffer,
MatchResult match,
int substitutionCount,
PatternMatcherInput originalInput,
PatternMatcher matcher,
Pattern pattern)
Appends the substitution to a buffer containing the original input
with substitutions applied for the pattern matches found so far.
void
setSubstitution(java.lang.String substitution)
Sets the substitution represented by this Perl5Substitution, also
setting the number of interpolations to
INTERPOLATE_ALL.
void
setSubstitution(java.lang.String substitution,
int numInterpolations)
Sets the substitution represented by this Perl5Substitution, also
setting the number of interpolations to the specified value.
Methods inherited from class org.apache.oro.text.regex.StringSubstitution
A constant used when creating a Perl5Substitution indicating that
interpolation variables should be computed relative to the most
recent pattern match.
INTERPOLATE_NONE
public static final int INTERPOLATE_NONE
A constant used when creating a Perl5Substitution indicating that
interpolation variables should be interpreted literally, effectively
disabling interpolation.
Constructor Detail
Perl5Substitution
public Perl5Substitution()
Default constructor initializing substitution to a zero length
String and the number of interpolations to
INTERPOLATE_ALL.
Perl5Substitution
public Perl5Substitution(java.lang.String substitution)
Creates a Perl5Substitution using the specified substitution
and setting the number of interpolations to
INTERPOLATE_ALL.
Parameters:
substitution - The string to use as a substitution.
Perl5Substitution
public Perl5Substitution(java.lang.String substitution,
int numInterpolations)
Creates a Perl5Substitution using the specified substitution
and setting the number of interpolations to the specified value.
Parameters:
substitution - The string to use as a substitution.
numInterpolations - If set to INTERPOLATE_NONE, interpolation variables are
interpreted literally and not as references to the saved
parenthesized groups of a pattern match. If set to
INTERPOLATE_ALL , all variable interpolations
are computed relative to the pattern match responsible for
the current substitution. If set to a positive integer,
the first numInterpolations substitutions have
their variable interpolation performed relative to the
most recent match, but the remaining substitutions have
their variable interpolations performed relative to the
numInterpolations 'th match.
Method Detail
setSubstitution
public void setSubstitution(java.lang.String substitution)
Sets the substitution represented by this Perl5Substitution, also
setting the number of interpolations to
INTERPOLATE_ALL.
You should use this method in order to avoid repeatedly allocating new
Perl5Substitutions. It is recommended that you allocate a single
Perl5Substitution and reuse it by using this method when appropriate.
substitution - The string to use as a substitution.
setSubstitution
public void setSubstitution(java.lang.String substitution,
int numInterpolations)
Sets the substitution represented by this Perl5Substitution, also
setting the number of interpolations to the specified value.
You should use this method in order to avoid repeatedly allocating new
Perl5Substitutions. It is recommended that you allocate a single
Perl5Substitution and reuse it by using this method when appropriate.
Parameters:
substitution - The string to use as a substitution.
numInterpolations - If set to INTERPOLATE_NONE, interpolation variables are
interpreted literally and not as references to the saved
parenthesized groups of a pattern match. If set to
INTERPOLATE_ALL , all variable interpolations
are computed relative to the pattern match responsible for
the current substitution. If set to a positive integer,
the first numInterpolations substitutions have
their variable interpolation performed relative to the
most recent match, but the remaining substitutions have
their variable interpolations performed relative to the
numInterpolations 'th match.
Appends the substitution to a buffer containing the original input
with substitutions applied for the pattern matches found so far.
See
Substitution.appendSubstition()
for more details regarding the expected behavior of this method.