uk.org.ogsadai.activity.files
Class SubstitutionStringParser

java.lang.Object
  |
  +--uk.org.ogsadai.activity.files.SubstitutionStringParser

public class SubstitutionStringParser

extends java.lang.Object

Implementation of a recursive-descent parser intended to parse strings which contain variables represented by $n or ${n}, where n is a non-negative integer.

The grammar from which valid strings are drawn is:

STRING	::=	CHAR | CHAR STRING
CHAR	::=	\ c | c | VAR
VAR	::=	$ INT | $ { INT }
INT	::=	n | n INT

where n is an integer, 0 <= n <= 9; c is a character.

This class is intended to be used in the following way:

String[] groups = matcher.groups();
SubstitutionStringParser parser = new SubstitutionStringParser(groups, string);
String result = parser.readString();

Initially, we have a matcher object, of type AbstractMatcher, which has already found a match of its regular expression. The string object, of type String, is a string containing group variables. The resulting result string contains the contents of string with group variables replaced by the matching text in the appropriate element of the groups array.

Author:

The OGSA-DAI Project Team

Field Summary

private static java.lang.String	COPYRIGHT_NOTICE Copyright statement
private java.lang.String[]	mGroups An array of the text matching each group in the matcher's regular expression.
private int	mIndex The offset of the character in the string that we are currently considering.
private java.lang.String	mString The string containing the group variables.
private char	mToken The character in the string that we are currently considering.

Constructor Summary

SubstitutionStringParser(java.lang.String[] groups, java.lang.String string)
Construct a new parser, with supplied text matched by groups in a regular expression, and a string containing group variables.

Method Summary

private static boolean	isNumber(char c) Return whether a character is an integer in the range [0, 9].
void	lex() Move forward to consider the next character in the string.
private java.lang.String	outputToken(char token) Convert a character to a string containing just that character.
private java.lang.String	readChar() From the current position in the string, read an instance of the CHAR non-terminal symbol in the grammar.
private int	readInt() From the current position in the string, read an instance of the INT non-terminal symbol in the grammar.
java.lang.String	readString() Return the original string, but with the group variables replaced by the corresponding values from the matched groups of text.
private java.lang.String	readVar() From the current position in the string, read an instance of the VAR non-terminal symbol in the grammar.
private java.lang.String	variable(int var) Return the value of the text match corresponding to a particular group in the regular expression.

Methods inherited from class java.lang.Object

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

Field Detail

COPYRIGHT_NOTICE

private static final java.lang.String COPYRIGHT_NOTICE

Copyright statement

See Also:

Constant Field Values

mString

private java.lang.String mString

The string containing the group variables.

mGroups

private java.lang.String[] mGroups

An array of the text matching each group in the matcher's regular expression.

mIndex

private int mIndex

The offset of the character in the string that we are currently considering.

mToken

private char mToken

The character in the string that we are currently considering.

Constructor Detail

SubstitutionStringParser

public SubstitutionStringParser(java.lang.String[] groups,
                                java.lang.String string)

Construct a new parser, with supplied text matched by groups in a regular expression, and a string containing group variables.

Parameters:

groups - The text matched by the parenthesised groups in the regular expression. The element at index zero is the string matched by the entire regular expression.

string - The string containing group variables

Method Detail

lex

public void lex()

Move forward to consider the next character in the string.

readString

public java.lang.String readString()
                            throws MalformedReplacementStringException

Return the original string, but with the group variables replaced by the corresponding values from the matched groups of text. This corresponds to the STRING non-terminal in the grammar.

Returns:

the string, with appropriate replacements made

Throws:

MalformedReplacementStringException - If the string could not be parsed

readChar

private java.lang.String readChar()
                           throws MalformedReplacementStringException

From the current position in the string, read an instance of the CHAR non-terminal symbol in the grammar.

Returns:

the value of the CHAR non-terminal

Throws:

MalformedReplacementStringException - If the CHAR could not be read

readVar

private java.lang.String readVar()
                          throws MalformedReplacementStringException

From the current position in the string, read an instance of the VAR non-terminal symbol in the grammar.

Returns:

the value of the VAR non-terminal

Throws:

MalformedReplacementStringException - If the VAR could not be read

readInt

private int readInt()
             throws MalformedReplacementStringException

From the current position in the string, read an instance of the INT non-terminal symbol in the grammar.

Returns:

the value of the INT non-terminal

Throws:

MalformedReplacementStringException - If the INT could not be read

isNumber

private static boolean isNumber(char c)

Return whether a character is an integer in the range [0, 9].

Parameters:

c - A character to test

Returns:

true if the character is a digit, false otherwise

variable

private java.lang.String variable(int var)

Return the value of the text match corresponding to a particular group in the regular expression.

Parameters:

var - The number of the group to obtain the value of

Returns:

the text matched by the parenthesised group of the regular expression

outputToken

private java.lang.String outputToken(char token)

Convert a character to a string containing just that character.

Parameters:

token - The character

Returns:

the corresponding string