/*---------------------------------------------------------------------------*\
$Id: ac4d589767743d2aab8f43b4e3c1e2530bf54f3f $
---------------------------------------------------------------------------
This software is released under a BSD-style license:
Copyright (c) 2004-2007 Brian M. Clapper. All rights reserved.
Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are
met:
1. Redistributions of source code must retain the above copyright notice,
this list of conditions and the following disclaimer.
2. The end-user documentation included with the redistribution, if any,
must include the following acknowlegement:
d
"This product includes software developed by Brian M. Clapper
(bmc@clapper.org, http://www.clapper.org/bmc/). That software is
copyright (c) 2004-2007 Brian M. Clapper."
Alternately, this acknowlegement may appear in the software itself,
if wherever such third-party acknowlegements normally appear.
3. Neither the names "clapper.org", "clapper.org Java Utility Library",
nor any of the names of the project contributors may be used to
endorse or promote products derived from this software without prior
written permission. For written permission, please contact
bmc@clapper.org.
4. Products derived from this software may not be called "clapper.org
Java Utility Library", nor may "clapper.org" appear in their names
without prior written permission of Brian M. Clapper.
THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN
NO EVENT SHALL BRIAN M. CLAPPER BE LIABLE FOR ANY DIRECT, INDIRECT,
INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
\*---------------------------------------------------------------------------*/
package org.clapper.util.text;
/**
* The UnixShellVariableSubstituter class implements the
* VariableSubstituter interface and provides an inline
* variable substitution capability using a simplified Unix Bourne (or GNU
* bash) shell variable syntax. This syntax recognizes the
* "$var", "${var}" and "${var?default} sequences
* as variable references. For example, given the string (variables in
* bold):
*
*
*
* file:$user.home/profiles/$PLATFORM/${cfg?config}.txt
*
*
*
* and the variable values:
*
*
* user.home=/home/bmc
* PLATFORM=freebsd
*
*
* a UnixShellVariableSubstituter will produce the result
* string (substitutions noted in bold):
*
*
* file:/home/bmc/profiles/freebsd/config.txt
*
*
* Notes and Caveats
*
*
* - To include a literal "$" character in a string, precede it with
* a backslash.
*
*
- If a variable doesn't have a value, its reference is replaced
* by an empty string, unless it is of the form ${var?default}.
* For instance, if variable foo does not have a value, the
* string $foo will substitute "", ${foo} will
* substitute "", and ${foo?foo value} will substitute
* "foo value".
*
*
- As with all VariableSubstituter classes, an instance
* of the UnixShellVariableSubstituter class enforces
* its own variable syntax (Unix Bourne shell-style, in this case),
* but defers actual variable value resolution to a separate
* VariableDereferencer object. One consequence of that
* approach is that variable names may be case-sensitive or
* case-insensitive, depending on how the supplied
* VariableDereferencer object interprets variable
* names.
*
*
* It's also possible to configure a UnixShellVariableSubstituter
* to throw a {@link UndefinedVariableException}, rather than substituting
* a blank, if a variable is undefined and a default value is not specified.
* See the {@link #setAbortOnUndefinedVariable} method.
*
* @see WindowsCmdVariableSubstituter
* @see VariableDereferencer
* @see VariableSubstituter
* @see java.lang.String
*
* @version $Revision$
*
* @author Copyright © 2004-2007 Brian M. Clapper
*/
public class UnixShellVariableSubstituter
extends AbstractVariableSubstituter
{
/*----------------------------------------------------------------------*\
Private Constants
\*----------------------------------------------------------------------*/
private static final char VAR_START = '$';
private static final char VAR_OPEN_BRACE = '{';
private static final char VAR_CLOSE_BRACE = '}';
private static final char VAR_IF_EXISTS_OP = '?';
private enum ParseState {NOT_IN_VAR, IN_VAR, IN_DEFAULT_VALUE};
/*----------------------------------------------------------------------*\
Public Constants
\*----------------------------------------------------------------------*/
/**
* List of metacharacters that are used to introduce a variable reference.
* These characters cannot be permitted in a variable name.
*/
public static final String VARIABLE_METACHARACTERS = new String
(new char[]
{
VAR_START,
VAR_OPEN_BRACE,
VAR_CLOSE_BRACE,
VAR_IF_EXISTS_OP
});
/*----------------------------------------------------------------------*\
Private Data Items
\*----------------------------------------------------------------------*/
private boolean honorEscapes = false;
/*----------------------------------------------------------------------*\
Constructor
\*----------------------------------------------------------------------*/
/**
* Default constructor.
*/
public UnixShellVariableSubstituter()
{
super();
}
/*----------------------------------------------------------------------*\
Public Methods
\*----------------------------------------------------------------------*/
/**
* Get the value of the flag that controls whether or not the
* substitute() method will honor backslash escapes within
* variable references.
*
* @return true if backslash escapes are honored,
* false if not.
*
* @see #setHonorEscapes
*/
public boolean getHonorEscapes()
{
return honorEscapes;
}
/**
* Set the value of the flag that controls whether or not the
* substitute() method will honor backslash escapes within
* variable references. The flag defaults to false.
*
* @param enable true if backslash escapes should be honored,
* false if not.
*
* @see #getHonorEscapes
*/
public void setHonorEscapes(boolean enable)
{
this.honorEscapes = enable;
}
/**
* Substitute all variable references in the supplied string, using
* a Unix Bourne Shell-style variable syntax. This method uses a
* supplied VariableDereferencer object to resolve variable
* values. Note that this method throws no exceptions. Syntax errors in
* the variable references are silently ignored. Variables that have no
* value are substituted as the empty string. If the
* nameChecker parameter is not null, this method calls its
* {@link VariableNameChecker#legalVariableCharacter(char)} method to
* determine whether a given character is a legal part of a variable
* name. If nameChecker is null, then this method assumes that
* variable names may consist solely of alphanumeric characters,
* underscores and periods. This syntax is sufficient to substitute
* variables from System.properties, for instance.
*
* @param s the string containing possible variable references
* @param deref the VariableDereferencer object
* to use to resolve the variables' values.
* @param nameChecker the VariableNameChecker object to be
* used to check for legal variable name characters,
* or null
* @param context an optional context object, passed through
* unmodified to the deref object's
* {@link VariableDereferencer#getVariableValue}
* method. This object can be anything at all (and,
* in fact, may be null if you don't care.) It's
* primarily useful for passing context information
* from the caller to the
* VariableDereferencer.
*
* @return The (possibly) expanded string.
*
* @throws UndefinedVariableException undefined variable, and
* {@link #getAbortOnUndefinedVariable}
* returns true
* @throws VariableSyntaxException syntax error, and
* {@link #getAbortOnSyntaxError}
* returns true
* @throws VariableSubstitutionException substitution error
*
* @see #substitute(String,VariableDereferencer,Object)
* @see VariableDereferencer#getVariableValue(String,Object)
*
* @deprecated As of version 2.3; please use {@link #setHonorEscapes}
*/
public String substitute(String s,
VariableDereferencer deref,
VariableNameChecker nameChecker,
Object context,
boolean allowEscapes)
throws VariableSyntaxException,
UndefinedVariableException,
VariableSubstitutionException
{
boolean save = getHonorEscapes();
setHonorEscapes(allowEscapes);
try
{
return substitute(s, deref, nameChecker, context);
}
finally
{
setHonorEscapes(save);
}
}
/**
* Substitute all variable references in the supplied string, using
* a Unix Bourne Shell-style variable syntax. This method uses a
* supplied VariableDereferencer object to resolve variable
* values. Note that this method throws no exceptions. Syntax errors in
* the variable references are silently ignored. Variables that have no
* value are substituted as the empty string. If the
* nameChecker parameter is not null, this method calls its
* {@link VariableNameChecker#legalVariableCharacter(char)} method to
* determine whether a given character is a legal part of a variable
* name. If nameChecker is null, then this method assumes that
* variable names may consist solely of alphanumeric characters,
* underscores and periods. This syntax is sufficient to substitute
* variables from System.properties, for instance.
*
* @param s the string containing possible variable references
* @param deref the VariableDereferencer object
* to use to resolve the variables' values.
* @param nameChecker the VariableNameChecker object to be
* used to check for legal variable name characters,
* or null
* @param context an optional context object, passed through
* unmodified to the deref object's
* {@link VariableDereferencer#getVariableValue}
* method. This object can be anything at all (and,
* in fact, may be null if you don't care.) It's
* primarily useful for passing context information
* from the caller to the
* VariableDereferencer.
*
* @return The (possibly) expanded string.
*
* @throws UndefinedVariableException undefined variable, and
* {@link #getAbortOnUndefinedVariable}
* returns true
* @throws VariableSyntaxException syntax error, and
* {@link #getAbortOnSyntaxError}
* returns true
* @throws VariableSubstitutionException substitution error
*
* @see #substitute(String,VariableDereferencer,Object)
* @see VariableDereferencer#getVariableValue(String,Object)
*/
public String substitute(String s,
VariableDereferencer deref,
VariableNameChecker nameChecker,
Object context)
throws VariableSyntaxException,
UndefinedVariableException,
VariableSubstitutionException
{
StringBuilder result = new StringBuilder();
int len = s.length();
StringBuilder var = new StringBuilder();
StringBuilder defaultValue = new StringBuilder();
ParseState state = ParseState.NOT_IN_VAR;
boolean braces = false;
boolean nextIsLiteral = false;
boolean syntaxError = false;
int i;
char ch[];
if (nameChecker == null)
nameChecker = this;
ch = s.toCharArray();
i = 0;
while ((i < len) && (! syntaxError))
{
char c = ch[i++];
if (nextIsLiteral)
{
// Literal
result.append(c);
nextIsLiteral = false;
}
else if (state == ParseState.NOT_IN_VAR)
{
// Not in a variable.
if (c == VAR_START) // Possible start of new variable.
state = ParseState.IN_VAR;
else if (honorEscapes && (c == '\\')) // next char is literal
nextIsLiteral = true;
else // Just a regular old character.
result.append(c);
}
else if (state == ParseState.IN_DEFAULT_VALUE)
{
if (c == VAR_CLOSE_BRACE)
{
state = ParseState.IN_VAR;
i--;
}
else
{
defaultValue.append(c);
}
}
// If we get here, we're currently assembling a variable name.
else if ( (var.length() == 0) && (c == VAR_OPEN_BRACE) )
{
// start of ${...} sequence
braces = true;
}
else if (braces && (c == VAR_IF_EXISTS_OP))
{
// Specification of default value.
state = ParseState.IN_DEFAULT_VALUE;
}
else if (nameChecker.legalVariableCharacter(c))
{
var.append (c);
}
else
{
// Not a legal variable character, so we're done assembling
// this variable name.
String varName = var.toString();
state = ParseState.NOT_IN_VAR;
if (braces)
{
if (c == VAR_CLOSE_BRACE) // final brace; substitute
{
result.append(dereference(varName,
defaultValue.toString(),
context,
deref));
}
else // Missing trailing '}'. No substitution.
{
result.append(VAR_START);
result.append(VAR_OPEN_BRACE);
result.append(var.toString());
i--; // push 'c' back on the stack
syntaxError = true;
}
braces = false;
}
else if (var.length() == 0)
{
// '$' followed by something illegal. Syntax error.
result.append (VAR_START);
i--; // push 'c' back on the stack
syntaxError = true;
}
else
{
// Legal, non-bracketed variable. Substitute.
result.append(dereference(varName,
defaultValue.toString(),
context,
deref));
i--; // push 'c' back on the stack
}
var.setLength (0);
}
} // end while
if (state == ParseState.IN_VAR)
{
// One last variable to handle.
if (braces) // No trailing '}'. Syntax error.
{
result.append(VAR_START);
result.append(VAR_OPEN_BRACE);
result.append(var.toString());
syntaxError = true;
}
else if (var.length() == 0) // just a trailing "$"
{
result.append(VAR_START);
}
else
{
result.append(dereference(var.toString(),
defaultValue.toString(),
context,
deref));
}
}
if (syntaxError && (getAbortOnSyntaxError() == true))
{
throw new VariableSyntaxException
("Syntax error in reference to variable \"" +
var.toString() + "\"");
}
return result.toString();
}
/**
* Determine whether a character is one of the variable metacharacters
* (i.e., the characters that identify a variable reference). Such
* characters cannot be part of a variable name.
*
* @param c the character to test
*
* @return true if the character is one of the variable
* metacharacters, false if not
*/
public static boolean isVariableMetacharacter (char c)
{
boolean isMeta = false;
char[] meta = VARIABLE_METACHARACTERS.toCharArray();
for (int i = 0; i < meta.length; i++)
{
if (c == meta[i])
{
isMeta = true;
break;
}
}
return isMeta;
}
/*----------------------------------------------------------------------*\
Private Methods
\*----------------------------------------------------------------------*/
private String dereference(String varName,
String defaultValue,
Object context,
VariableDereferencer deref)
throws VariableSubstitutionException
{
String result = deref.getVariableValue(varName, context);
if ((result == null) || (result.length() == 0))
{
if ((defaultValue.length() == 0) &&
(getAbortOnUndefinedVariable() == true))
{
throw new UndefinedVariableException
("Variable \"" + varName + "\" is undefined.");
}
result = defaultValue;
}
return result;
}
}
Ads help maintain this website.