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Tools to assist in the reading of configuration/preferences files in
various formats
/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.commons.configuration2.convert;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.Iterator;
import java.util.List;
import org.apache.commons.lang3.StringUtils;
/**
*
* A specialized implementation of {@code ListDelimiterHandler} which simulates
* the list delimiter handling as it was used by {@code PropertiesConfiguration}
* in Commons Configuration 1.x.
*
*
* This class mainly exists for compatibility reasons. It is intended to be used
* by applications which have to deal with properties files created by an older
* version of this library.
*
*
* In the 1.x series of Commons Configuration list handling was not fully
* consistent. The escaping of property values was done in a different way if
* they contained a list delimiter or not. From version 2.0 on, escaping is more
* stringent which might cause slightly different results when parsing
* properties files created by or for Configuration 1.x. If you encounter such
* problems, you can switch to this {@code ListDelimiterHandler} implementation
* rather than the default one. In other cases, this class should not be used!
*
*
* Implementation note: An instance of this class can safely be shared between
* multiple {@code Configuration} instances.
*
*
* @since 2.0
*/
public class LegacyListDelimiterHandler extends AbstractListDelimiterHandler
{
/** Constant for the escaping character. */
private static final String ESCAPE = "\\";
/** Constant for the escaped escaping character. */
private static final String DOUBLE_ESC = ESCAPE + ESCAPE;
/** Constant for a duplicated sequence of escaping characters. */
private static final String QUAD_ESC = DOUBLE_ESC + DOUBLE_ESC;
/** The list delimiter character. */
private final char delimiter;
/**
* Creates a new instance of {@code LegacyListDelimiterHandler} and sets the
* list delimiter character.
*
* @param listDelimiter the list delimiter character
*/
public LegacyListDelimiterHandler(final char listDelimiter)
{
delimiter = listDelimiter;
}
/**
* Returns the list delimiter character.
*
* @return the list delimiter character
*/
public char getDelimiter()
{
return delimiter;
}
/**
* {@inheritDoc} This implementation performs delimiter escaping for a
* single value (which is not part of a list).
*/
@Override
public Object escape(final Object value, final ValueTransformer transformer)
{
return escapeValue(value, false, transformer);
}
/**
* {@inheritDoc} This implementation performs a special encoding of
* backslashes at the end of a string so that they are not interpreted as
* escape character for a following list delimiter.
*/
@Override
public Object escapeList(final List values, final ValueTransformer transformer)
{
if (!values.isEmpty())
{
final Iterator it = values.iterator();
String lastValue = escapeValue(it.next(), true, transformer);
final StringBuilder buf = new StringBuilder(lastValue);
while (it.hasNext())
{
// if the last value ended with an escape character, it has
// to be escaped itself; otherwise the list delimiter will
// be escaped
if (lastValue.endsWith(ESCAPE)
&& (countTrailingBS(lastValue) / 2) % 2 != 0)
{
buf.append(ESCAPE).append(ESCAPE);
}
buf.append(getDelimiter());
lastValue = escapeValue(it.next(), true, transformer);
buf.append(lastValue);
}
return buf.toString();
}
return null;
}
/**
* {@inheritDoc} This implementation simulates the old splitting algorithm.
* The string is split at the delimiter character if it is not escaped. If
* the delimiter character is not found, the input is returned unchanged.
*/
@Override
protected Collection splitString(final String s, final boolean trim)
{
if (s.indexOf(getDelimiter()) < 0)
{
return Collections.singleton(s);
}
final List list = new ArrayList<>();
StringBuilder token = new StringBuilder();
int begin = 0;
boolean inEscape = false;
final char esc = ESCAPE.charAt(0);
while (begin < s.length())
{
final char c = s.charAt(begin);
if (inEscape)
{
// last character was the escape marker
// can current character be escaped?
if (c != getDelimiter() && c != esc)
{
// no, also add escape character
token.append(esc);
}
token.append(c);
inEscape = false;
}
else
{
if (c == getDelimiter())
{
// found a list delimiter -> add token and
// resetDefaultFileSystem buffer
String t = token.toString();
if (trim)
{
t = t.trim();
}
list.add(t);
token = new StringBuilder();
}
else if (c == esc)
{
// eventually escape next character
inEscape = true;
}
else
{
token.append(c);
}
}
begin++;
}
// Trailing delimiter?
if (inEscape)
{
token.append(esc);
}
// Add last token
String t = token.toString();
if (trim)
{
t = t.trim();
}
list.add(t);
return list;
}
/**
* {@inheritDoc} This is just a dummy implementation. It is never called.
*/
@Override
protected String escapeString(final String s)
{
return null;
}
/**
* Performs the escaping of backslashes in the specified properties value.
* Because a double backslash is used to escape the escape character of a
* list delimiter, double backslashes also have to be escaped if the
* property is part of a (single line) list. In addition, because the output
* is written into a properties file, each occurrence of a backslash again
* has to be doubled. This method is called by {@code escapeValue()}.
*
* @param value the value to be escaped
* @param inList a flag whether the value is part of a list
* @return the value with escaped backslashes as string
*/
protected String escapeBackslashs(final Object value, final boolean inList)
{
String strValue = String.valueOf(value);
if (inList && strValue.indexOf(DOUBLE_ESC) >= 0)
{
strValue = StringUtils.replace(strValue, DOUBLE_ESC, QUAD_ESC);
}
return strValue;
}
/**
* Escapes the given property value. This method is called on saving the
* configuration for each property value. It ensures a correct handling of
* backslash characters and also takes care that list delimiter characters
* in the value are escaped.
*
* @param value the property value
* @param inList a flag whether the value is part of a list
* @param transformer the {@code ValueTransformer}
* @return the escaped property value
*/
protected String escapeValue(final Object value, final boolean inList,
final ValueTransformer transformer)
{
String escapedValue =
String.valueOf(transformer.transformValue(escapeBackslashs(
value, inList)));
if (getDelimiter() != 0)
{
escapedValue =
StringUtils.replace(escapedValue,
String.valueOf(getDelimiter()), ESCAPE
+ getDelimiter());
}
return escapedValue;
}
/**
* Returns the number of trailing backslashes. This is sometimes needed for
* the correct handling of escape characters.
*
* @param line the string to investigate
* @return the number of trailing backslashes
*/
private static int countTrailingBS(final String line)
{
int bsCount = 0;
for (int idx = line.length() - 1; idx >= 0 && line.charAt(idx) == '\\'; idx--)
{
bsCount++;
}
return bsCount;
}
}