AbstractListDelimiterHandler.java
/*
* 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.lang.reflect.Array;
import java.nio.file.Path;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Iterator;
import java.util.LinkedList;
import java.util.Set;
/**
* <p>
* An abstract base class for concrete {@code ListDelimiterHandler} implementations.
* </p>
* <p>
* This base class provides a fully functional implementation for parsing a value object which can deal with different
* cases like collections, arrays, iterators, etc. This logic is typically needed by every concrete subclass. Other
* methods are partly implemented handling special corner cases like <b>null</b> values; concrete subclasses do not have
* do implement the corresponding checks.
* </p>
*
* @since 2.0
*/
public abstract class AbstractListDelimiterHandler implements ListDelimiterHandler {
static Collection<?> flatten(final ListDelimiterHandler handler, final Object value, final int limit, final Set<Object> dejaVu) {
dejaVu.add(value);
if (value instanceof String) {
return handler.split((String) value, true);
}
final Collection<Object> result = new LinkedList<>();
if (value instanceof Path) {
// Don't handle as an Iterable.
result.add(value);
} else if (value instanceof Iterable) {
flattenIterator(handler, result, ((Iterable<?>) value).iterator(), limit, dejaVu);
} else if (value instanceof Iterator) {
flattenIterator(handler, result, (Iterator<?>) value, limit, dejaVu);
} else if (value != null) {
if (value.getClass().isArray()) {
for (int len = Array.getLength(value), idx = 0, size = 0; idx < len && size < limit; idx++, size = result.size()) {
result.addAll(handler.flatten(Array.get(value, idx), limit - size));
}
} else {
result.add(value);
}
}
return result;
}
/**
* Flattens the given iterator. For each element in the iteration {@code flatten()} is called recursively.
*
* @param handler the working handler
* @param target the target collection
* @param iterator the iterator to process
* @param limit a limit for the number of elements to extract
* @param dejaVue Previously visited objects.
*/
static void flattenIterator(final ListDelimiterHandler handler, final Collection<Object> target, final Iterator<?> iterator, final int limit,
final Set<Object> dejaVue) {
int size = target.size();
while (size < limit && iterator.hasNext()) {
final Object next = iterator.next();
if (!dejaVue.contains(next)) {
target.addAll(flatten(handler, next, limit - size, dejaVue));
size = target.size();
}
}
}
/**
* {@inheritDoc} This implementation checks whether the object to be escaped is a string. If yes, it delegates to
* {@link #escapeString(String)}, otherwise no escaping is performed. Eventually, the passed in transformer is invoked
* so that additional encoding can be performed.
*/
@Override
public Object escape(final Object value, final ValueTransformer transformer) {
return transformer.transformValue(value instanceof String ? escapeString((String) value) : value);
}
/**
* Escapes the specified string. This method is called by {@code escape()} if the passed in object is a string. Concrete
* subclasses have to implement their specific escaping logic here, so that the list delimiters they support are
* properly escaped.
*
* @param s the string to be escaped (not <b>null</b>)
* @return the escaped string
*/
protected abstract String escapeString(String s);
/**
* Performs the actual work as advertised by the {@code parse()} method. This method delegates to
* {@link #flatten(Object, int)} without specifying a limit.
*
* @param value the value to be processed
* @return a "flat" collection containing all primitive values of the passed in object
*/
private Collection<?> flatten(final Object value) {
return flatten(value, Integer.MAX_VALUE);
}
/**
* {@inheritDoc} Depending on the type of the passed in object the following things happen:
* <ul>
* <li>Strings are checked for delimiter characters and split if necessary. This is done by calling the {@code split()}
* method.</li>
* <li>For objects implementing the {@code Iterable} interface, the corresponding {@code Iterator} is obtained, and
* contained elements are added to the resulting iteration.</li>
* <li>Arrays are treated as {@code Iterable} objects.</li>
* <li>All other types are directly inserted.</li>
* <li>Recursive combinations are supported, e.g. a collection containing an array that contains strings: The resulting
* collection will only contain primitive objects.</li>
* </ul>
*/
@Override
public Iterable<?> parse(final Object value) {
return flatten(value);
}
/**
* {@inheritDoc} This implementation handles the case that the passed in string is <b>null</b>. In this case, an empty
* collection is returned. Otherwise, this method delegates to {@link #splitString(String, boolean)}.
*/
@Override
public Collection<String> split(final String s, final boolean trim) {
return s == null ? new ArrayList<>(0) : splitString(s, trim);
}
/**
* Actually splits the passed in string which is guaranteed to be not <b>null</b>. This method is called by the base
* implementation of the {@code split()} method. Here the actual splitting logic has to be implemented.
*
* @param s the string to be split (not <b>null</b>)
* @param trim a flag whether the single components have to be trimmed
* @return a collection with the extracted components of the passed in string
*/
protected abstract Collection<String> splitString(String s, boolean trim);
}