/
CharsetDeterminer.java
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/
CharsetDeterminer.java
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/*
* Copyright (c) 2017 Contributors to the Eclipse Foundation
*
* See the NOTICE file(s) distributed with this work for additional
* information regarding copyright ownership.
*
* This program and the accompanying materials are made available under the
* terms of the Eclipse Public License 2.0 which is available at
* http://www.eclipse.org/legal/epl-2.0
*
* SPDX-License-Identifier: EPL-2.0
*/
package org.eclipse.ditto.model.base.common;
import java.nio.charset.Charset;
import java.nio.charset.StandardCharsets;
import java.util.function.Function;
import java.util.regex.Pattern;
import javax.annotation.Nullable;
import javax.annotation.concurrent.Immutable;
/**
* Determines the charset from a given content-type or falls back to UTF-8 if no specific one was present
* in content-type.
*/
@Immutable
public final class CharsetDeterminer implements Function<CharSequence, Charset> {
private static final Pattern CHARSET_PATTERN = Pattern.compile(";.?charset=");
@Nullable private static CharsetDeterminer instance = null;
private CharsetDeterminer() {
super();
}
/**
* Returns an instance of {@code CharsetDeterminer}.
*
* @return the instance.
*/
public static CharsetDeterminer getInstance() {
CharsetDeterminer result = instance;
if (null == result) {
result = new CharsetDeterminer();
instance = result;
}
return result;
}
@Override
public Charset apply(@Nullable final CharSequence contentType) {
if (null != contentType) {
final String[] withCharset = CHARSET_PATTERN.split(contentType, 2);
if (2 == withCharset.length && Charset.isSupported(withCharset[1])) {
return Charset.forName(withCharset[1]);
}
}
return StandardCharsets.UTF_8;
}
}