org.jolokia.docker.maven.util.DockerFileUtil Maven / Gradle / Ivy
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package org.jolokia.docker.maven.util;/*
*
* Copyright 2015 Roland Huss
*
* Licensed 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.
*/
import java.io.*;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
/**
* Utility class for dealing with dockerfiles
* @author roland
* @since 21/01/16
*/
public class DockerFileUtil {
private DockerFileUtil() {}
/**
* Extract the base image from a dockerfile. The first line containing a FROM is
* taken.
*
* @param dockerfile file from where to extract the base image
* @return the base image name or null if none is found.
*/
public static String extractBaseImage(File dockerfile) throws IOException {
try (BufferedReader reader = new BufferedReader(new FileReader(dockerfile))) {
String line;
Pattern fromPattern = Pattern.compile("^\\s*FROM\\s+([^\\s]+).*$", Pattern.CASE_INSENSITIVE);
while ((line = reader.readLine()) != null) {
Matcher matcher = fromPattern.matcher(line);
if (matcher.matches()) {
return matcher.group(1);
}
}
return null;
}
}
}