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 *  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
 *
 *      https://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.tools.ant.types.selectors;

import org.apache.tools.ant.BuildException;

import java.io.File;
import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.LinkOption;
import java.nio.file.attribute.GroupPrincipal;
import java.nio.file.attribute.PosixFileAttributes;

A selector that selects files based on their POSIX group.
Group is defined in terms of Files.readAttributes group attribute as provided by PosixFileAttributes, this means the selector will accept any file that exists and has the given group attribute.
Since:
Ant 1.10.4/**
 * A selector that selects files based on their POSIX group.
 *
 * <p>Group is defined in terms of {@link java.nio.file.Files#readAttributes}
 * group attribute as provided by {@link java.nio.file.attribute.PosixFileAttributes},
 * this means the selector will accept any file that exists and has the given
 * group attribute.</p>
 *
 * @since Ant 1.10.4
 */
public class PosixGroupSelector implements FileSelector {

    private String group;

    private boolean followSymlinks = true;

    
Sets the group name to look for.
Params:
group – the group name/**
     * Sets the group name to look for.
     * @param group the group name
     */
    public void setGroup(String group) {
        this.group = group;
    }

    
Sets the "follow symbolic links" option.
Params:
followSymlinks – whether or not symbolic links should be followed./**
     * Sets the "follow symbolic links" option.
     * @param followSymlinks whether or not symbolic links should be followed.
     */
    public void setFollowSymlinks(boolean followSymlinks) {
        this.followSymlinks = followSymlinks;
    }

    @Override
    public boolean isSelected(File basedir, String filename, File file) {
        if (group == null) {
            throw new BuildException("the group attribute is required");
        }
        try {
            GroupPrincipal actualGroup = followSymlinks ? Files.readAttributes(file.toPath(),
                    PosixFileAttributes.class).group() : Files.readAttributes(file.toPath(),
                    PosixFileAttributes.class, LinkOption.NOFOLLOW_LINKS).group();
            return actualGroup != null && actualGroup.getName().equals(group);
        } catch (IOException e) {
            // => not the expected group
        }
        return false;
    }
}