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 *  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
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 */

package org.apache.tools.ant.types.selectors;

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

import org.apache.tools.ant.BuildException;

A selector that selects files based on their owner.
Owner is defined in terms of Files.getOwner, this means the selector will accept any file that exists and is owned by the given user. If the 
getOwner method throws an UnsupportedOperationException the file in question is not included.
Since:
Ant 1.10.0/**
 * A selector that selects files based on their owner.
 *
 * <p>Owner is defined in terms of {@link
 * java.nio.file.Files#getOwner}, this means the selector will accept
 * any file that exists and is owned by the given user. If the {@code
 * getOwner} method throws an {@code UnsupportedOperationException}
 * the file in question is not included.</p>
 *
 * @since Ant 1.10.0
 */
public class OwnedBySelector implements FileSelector {

    private String owner;

    private boolean followSymlinks = true;

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

    
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 (owner == null) {
            throw new BuildException("the owner attribute is required");
        }
        if (file != null) {
            try {
                UserPrincipal user = followSymlinks ? Files.getOwner(file.toPath())
                        : Files.getOwner(file.toPath(), LinkOption.NOFOLLOW_LINKS);
                return user != null && owner.equals(user.getName());
            } catch (UnsupportedOperationException | IOException ex) {
                // => not the expected owner
            }
        }
        return false;
    }

}