com.netflix.exhibitor.core.controlpanel.FileBasedPreferences.java Source code

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Here is the source code for com.netflix.exhibitor.core.controlpanel.FileBasedPreferences.java

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/*
 * Copyright 2013 Netflix, Inc.
 *
 *    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.
 */

package com.netflix.exhibitor.core.controlpanel;

import com.google.common.io.Closeables;
import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.OutputStream;
import java.util.Properties;
import java.util.prefs.AbstractPreferences;
import java.util.prefs.BackingStoreException;

/**
 * A wrapper around the JDK Preferences API that uses a file. IMPORTANT:
 * this class does NOT support multiple processes using the file.
 */
public class FileBasedPreferences extends AbstractPreferences {
    private final File file;
    private final Properties properties = new Properties();

    /**
     * @param file file to use as backing store
     * @throws IOException errors
     */
    public FileBasedPreferences(File file) throws IOException {
        super(null, "");
        this.file = file;

        if (file.exists()) {
            BufferedInputStream in = new BufferedInputStream(new FileInputStream(file));
            try {
                properties.load(in);
            } finally {
                Closeables.closeQuietly(in);
            }
        }
    }

    @Override
    protected void putSpi(String key, String value) {
        properties.setProperty(key, value);
    }

    @Override
    protected String getSpi(String key) {
        return properties.getProperty(key);
    }

    @Override
    protected void removeSpi(String key) {
        properties.remove(key);
    }

    @Override
    protected void removeNodeSpi() throws BackingStoreException {
        throw new UnsupportedOperationException();
    }

    @Override
    protected String[] keysSpi() throws BackingStoreException {
        return new String[0];
    }

    @Override
    protected String[] childrenNamesSpi() throws BackingStoreException {
        return new String[0];
    }

    @Override
    protected AbstractPreferences childSpi(String name) {
        throw new UnsupportedOperationException();
    }

    @Override
    protected void syncSpi() throws BackingStoreException {
    }

    @Override
    protected void flushSpi() throws BackingStoreException {
        if (!file.getParentFile().exists() && !file.getParentFile().mkdirs()) {
            throw new BackingStoreException("Could not create parent directories for: " + file);
        }

        OutputStream out = null;
        try {
            out = new BufferedOutputStream(new FileOutputStream(file));
            properties.store(out, "# Auto-generated by " + FileBasedPreferences.class.getName());
        } catch (IOException e) {
            throw new BackingStoreException(e);
        } finally {
            Closeables.closeQuietly(out);
        }
    }
}