com.lithium.flow.store.FileStore.java Source code

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Here is the source code for com.lithium.flow.store.FileStore.java

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/*
 * Copyright 2015 Lithium Technologies, 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.lithium.flow.store;

import static com.fasterxml.jackson.databind.SerializationFeature.INDENT_OUTPUT;
import static com.google.common.base.Preconditions.checkNotNull;
import static java.nio.file.attribute.PosixFilePermission.GROUP_READ;
import static java.nio.file.attribute.PosixFilePermission.GROUP_WRITE;
import static java.nio.file.attribute.PosixFilePermission.OWNER_READ;
import static java.nio.file.attribute.PosixFilePermission.OWNER_WRITE;

import java.io.File;
import java.io.IOException;
import java.nio.file.Files;
import java.util.HashMap;
import java.util.Map;
import java.util.Set;

import javax.annotation.Nonnull;
import javax.annotation.Nullable;

import com.fasterxml.jackson.databind.ObjectMapper;
import com.google.common.collect.Sets;

/**
 * @author Matt Ayres
 */
public class FileStore implements Store {
    private final File file;
    private final ObjectMapper mapper = new ObjectMapper().enable(INDENT_OUTPUT);

    public FileStore(@Nonnull File file) {
        this.file = checkNotNull(file);
    }

    @Override
    public void putValue(@Nonnull String key, @Nullable String value) {
        Map<String, String> map = read();
        if (value != null) {
            map.put(key, value);
        } else {
            map.remove(key);
        }
        write(map);
    }

    @Override
    @Nullable
    public String getValue(@Nonnull String key) {
        return read().get(key);
    }

    @Override
    @Nonnull
    public Set<String> getKeys() {
        return read().keySet();
    }

    @SuppressWarnings("unchecked")
    private Map<String, String> read() {
        if (file.exists()) {
            try {
                return mapper.readValue(file, Map.class);
            } catch (IOException e) {
                throw new StoreException("failed to read " + file, e);
            }
        } else {
            return new HashMap<>();
        }
    }

    private void write(@Nonnull Map<String, String> map) {
        try {
            mapper.writeValue(file, map);
            Files.setPosixFilePermissions(file.toPath(),
                    Sets.newHashSet(OWNER_READ, OWNER_WRITE, GROUP_READ, GROUP_WRITE));
        } catch (IOException e) {
            throw new StoreException("failed to write " + file, e);
        }
    }
}