co.cask.cdap.filetailer.state.FileTailerStateProcessorImpl.java Source code

Introduction

Here is the source code for co.cask.cdap.filetailer.state.FileTailerStateProcessorImpl.java

Source

/*
 * Copyright  2014 Cask Data, 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 co.cask.cdap.filetailer.state;

import co.cask.cdap.filetailer.state.exception.FileTailerStateProcessorException;
import com.google.common.base.Preconditions;
import com.google.common.io.Closeables;
import com.google.common.io.Files;
import com.google.gson.Gson;
import com.google.gson.stream.JsonWriter;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.io.BufferedReader;
import java.io.File;
import java.io.IOException;
import java.nio.charset.Charset;

/**
 * File Tailer state processor
 */
public class FileTailerStateProcessorImpl implements FileTailerStateProcessor {

    private static final Logger LOG = LoggerFactory.getLogger(FileTailerStateProcessorImpl.class);
    private static final Charset UTF_8 = Charset.forName("UTF-8");
    private static final Gson GSON = new Gson();

    private final File stateDir;
    private final File stateFile;

    public FileTailerStateProcessorImpl(File stateDir, String stateFileName) {
        this.stateDir = stateDir;
        stateFile = new File(stateDir, stateFileName);
    }

    @Override
    public void saveState(FileTailerState state) throws FileTailerStateProcessorException {
        try {
            Preconditions.checkNotNull(state);
        } catch (NullPointerException e) {
            LOG.info("Cannot save null state");
            return;
        }
        createDirs(stateDir);
        LOG.debug("Start saving File Tailer state ..");
        try {
            JsonWriter jsonWriter = new JsonWriter(Files.newWriter(stateFile, UTF_8));
            try {
                GSON.toJson(state, FileTailerState.class, jsonWriter);
                LOG.debug("File Tailer state saved successfully");
            } finally {
                try {
                    jsonWriter.close();
                } catch (IOException e) {
                    LOG.error("Cannot close JSON Writer for file {}: {}", stateFile.getAbsolutePath(),
                            e.getMessage(), e);
                }
            }
        } catch (IOException e) {
            LOG.error("Cannot close JSON Writer for file {}: {}", stateFile.getAbsolutePath(), e.getMessage(), e);
        }
    }

    @Override
    public FileTailerState loadState() throws FileTailerStateProcessorException {
        if (!stateFile.exists()) {
            LOG.info("Not found state file: {}", stateFile.getAbsolutePath());
            return null;
        }
        LOG.debug("Start loading File Tailer state ..");
        try {
            BufferedReader reader = Files.newReader(stateFile, UTF_8);
            try {
                FileTailerState state = GSON.fromJson(reader, FileTailerState.class);
                LOG.debug("File Tailer state loaded successfully");
                return state;
            } finally {
                Closeables.closeQuietly(reader);
            }
        } catch (IOException e) {
            LOG.error("Can not load File Tailer state: {}", e);
            throw new FileTailerStateProcessorException(e.getMessage());
        }
    }

    /**
     * Creates all directories according to the {@link java.io.File directory}.
     *
     * @param directory the directory
     * @throws FileTailerStateProcessorException in case directories creating result where false
     */
    private void createDirs(File directory) throws FileTailerStateProcessorException {
        LOG.debug("Starting create directory with path: {}", directory.getAbsolutePath());
        if (!directory.exists()) {
            boolean result = directory.mkdirs();
            LOG.debug("Creating directory result: {}", result);
            if (!result) {
                throw new FileTailerStateProcessorException("Can not create File Tailer state directory");
            }
        } else {
            LOG.debug("Directory/File with path: {} already exist", directory.getAbsolutePath());
        }
    }
}