gobblin.example.simplejson.SimpleJsonExtractor.java Source code

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Here is the source code for gobblin.example.simplejson.SimpleJsonExtractor.java

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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
 *
 *    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 gobblin.example.simplejson;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;

import org.apache.commons.vfs2.FileObject;
import org.apache.commons.vfs2.FileSystemException;
import org.apache.commons.vfs2.FileSystemOptions;
import org.apache.commons.vfs2.UserAuthenticator;
import org.apache.commons.vfs2.VFS;
import org.apache.commons.vfs2.auth.StaticUserAuthenticator;
import org.apache.commons.vfs2.impl.DefaultFileSystemConfigBuilder;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import com.google.common.io.Closer;

import gobblin.configuration.ConfigurationKeys;
import gobblin.configuration.WorkUnitState;
import gobblin.password.PasswordManager;
import gobblin.source.extractor.DataRecordException;
import gobblin.source.extractor.Extractor;

/**
 * An implementation of {@link Extractor} for the simple JSON example.
 *
 * <p>
 *   This extractor uses the commons-vfs library to read the assigned input file storing
 *   json documents confirming to a schema. Each line of the file is a json document.
 * </p>
 *
 * @author Yinan Li
 */
public class SimpleJsonExtractor implements Extractor<String, String> {

    private static final Logger LOGGER = LoggerFactory.getLogger(SimpleJsonExtractor.class);

    private static final String SOURCE_FILE_KEY = "source.file";

    private final WorkUnitState workUnitState;
    private final FileObject fileObject;
    private final BufferedReader bufferedReader;
    private final Closer closer = Closer.create();

    public SimpleJsonExtractor(WorkUnitState workUnitState) throws FileSystemException {
        this.workUnitState = workUnitState;

        // Resolve the file to pull
        if (workUnitState.getPropAsBoolean(ConfigurationKeys.SOURCE_CONN_USE_AUTHENTICATION, false)) {
            // Add authentication credential if authentication is needed
            UserAuthenticator auth = new StaticUserAuthenticator(
                    workUnitState.getProp(ConfigurationKeys.SOURCE_CONN_DOMAIN, ""),
                    workUnitState.getProp(ConfigurationKeys.SOURCE_CONN_USERNAME),
                    PasswordManager.getInstance(workUnitState)
                            .readPassword(workUnitState.getProp(ConfigurationKeys.SOURCE_CONN_PASSWORD)));
            FileSystemOptions opts = new FileSystemOptions();
            DefaultFileSystemConfigBuilder.getInstance().setUserAuthenticator(opts, auth);
            this.fileObject = VFS.getManager().resolveFile(workUnitState.getProp(SOURCE_FILE_KEY), opts);
        } else {
            this.fileObject = VFS.getManager().resolveFile(workUnitState.getProp(SOURCE_FILE_KEY));
        }

        // Open the file for reading
        LOGGER.info("Opening file " + this.fileObject.getURL().toString());
        this.bufferedReader = this.closer
                .register(new BufferedReader(new InputStreamReader(this.fileObject.getContent().getInputStream(),
                        ConfigurationKeys.DEFAULT_CHARSET_ENCODING)));
    }

    @Override
    public String getSchema() {
        return this.workUnitState.getProp(ConfigurationKeys.SOURCE_SCHEMA);
    }

    @Override
    public String readRecord(@Deprecated String reuse) throws DataRecordException, IOException {
        // Read the next line
        return this.bufferedReader.readLine();
    }

    @Override
    public long getExpectedRecordCount() {
        // We don't know how many records are in the file before actually reading them
        return 0;
    }

    @Override
    public long getHighWatermark() {
        // Watermark is not applicable for this type of extractor
        return 0;
    }

    @Override
    public void close() throws IOException {
        try {
            this.closer.close();
        } catch (IOException ioe) {
            LOGGER.error("Failed to close the input stream", ioe);
        }

        try {
            this.fileObject.close();
        } catch (IOException ioe) {
            LOGGER.error("Failed to close the file object", ioe);
        }
    }
}