Read Google Calendar

This example accesses and extracts data from Google Calendar. It allows you to read calendar events, schedules, and associated metadata to enable a wide range of use cases. For example: event synchronization, calendar integration with productivity tools, automated reminders, and generating reports on scheduled activities within Java-based projects.

DataPipeline also supports other Google APIs such as Google Analytics: 

1. Read Google Analytics Social Interactions
2. Read Google Analytics goal conversions
3. Read Google Analytics Views.

As well as contacts and emails:

1. Read Google Contacts
2. Read Gmail Messages. 

Java Code Listing

package com.northconcepts.datapipeline.examples.google.calendar;

import java.io.File;
import java.io.InputStreamReader;
import java.util.Collections;
import java.util.Date;
import java.util.List;

import com.google.api.client.auth.oauth2.Credential;
import com.google.api.client.extensions.java6.auth.oauth2.AuthorizationCodeInstalledApp;
import com.google.api.client.extensions.jetty.auth.oauth2.LocalServerReceiver;
import com.google.api.client.googleapis.auth.oauth2.GoogleAuthorizationCodeFlow;
import com.google.api.client.googleapis.auth.oauth2.GoogleClientSecrets;
import com.google.api.client.googleapis.javanet.GoogleNetHttpTransport;
import com.google.api.client.http.javanet.NetHttpTransport;
import com.google.api.client.json.JsonFactory;
import com.google.api.client.json.gson.GsonFactory;
import com.google.api.client.util.store.FileDataStoreFactory;
import com.google.api.services.calendar.CalendarScopes;
import com.northconcepts.datapipeline.core.DataReader;
import com.northconcepts.datapipeline.core.DataWriter;
import com.northconcepts.datapipeline.core.LimitReader;
import com.northconcepts.datapipeline.core.StreamWriter;
import com.northconcepts.datapipeline.google.calendar.GoogleCalendarReader;
import com.northconcepts.datapipeline.job.Job;

public class ReadGoogleCalendar {

    private static final int MAX_RESULTS = 10;
    private static final String APPLICATION_NAME = "GoogleCalendarScratch";
    private static final JsonFactory JSON_FACTORY = GsonFactory.getDefaultInstance();
    private static final String TOKENS_DIRECTORY_PATH = "tokens/calendar";
    private static final List SCOPES = Collections.singletonList(CalendarScopes.CALENDAR_READONLY);
    private static final String CLIENT_SECRET = "/integrations.json";

    /** Authorizes the installed application to access user's protected data. */
    private static Credential authorize(NetHttpTransport httpTransport) throws Throwable {

        // load client secrets
        GoogleClientSecrets clientSecrets = GoogleClientSecrets.load(JSON_FACTORY,
                new InputStreamReader(ReadGoogleCalendar.class.getResourceAsStream(CLIENT_SECRET)));
        // set up authorization code flow
        GoogleAuthorizationCodeFlow flow = new GoogleAuthorizationCodeFlow.Builder(
                httpTransport, JSON_FACTORY, clientSecrets, SCOPES)
                .setDataStoreFactory(new FileDataStoreFactory(new File(TOKENS_DIRECTORY_PATH)))
                .setAccessType("offline")
                .build();
        // authorize
        LocalServerReceiver receier = new LocalServerReceiver.Builder().setPort(8888).build();
        return new AuthorizationCodeInstalledApp(flow, receier).authorize("user");
    }

    public static void main(String[] args) throws Throwable {

        NetHttpTransport httpTransport = GoogleNetHttpTransport.newTrustedTransport();

        DataReader reader = new GoogleCalendarReader(authorize(httpTransport), httpTransport)
                    .setBatchSize(MAX_RESULTS)
                    .setTimeMin(new Date())
                    .setTimeMax(null)
                    .setUpdatedMin(null)
                    .setOrderBy("startTime")
                    .setSingleEvent(true)
                    .setAlwaysIncludeEmail(true)
                    .setApplicationName(APPLICATION_NAME);

        reader = new LimitReader(reader, MAX_RESULTS);

        DataWriter writer = StreamWriter.newSystemOutWriter();

        Job.run(reader, writer);
    }
}

Code Walkthrough

1. authorize() method authorizes the installed application to access the user's protected data. First, the client secret (i.e. your service account credentials created in the Google Developer Console) is loaded using GoogleClientSecrets.load() method. Next, the authorization code flow is set up, and, finally, the application is authorized to retrieve data from Google API. 
2. NetHttpTransport instance is created for thread-safe HTTP low-level transport.
3. GoogleCalendarReader uses an API to get calendar data from a Google account. The constructor of the instance accepts Credential and HttpTransport. Additional parameters such as batch size, minimum-maximum time, sorting, and application name are specified using corresponding methods.
4. LimitReader is created to limit the number of records in a reader.
5. StreamWriter.newSystemOutWriter() method is used to create DataWriter instance.
6. Job.run() method is used to transfer the data from reader to writer to print out the records on the console. See how to compile and run data pipeline jobs.