Java Quickstart

Complete the steps described in the rest of this page, and in about five minutes you'll have a simple Java command-line application that makes requests to the Google Tasks API.

Prerequisites

To run this quickstart, you'll need:

Step 1: Turn on the Google Tasks API

Click this button to create a new console project and automatically enable the Google Tasks API:

Enable the Google Tasks API

This opens a new dialog. In the dialog, do the following:

  1. Select + Create a new project.
  2. Enter the name "Google Tasks API Quickstart".
  3. Download the configuration file.
  4. Move the downloaded file to your working directory and rename it client_secret.json.

Step 2: Prepare the project

  1. In your working directory, run the following commands to create a new project structure:

    gradle init --type basic
    mkdir -p src/main/java src/main/resources 
    
  2. Copy the client_secret.json file you downloaded in Step 1 into the src/main/resources/ directory you just created.

  3. Open the default build.gradle file and replace its contents with the following code:

tasks/quickstart/build.gradle
apply plugin: 'java'
apply plugin: 'application'

mainClassName = 'TasksQuickstart'
sourceCompatibility = 1.7
targetCompatibility = 1.7
version = '1.0'

repositories {
    mavenCentral()
}

dependencies {
    compile 'com.google.api-client:google-api-client:1.23.0'
    compile 'com.google.oauth-client:google-oauth-client-jetty:1.23.0'
    compile 'com.google.apis:google-api-services-tasks:v1-rev49-1.23.0'
}

Step 3: Set up the sample

Create a file in the src/main/java/ folder with the following filename and code:

tasks/quickstart/src/main/java/TasksQuickstart.java
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.jackson2.JacksonFactory;
import com.google.api.client.util.store.FileDataStoreFactory;
import com.google.api.services.tasks.Tasks;
import com.google.api.services.tasks.TasksScopes;
import com.google.api.services.tasks.model.TaskList;
import com.google.api.services.tasks.model.TaskLists;

import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.security.GeneralSecurityException;
import java.util.Collections;
import java.util.List;

public class TasksQuickstart {
    private static final String APPLICATION_NAME = "Google Tasks API Java Quickstart";
    private static final JsonFactory JSON_FACTORY = JacksonFactory.getDefaultInstance();
    private static final String CREDENTIALS_FOLDER = "credentials"; // Directory to store user credentials.

    /**
     * Global instance of the scopes required by this quickstart.
     * If modifying these scopes, delete your previously saved credentials/ folder.
     */
    private static final List<String> SCOPES = Collections.singletonList(TasksScopes.TASKS_READONLY);
    private static final String CLIENT_SECRET_DIR = "client_secret.json";

    /**
     * Creates an authorized Credential object.
     * @param HTTP_TRANSPORT The network HTTP Transport.
     * @return An authorized Credential object.
     * @throws IOException If there is no client_secret.
     */
    private static Credential getCredentials(final NetHttpTransport HTTP_TRANSPORT) throws IOException {
        // Load client secrets.
        InputStream in = TasksQuickstart.class.getResourceAsStream(CLIENT_SECRET_DIR);
        GoogleClientSecrets clientSecrets = GoogleClientSecrets.load(JSON_FACTORY, new InputStreamReader(in));

        // Build flow and trigger user authorization request.
        GoogleAuthorizationCodeFlow flow = new GoogleAuthorizationCodeFlow.Builder(
                HTTP_TRANSPORT, JSON_FACTORY, clientSecrets, SCOPES)
                .setDataStoreFactory(new FileDataStoreFactory(new java.io.File(CREDENTIALS_FOLDER)))
                .setAccessType("offline")
                .build();
        return new AuthorizationCodeInstalledApp(flow, new LocalServerReceiver()).authorize("user");
    }

    public static void main(String... args) throws IOException, GeneralSecurityException {
        // Build a new authorized API client service.
        final NetHttpTransport HTTP_TRANSPORT = GoogleNetHttpTransport.newTrustedTransport();
        Tasks service = new Tasks.Builder(HTTP_TRANSPORT, JSON_FACTORY, getCredentials(HTTP_TRANSPORT))
                .setApplicationName(APPLICATION_NAME)
                .build();

        // Print the first 10 task lists.
        TaskLists result = service.tasklists().list()
                .setMaxResults(10L)
                .execute();
        List<TaskList> taskLists = result.getItems();
        if (taskLists == null || taskLists.isEmpty()) {
            System.out.println("No task lists found.");
        } else {
            System.out.println("Task lists:");
            for (TaskList tasklist : taskLists) {
                System.out.printf("%s (%s)\n", tasklist.getTitle(), tasklist.getId());
            }
        }
    }
}

Step 4: Run the sample

Build and run the quickstart with the command:

gradle -q run

The first time you run the sample, it will prompt you to authorize access:

  1. The sample will attempt to open a new window or tab in your default browser. If this fails, copy the URL from the console and manually open it in your browser.

    If you are not already logged into your Google account, you will be prompted to log in. If you are logged into multiple Google accounts, you will be asked to select one account to use for the authorization.

  2. Click the Accept button.
  3. The sample will proceed automatically, and you may close the window/tab.

Notes

  • Authorization information is stored on the file system, so subsequent executions will not prompt for authorization.
  • The authorization flow in this example is designed for a command-line application. For information on how to perform authorization in a web application, see Using OAuth 2.0 for Web Server Applications.

Further reading

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