Java Quickstart

Complete the steps described in the rest of this page to create a simple Java command-line application that makes requests to the Google Docs API.

Prerequisites

To run this quickstart, you need the following prerequisites:

Java 1.8 or greater.
Gradle 2.3 or greater.
A Google Cloud project with the API enabled. To create a project and enable an API, refer to Create a project and enable the API.

Authorization credentials for a desktop application. To learn how to create credentials for a desktop application, refer to Create credentials.

A Google account.

Step 1: Prepare the project

To prepare the project:

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 
```
Copy the credentials.json file you downloaded as a prerequisite into the newly-created src/main/resources/ directory.
Open the default build.gradle file and replace its contents with the following code:

docs/quickstart/build.gradle

View on GitHub
```
apply plugin: 'java'
apply plugin: 'application'

mainClassName = 'DocsQuickstart'
sourceCompatibility = 11
targetCompatibility = 11
version = '1.0'

repositories {
    mavenCentral()
}

dependencies {
    implementation 'com.google.api-client:google-api-client:1.33.0'
    implementation 'com.google.oauth-client:google-oauth-client-jetty:1.32.1'
    implementation 'com.google.apis:google-api-services-docs:v1-rev20210707-1.32.1'
}
```

Step 2: Set up the sample

To set up the sample:

In src/main/java/, create a new Java file with a name that matches the mainClassName value in your build.gradle file.

Include the following code in your new Java file:

docs/quickstart/src/main/java/DocsQuickstart.java

View on GitHub

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.docs.v1.Docs;
import com.google.api.services.docs.v1.DocsScopes;
import com.google.api.services.docs.v1.model.Document;

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

/* class to demonstarte use of Docs get documents API */
public class DocsQuickstart {
  /**
   * Application name.
   */
  private static final String APPLICATION_NAME = "Google Docs API Java Quickstart";
  /**
   * Global instance of the JSON factory.
   */
  private static final JsonFactory JSON_FACTORY = GsonFactory.getDefaultInstance();
  /**
   * Directory to store authorization tokens for this application.
   */
  private static final String TOKENS_DIRECTORY_PATH = "tokens";
  private static final String DOCUMENT_ID = "195j9eDD3ccgjQRttHhJPymLJUCOUjs-jmwTrekvdjFE";

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

  /**
   * Creates an authorized Credential object.
   *
   * @param HTTP_TRANSPORT The network HTTP Transport.
   * @return An authorized Credential object.
   * @throws IOException If the credentials.json file cannot be found.
   */
  private static Credential getCredentials(final NetHttpTransport HTTP_TRANSPORT)
      throws IOException {
    // Load client secrets.
    InputStream in = DocsQuickstart.class.getResourceAsStream(CREDENTIALS_FILE_PATH);
    if (in == null) {
      throw new FileNotFoundException("Resource not found: " + CREDENTIALS_FILE_PATH);
    }
    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(TOKENS_DIRECTORY_PATH)))
        .setAccessType("offline")
        .build();
    LocalServerReceiver receiver = new LocalServerReceiver.Builder().setPort(8888).build();
    Credential credential = new AuthorizationCodeInstalledApp(flow, receiver).authorize("user");
    //returns an authorized Credential object.
    return credential;
  }

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

    // Prints the title of the requested doc:
    // https://docs.google.com/document/d/195j9eDD3ccgjQRttHhJPymLJUCOUjs-jmwTrekvdjFE/edit
    Document response = service.documents().get(DOCUMENT_ID).execute();
    String title = response.getTitle();

    System.out.printf("The title of the doc is: %s\n", title);
  }
}

Step 3: Run the sample

To run the sample:

Execute the following command:
```
gradle run
```
This command builds and runs the sample.
(optional). If this is your first time running the sample, the sample opens a new window prompting you to authorize access to your data:
1. If you are not already signed in to your Google account, you are prompted to sign in. If you are signed in to multiple Google accounts, you are asked to select one account to use for authorization.
Note: Authorization information is stored on the file system, so subsequent executions don't prompt for authorization.
1. Click Accept. The app is authorized to access your data.
The sample executes.

If you have problems, refer to the Troubleshoot the sample section.

Troubleshoot the sample

This section describes a common issue that you can encounter while attempting to run this quickstart.

`This app isn't verified`

If the OAuth consent screen displays the warning "This app isn't verified," your app is requesting scopes that provide access to sensitive user data. If your application uses sensitive scopes, your app must go through the verification process to remove that warning and other limitations. During the development phase, you can continue past this warning by selecting Advanced > Go to {Project Name} (unsafe).

`File not found error for credentials.json`

When running the sample, you might receive a file not found or no such file error regarding credentials.json.

This error occurs when you have not authorized the desktop application credentials as detailed in the Prerequisites section above. To learn how to create credentials for a desktop application, go to Create credentials.

Once you create the credentials, make sure the downloaded JSON file is saved as credentials.json. Then move the file to your working directory with the rest of the sample quickstart code.