google-api-client overview (2.1.2)

Version 2.1.2

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• 1.33.4

com.google.api.client.googleapis

Google APIs.

com.google.api.client.googleapis.apache.v2

Google APIs support based on the Apache HTTP Client.

com.google.api.client.googleapis.auth.oauth2

Google's additions to OAuth 2.0 authorization as specified in Using OAuth 2.0 to Access Google APIs.

Before using this library, you must register your application at the APIs Console. The result of this registration process is a set of values that are known to both Google and your application, such as the "Client ID", "Client Secret", and "Redirect URIs".

These are the typical steps of the web server flow based on an authorization code, as specified in Using OAuth 2.0 for Web Server Applications:

• Redirect the end user in the browser to the authorization page using com.google.api.client.googleapis.auth.oauth2.GoogleAuthorizationCodeRequestUrl to grant your application access to the end user's protected data.
• Process the authorization response using com.google.api.client.auth.oauth2.AuthorizationCodeResponseUrl to parse the authorization code.
• Request an access token and possibly a refresh token using com.google.api.client.googleapis.auth.oauth2.GoogleAuthorizationCodeTokenRequest.
• Access protected resources using com.google.api.client.googleapis.auth.oauth2.GoogleCredential. Expired access tokens will automatically be refreshed using the refresh token (if applicable).

These are the typical steps of the the browser-based client flow specified in Using OAuth 2.0 for Client-side Applications:

• Redirect the end user in the browser to the authorization page using com.google.api.client.googleapis.auth.oauth2.GoogleBrowserClientRequestUrl to grant your browser application access to the end user's protected data.
• Use the Google API Client library for JavaScript to process the access token found in the URL fragment at the redirect URI registered at the APIs Console.

com.google.api.client.googleapis.batch

Batch for Google API's.

com.google.api.client.googleapis.batch.json

JSON batch for Google API's.

com.google.api.client.googleapis.compute

com.google.api.client.util.Beta
Support for Google Compute Engine.

com.google.api.client.googleapis.extensions.android.accounts

com.google.api.client.util.Beta
Utilities for Account Manager for Google accounts on Android Eclair (SDK 2.1) and later.

com.google.api.client.googleapis.extensions.android.gms.auth

com.google.api.client.util.Beta
Utilities based on Google Play services.

com.google.api.client.googleapis.extensions.appengine.auth.oauth2

Google App Engine utilities for OAuth 2.0 for Google APIs.

com.google.api.client.googleapis.extensions.appengine.notifications

com.google.api.client.util.Beta
Support for subscribing to topics and receiving notifications on servlet-based platforms.

com.google.api.client.googleapis.extensions.appengine.testing.auth.oauth2

com.google.api.client.util.Beta
Test utilities for the com.google.api.client.googleapis.extensions.appengine.auth.oauth2 package.

com.google.api.client.googleapis.extensions.java6.auth.oauth2

Google OAuth 2.0 utilities that help simplify the authorization flow on Java 6.

com.google.api.client.googleapis.extensions.servlet.notifications

com.google.api.client.util.Beta
Support for subscribing to topics and receiving notifications on servlet-based platforms.

com.google.api.client.googleapis.javanet

Google API's support based on the java.net package.

com.google.api.client.googleapis.json

Google's JSON support (see detailed package specification).

Package Specification

User-defined Partial JSON data models allow you to defined Plain Old Java Objects (POJO's) to define how the library should parse/serialize JSON. Each field that should be included must have an @com.google.api.client.util.Key annotation. The field can be of any visibility (private, package private, protected, or public) and must not be static. By default, the field name is used as the JSON key. To override this behavior, simply specify the JSON key use the optional value parameter of the annotation, for example @Key("name"). Any unrecognized keys from the JSON are normally simply ignored and not stored. If the ability to store unknown keys is important, use com.google.api.client.json.GenericJson.

Let's take a look at a typical partial JSON-C video feed from the YouTube Data API (as specified in YouTube Developer's Guide: JSON-C / JavaScript)

 "data":{
  "updated":"2010-01-07T19:58:42.949Z",
                  "totalItems":800,
                  "startIndex":1,
                  "itemsPerPage":1,
                  "items":[
                          {"id":"hYB0mn5zh2c",
                                  "updated":"2010-01-07T13:26:50.000Z",
                                  "title":"Google Developers Day US - Maps API Introduction",
                                  "description":"Google Maps API Introduction ...",
                                  "tags":[
                                          "GDD07","GDD07US","Maps"],
                              "player":{
                              "default":"http://www.youtube.com/watch?v=hYB0mn5zh2c" },
                              ...
                          }]}
 

Here's one possible way to design the Java data classes for this (each class in its own Java file):

 import com.google.api.client.util.*;
 import java.util.List;

 public class VideoFeed {
   @Key public int itemsPerPage;
   @Key public int startIndex;
   @Key public int totalItems;
   @Key public DateTime updated;
   @Key public List<Video> items;
 }

 public class Video {
   @Key public String id;
   @Key public String title;
   @Key public DateTime updated;
   @Key public String description;
   @Key public List<String> tags;
   @Key public Player player;
 }

 public class Player {
   // "default" is a Java keyword, so need to specify the JSON key manually
   @Key("default")
   public String defaultUrl;
 }
 

You can also use the @com.google.api.client.util.Key annotation to defined query parameters for a URL. For example:

{@code public class YouTubeUrl extends GoogleUrl {

@Key public String author;

@Key("max-results") public Integer maxResults;

public YouTubeUrl(String encodedUrl) { super(encodedUrl); this.alt = "jsonc"; } }

To work with the YouTube API, you first need to set up the com.google.api.client.http.HttpTransport. For example:

{@code private static HttpTransport setUpTransport() throws IOException { HttpTransport result = new NetHttpTransport(); GoogleUtils.useMethodOverride(result); HttpHeaders headers = new HttpHeaders(); headers.setApplicationName("Google-YouTubeSample/1.0"); headers.gdataVersion = "2"; JsonCParser parser = new JsonCParser(); parser.jsonFactory = new GsonFactory(); transport.addParser(parser); // insert authentication code... return transport; } }

Now that we have a transport, we can execute a request to the YouTube API and parse the result:

{@code public static VideoFeed list(HttpTransport transport, YouTubeUrl url) throws IOException { HttpRequest request = transport.buildGetRequest(); request.url = url; return request.execute().parseAs(VideoFeed.class); } }

If the server responds with an error the com.google.api.client.http.HttpRequest#execute method will throw an com.google.api.client.http.HttpResponseException, which has an com.google.api.client.http.HttpResponse field which can be parsed the same way as a success response inside of a catch block. For example:

{@code try { ... } catch (HttpResponseException e) { if (e.response.getParser() != null) { Error error = e.response.parseAs(Error.class); // process error response } else { String errorContentString = e.response.parseAsString(); // process error response as string } throw e; } }

NOTE: As you might guess, the library uses reflection to populate the user-defined data model. It's not quite as fast as writing the wire format parsing code yourself can potentially be, but it's a lot easier.

NOTE: If you prefer to use your favorite JSON parsing library instead (there are many of them listed for example on json.org), that's supported as well. Just call com.google.api.client.http.HttpRequest#execute() and parse the returned byte stream.

com.google.api.client.googleapis.media

Media for Google API's.

com.google.api.client.googleapis.mtls

Mutual TLS utilities for the Google API Client Library.

com.google.api.client.googleapis.notifications

com.google.api.client.util.Beta
Support for notification channels to listen for changes to watched Google API resources.

com.google.api.client.googleapis.notifications.json

com.google.api.client.util.Beta
JSON-based notification handling for notification channels.

com.google.api.client.googleapis.notifications.json.gson

com.google.api.client.util.Beta
Notification channel handling based on the GSON JSON library.

com.google.api.client.googleapis.notifications.json.jackson2

com.google.api.client.util.Beta
Notification channel handling based on the Jackson 2 JSON library.

com.google.api.client.googleapis.services

Contains the basis for the generated service-specific libraries.

com.google.api.client.googleapis.services.json

Contains the basis for the generated service-specific libraries based on the JSON format.

com.google.api.client.googleapis.services.protobuf

com.google.api.client.util.Beta
Contains the basis for the generated service-specific libraries based on the Protobuf format.

com.google.api.client.googleapis.testing

com.google.api.client.util.Beta
Test utilities for the com.google.api.client.googleapis package.

com.google.api.client.googleapis.testing.auth.oauth2

com.google.api.client.util.Beta
Test utilities for the com.google.api.client.googleapis.auth.oauth2 package.

com.google.api.client.googleapis.testing.compute

com.google.api.client.util.Beta
Test utilities for the com.google.api.client.googleapis.compute package.

com.google.api.client.googleapis.testing.json

com.google.api.client.util.Beta
Test utilities for the com.google.api.client.googleapis.json package.

com.google.api.client.googleapis.testing.notifications

com.google.api.client.util.Beta
Test utilities for the com.google.api.client.googleapis.notifications package.

com.google.api.client.googleapis.testing.services

com.google.api.client.util.Beta
Test utilities for the com.google.api.client.googleapis.services package.

com.google.api.client.googleapis.testing.services.json

com.google.api.client.util.Beta
Test utilities for the com.google.api.client.googleapis.services.json package.

com.google.api.client.googleapis.testing.services.protobuf

com.google.api.client.util.Beta
Test utilities for the com.google.api.client.googleapis.protobuf package.

com.google.api.client.googleapis.util

Utilities for the Google API Client Library.

com.google.api.client.googleapis.xml.atom

com.google.api.client.util.Beta
Utilities for Google's Atom XML implementation (see detailed package specification).

Package Specification

User-defined Partial XML data models allow you to defined Plain Old Java Objects (POJO's) to define how the library should parse/serialize XML. Each field that should be included must have an @com.google.api.client.util.Key annotation. The field can be of any visibility (private, package private, protected, or public) and must not be static.

The optional value parameter of this @com.google.api.client.util.Key annotation specifies the XPath name to use to represent the field. For example, an XML attribute a has an XPath name of @a, an XML element <a> has an XPath name of a , and an XML text content has an XPath name of text(). These are named based on their usage with the partial response/update syntax for Google API's. If the @com.google.api.client.util.Key annotation is missing, the default is to use the Atom XML namespace and the Java field's name as the local XML name. By default, the field name is used as the JSON key. Any unrecognized XML is normally simply ignored and not stored. If the ability to store unknown keys is important, use com.google.api.client.xml.GenericXml.

Let's take a look at a typical partial Atom XML album feed from the Picasa Web Albums Data API:

 <?xml version='1.0' encoding='utf-8'?>
 <feed xmlns='http://www.w3.org/2005/Atom'
 xmlns:openSearch='http://a9.com/-/spec/opensearch/1.1/'
 xmlns:gphoto='http://schemas.google.com/photos/2007'>
 <link rel='http://schemas.google.com/g/2005#post'
 type='application/atom+xml'
 href='http://picasaweb.google.com/data/feed/api/user/liz' />
 <author>
 <name>Liz</name>
 </author>
 <openSearch:totalResults>1</openSearch:totalResults>
 <entry gd:etag='"RXY8fjVSLyp7ImA9WxVVGE8KQAE."'>
 <category scheme='http://schemas.google.com/g/2005#kind'
 term='http://schemas.google.com/photos/2007#album' />
 <title>lolcats</title>
 <summary>Hilarious Felines</summary>
 <gphoto:access>public</gphoto:access>
 </entry>
 </feed>
 

Here's one possible way to design the Java data classes for this (each class in its own Java file):

 import com.google.api.client.util.*;
 import java.util.List;

 public class Link {

   @Key("@href")
   public String href;

   @Key("@rel")
   public String rel;

   public static String find(List<Link> links, String rel) {
     if (links != null) {
       for (Link link : links) {
         if (rel.equals(link.rel)) {
           return link.href;
         }
       }
     }
     return null;
   }
 }

 public class Category {

   @Key("@scheme")
   public String scheme;

   @Key("@term")
   public String term;

   public static Category newKind(String kind) {
     Category category = new Category();
     category.scheme = "http://schemas.google.com/g/2005#kind";
     category.term = "http://schemas.google.com/photos/2007#" + kind;
     return category;
   }
 }

 public class AlbumEntry {

   @Key
   public String summary;

   @Key
   public String title;

   @Key("gphoto:access")
   public String access;

   public Category category = newKind("album");

   private String getEditLink() {
     return Link.find(links, "edit");
   }
 }

 public class Author {

   @Key
   public String name;
 }

 public class AlbumFeed {

   @Key
   public Author author;

   @Key("openSearch:totalResults")
   public int totalResults;

   @Key("entry")
   public List<AlbumEntry> photos;

   @Key("link")
   public List<Link> links;

   private String getPostLink() {
     return Link.find(links, "http://schemas.google.com/g/2005#post");
   }
 }
 

You can also use the @com.google.api.client.util.Key annotation to defined query parameters for a URL. For example:

 public class PicasaUrl extends GoogleUrl {

   @Key("max-results")
   public Integer maxResults;

   @Key
   public String kinds;

   public PicasaUrl(String url) {
     super(url);
   }

   public static PicasaUrl fromRelativePath(String relativePath) {
     PicasaUrl result = new PicasaUrl(PicasaWebAlbums.ROOT_URL);
     result.path += relativePath;
     return result;
   }
 }
 

To work with a Google API, you first need to set up the com.google.api.client.http.HttpTransport. For example:

 private static HttpTransport setUpTransport() throws IOException {
   HttpTransport result = new NetHttpTransport();
   GoogleUtils.useMethodOverride(result);
   HttpHeaders headers = new HttpHeaders();
   headers.setApplicationName("Google-PicasaSample/1.0");
   headers.gdataVersion = "2";
   AtomParser parser = new AtomParser();
   parser.namespaceDictionary = PicasaWebAlbumsAtom.NAMESPACE_DICTIONARY;
   transport.addParser(parser);
   // insert authentication code...
   return transport;
 }
 

Now that we have a transport, we can execute a partial GET request to the Picasa Web Albums API and parse the result:

 public static AlbumFeed executeGet(HttpTransport transport, PicasaUrl url) throws IOException {
   url.fields = GoogleAtom.getFieldsFor(AlbumFeed.class);
   url.kinds = "photo";
   url.maxResults = 5;
   HttpRequest request = transport.buildGetRequest();
   request.url = url;
   return request.execute().parseAs(AlbumFeed.class);
 }
 

If the server responds with an error the com.google.api.client.http.HttpRequest#execute method will throw an com.google.api.client.http.HttpResponseException, which has an com.google.api.client.http.HttpResponse field which can be parsed the same way as a success response inside of a catch block. For example:

 try {
   ...
 } catch (HttpResponseException e) {
   if (e.response.getParser() != null) {
     Error error = e.response.parseAs(Error.class);
     // process error response
   } else {
     String errorContentString = e.response.parseAsString();
     // process error response as string
   }
   throw e;
 }
 

To update an album, we use the transport to execute an efficient partial update request using the PATCH method to the Picasa Web Albums API:

 public AlbumEntry executePatchRelativeToOriginal
     (HttpTransport transport, AlbumEntry original) throws IOException {
   HttpRequest request = transport.buildPatchRequest();
   request.setUrl(getEditLink());
   request.headers.ifMatch = etag;
   AtomPatchRelativeToOriginalContent content = new AtomPatchRelativeToOriginalContent();
   content.namespaceDictionary = PicasaWebAlbumsAtom.NAMESPACE_DICTIONARY;
   content.originalEntry = original;
   content.patchedEntry = this;
   request.content = content;
   return request.execute().parseAs(AlbumEntry.class);
 }

 private static AlbumEntry updateTitle
     (HttpTransport transport, AlbumEntry album) throws IOException {
   AlbumEntry patched = album.clone();
   patched.title = "An alternate title";
   return patched.executePatchRelativeToOriginal(transport, album);
 }
 

To insert an album, we use the transport to execute a POST request to the Picasa Web Albums API:

 public AlbumEntry insertAlbum(HttpTransport transport, AlbumEntry entry) throws IOException {
   HttpRequest request = transport.buildPostRequest();
   request.setUrl(getPostLink());
   AtomContent content = new AtomContent();
   content.namespaceDictionary = PicasaWebAlbumsAtom.NAMESPACE_DICTIONARY;
   content.entry = entry;
   request.content = content;
   return request.execute().parseAs(AlbumEntry.class);
 }
 

To delete an album, we use the transport to execute a DELETE request to the Picasa Web Albums API:

 public void executeDelete(HttpTransport transport) throws IOException {
   HttpRequest request = transport.buildDeleteRequest();
   request.setUrl(getEditLink());
   request.headers.ifMatch = etag;
   request.execute().ignore();
 }
 

NOTE: As you might guess, the library uses reflection to populate the user-defined data model. It's not quite as fast as writing the wire format parsing code yourself can potentially be, but it's a lot easier.

NOTE: If you prefer to use your favorite XML parsing library instead (there are many of them), that's supported as well. Just call com.google.api.client.http.HttpRequest#execute() and parse the returned byte stream.