Google APIs support based on the Apache HTTP Client.
JSON batch for Google API's.
Google App Engine utilities for OAuth 2.0 for Google APIs.
Google OAuth 2.0 utilities that help simplify the authorization flow on Java 6.
Google API's support based on the
java.net
package.
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.
Mutual TLS utilities for the Google API Client Library.
Contains the basis for the generated service-specific libraries.
Contains the basis for the generated service-specific libraries based on the JSON format.
Utilities for the Google API Client Library.
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.