昨天Google官方发布新闻(Getting started on the Google+ API)，Google Plus开放了一个只读的API，允许抓取用户的公开Profile和公开的Activity信息流，其中Google+ Platform的具体开发API介绍详见官网。

今天我就带领大家熟悉一下基于Google+ 开放API的程序设计，本程序基于SAE平台，采用PHP语言开发，基于Java语言和Python语言也都比较好开发，google官方都有开放的lib可以直接使用，不用自己再做底层封装了。

实现步骤

1. 访问 Google API Console 开启Google+ API权限.
   
2. 访问 Google API Console 生成  developer key, OAuth2 client id, OAuth2 client secret, 和 注册 OAuth2 redirect uri.
   
   
3. 下载 google api的php开发库，google-api-php-client.
4. 更新google api开发库，因为我的运行环境基于新浪云SAE平台，所以要做一些特别的改动：
   1. 实现SAE平台的MemCache，在google-api-php-clientsrccache中建立apiSAEMemcacheCache.php文件，具体内容如下

   <?php
   /**
    * SAE Memcache
    *
    * @author Carey Zhou <zhourunsheng2008@google.com>
    */
   class apiSAEMemcacheCache extends apiCache {
     private $connection = false;
   
     public function __construct() {
   	//do nothing
     }
   
     private function connect() {
       if (! $this->connection = @memcache_init()) {
         throw new apiCacheException("Memcache init failed");
       }
     }
   
     private function check() {
       if (! $this->connection) {
         $this->connect();
       }
     }
   
     /**
      * @inheritDoc
      */
     public function get($key, $expiration = false) {
       $this->check();
       if (($ret = @memcache_get($this->connection, $key)) === false) {
         return false;
       }
       if (! $expiration || (time() - $ret['time'] > $expiration)) {
         $this->delete($key);
         return false;
       }
       return $ret['data'];
     }
   
     /**
      * @inheritDoc
      */
     public function set($key, $value) {
       $this->check();
       // we store it with the cache_time default expiration so objects will at least get cleaned eventually.
       if (@memcache_set($this->connection, $key, array('time' => time(),
           'data' => $value), false) == false) {
         throw new apiCacheException("Couldn't store data in cache");
       }
     }
   
     /**
      * @inheritDoc
      */
     public function delete($key) {
       $this->check();
       @memcache_delete($this->connection, $key);
     }
   }

   2. 更新 google-api-php-clientsrccacheapiCache.php文件，将我们新添加的SAEMemcache加进去，代码如下：

   require_once "apiSAEMemcacheCache.php";

   3. 更新 google-api-php-clientsrcioapiCurlIO.php文件，修正一个bug【当Header中出现"HTTP/1.1 100 Continue"的时候，原程序会出现解析错误，导致程序崩溃，估计也是SAE环境的特殊性导致的】，具体改正如下：

   原来的代码：

   // Parse out the raw response into usable bits
       list($rawResponseHeaders, $responseBody) = explode("rnrn", $data, 2);

   现在的代码：

   // Parse out the raw response into usable bits
       list($rawResponseHeaders, $responseBody) = explode("rnrn", $data, 2);
       if ($rawResponseHeaders == "HTTP/1.1 100 Continue") {
   	list($rawResponseHeaders, $responseBody) = explode("rnrn", $responseBody, 2);
       }

   更改原因：如果出现了"HTTP/1.1 100 Continue"的时候，还要继续向下解析一次，即出现了特殊的“双Header现象”，否则的话就会导致Header解析出错，真正的Header没有被解析出来，也混到body里面去了。

5. google plus 代码编写，获取用户公开的Activity信息流，核心代码如下：

   <?php
   /*
    * Google Plus
    *
    * @author Carey Zhou(zhourunsheng2008@gmail.com)
    */
   require_once '../libs/google-api-php-client/src/apiClient.php';
   require_once '../libs/google-api-php-client/src/contrib/apiPlusService.php';
   
   //sae_set_display_errors(true);
   
   session_start();
   
   $client = new apiClient();
   $client->setApplicationName("Google Plus Application");
   
   $client->setClientId('800611776987-kp6h5nfv5l9gp5v2qipqhc5l8dkqe0lu.apps.googleusercontent.com');
   $client->setClientSecret('5o-eK5M4iftPxB7_fhNqEAhm');
   $client->setRedirectUri('https://carey.sinaapp.com/googleplus/index.php');
   $client->setDeveloperKey('AIzaSyD6FERuKcWPn2xGUcgFmKW9Ush50nu6PYQ');
   
   $client->setScopes(array('https://www.googleapis.com/auth/plus.me'));
   $plus = new apiPlusService($client);
   
   if (isset($_REQUEST['logout'])) {
     unset($_SESSION['access_token']);
   }
   
   if (isset($_GET['code'])) {
     $client->authenticate();
     $_SESSION['access_token'] = $client->getAccessToken();
     //header('Location: http://' . $_SERVER['HTTP_HOST'] . $_SERVER['PHP_SELF']);
     $url = 'http://' . $_SERVER['HTTP_HOST'] . $_SERVER['PHP_SELF'];
     echo "<script language='javascript' type='text/javascript'>";
     echo "window.location.href='$url'";
     echo "</script>";
   }
   
   if (isset($_SESSION['access_token'])) {
     $client->setAccessToken($_SESSION['access_token']);
   }
   
   if ($client->getAccessToken()) {
     $me = $plus->people->get('me');
   
     $optParams = array('maxResults' => 100);
     $activities = $plus->activities->listActivities('me', 'public', $optParams);
   
     // The access token may have been updated lazily.
     $_SESSION['access_token'] = $client->getAccessToken();
   } else {
     $authUrl = $client->createAuthUrl();
   }
   ?>

   可以注意到，在程序中我们配置了ClientID，ClientSecret，RedirectUri，DeveloperKey和Google+的scope，然后通过OAuth2机制获取用户的授权，进而来获得用户公开的Activity信息流。

程序部署和验证

1. 把上面的代码部署到SAE平台，https://carey.sinaapp.com/googleplus/index.php
   
2. 点击Connet Me进行OAuth2用户授权
   
3. 点击Allow Access允许访问，则会回到刚才的页面，把用户的信息流抓取出来
   

小结

到此为止，google plus 基于PHP开发的基本流程就都OK了，希望google过几天能开放出更多的API来，毕竟google+是个圈，所以圈子的API才是最核心的，O(∩_∩)O哈哈~,期待中

源码下载google_plus_sae_source