scala学习十三 开发twitter客户端

通过Http与twitter服务器通信：

如何构建 Scitter 客户机来处理经过验证和未经过验证的调用。目前，我将采用典型的 Scala 方式，假定验证是 “按对象” 执行的，因此将需要验证的调用放在类定义中，并在未验证的调用放在对象定义中，测试代码（apache common httpclient包）： 

package com.tedneward.scitter
{
  /**
   * Object for consuming "non-specific" Twitter feeds, such as the public timeline.
   * Use this to do non-authenticated requests of Twitter feeds.
   */
  object Scitter
  {
    import org.apache.commons.httpclient._, methods._, params._, cookie._

    /**
     * Ping the server to see if it's up and running.
     *
     * Twitter docs say:
     * test
     * Returns the string "ok" in the requested format with a 200 OK HTTP status code.
     * URL: http://twitter.com/help/test.format
     * Formats: xml, json
     * Method(s): GET
     */
    def test : Boolean =
    {
      val client = new HttpClient()

      val method = new GetMethod("http://twitter.com/help/test.xml")

      method.getParams().setParameter(HttpMethodParams.RETRY_HANDLER, 
        new DefaultHttpMethodRetryHandler(3, false))

      client.executeMethod(method)
      
      val statusLine = method.getStatusLine()
      statusLine.getStatusCode() == 200
    }
  }
  /**
   * Class for consuming "authenticated user" Twitter APIs. Each instance is
   * thus "tied" to a particular authenticated user on Twitter, and will
   * behave accordingly (according to the Twitter API documentation).
   */
  class Scitter(username : String, password : String)
  {
  }
}

实现用户验证的api实现：

package com.tedneward.scitter
{
  import org.apache.commons.httpclient._, auth._, methods._, params._

  // ...

  /**
   * Class for consuming "authenticated user" Twitter APIs. Each instance is
   * thus "tied" to a particular authenticated user on Twitter, and will
   * behave accordingly (according to the Twitter API documentation).
   */
  class Scitter(username : String, password : String)
  {
    /**
     * Verify the user credentials against Twitter.
     *
     * Twitter docs say:
     * verify_credentials
     * Returns an HTTP 200 OK response code and a representation of the
     * requesting user if authentication was successful; returns a 401 status
     * code and an error message if not.  Use this method to test if supplied
     * user credentials are valid.
     * URL: http://twitter.com/account/verify_credentials.format
     * Formats: xml, json
     * Method(s): GET
     */
    def verifyCredentials : Boolean =
    {
      val client = new HttpClient()

      val method = new GetMethod("http://twitter.com/help/test.xml")

      method.getParams().setParameter(HttpMethodParams.RETRY_HANDLER, 
        new DefaultHttpMethodRetryHandler(3, false))
        
      client.getParams().setAuthenticationPreemptive(true)
      val creds = new UsernamePasswordCredentials(username, password)
      client.getState().setCredentials(
        new AuthScope("twitter.com", 80, AuthScope.ANY_REALM), creds)

      client.executeMethod(method)
      
      val statusLine = method.getStatusLine()
      statusLine.getStatusCode() == 200
    }
  }
}

现在可以添加的最简单的 API 是 public_timeline，它收集 Twitter 从所有用户处接收到的最新的  n  更新，并返回它们以便于进行使用。与之前讨论的另外两个 API 不同，public_timeline API 返回一个响应主体（而不是仅依赖于状态码），因此我们需要分解生成的 XML/RSS/ATOM/，然后将它们返回给 Scitter 客户机。

package com.tedneward.scitter.test
{
  class ExplorationTests
  {
    // ...
  
    @Test def callTwitterPublicTimeline =
    {
      val publicFeedURL = "http://twitter.com/statuses/public_timeline.xml"
      
      // HttpClient API 101
      val client = new HttpClient()
      val method = new GetMethod(publicFeedURL)
      method.getParams().setParameter(HttpMethodParams.RETRY_HANDLER, 
        new DefaultHttpMethodRetryHandler(3, false))
      
      client.executeMethod(method)
      
      val statusLine = method.getStatusLine()
      assertEquals(statusLine.getStatusCode(), 200)
      assertEquals(statusLine.getReasonPhrase(), "OK")
      
      val responseBody = method.getResponseBodyAsString()
      System.out.println("callTwitterPublicTimeline got... ")
      System.out.println(responseBody)
    }
  }
}

这样就获得了返回的主体，接下来，我们要实现通过客户端完成twitter的更新

package com.tedneward.scitter

{

  class Scitter

  {

    // ...


    def update(message : String, options : OptionalParam*) : Option[Status] =

    {

      def optionsToMap(options : List[OptionalParam]) : Map[String, String]=

      {

        options match

        {

          case hd :: tl =>

            hd match {

              case InReplyToStatusId(id) =>

                Map("in_reply_to_status_id" -> id.toString) ++ optionsToMap(tl)

              case _ =>

                optionsToMap(tl)

            }

          case List() => Map()

        }

      }

      
      val paramsMap = Map("status" -> message) ++ optionsToMap(options.toList)


      val (statusCode, body) =

        Scitter.execute("http://twitter.com/statuses/update.xml", 
           paramsMap, username, password)

      if (statusCode == 200)

      {

        Some(Status.fromXml(XML.loadString(body)))

      }

      else

      {

        None

      }

    }

  }

}