面向 Java 开发人员的 Scala 指南 增强 Scitter 库-1
|
- UID
- 1066743
|
面向 Java 开发人员的 Scala 指南 增强 Scitter 库-1
欢迎回来，Scala 迷们。，我们谈到了 Twitter，这个微博客站点目前正引起社会性网络的极大兴趣，我们还谈到它的基于 XML-/REST 的 API 如何使它成为开发人员进行研究和探索的一个有趣平台。为此，我们首先充实了 “Scitter” 的基本结构，Scitter 是用于访问 Twitter 的一个 Scala 库。
关于本系列Ted Neward 将和您一起深入探讨 Scala 编程语言。在这个 developerWorks 中，您将了解有关 Scala 的所有最新讨论，并在实践中看到 Scala 的语言功能。在进行相关比较时，Scala 代码和 Java™ 代码将放在一起展示，但是（您将发现）Scala 与 Java 中的许多东西都没有直接的关联，这正是 Scala 的魅力所在！如果用 Java 代码就能够实现的话，又何必再学习 Scala 呢？
我们对于 Scitter 有几个目标：
- 简化 Twitter 访问，比过去打开 HTTP 连接然后 “手动” 执行操作更容易。
- 可以从 Java 客户机轻松访问它。
- 轻松模拟以便进行测试。
在这一期，我们不必完成整个 Twitter API，但是我们将完成一些核心部分，目的是让这个库达到公共源代码控制库的程度，便于其他人来完成这项工作。
到目前为止：Scitter 0.1首先我们简单回顾一下到目前为止我们所处的阶段：
清单 1. Scitter v0.11
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
| package com.tedneward.scitter
{
import org.apache.commons.httpclient._, auth._, methods._, params._
import scala.xml._
/**
* Status message type. This will typically be the most common message type
* sent back from Twitter (usually in some kind of collection form). Note
* that all optional elements in the Status type are represented by the
* Scala Option[T] type, since that's what it's there for.
*/
abstract class Status
{
/**
* Nested User type. This could be combined with the top-level User type,
* if we decide later that it's OK for this to have a boatload of optional
* elements, including the most-recently-posted status update (which is a
* tad circular).
*/
abstract class User
{
val id : Long
val name : String
val screenName : String
val description : String
val location : String
val profileImageUrl : String
val url : String
val protectedUpdates : Boolean
val followersCount : Int
}
/**
* Object wrapper for transforming (format) into User instances.
*/
object User
{
/*
def fromAtom(node : Node) : Status =
{
}
*/
/*
def fromRss(node : Node) : Status =
{
}
*/
def fromXml(node : Node) : User =
{
new User {
val id = (node \ "id").text.toLong
val name = (node \ "name").text
val screenName = (node \ "screen_name").text
val description = (node \ "description").text
val location = (node \ "location").text
val profileImageUrl = (node \ "profile_image_url").text
val url = (node \ "url").text
val protectedUpdates = (node \ "protected").text.toBoolean
val followersCount = (node \ "followers_count").text.toInt
}
}
}
val createdAt : String
val id : Long
val text : String
val source : String
val truncated : Boolean
val inReplyToStatusId : Option[Long]
val inReplyToUserId : Option[Long]
val favorited : Boolean
val user : User
}
/**
* Object wrapper for transforming (format) into Status instances.
*/
object Status
{
/*
def fromAtom(node : Node) : Status =
{
}
*/
/*
def fromRss(node : Node) : Status =
{
}
*/
def fromXml(node : Node) : Status =
{
new Status {
val createdAt = (node \ "created_at").text
val id = (node \ "id").text.toLong
val text = (node \ "text").text
val source = (node \ "source").text
val truncated = (node \ "truncated").text.toBoolean
val inReplyToStatusId =
if ((node \ "in_reply_to_status_id").text != "")
Some((node \"in_reply_to_status_id").text.toLong)
else
None
val inReplyToUserId =
if ((node \ "in_reply_to_user_id").text != "")
Some((node \"in_reply_to_user_id").text.toLong)
else
None
val favorited = (node \ "favorited").text.toBoolean
val user = User.fromXml((node \ "user")(0))
}
}
}
/**
* Object for consuming "non-specific" Twitter feeds, such as the public timeline.
* Use this to do non-authenticated requests of Twitter feeds.
*/
object Scitter
{
/**
* 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
}
/**
* Query the public timeline for the most recent statuses.
*
* Twitter docs say:
* public_timeline
* Returns the 20 most recent statuses from non-protected users who have set
* a custom user icon. Does not require authentication. Note that the
* public timeline is cached for 60 seconds so requesting it more often than
* that is a waste of resources.
* URL: http://twitter.com/statuses/public_timeline.format
* Formats: xml, json, rss, atom
* Method(s): GET
* API limit: Not applicable
* Returns: list of status elements
*/
def publicTimeline : List[Status] =
{
import scala.collection.mutable.ListBuffer
val client = new HttpClient()
val method = new GetMethod("http://twitter.com/statuses/public_timeline.xml")
method.getParams().setParameter(HttpMethodParams.RETRY_HANDLER,
new DefaultHttpMethodRetryHandler(3, false))
client.executeMethod(method)
val statusLine = method.getStatusLine()
if (statusLine.getStatusCode() == 200)
{
val responseXML =
XML.loadString(method.getResponseBodyAsString())
val statusListBuffer = new ListBuffer[Status]
for (n <- (responseXML \\ "status").elements)
statusListBuffer += (Status.fromXml(n))
statusListBuffer.toList
}
else
{
Nil
}
}
}
/**
* 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
}
}
}
|
代码有点长，但是很容易分为几个基本部分：
- case 类 User 和 Status，表示 Twitter 在对 API 调用的响应中发回给客户机的基本类型，包括用于构造或提取 XML 的一些方法。
- 一个 Scitter 独立对象，处理那些不需要对用户进行验证的操作。
- 一个 Scitter 实例（用 username 和 password 参数化），用于那些需要对用户执行验证的操作。
|
|
|
|
|
|
