我是 Scala 的新手,我正在编写一个简单的 rss 阅读器。我有用于管理提要和内容的类管理器。
package lib
import scala.xml._
import java.net.URL
import net.liftweb.couchdb.{CouchDB, Database}
import dispatch.{Http, StatusCode}
/**
* @author smix
*
* Feeds manager
*/
object Manager {
var db = List[Database]()
/*
* Initialize CouchDb databases
*/
def init = {
this.appendDb(new Database("myserver.com", 5984, "content"))
}
/*
* Append a new database to the databases list
*/
private def appendDb(database: Database) : Unit = {
database :: db
// Strange exception if database has been already created
/* try {
this.db.head.createIfNotCreated(new Http())
} catch {
case e:java.lang.NoClassDefFoundError => {}
} */
}
/*
* Fetch articles from feed by url
*/
def fetchItems(feedUrl: String): List[scala.xml.Elem] = {
val rssFeed = XML.load( (new URL(feedUrl)).openConnection.getInputStream )
val items = rssFeed \ "channel" \ "item"
val articles: List[scala.xml.Elem] = List()
for(item <- items) {
item :: articles
}
articles
}
}
我想将内容存储在 CouchDb 中。我需要有沙发数据库列表(提要、文章等......)。我写了类,但是当我调用 appendDb 时出现错误:
Exception in thread "main" java.lang.NoClassDefFoundError: lib/Manager$
at collector$.main(collector.scala:5)
at collector.main(collector.scala)
Caused by: java.lang.ClassNotFoundException: lib.Manager$
at java.net.URLClassLoader$1.run(URLClassLoader.java:202)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(URLClassLoader.java:190)
at java.lang.ClassLoader.loadClass(ClassLoader.java:307)
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:301)
at java.lang.ClassLoader.loadClass(ClassLoader.java:248)
... 2 more
当我重写db
定义时:var db = List[Int]()
并且appendDb的第一行:1 :: this.db
项目运行良好......奇怪。
此外,有趣的是,为什么当我为现有数据库调用 createIfNotCreated 时会出现异常(在 appendDb 中注释了 try-catch 块)。