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ClassFinder.scala
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ClassFinder.scala
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/**
* Copyright (C) 2009-2011 the original author or authors.
* See the notice.md file distributed with this work for additional
* information regarding copyright ownership.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.fusesource.scalate.util
import java.io.InputStream
import java.util.Properties
/**
* <p>
* </p>
*
* @author <a href="http://hiramchirino.com">Hiram Chirino</a>
*/
object ClassFinder {
val log = Log(getClass); import log._
def discoverCommands[T](
indexPath: String,
classLoaders: List[ClassLoader] = ClassLoaders.defaultClassLoaders): List[T] = {
classLoaders.flatMap { cl =>
ClassLoaders.withContextClassLoader(cl) {
discoverCommandClasses(indexPath, cl).flatMap {
name =>
try {
val clazz = cl.loadClass(name)
try {
Some(clazz.getConstructor().newInstance().asInstanceOf[T])
} catch {
case e: Exception =>
// It may be a scala object.. check for a module class
try {
val moduleField = cl.loadClass(name + "$").getDeclaredField("MODULE$")
Some(moduleField.get(null).asInstanceOf[T])
} catch {
case e2: Throwable =>
// throw the original error...
throw e
}
}
} catch {
case e: Throwable =>
debug(e, "Invalid class: %s", name)
None
}
}
}
}.distinct
}
def discoverCommandClasses(
indexPath: String,
cl: ClassLoader = getClass.getClassLoader): List[String] = {
var rc: List[String] = Nil
val resources = cl.getResources(indexPath)
while (resources.hasMoreElements) {
val url = resources.nextElement
debug("loaded commands from %s", url)
val p = loadProperties(url.openStream)
if (p == null) {
warn("Could not load class list from: %s", url)
}
val enum = p.keys
while (enum.hasMoreElements) {
rc = rc ::: enum.nextElement.asInstanceOf[String] :: Nil
}
}
rc = rc.distinct
debug("loaded classes: %s", rc)
rc
}
def loadProperties(is: InputStream): Properties = {
if (is == null) {
null
} else {
try {
val p = new Properties()
p.load(is)
p
} catch {
case e: Exception => null
} finally {
try {
is.close()
} catch {
case _: Exception =>
}
}
}
}
}