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/* =========================================================================================
* Copyright © 2013-2015 the kamon project <http://kamon.io/>
*
* 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 kamon.autoweave.loader
import java.io.{File, FileOutputStream, InputStream}
import java.lang.management.ManagementFactory
import java.util.jar.Attributes.Name
import java.util.jar.{JarEntry, JarOutputStream, Manifest}
import scala.util.control.NoStackTrace
object AgentLoader {
/**
* Gets the current JVM PID
*
* @return Returns the PID
*/
private def getPidFromRuntimeMBean: String = {
val jvm = ManagementFactory.getRuntimeMXBean.getName
val pid = jvm.substring(0, jvm.indexOf('@'))
pid
}
/**
* Loads an agent into a JVM.
*
* @param agent The main agent class.
* @param resources Array of classes to be included with agent.
*/
def attachAgentToJVM(agent: Class[_], resources: Seq[Class[_]] = Seq.empty): Unit = attachToRunningJVM(agent, resources)
/**
* Java variant
*
* @param agent
*/
def attachAgentToJVM(agent: Class[_]): Unit = attachAgentToJVM(agent, Seq.empty)
/**
* Generates a temporary agent file to be loaded.
*
* @param agent The main agent class.
* @param resources Array of classes to be included with agent.
* @return Returns a temporary jar file with the specified classes included.
*/
private def generateAgentJar(agent: Class[_], resources: Seq[Class[_]]): File = {
val jarFile = File.createTempFile("agent", ".jar")
jarFile.deleteOnExit()
val manifest = new Manifest()
val mainAttributes = manifest.getMainAttributes
// Create manifest stating that agent is allowed to transform classes
mainAttributes.put(Name.MANIFEST_VERSION, "1.0")
mainAttributes.put(new Name("Agent-Class"), agent.getName)
mainAttributes.put(new Name("Can-Retransform-Classes"), "true")
mainAttributes.put(new Name("Can-Redefine-Classes"), "true")
mainAttributes.put(new Name("Can-Set-Native-Method-Prefix"), "true")
val jos = new JarOutputStream(new FileOutputStream(jarFile), manifest)
jos.putNextEntry(new JarEntry(agent.getName.replace('.', '/') + ".class"))
jos.write(getBytesFromStream(agent.getClassLoader.getResourceAsStream(unqualify(agent))))
jos.closeEntry()
for (clazz ← resources) {
val name = unqualify(clazz)
jos.putNextEntry(new JarEntry(name))
jos.write(getBytesFromStream(clazz.getClassLoader.getResourceAsStream(name)))
jos.closeEntry()
}
jos.close()
jarFile
}
/**
* Attach to the running JVM.
*
* @return
* Returns the attached VirtualMachine
*/
private def attachToRunningJVM(agent: Class[_], resources: Seq[Class[_]]): Unit = {
AttachmentProviders.resolve() match {
case Some(virtualMachine) ⇒
val virtualMachineInstance = virtualMachine.getDeclaredMethod("attach", classOf[String]).invoke(null, getPidFromRuntimeMBean)
virtualMachine.getDeclaredMethod("loadAgent", classOf[String], classOf[String]).invoke(virtualMachineInstance, generateAgentJar(agent, resources).getAbsolutePath, "")
virtualMachine.getDeclaredMethod("detach").invoke(virtualMachineInstance)
case None ⇒ throw new IllegalStateException("Cannot read the virtual machine type...") with NoStackTrace
}
}
/**
* Gets bytes from InputStream.
*
* @param stream
* The InputStream.
* @return
* Returns a byte[] representation of given stream.
*/
private def getBytesFromStream(stream: InputStream): Array[Byte] = {
Stream.continually(stream.read).takeWhile(_ != -1).map(_.toByte).toArray
}
private def unqualify(clazz: Class[_]): String = clazz.getName.replace('.', '/') + ".class"
}
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