AspectJ 1.8.7

The full list of resolved issues in 1.8.7 is available here

Release info: 1.8.7 available 9-Sep-2015

Notable changes

ajdoc

The ajdoc tool has been fixed! It is now working again if run on a 1.7 JDK.

Dynamic weaver attachment

The AspectJ loadtime weaving agent can now be dynamically attached to a JVM after it has started (you don’t need to use -javaagent). This offers extra flexibility but obviously any classes loaded before attachment will not be woven.

Here is a simple aspect:

public aspect Azpect {
  before(): execution(* *(..)) {
    System.out.println(thisJoinPointStaticPart);
  }
}

Compiled via:

ajc -1.8 Azpect.java -outxml

This produces a compiled class Azpect.class and a file META-INF/aop-ajc.xml.

I then have this sample application (same directory):

import java.lang.management.ManagementFactory;
import org.aspectj.weaver.loadtime.Agent;
import com.sun.tools.attach.VirtualMachine;

public class Application {

  public static void main(String[] args) {
    if (!isAspectJAgentLoaded())
      System.err.println("WARNING: AspectJ weaving agent not loaded");
    new Sample().doSomething();
  }

  public static boolean isAspectJAgentLoaded() {
    try {
      Agent.getInstrumentation();
    } catch (NoClassDefFoundError e) {
      System.out.println(e);
      return false;
    } catch (UnsupportedOperationException e) {
      System.out.println(e);
      return dynamicallyLoadAspectJAgent();
    }
    return true;
  }

  public static boolean dynamicallyLoadAspectJAgent() {
    String nameOfRunningVM = ManagementFactory.getRuntimeMXBean().getName();
    int p = nameOfRunningVM.indexOf('@');
    String pid = nameOfRunningVM.substring(0, p);
    try {
      VirtualMachine vm = VirtualMachine.attach(pid);
      String jarFilePath = System.getProperty("AGENT_PATH");
      vm.loadAgent(jarFilePath);
      vm.detach();
    } catch (Exception e) {
      System.out.println(e);
      return false;
    }
    return true;
  }
}

And this Sample class:

public class Sample {
    public void doSomething() {
        System.out.println("Do something");
        System.out.println("Square of 7 = " + square(7));
    }

    private int square(int i) {
        return i * i;
    }
}

Compile these with javac, but you must have the aspectjweaver and the JDK tools.jar on your classpath.

Once compiled we can run it:

java -DAGENT_PATH=<path-to>/aspectjweaver.jar Application

What does it do? The main method calls the function that detects whether the agent is attached, if it is not then it programmatically attaches it using the VirtualMachine class. Then the main method accesses the Sample class. At this point in program execution the Sample class is loaded and because the agent has been attached it gets woven. Notice that the Application class itself is not woven because it was loaded prior to agent attachment.

Thanks to Alexander Kriegisch for the sample code and the patch to add this behaviour to AspectJ.