invesdwin-instrument

This is an instrumentation java agent that is able to load itself into the running JVM. It is able to dynamically setup springs InstrumentationLoadTimeWeaver to enable support for aspects without having to start the JVM with an explicit java agent.

Maven

Releases and snapshots are deployed to this maven repository:

https://invesdwin.de/repo/invesdwin-oss-remote/

Dependency declaration:

<dependency>
	<groupId>de.invesdwin</groupId>
	<artifactId>invesdwin-instrument</artifactId>
	<version>1.0.14</version><!---project.version.invesdwin-instrument-->
</dependency>

There is no plan to publish artifacts to maven central, see answer here for alternatives.

Usage

Simply define a static initializer like this:

static {
  DynamicInstrumentationLoader.waitForInitialized(); //dynamically attach java agent to jvm if not already present
  DynamicInstrumentationLoader.initLoadTimeWeavingContext(); //weave all classes before they are loaded as beans
}

Spring-Boot

With spring-boot you have to ensure that the context in the aspects is updated by importing the one responsible for initializing the load time weaving into the spring-boot configuration:

@SpringBootApplication
/** 
 * Make @Configurable work via @EnableLoadTimeWeaving.
 * If it does not work, alternatively you can try: 
 * @ImportResource(locations = "classpath:/META-INF/ctx.spring.weaving.xml") 
 */
@EnableLoadTimeWeaving
public class MySpringBootApplication {
    public static void main(final String[] args) {
        DynamicInstrumentationLoader.waitForInitialized(); //dynamically attach java agent to jvm if not already present
        DynamicInstrumentationLoader.initLoadTimeWeavingContext(); //weave all classes before they are loaded as beans
	//org.aspectj.weaver.loadtime.Agent.agentmain("", InstrumentationSavingAgent.getInstrumentation()); //workaround for spring-boot-devtools RestartLauncher
        SpringApplication.run(MySpringBootApplication.class, args); //start application, load some classes
    }
}

To enable the spring aspects, just add the spring-aspects.jar dependency to your project, they are enabled directly, others might need a aop.xml to be enabled. Note that the "ctx.spring.weaving.xml" is part of the invesdwin-instrument jar.

Make sure that the instrumentation is loaded before the classes of the aspects or the classes that use the aspects are loaded by the classloader. Only classes that get loaded after initializing load time weaving will be successfully woven by aspectj.

Please note that you need to have a JDK installed with tools.jar available in it for this to work properly (this is not required anymore since Java 9). Alternatively just load the invesdwin-instrument jar via the -javaagent:/path/to/invesdwin-instrument.jar JVM parameter if you only have a JRE installed. The dynamic loading will be skipped then.

For a sample usage see the junit test cases in the invesdwin-aspects project or the spring-boot example project in invesdwin-nowicket.

Spring-Boot-Devtools

Note that spring-boot-devtools uses a org.springframework.boot.devtools.restart.RestartLauncher that reinitializes the application in a nested classloader. This restart mechanism can be disabled via the system property spring.devtools.restart.enabled=false, but that might disable functionality of spring-boot-devtools. To work around this, use org.aspectj.weaver.loadtime.Agent.agentmain("", InstrumentationSavingAgent.getInstrumentation()); inside the nested classloader to reinitialize AspectJ. Also you might have to add the AspectJ weaver option -Xreweavable to make it work properly. For more details see: #24

Testing Aspects inside Unit Tests

See discussion here. The workaround is to use the aspects inside nested classes that are loaded after invesdwin-instrument is initialized by the unit test class. Example here.

Burningwave Java Agent

With invesdwin-instrument-burningwave you can sometimes launch external applications on newer Java versions without having to add any --add-opens arguments (or at least test if this is the only problem with newer Java versions). The java agent automatically opens all modules when being used via StaticComponentContainer.Modules.exportAllToAll() from burningwave. This agent needs to be specified manually via -javaagent:/path/to/invesdwin-instrument-burningwave.jar. It does not load itself into the running process because you can just call burningwave yourself if you can modify your application anyway.

Support

If you need further assistance or have some ideas for improvements and don't want to create an issue here on github, feel free to start a discussion in our invesdwin-platform mailing list.