byte-buddy agentBuilder.transform

AgentBuilder.transform.java

 /**
   * https://github.com/stagemonitor/stagemonitor/blob/80793ac6c582944c9078b420138dda4d23517a69/stagemonitor-core/src/main/java/org/stagemonitor/core/instrument/AgentAttacher.java#L149-L166
   */
  private static ClassFileTransformer initByteBuddyClassFileTransformer(AutoEvictingCachingBinaryLocator binaryLocator) {
		AgentBuilder agentBuilder = createAgentBuilder(binaryLocator);
		for (StagemonitorByteBuddyTransformer transformer : getStagemonitorByteBuddyTransformers()) {
			agentBuilder = agentBuilder
					.type(transformer.getMatcher())
					.transform(transformer.getTransformer())
					.asDecorator();
		}

		final long start = System.currentTimeMillis();
		try {
			return agentBuilder.installOn(instrumentation);
		} finally {
			if (corePlugin.isDebugInstrumentation()) {
				logger.info("Installed agent in {} ms", System.currentTimeMillis() - start);
			}
		}
	}

	private static Iterable<StagemonitorByteBuddyTransformer> getStagemonitorByteBuddyTransformers() {
		List<StagemonitorByteBuddyTransformer> transformers = new ArrayList<StagemonitorByteBuddyTransformer>();
    		// ref source: 
    		//    https://github.com/stagemonitor/stagemonitor/blob/c1c76e57825d60b179ce1157c28ecac9369ee51d/stagemonitor-core/src/main/java/org/stagemonitor/core/instrument/StagemonitorByteBuddyTransformer.java
		for (StagemonitorByteBuddyTransformer transformer : ServiceLoader.load(StagemonitorByteBuddyTransformer.class, Stagemonitor.class.getClassLoader())) {
			if (transformer.isActive() && !isExcluded(transformer)) {
				transformers.add(transformer);
				if (corePlugin.isDebugInstrumentation()) {
					logger.info("Registering {}", transformer.getClass().getSimpleName());
				}
			} else if (corePlugin.isDebugInstrumentation()) {
				logger.info("Excluding {}", transformer.getClass().getSimpleName());
			}
		}
		Collections.sort(transformers, new Comparator<StagemonitorByteBuddyTransformer>() {
			@Override
			public int compare(StagemonitorByteBuddyTransformer o1, StagemonitorByteBuddyTransformer o2) {
				return o1.getOrder() > o2.getOrder() ? -1 : 1;
			}
		});
		return transformers;
	}

  /**
   * https://github.com/stagemonitor/stagemonitor/blob/c1c76e57825d60b179ce1157c28ecac9369ee51d/stagemonitor-core/src/main/java/org/stagemonitor/core/instrument/StagemonitorByteBuddyTransformer.java#L99-L113
   */
  public AgentBuilder.Transformer getTransformer() {
		return new AgentBuilder.Transformer() {

			private AsmVisitorWrapper.ForDeclaredMethods advice = registerDynamicValues()
					.to(getAdviceClass())
					.on(timed("method", transformerName, getMethodElementMatcher()));

			@Override
			public DynamicType.Builder<?> transform(DynamicType.Builder<?> builder, TypeDescription typeDescription, ClassLoader classLoader) {
				beforeTransformation(typeDescription, classLoader);
				return builder.visit(advice);
			}

		};
	}