Java Collections Advisor

1. Introduction

2. Build and Running

In order to just try the agent you have two options:

• run the com.manoelcampos.collectionsadvisor.AgentEntry class from the agent dir in your IDE;
• or execute the agent/run.sh script.

2.1. Running an independent app

If you are building your own app and want to load the agent during application startup, check the sample-app project. Execute the sample-app/run.sh script to build and run the app using the agent.

The sample app has no agent code and the instrumentation happens in runtime.

3. Results after running the agent with your app

Current results are very basic since this is a working in progress. The agent is not giving any advice about collections utilization yet. Check an example of the agent results over a sample app using some Collections.

# Collections Advisor Agent
## Intercepted java.util.Collection methods calls from com.sample package

java.util.ArrayList from com.sample.ArrayListRegularSample:
  	Calls: 23 Lookups: 10 Clear Ups: 0
	Capacity changes: 1 -> inc 1 dec 0 | Size changes: 11 -> inc 10 dec 1
	Inserts: 10 -> head 0 middle 0 tail 10 moves 0
	Removals: 1 -> head 0 middle 0 tail 1 moves 0
java.util.ArrayList from com.sample.ArrayListAsQueueSample:
  	Calls: 31 Lookups: 0 Clear Ups: 0
	Capacity changes: 1 -> inc 1 dec 0 | Size changes: 20 -> inc 10 dec 10
	Inserts: 10 -> head 0 middle 0 tail 10 moves 0
	Removals: 10 -> head 9 middle 0 tail 1 moves 45
java.util.ArrayList from com.sample.ArrayListHeadAddSample:
  	Calls: 10 Lookups: 0 Clear Ups: 0
	Capacity changes: 1 -> inc 1 dec 0 | Size changes: 10 -> inc 10 dec 0
	Inserts: 10 -> head 9 middle 0 tail 1 moves 45
	Removals: 0 -> head 0 middle 0 tail 0 moves 0
java.util.LinkedList from com.sample.LinkedListSample:
  	Calls: 22 Lookups: 10 Clear Ups: 1
	Capacity changes: 0 -> inc 0 dec 0 | Size changes: 11 -> inc 10 dec 1
	Inserts: 10 -> head 0 middle 0 tail 10 moves 0
	Removals: 0 -> head 0 middle 0 tail 0 moves 0

4. References

• ByteBuddy Tutorial
• Runtime Code Generation with Byte Buddy
• Fixing Bugs in Running Java Code with Dynamic Attach
• How to Make Java More Dynamic with Runtime Java Code Generation (1/2)
• Using Byte Buddy for Annotation Driven Java (2/2)
• Rafael Winterhalter - The definitive guide to Java agents (JPoint 2019)