Sample Java Instrumentation Agent

This project demonstrates how to create and use a Java instrumentation agent. It consists of two main components:

1. Agent: The instrumentation agent responsible for modifying the behavior of the target application.
2. Application: A simple vending machine application to be instrumented.

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Application

The Application module represents a straightforward implementation of a vending machine.

Build the Application

To compile and package the application, navigate to the Application directory and execute the following command:

mvn clean package

This will generate the application JAR file in the target directory.

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Agent

The Agent module contains the code for the Java instrumentation agent.

Build the Agent

To compile and package the agent, run the following command from the Agent directory:

mvn clean package

The resulting JAR file will be located in the target directory.

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Running the Instrumentation Agent

There are two ways to load a Java instrumentation agent: Premain (static loading) and Agentmain (dynamic loading). Below are detailed instructions for both methods.

Premain Loading (Static Loading)

In static loading, the agent is loaded at JVM startup using the -javaagent flag.

1. Navigate to the root directory of the project.
2. Run the following command:

java -javaagent:./Agent/target/Agent-jar-with-dependencies.jar -jar ./Application/target/Application-jar-with-dependencies.jar

This will start the application with the agent attached, allowing the agent to modify the application during startup.

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Agentmain Loading (Dynamic Loading)

In dynamic loading, the agent is attached to a running JVM process at runtime.

1. First, start the application using the following command:

java -jar ./Application/target/Application-jar-with-dependencies.jar

2. Then, load the agent dynamically into the running application:

java -jar ./Agent/target/Agent-jar-with-dependencies.jar

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By following these steps, you can successfully experiment with Java instrumentation using the provided sample project.