How to instrument .jar programmatically?

[Charlie Gordon]

Hello, dear developers.

I have a .jar file of the compiler that I want to instrument by passing it one program or another. How can I do this programmatically?

I saw your instrumentation API example "CoreTutorial.java", which instruments, executes and analyzes a single target class. 

But it remains unclear how to do the part related to instrumentation and obtaining the result, 

if you need to execute a command like this programmatically, and preferably not writing the result to a file, but immediately passing it to the report generation module:

java -javaagent:pathToJacocoAgent=destfile=pathToJacocoExec -jar pathToCompiler.jar fileForCompiler

I would be grateful if you would help with this.

Thanks for your work.

[Marc Hoffmann]

Hello Charlie,

if you don’t want to write the execution data to a file you can start the agent e.g. in tcpclient mode. This is how for example our coverage launcher in Eclipse works:

1) Start an TCP server on an arbitrary port

2) Programmatically launch the JVM with the parameter -javaagent:pathToJacocoAgent=output=tcspclient,port=<port allocated in step 1>

The agent will connect to the server and send execution data when the JVM shuts down or you can also request dumps at arbitrary points in time.

Our example comes with basic execution data server: https://www.jacoco.org/jacoco/trunk/doc/api.html

You might also take a look at the implementation for the Eclipse plugin: https://github.com/eclipse/eclemma/blob/master/org.eclipse.eclemma.core/src/org/eclipse/eclemma/internal/core/launching/AgentServer.java

Regards,

-marc

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