feat: Support CRaC and priming of powertools batch

[David-DAM]

Issue number: Closes #1998

Description of changes:

• Added CRaC support in powertools-batch, following the guide and blogs mentioned on the ticket.
• Added automatic priming for powertools-batch by preloading all the required classes, the list of classes is fetched from the JVM at compile time.

Checklist

• Meet tenets criteria
• Update tests
• Update docs
• PR title follows conventional commit semantics

Breaking change checklist

RFC issue #:

• Migration process documented
• Implement warnings (if it can live side by side)

By submitting this pull request, I confirm that you can use, modify, copy, and redistribute this contribution, under the terms of your choice.

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[David-DAM]

Hi @phipag I have tested the changes in my own AWS account, let me explain the process to validate that the steps are correct

1. I have created a lambda function with only the dependency that I have changed, in this case powertools-batch and I have instantiate the class BatchMessageHandlerBuilder simulating the use

package com.davinchicoder;

import com.amazonaws.services.lambda.runtime.Context;
import com.amazonaws.services.lambda.runtime.RequestHandler;
import software.amazon.lambda.powertools.batch.BatchMessageHandlerBuilder;

import java.util.Map;

public class App implements RequestHandler<Map<String, String>, String> {


    static {
        System.out.println("Static initializer");
        new BatchMessageHandlerBuilder();
    }

    public App() {
        System.out.println("Constructor");
    }

    @Override
    public String handleRequest(Map<String, String> input, Context context) {
        context.getLogger().log("Handling request\n");
        return "OK";
    }
}

2. I have enabled SnapStart for my lambda and when I published a new version of the lambda it triggers the primming call
3. After that i can see the next logs

2026-07-25T12:32:00.889Z | INIT_START | Runtime Version: java:21.v77 | Runtime Version ARN: arn:aws:lambda:eu-west-3::runtime:29631c218b0f9e989981a51acd20da540e38940efec45dec7a8addf28ca349b1
2026-07-25T12:32:01.630Z | Static initializer
2026-07-25T12:32:01.731Z | Constructor
2026-07-25T12:32:03.433Z | [main] DEBUG software.amazon.lambda.powertools.batch.internal.XRayTraceEntityPropagator - X-Ray SDK not detected. Trace context propagation disabled
2026-07-25T12:32:06.295Z | [main] DEBUG software.amazon.lambda.powertools.common.internal.ClassPreLoader - SnapStart priming: preloaded 4102 class(es) from classesloaded.txt
2026-07-25T12:32:06.393Z | INIT_REPORT | Init Duration: 5504.55 ms

After that I suppose is working fine but just to let you know during the tests I got some errors before in the class ClassPreLoader, specifically in this method because it doesn't handle the LinkageError, in my case I was getting the NoClassDefFoundError, maybe because I got misconfigured my dependencies and I had to add some of them but just to let you know

private static boolean loadClassIfFound(String className) {
        try {
            Class.forName(className, true, ClassPreLoader.class.getClassLoader());
            return true;
        } catch (ClassNotFoundException e) {
            // No action is required if the class with given name cannot be found
            return false;
        }
    }