[Bug] The replaceParam method of AbstractLogger behaves unexpectedly when the replaced string contains a replacement marker

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I had searched in the issues and found no similar issues.

Apache SkyWalking Component

Java Agent (apache/skywalking-java)

What happened

The replaceParam method of AbstractLogger behaves unexpectedly when the replaced string contains a replacement marker.

What you expected to happen

log.info("sample rule update: {} -> {}", "Config{a={}}", "Config{b={}}")

expect: sample rule update: Config{a={}} -> Config{b={}}

but actual: sample rule update: Config{a=Config{b={}}} -> {}

How to reproduce

just run code above

Anything else

https://github.com/apache/skywalking-java/blob/67ab8b222fbb9a71b450665eb9f733380d813b8a/apm-sniffer/apm-agent-core/src/main/java/org/apache/skywalking/apm/agent/core/logging/core/AbstractLogger.java#L185-L203

            tmpMessage = tmpMessage.replaceFirst("\\{\\}", Matcher.quoteReplacement(String.valueOf(parameters[parametersIndex++])));
            startSize = index + 2;

The index should not just increase by 2, but should increase by the length of the string to be replaced.

Are you willing to submit a pull request to fix on your own?

Yes I am willing to submit a pull request on my own!

Code of Conduct

I agree to follow this project's Code of Conduct

We don't want to use complex regex to be honest.
Why we need to put agent logs so complex? It should be just a simple version implementation, as agent plugin is the only one using it.
This is not an app logger.

We don't want to use complex regex to be honest. Why we need to put agent logs so complex? It should be just a simple version implementation, as agent plugin is the only one using it. This is not an app logger.

I fully agree with your point. Regular expressions are unnecessary here, simple string replacement would suffice for implementation.

    protected String replaceParam(String message, Object... parameters) {
        if (message == null) {
            return message;
        }
        int startSize = 0;
        int parametersIndex = 0;
        int index;
        StringBuilder sb = new StringBuilder(message);
        while ((index = sb.indexOf("{}", startSize)) != -1) {
            if (parametersIndex >= parameters.length) {
                break;
            }

            String tmp = String.valueOf(parameters[parametersIndex++]);
            sb.replace(index, index+2, tmp);
            startSize = index + tmp.length();
        }
        return sb.toString();
    }

Could you explain more about which is the bug now? Or file a PR to show the code change without using regex.

Could you explain more about which is the bug now? Or file a PR to show the code change without using regex.

I submitted a PR apache/skywalking-java#782

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[Bug] The `replaceParam` method of `AbstractLogger` behaves unexpectedly when the replaced string contains a replacement marker #13591

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[Bug] The replaceParam method of AbstractLogger behaves unexpectedly when the replaced string contains a replacement marker #13591

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Apache SkyWalking Component

What happened

What you expected to happen

How to reproduce

Anything else

Are you willing to submit a pull request to fix on your own?

Code of Conduct

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wu-sheng commented on Nov 26, 2025

shichaoyuan commented on Nov 26, 2025

wu-sheng commented on Nov 26, 2025

shichaoyuan commented on Nov 26, 2025

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[Bug] The `replaceParam` method of `AbstractLogger` behaves unexpectedly when the replaced string contains a replacement marker #13591