[java] GuardLogStatement reports violation for Log4j parameterized logs

[ThorodanBrom]

Affects PMD Version: 6.53.0, 6.55.0

Rule: GuardLogStatement

• https://docs.pmd-code.org/pmd-doc-6.53.0/pmd_rules_java_bestpractices.html#guardlogstatement
• https://docs.pmd-code.org/pmd-doc-6.55.0/pmd_rules_java_bestpractices.html#guardlogstatement

Description:

PMD reports a violation when Log4j parameterized logs are used. We are in the process of converting all logs from concatenated strings to parameterized logs, using PMD to find offending logs. But PMD reports the same logs even after updating.

Code Sample demonstrating the issue:

import org.apache.logging.log4j.LogManager;
import org.apache.logging.log4j.Logger;

class Test {
    private static final Logger LOGGER = LogManager.getLogger(Test.class);

    public static void main() {
        LOGGER.info("Info : {} : Request received", LOGGER.getName());
        String s = "Hello World";
        LOGGER.debug("Logging string {}", s);
    }
}

Expected outcome:

• Both logs do not use concatenation and make use of parameters as specified in the GuardLogStatement examples

PMD reports a violation at lines 8 and 10, but that's wrong. That's a false positive.

Running PMD through: Maven

---

P.S. I saw someone else report the same false-positive on another issue - #3144 (comment)

[jsotuyod]

Under PMD 7.0.0 the second line will not be reported.

The first one, however, will.

LOGGER.info("Info : {} : Request received", LOGGER.getName());

this line will always perform a call to LOGGER.getName() regardless of the logging level. As any method calls done here can be potentially expensive, they still get flagged. The correct approach would be to use a Callable here through a lambda such as:

LOGGER.info("Info : {} : Request received", () -> LOGGER.getName());