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Non-constant string concatenation as argument to logging call

Reports non-constant string concatenations that are used as arguments to SLF4J and Log4j 2 logging methods. Non-constant concatenations are evaluated at runtime even when the logging message is not logged; this can negatively impact performance. It is recommended to use a parameterized log message instead, which will not be evaluated when logging is disabled.

Example:

public class Vital { private static final Logger LOG = LoggerFactory.getLogger(Vital.class); public void saveTheWorld(int i, String s, boolean b) { LOG.info("saveTheWorld(" + i + ", " + s + ", " + b + ")"); // todo } }

After the quick-fix is applied:

public class Vital { private static final Logger LOG = LoggerFactory.getLogger(Vital.class); public void saveTheWorld(int i, String s, boolean b) { LOG.info("saveTheWorld({}, {}, {})", i, s, b); // todo } }

Configure the inspection:

  • Use the Warn on list to ignore certain higher logging levels. Higher logging levels may be enabled even in production, and the arguments will always be evaluated.

Inspection options

Option

Type

Default

Warn on

Dropdown

all log levels

Inspection Details

Available in:

IntelliJ IDEA 2023.3, Qodana for JVM 2023.3

Plugin:

Java, 233.SNAPSHOT

Last modified: 13 July 2023