mybatis/mybatis-3 · error · LogException

Error creating logger for logger

Error message

Error creating logger for logger {}.  Cause: {}

What it means

LogFactory.getLog(String) throws LogException when instantiating the selected Log implementation fails — logConstructor.newInstance(logger) threw. The constructor was resolved earlier by setImplementation(); failure at this point usually means the underlying logging library threw in its constructor or the class could not be initialized at runtime (missing dependency after repackaging, classloader isolation).

Solutions

1. Check the chained cause — it names the exact class/init failure (NoClassDefFoundError, ClassNotFoundException, backend exception).
2. Ensure the chosen logging backend jar (slf4j-api, log4j, etc.) is on the runtime classpath at the same classloader level as mybatis.
3. Switch to a backend you actually ship, e.g. LogFactory.useSlf4jLogging() when only SLF4J is present, or useStdOutLogging() for isolated tests.
4. In shaded jars, keep META-INF services and logging packages un-relocated or exclude them from shading.

Example fix

// before: backend classes missing at runtime
LogFactory.useLog4J2Logging(); // resolves, then fails per-logger

// after: force a backend you control
LogFactory.useSlf4jLogging(); // slf4j-api is on the classpath

// Probe the backend once at startup before any mapper work
try {
  LogFactory.getLog("startup-probe");
} catch (LogException e) {
  LogFactory.useStdOutLogging(); // known-good fallback for isolated environments
  LogFactory.getLog("startup-probe");
}

try {
  log = LogFactory.getLogger(Xxx.class);
} catch (LogException e) {
  // fall back to a logger you control; do not let logging kill initialization
  log = internalStdOutLog;
}

When it happens

Trigger: Any first use of MyBatis logging (getLog called during mapper initialization) after a setImplementation/useSlf4jLogging-style call succeeded but the adapter's constructor (or static init of the underlying logger like Log4j2/Slf4j classes) fails in the deployment classloader.

Common situations: Application-server classloader hierarchies where the logging jar is visible to LogFactory but not instantiable; shaded/uber-jar builds stripping logging classes; OSGi deployments; logging backend throwing during initialization (misconfigured Log4j2 config).

Related errors

• Error setting driver on UnpooledDataSource.
• Error setting Log implementation. Cause
• Bad zip entry
• Cannot enable lazy loading because CGLIB is not available…
• Cannot enable lazy loading because Javassist is not…

AI-assisted analysis of mybatis/mybatis-3@008069adb1 (2026-08-14). Data as JSON: /api/errors/cb1939583c75fe72. Report an issue: GitHub.

Appendix: source

Thrown at src/main/java/org/apache/ibatis/logging/LogFactory.java:56

    tryImplementation(LogFactory::useLog4J2Logging);
    tryImplementation(LogFactory::useLog4JLogging);
    tryImplementation(LogFactory::useJdkLogging);
    tryImplementation(LogFactory::useNoLogging);
  }

  private LogFactory() {
    // disable construction
  }

  public static Log getLog(Class<?> clazz) {
    return getLog(clazz.getName());
  }

  public static Log getLog(String logger) {
    try {
      return logConstructor.newInstance(logger);
    } catch (Throwable t) {
      throw new LogException("Error creating logger for logger " + logger + ".  Cause: " + t, t);
    }
  }

  public static void useCustomLogging(Class<? extends Log> clazz) {
    setImplementation(clazz);
  }

  public static void useSlf4jLogging() {
    setImplementation(org.apache.ibatis.logging.slf4j.Slf4jImpl.class);
  }

  public static void useCommonsLogging() {
    setImplementation(org.apache.ibatis.logging.commons.JakartaCommonsLoggingImpl.class);
  }

  /**
   * @deprecated Since 3.5.9 - See https://github.com/mybatis/mybatis-3/issues/1223. This method will remove future.
   */

View on GitHub (pinned to 008069adb1)