alibaba/druid · error · IllegalArgumentException

{className}

Error message

{className}

What it means

DruidAbstractDataSource.setStatLoggerClassName reflectively loads, instantiates, and casts a class to DruidDataSourceStatLogger. Any failure (ClassNotFoundException, InstantiationException, IllegalAccessException, ClassCastException, or a constructor-thrown exception) is wrapped as IllegalArgumentException(className, e) - note the message is just the class name and the real cause is in the exception's cause.

Solutions

1. Confirm the class is on the classpath and implements com.alibaba.druid.stat.DruidDataSourceStatLogger.
2. Ensure a public no-arg constructor exists and the class is concrete/public.
3. Prefer setStatLogger(new MyStatLogger()) to get a compile-time type check instead of reflective loading.
4. Read IllegalArgumentException.getCause() to identify ClassNotFoundException vs ClassCastException vs InstantiationException.

Example fix

// before
// ds.setStatLoggerClassName("com.example.MyStatLogger"); // reflective, runtime-only

// after
// ds.setStatLogger(new com.example.MyStatLogger()); // compile-time checked

Class<?> c = Class.forName(className);
if (!com.alibaba.druid.stat.DruidDataSourceStatLogger.class.isAssignableFrom(c))
    throw new IllegalStateException(className + " is not a DruidDataSourceStatLogger");
com.alibaba.druid.stat.DruidDataSourceStatLogger probe =
    (com.alibaba.druid.stat.DruidDataSourceStatLogger) c.newInstance();

static boolean isValidStatLoggerClass(String name) {
    try {
        Class<?> c = Class.forName(name);
        return com.alibaba.druid.stat.DruidDataSourceStatLogger.class.isAssignableFrom(c)
            && !java.lang.reflect.Modifier.isAbstract(c.getModifiers());
    } catch (Throwable t) { return false; }
}

try {
    ds.setStatLoggerClassName(className);
} catch (IllegalArgumentException e) {
    // e.getMessage() == className; e.getCause() tells you which: CNFE/CCE/IE/IAE
    // prefer ds.setStatLogger(new MyStatLogger()) instead
    throw e;
}

When it happens

Trigger: Calling setStatLoggerClassName("foo.Bar") where Bar is not on the classpath, is abstract/inaccessible, does not implement DruidDataSourceStatLogger, or its constructor throws.

Common situations: Typo in the stat logger class name; the logger class lives in a JAR not on the datasource's classloader; providing a class that implements a different Druid version's DruidDataSourceStatLogger interface.

Related errors

• create exceptionSorter error
• Config DataSource error.
• ConfigLoader only support DruidDataSource
• driverClassName length > 256.
• load managed jdbc driver event listener error.

AI-assisted analysis of alibaba/druid@fa8dc99126 (2026-08-14). Data as JSON: /api/errors/eddfbf56e63c6a97. Report an issue: GitHub.

Appendix: source

Thrown at core/src/main/java/com/alibaba/druid/pool/DruidAbstractDataSource.java:343

        return keepConnectionUnderlyingTransactionIsolation;
    }

    public void setKeepConnectionUnderlyingTransactionIsolation(boolean keepConnectionUnderlyingTransactionIsolation) {
        this.keepConnectionUnderlyingTransactionIsolation = keepConnectionUnderlyingTransactionIsolation;
    }

    public DruidDataSourceStatLogger getStatLogger() {
        return statLogger;
    }

    public void setStatLoggerClassName(String className) {
        Class<?> clazz;
        try {
            clazz = Class.forName(className);
            DruidDataSourceStatLogger statLogger = (DruidDataSourceStatLogger) clazz.newInstance();
            this.setStatLogger(statLogger);
        } catch (Exception e) {
            throw new IllegalArgumentException(className, e);
        }
    }

    public void setStatLogger(DruidDataSourceStatLogger statLogger) {
        this.statLogger = statLogger;
    }

    public long getTimeBetweenLogStatsMillis() {
        return timeBetweenLogStatsMillis;
    }

    public void setTimeBetweenLogStatsMillis(long timeBetweenLogStatsMillis) {
        this.timeBetweenLogStatsMillis = timeBetweenLogStatsMillis;
    }

    public boolean isOracle() {
        return isOracle;
    }

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