Extract ILoggerFactory interface from LoggerFactory

LoggerFactory was an abstract class holding a static reference to itself.
Replace with the SLF4J-style pattern: ILoggerFactory is the interface
that backends implement, and LoggerFactory is a final utility class
that delegates to the current ILoggerFactory.

Author: mihaimitrea-db

databricks-sdk-java/src/main/java/com/databricks/sdk/core/logging/ILoggerFactory.java

@@ -0,0 +1,16 @@
+package com.databricks.sdk.core.logging;
+
+/**
+ * Contract for creating {@link Logger} instances.
+ *
+ * <p>Implement this interface to provide a custom logging backend, then register it via {@link
+ * LoggerFactory#setDefault(ILoggerFactory)}.
+ */
+public interface ILoggerFactory {
+
+  /** Creates a logger for the given class. */
+  Logger createLogger(Class<?> type);
+
+  /** Creates a logger with the given name. */
+  Logger createLogger(String name);
+}

databricks-sdk-java/src/main/java/com/databricks/sdk/core/logging/LoggerFactory.java

@@ -3,7 +3,7 @@
 import java.util.concurrent.atomic.AtomicReference;
 
 /**
- * Creates and configures {@link Logger} instances for the SDK.
+ * Static entry point for obtaining {@link Logger} instances.
  *
  * <p>By default, logging goes through SLF4J. Users can override the backend programmatically before
  * creating any SDK client:
@@ -13,11 +13,13 @@
  * WorkspaceClient ws = new WorkspaceClient();
  * }</pre>
  *
- * <p>Extend this class to provide a fully custom logging backend.
+ * <p>Implement {@link ILoggerFactory} to provide a fully custom logging backend.
  */
-public abstract class LoggerFactory {
+public final class LoggerFactory {
 
-  private static final AtomicReference<LoggerFactory> defaultFactory = new AtomicReference<>();
+  private static final AtomicReference<ILoggerFactory> defaultFactory = new AtomicReference<>();
+
+  private LoggerFactory() {}
 
   /** Returns a logger for the given class, using the current default factory. */
   public static Logger getLogger(Class<?> type) {
@@ -35,31 +37,19 @@ public static Logger getLogger(String name) {
    * <p>Must be called before creating any SDK client or calling {@link #getLogger}. Loggers already
    * obtained will not be affected by subsequent calls.
    */
-  public static void setDefault(LoggerFactory factory) {
+  public static void setDefault(ILoggerFactory factory) {
     if (factory == null) {
-      throw new IllegalArgumentException("LoggerFactory must not be null");
+      throw new IllegalArgumentException("ILoggerFactory must not be null");
     }
     defaultFactory.set(factory);
   }
 
-  static LoggerFactory getDefault() {
-    LoggerFactory f = defaultFactory.get();
+  static ILoggerFactory getDefault() {
+    ILoggerFactory f = defaultFactory.get();
     if (f != null) {
       return f;
     }
     defaultFactory.compareAndSet(null, Slf4jLoggerFactory.INSTANCE);
     return defaultFactory.get();
   }
-
-  /**
-   * Creates a {@link Logger} for the given class. Subclasses obtain the backend logger (e.g. SLF4J)
-   * and return an adapter.
-   */
-  protected abstract Logger createLogger(Class<?> type);
-
-  /**
-   * Creates a {@link Logger} for the given name. Subclasses obtain the backend logger and return an
-   * adapter.
-   */
-  protected abstract Logger createLogger(String name);
 }

databricks-sdk-java/src/main/java/com/databricks/sdk/core/logging/Slf4jLoggerFactory.java

@@ -1,17 +1,17 @@
 package com.databricks.sdk.core.logging;
 
-/** A {@link LoggerFactory} backed by SLF4J. */
-public class Slf4jLoggerFactory extends LoggerFactory {
+/** An {@link ILoggerFactory} backed by SLF4J. */
+public class Slf4jLoggerFactory implements ILoggerFactory {
 
   public static final Slf4jLoggerFactory INSTANCE = new Slf4jLoggerFactory();
 
   @Override
-  protected Logger createLogger(Class<?> type) {
+  public Logger createLogger(Class<?> type) {
     return new Slf4jLogger(org.slf4j.LoggerFactory.getLogger(type));
   }
 
   @Override
-  protected Logger createLogger(String name) {
+  public Logger createLogger(String name) {
     return new Slf4jLogger(org.slf4j.LoggerFactory.getLogger(name));
   }
 }