fix: Allow registering custom logger handlers (#1156)

Author: antusus

src/main/java/com/box/sdk/BoxLogger.java

@@ -7,6 +7,7 @@
 import static java.util.logging.Level.SEVERE;
 import static java.util.logging.Level.WARNING;
 
+import java.util.logging.Handler;
 import java.util.logging.Level;
 import java.util.logging.Logger;
 
@@ -146,4 +147,23 @@ public void turnLoggingOff() {
     public void setUseParentHandlers(boolean useParentHandlers) {
         this.logger.setUseParentHandlers(useParentHandlers);
     }
+
+    /**
+     * Adds handler to logger.
+     * Check {@link Logger#addHandler(Handler)}
+     * @param handler a logging handler to add.
+     */
+    public void addHandler(Handler handler) {
+        logger.addHandler(handler);
+    }
+
+    /**
+     * Removes handler from logger.
+     * Will not fail if handler is null or not registered.
+     * Check {@link Logger#removeHandler(Handler)}
+     * @param handler a logging handler to remove.
+     */
+    public void removeHandler(Handler handler) {
+        logger.removeHandler(handler);
+    }
 }

src/test/java/com/box/sdk/BoxLoggerTest.java

@@ -0,0 +1,54 @@
+package com.box.sdk;
+
+import static org.hamcrest.CoreMatchers.is;
+import static org.hamcrest.MatcherAssert.assertThat;
+import static org.hamcrest.Matchers.empty;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.logging.Handler;
+import java.util.logging.LogRecord;
+import org.junit.Test;
+
+public class BoxLoggerTest {
+    @Test
+    public void canAddHandler() {
+        HandlerForTests handler = new HandlerForTests();
+        BoxLogger boxLogger = BoxLogger.defaultLogger();
+
+        boxLogger.addHandler(handler);
+        boxLogger.info("Test");
+
+        LogRecord logRecord = handler.logEntries.get(0);
+        assertThat(logRecord.getMessage(), is("Test"));
+    }
+
+    @Test
+    public void canRemoveHandler() {
+        HandlerForTests handler = new HandlerForTests();
+        BoxLogger boxLogger = BoxLogger.defaultLogger();
+
+        boxLogger.addHandler(handler);
+        boxLogger.removeHandler(handler);
+        boxLogger.info("Test");
+
+        assertThat(handler.logEntries, empty());
+    }
+
+    private static final class HandlerForTests extends Handler {
+        List<LogRecord> logEntries = new ArrayList<>();
+
+        @Override
+        public void publish(LogRecord record) {
+            logEntries.add(record);
+        }
+
+        @Override
+        public void flush() {
+        }
+
+        @Override
+        public void close() throws SecurityException {
+        }
+    }
+}