Add java docs and update ut

Signed-off-by: Louis Chu <[email protected]>

flint-core/src/main/java/org/opensearch/flint/core/logging/CustomJsonLayout.java

@@ -18,6 +18,13 @@
 import java.util.HashMap;
 import java.util.Map;
 
+/**
+ * CustomJsonLayout is a plugin for formatting log events as JSON strings.
+ *
+ * <p>The layout is designed to be used with OpenSearch Flint logging. It extracts environment-specific information,
+ * such as the cluster name, from the environment variable "FLINT_CLUSTER_NAME" and splits it into domain name and client ID.</p>
+ *
+ */
 @Plugin(name = "CustomJsonLayout", category = "Core", elementType = Layout.ELEMENT_TYPE, printObject = true)
 public class CustomJsonLayout extends AbstractStringLayout {
     private static final ObjectMapper OBJECT_MAPPER = new ObjectMapper();
@@ -41,24 +48,33 @@ protected CustomJsonLayout(Charset charset) {
         super(charset);
     }
 
+    /**
+     * Plugin factory method to create an instance of CustomJsonLayout.
+     *
+     * @param charset The charset for encoding the log event. If not specified, defaults to UTF-8.
+     * @return A new instance of CustomJsonLayout with the specified charset.
+     */
     @PluginFactory
     public static CustomJsonLayout createLayout(@PluginAttribute(value = "charset", defaultString = "UTF-8")  Charset charset) {
         return new CustomJsonLayout(charset);
     }
 
+    /**
+     * Converts the log event to a JSON string.
+     * If the log event's message does not follow the expected format, it returns the formatted message directly.
+     *
+     * @param event the log event to format.
+     * @return A string representation of the log event in JSON format.
+     */
     @Override
     public String toSerializable(LogEvent event) {
-        if (!(event.getMessage() instanceof OperationMessage)) {
-            return event.getMessage().getFormattedMessage() + System.lineSeparator();
-        }
-
         Map<String, Object> logEventMap = new HashMap<>();
         logEventMap.put("timestamp", event.getTimeMillis());
         logEventMap.put("message", event.getMessage().getFormattedMessage());
         logEventMap.put("domainName", DOMAIN_NAME);
         logEventMap.put("clientId", CLIENT_ID);
 
-        if (event.getMessage().getParameters().length == 1) {
+        if (event.getMessage() instanceof OperationMessage && event.getMessage().getParameters().length == 1) {
             logEventMap.put("StatusCode", event.getMessage().getParameters()[0]);
         }
 

flint-core/src/main/java/org/opensearch/flint/core/logging/CustomLogging.java

@@ -0,0 +1,36 @@
+package org.opensearch.flint.core.logging;
+
+import org.apache.logging.log4j.LogManager;
+import org.apache.logging.log4j.Logger;
+
+/**
+ * CustomLogging class using the {@link CustomJsonLayout} for logging.
+ */
+public class CustomLogging {
+    // Define a static logger variable so that it references the custom logger
+    private static final Logger logger = LogManager.getLogger(CustomLogging.class);
+
+    public static void logDebug(String message) {
+        logger.debug(message);
+    }
+
+    public static void logInfo(String message) {
+        logger.info(message);
+    }
+
+    public static void logWarning(String message) {
+        logger.warn(message);
+    }
+
+    public static void logWarning(String message, Throwable e) {
+        logger.warn(message, e);
+    }
+
+    public static void logError(String message) {
+        logger.error(message);
+    }
+
+    public static void logError(String message, Throwable throwable) {
+        logger.error(message, throwable);
+    }
+}

flint-core/src/main/scala/org/opensearch/flint/core/http/handler/HttpStatusCodeResultPredicate.java

@@ -18,6 +18,7 @@
  * @param <T> result type (supposed to be HttpResponse for OS client)
  */
 public class HttpStatusCodeResultPredicate<T> implements CheckedPredicate<T> {
+
   private static final Logger LOG = Logger.getLogger(HttpStatusCodeResultPredicate.class.getName());
 
   /**

flint-core/src/test/java/org/opensearch/flint/core/logging/CustomJsonLayoutTest.java

@@ -1,51 +1,76 @@
-/*
- * Copyright OpenSearch Contributors
- * SPDX-License-Identifier: Apache-2.0
- */
-
 package org.opensearch.flint.core.logging;
 
 import org.apache.logging.log4j.core.LogEvent;
 import org.apache.logging.log4j.message.Message;
+import org.junit.Before;
 import org.junit.Test;
 
 import java.lang.reflect.Field;
 import java.nio.charset.StandardCharsets;
 import java.util.Map;
 
-import static org.junit.Assert.assertEquals;
-import static org.junit.Assert.assertNotNull;
-import static org.junit.Assert.assertTrue;
+import static org.junit.Assert.*;
 import static org.mockito.Mockito.mock;
 import static org.mockito.Mockito.when;
 
-
 public class CustomJsonLayoutTest {
-    @Test
-    public void testSuccessfulLogPlainMessage() {
-        LogEvent event = mock(LogEvent.class);
-        when(event.getMessage()).thenReturn(mock(Message.class));
-        when(event.getMessage().getFormattedMessage()).thenReturn("Test message");
+    private Map<String, String> writeableEnvironmentVariables;
 
-        CustomJsonLayout layout = CustomJsonLayout.createLayout(StandardCharsets.UTF_8);
-        String result = layout.toSerializable(event);
-        assertNotNull(result);
-        assertEquals(result, "Test message" + System.lineSeparator());
-    }
-
-    @Test
-    public void testSuccessfulLogOperationMessage() throws NoSuchFieldException, IllegalAccessException {
+    @Before
+    public void setUp() throws NoSuchFieldException, IllegalAccessException {
+        // Setup writable environment variables
         Class<?> classOfMap = System.getenv().getClass();
         Field field = classOfMap.getDeclaredField("m");
         field.setAccessible(true);
-        Map<String, String> writeableEnvironmentVariables = (Map<String, String>)field.get(System.getenv());
+        writeableEnvironmentVariables = (Map<String, String>) field.get(System.getenv());
         writeableEnvironmentVariables.put("FLINT_CLUSTER_NAME", "1234567890:testDomain");
+    }
 
+    private void cleanUp() {
+        // Clean up environment variables
+        writeableEnvironmentVariables.remove("FLINT_CLUSTER_NAME");
+    }
+
+    private LogEvent setupLogEvent(Class<? extends Message> messageClass, String formattedMessage, Object... parameters) {
         LogEvent event = mock(LogEvent.class);
         when(event.getTimeMillis()).thenReturn(System.currentTimeMillis());
-        when(event.getMessage()).thenReturn(mock(OperationMessage.class));
-        when(event.getMessage().getFormattedMessage()).thenReturn("Test message");
-        when(event.getMessage().getParameters()).thenReturn(new Object[] {new Integer(200)});
+
+        Message message = mock(messageClass);
+        when(message.getFormattedMessage()).thenReturn(formattedMessage);
+        if (parameters.length > 0) {
+            when(message.getParameters()).thenReturn(parameters);
+        }
+        when(event.getMessage()).thenReturn(message);
+
+        Exception mockException = new Exception("Test exception message");
+        when(event.getThrown()).thenReturn(mockException);
+
+        return event;
+    }
+
+    @Test
+    public void testSuccessfulLogPlainMessage() {
+        LogEvent event = setupLogEvent(Message.class, "Test message");
+
+        try {
+            CustomJsonLayout layout = CustomJsonLayout.createLayout(StandardCharsets.UTF_8);
+
+            String result = layout.toSerializable(event);
+            assertNotNull(result);
+            assertTrue(result.contains("\"message\":\"Test message\""));
+            assertTrue(result.contains("\"clientId\":\"1234567890\""));
+            assertTrue(result.contains("\"domainName\":\"testDomain\""));
+            assertFalse(result.contains("\"StatusCode\""));
+            assertTrue(result.contains("\"Exception\":\"java.lang.Exception\""));
+            assertTrue(result.contains("\"ExceptionMessage\":\"Test exception message\""));
+        } finally {
+            cleanUp();
+        }
+    }
+
+    @Test
+    public void testSuccessfulLogOperationMessage() {
+        LogEvent event = setupLogEvent(OperationMessage.class, "Test message", 200);
 
         try {
             CustomJsonLayout layout = CustomJsonLayout.createLayout(StandardCharsets.UTF_8);
@@ -56,9 +81,10 @@ public void testSuccessfulLogOperationMessage() throws NoSuchFieldException, Ill
             assertTrue(result.contains("\"clientId\":\"1234567890\""));
             assertTrue(result.contains("\"domainName\":\"testDomain\""));
             assertTrue(result.contains("\"StatusCode\":200"));
+            assertTrue(result.contains("\"Exception\":\"java.lang.Exception\""));
+            assertTrue(result.contains("\"ExceptionMessage\":\"Test exception message\""));
         } finally {
-            // since system environment is shared by other tests. Make sure to remove them before exiting.
-            writeableEnvironmentVariables.remove("FLINT_CLUSTER_NAME");
+            cleanUp();
         }
     }
 }