convert Log4j mdc test from groovy to java (#8170)

Related to #7195

Author: niteshs7

instrumentation/log4j/log4j-mdc-1.2/javaagent/src/test/groovy/ListAppender.groovy

@@ -0,0 +1,37 @@
+/*
+ * Copyright The OpenTelemetry Authors
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package io.opentelemetry.javaagent.instrumentation.log4j.mdc.v1_2;
+
+import java.util.ArrayList;
+import java.util.List;
+import org.apache.log4j.AppenderSkeleton;
+import org.apache.log4j.spi.LoggingEvent;
+
+public class ListAppender extends AppenderSkeleton {
+
+  private static final List<LoggingEvent> events = new ArrayList<LoggingEvent>();
+
+  @Override
+  protected void append(LoggingEvent loggingEvent) {
+    events.add(loggingEvent);
+  }
+
+  @Override
+  public boolean requiresLayout() {
+    return false;
+  }
+
+  @Override
+  public void close() {}
+
+  public static void clearEvents() {
+    events.clear();
+  }
+
+  public static List<LoggingEvent> getEvents() {
+    return events;
+  }
+}

instrumentation/log4j/log4j-mdc-1.2/javaagent/src/test/groovy/Log4j1MdcTest.groovy

@@ -0,0 +1,93 @@
+/*
+ * Copyright The OpenTelemetry Authors
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package io.opentelemetry.javaagent.instrumentation.log4j.mdc.v1_2;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertNull;
+
+import io.opentelemetry.api.trace.Span;
+import io.opentelemetry.instrumentation.testing.junit.AgentInstrumentationExtension;
+import io.opentelemetry.instrumentation.testing.junit.InstrumentationExtension;
+import java.util.List;
+import org.apache.log4j.LogManager;
+import org.apache.log4j.Logger;
+import org.apache.log4j.spi.LoggingEvent;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.extension.RegisterExtension;
+
+public class Log4j1MdcTest {
+
+  @RegisterExtension
+  private static final InstrumentationExtension testing = AgentInstrumentationExtension.create();
+
+  private static final Logger logger = LogManager.getLogger("TestLogger");
+
+  @BeforeEach
+  void cleanup() {
+    ListAppender.clearEvents();
+  }
+
+  @Test
+  void noIdsWhenNoSpan() {
+    logger.info("log message 1");
+    logger.info("log message 2");
+
+    List<LoggingEvent> events = ListAppender.getEvents();
+
+    assertEquals(2, events.size());
+    assertEquals("log message 1", events.get(0).getMessage());
+    assertNull(events.get(0).getMDC("trace_id"));
+    assertNull(events.get(0).getMDC("span_id"));
+    assertNull(events.get(0).getMDC("trace_flags"));
+
+    assertEquals("log message 2", events.get(1).getMessage());
+    assertNull(events.get(1).getMDC("trace_id"));
+    assertNull(events.get(1).getMDC("span_id"));
+    assertNull(events.get(1).getMDC("trace_flags"));
+  }
+
+  @Test
+  void idsWhenSpan() {
+    Span span1 =
+        testing.runWithSpan(
+            "test",
+            () -> {
+              logger.info("log message 1");
+              return Span.current();
+            });
+
+    logger.info("log message 2");
+
+    Span span2 =
+        testing.runWithSpan(
+            "test 2",
+            () -> {
+              logger.info("log message 3");
+              return Span.current();
+            });
+
+    List<LoggingEvent> events = ListAppender.getEvents();
+
+    assertEquals(3, events.size());
+    assertEquals("log message 1", events.get(0).getMessage());
+    assertEquals(events.get(0).getMDC("trace_id"), span1.getSpanContext().getTraceId());
+    assertEquals(events.get(0).getMDC("span_id"), span1.getSpanContext().getSpanId());
+    assertEquals(events.get(0).getMDC("trace_flags"), "01");
+
+    assertEquals("log message 2", events.get(1).getMessage());
+    assertNull(events.get(1).getMDC("trace_id"));
+    assertNull(events.get(1).getMDC("span_id"));
+    assertNull(events.get(1).getMDC("trace_flags"));
+
+    assertEquals("log message 3", events.get(2).getMessage());
+    // this explicit getMDCCopy() call here is to make sure that whole instrumentation is tested
+    events.get(2).getMDCCopy();
+    assertEquals(events.get(2).getMDC("trace_id"), span2.getSpanContext().getTraceId());
+    assertEquals(events.get(2).getMDC("span_id"), span2.getSpanContext().getSpanId());
+    assertEquals(events.get(2).getMDC("trace_flags"), "01");
+  }
+}

instrumentation/log4j/log4j-mdc-1.2/javaagent/src/test/java/io/opentelemetry/javaagent/instrumentation/log4j/mdc/v1_2/ListAppender.java

@@ -1,2 +1,2 @@
 log4j.rootLogger=INFO, LIST
-log4j.appender.LIST=ListAppender
+log4j.appender.LIST=io.opentelemetry.javaagent.instrumentation.log4j.mdc.v1_2.ListAppender