feat: add custom logging provider to support structured logging for SLF4J 1.x + Logback 1.2.x

java-sdk-logging/logback-extension/src/main/java/com/google/api/logging/SDKLoggingMdcJsonProvider.java

@@ -0,0 +1,82 @@
+/*
+ * Copyright 2025 Google LLC
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google LLC nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+package com.google.api.logging;
+
+import ch.qos.logback.classic.spi.ILoggingEvent;
+import com.fasterxml.jackson.core.JsonGenerator;
+import com.fasterxml.jackson.core.JsonProcessingException;
+import com.fasterxml.jackson.databind.JsonNode;
+import com.fasterxml.jackson.databind.ObjectMapper;
+import java.io.IOException;
+import java.util.Map;
+import net.logstash.logback.composite.loggingevent.MdcJsonProvider;
+
+public class SDKLoggingMdcJsonProvider extends MdcJsonProvider {
+
+  private final ObjectMapper objectMapper = new ObjectMapper();
+
+  @Override
+  public void writeTo(JsonGenerator generator, ILoggingEvent event) throws IOException {
+    Map<String, String> mdcProperties = event.getMDCPropertyMap();
+    if (mdcProperties == null || mdcProperties.isEmpty()) {
+      return;
+    }
+
+    boolean hasWrittenStart = false;
+    for (Map.Entry<String, String> entry : mdcProperties.entrySet()) {
+      String fieldName = entry.getKey();
+      String entryValueString = entry.getValue();
+      if (fieldName == null || entryValueString == null) {
+        return;
+      }
+
+      if (!hasWrittenStart && getFieldName() != null) {
+        generator.writeObjectFieldStart(getFieldName());
+        hasWrittenStart = true;
+      }
+      generator.writeFieldName(fieldName);
+
+      try {
+        generator.writeTree(convertToTreeNode(entryValueString));
+      } catch (JsonProcessingException e) {
+        // in case of conversion exception, just use String
+        generator.writeObject(entryValueString);
+      }
+    }
+    if (hasWrittenStart) {
+      generator.writeEndObject();
+    }
+  }
+
+  private JsonNode convertToTreeNode(String jsonString) throws JsonProcessingException {
+    return objectMapper.readTree(jsonString);
+  }
+}

java-sdk-logging/logback-extension/src/test/java/com/google/api/logging/SDKLoggingMdcJsonProviderTest.java

@@ -0,0 +1,141 @@
+/*
+ * Copyright 2025 Google LLC
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google LLC nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+package com.google.api.logging;
+
+import static org.mockito.ArgumentMatchers.any;
+import static org.mockito.ArgumentMatchers.anyString;
+import static org.mockito.Mockito.inOrder;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.never;
+import static org.mockito.Mockito.verify;
+import static org.mockito.Mockito.when;
+
+import ch.qos.logback.classic.spi.ILoggingEvent;
+import com.fasterxml.jackson.core.JsonGenerator;
+import com.fasterxml.jackson.databind.JsonNode;
+import java.io.IOException;
+import java.util.HashMap;
+import java.util.Map;
+import org.junit.jupiter.api.AfterEach;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+import org.mockito.InOrder;
+
+class SDKLoggingMdcJsonProviderTest {
+
+  private SDKLoggingMdcJsonProvider provider = new SDKLoggingMdcJsonProvider();
+  private JsonGenerator generator = mock(JsonGenerator.class);
+  private ILoggingEvent event = mock(ILoggingEvent.class);
+  private Map<String, String> mdc;
+
+  @BeforeEach
+  void init() {
+    mdc = new HashMap<>();
+    when(event.getMDCPropertyMap()).thenReturn(mdc);
+  }
+
+  @AfterEach
+  void post() {
+    mdc.clear();
+  }
+
+  @Test
+  void testWriteNullMdcMap() throws IOException {
+    when(event.getMDCPropertyMap()).thenReturn(null);
+    provider.writeTo(generator, event);
+    verify(generator, never()).writeFieldName(anyString());
+    verify(generator, never()).writeTree(any(JsonNode.class));
+  }
+
+  @Test
+  void testWriteEmptyMdcMap() throws IOException {
+    provider.writeTo(generator, event);
+    verify(generator, never()).writeFieldName(anyString());
+    verify(generator, never()).writeTree(any(JsonNode.class));
+  }
+
+  @Test
+  void testWriteValidJsonStringToJsonTree() throws IOException {
+    mdc.put(
+        "json1",
+        "{\n"
+            + "  \"@version\": \"1\",\n"
+            + "  \"textPayload\": \"Received response\",\n"
+            + "  \"response.payload\": {\n"
+            + "    \"name\": \"example\",\n"
+            + "    \"state\": \"ACTIVE\"\n"
+            + "  }\n"
+            + "}");
+
+    provider.setFieldName("log-name");
+    provider.writeTo(generator, event);
+    InOrder inOrder = inOrder(generator);
+    inOrder.verify(generator).writeObjectFieldStart("log-name");
+    inOrder.verify(generator).writeFieldName("json1");
+    inOrder.verify(generator).writeTree(any(JsonNode.class));
+    inOrder.verify(generator).writeEndObject();
+  }
+
+  @Test
+  void testWriteInvalidJsonStringToString() throws IOException {
+    mdc.put(
+        "json1",
+        "{\n"
+            + "  \"@version\": \"1\",\n"
+            + "  \"textPayload\": \"Received response\",\n"
+            + "  \"response.payload\": {\n"
+            + "    \"name\": \"example\",\n"
+            + "    \"state\": \"ACTIVE\",\n" // the last semicolon is redundant.
+            + "  }\n"
+            + "}");
+    provider.writeTo(generator, event);
+    verify(generator).writeFieldName("json1");
+    verify(generator).writeObject(anyString());
+    // should not write tree node because the json string is invalid.
+    verify(generator, never()).writeTree(any(JsonNode.class));
+  }
+
+  @Test
+  void testWriteNullValueDoesNotThrowsException() throws IOException {
+    mdc.put("json1", null);
+    provider.writeTo(generator, event);
+    verify(generator, never()).writeObject(anyString());
+    verify(generator, never()).writeTree(any(JsonNode.class));
+  }
+
+  @Test
+  void testWriteNullKeyDoesNotThrowsException() throws IOException {
+    mdc.put(null, "example value");
+    provider.writeTo(generator, event);
+    verify(generator, never()).writeObject(anyString());
+    verify(generator, never()).writeTree(any(JsonNode.class));
+  }
+}

java-showcase/gapic-showcase/pom.xml

@@ -258,6 +258,8 @@
                 <testExclude>**/com/google/showcase/v1beta1/it/*.java</testExclude>
                 <testExclude>**/com/google/showcase/v1beta1/it/logging/ITLoggingDisabled.java</testExclude>
                 <testExclude>**/com/google/showcase/v1beta1/it/logging/ITLogging1x.java</testExclude>
+                <!-- this profile doesn't have logstash deps -->
+                <testExclude>**/com/google/showcase/v1beta1/it/logging/TestMdcAppender.java</testExclude>
               </testExcludes>
             </configuration>
           </plugin>
@@ -291,6 +293,12 @@
           <version>${slf4j1-logback.version}</version>
           <scope>test</scope>
         </dependency>
+        <dependency>
+          <groupId>com.google.api</groupId>
+          <artifactId>logback-extension</artifactId>
+          <version>0.1.0-SNAPSHOT</version>
+          <scope>test</scope>
+        </dependency>
       </dependencies>
       <build>
         <plugins>
@@ -347,6 +355,8 @@
                 <testExclude>**/com/google/showcase/v1beta1/it/*.java</testExclude>
                 <testExclude>**/com/google/showcase/v1beta1/it/logging/ITLogging1x.java</testExclude>
                 <testExclude>**/com/google/showcase/v1beta1/it/logging/ITLogging.java</testExclude>
+                <!-- this profile doesn't have logstash deps -->
+                <testExclude>**/com/google/showcase/v1beta1/it/logging/TestMdcAppender.java</testExclude>
               </testExcludes>
             </configuration>
           </plugin>