Fix context data with non-String values

src/main/java/biz/paluch/logging/gelf/log4j2/Log4j2LogEvent.java

@@ -4,10 +4,10 @@
 import java.util.Set;
 
 import org.apache.logging.log4j.Level;
+import org.apache.logging.log4j.util.ReadOnlyStringMap;
 
 import biz.paluch.logging.gelf.*;
 import biz.paluch.logging.gelf.intern.GelfMessage;
-import org.apache.logging.log4j.util.ReadOnlyStringMap;
 
 /**
  * @author Mark Paluch
@@ -173,7 +173,11 @@ private String getValue(MdcMessageField field) {
     public String getMdcValue(String mdcName) {
         ReadOnlyStringMap contextData = logEvent.getContextData();
         if (null != contextData && contextData.containsKey(mdcName)) {
-            return contextData.getValue(mdcName);
+            // Values in the context data are not guaranteed to be String, e.g. if
+            // log4j2.threadContextMap is set to
+            // org.apache.logging.log4j.spi.CopyOnWriteSortedArrayThreadContextMap
+            Object value = contextData.getValue(mdcName);
+            return value != null ? value.toString() : null;
         }
 
         return null;

src/test/java/biz/paluch/logging/gelf/log4j2/GelfLogAppenderNonStringMdcTests.java

@@ -0,0 +1,111 @@
+package biz.paluch.logging.gelf.log4j2;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+import java.util.Map;
+
+import org.apache.logging.log4j.LogManager;
+import org.apache.logging.log4j.Logger;
+import org.apache.logging.log4j.ThreadContext;
+import org.apache.logging.log4j.core.LoggerContext;
+import org.apache.logging.log4j.core.config.ConfigurationFactory;
+import org.apache.logging.log4j.spi.ObjectThreadContextMap;
+import org.junit.jupiter.api.AfterAll;
+import org.junit.jupiter.api.BeforeAll;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+
+import biz.paluch.logging.gelf.GelfTestSender;
+import biz.paluch.logging.gelf.JsonUtil;
+import biz.paluch.logging.gelf.intern.GelfMessage;
+
+/**
+ * @author Mark Paluch, Daniel Lundsgaard Skovenborg
+ */
+class GelfLogAppenderNonStringMdcTests {
+    private static final String LOG_MESSAGE = "foo bar test log message";
+
+    private static LoggerContext loggerContext;
+
+    @BeforeAll
+    static void setupClass() {
+        System.setProperty("log4j2.threadContextMap", "org.apache.logging.log4j.spi.CopyOnWriteSortedArrayThreadContextMap");
+        System.setProperty(ConfigurationFactory.CONFIGURATION_FILE_PROPERTY, "log4j2/log4j2-dynamic-mdc.xml");
+        loggerContext = (LoggerContext) LogManager.getContext(false);
+        loggerContext.reconfigure();
+    }
+
+    @AfterAll
+    static void afterClass() throws Exception {
+        System.clearProperty("log4j2.threadContextMap");
+        System.clearProperty(ConfigurationFactory.CONFIGURATION_FILE_PROPERTY);
+        loggerContext.reconfigure();
+        // Assert that setup worked.
+        assert ThreadContext.getThreadContextMap() instanceof ObjectThreadContextMap;
+    }
+
+    @BeforeEach
+    void before() throws Exception {
+        GelfTestSender.getMessages().clear();
+        ThreadContext.clearAll();
+    }
+
+    /**
+     * Copy of GelfLogAppenderDynamicMdcTests#testWithMdcFieldTypes() with raw types instead of String values
+     */
+    @Test
+    void testWithRawMdcFieldTypes() throws Exception {
+
+        Logger logger = loggerContext.getLogger(getClass().getName());
+        ObjectThreadContextMap contextMap = (ObjectThreadContextMap) ThreadContext.getThreadContextMap();
+        contextMap.putValue("myMdcs", "String");
+        contextMap.putValue("myMdcl", 1);
+        contextMap.putValue("myMdci", 2L);
+        contextMap.putValue("myMdcd", 2.1);
+        contextMap.putValue("myMdcf", 2.2d);
+
+        logger.info(LOG_MESSAGE);
+        assertThat(GelfTestSender.getMessages()).hasSize(1);
+
+        GelfMessage gelfMessage = GelfTestSender.getMessages().get(0);
+        Map<String, Object> jsonObject = JsonUtil.parseToMap(gelfMessage.toJson(""));
+
+        assertThat(jsonObject.get("myMdcs")).isEqualTo("String");
+        assertThat(jsonObject.get("myMdcl")).isEqualTo(1);
+        assertThat(jsonObject.get("myMdci")).isEqualTo(2);
+
+        assertThat(jsonObject.get("myMdcd")).isEqualTo(2.1);
+        assertThat(jsonObject.get("myMdcf")).isEqualTo(2.2);
+
+        ThreadContext.put("myMdcl", "1.1");
+        ThreadContext.put("myMdci", "2.1");
+        ThreadContext.put("myMdcd", "wrong");
+        ThreadContext.put("myMdcf", "wrong");
+
+        GelfTestSender.getMessages().clear();
+        logger.info(LOG_MESSAGE);
+        assertThat(GelfTestSender.getMessages()).hasSize(1);
+
+        gelfMessage = GelfTestSender.getMessages().get(0);
+        jsonObject = JsonUtil.parseToMap(gelfMessage.toJson(""));
+
+        assertThat(jsonObject.get("myMdcl")).isEqualTo(1);
+        assertThat(jsonObject.get("myMdci")).isEqualTo(2);
+
+        assertThat(jsonObject.get("myMdcd")).isNull();
+        assertThat(jsonObject.get("myMdcf")).isEqualTo(0.0);
+
+        ThreadContext.put("myMdcl", "b");
+        ThreadContext.put("myMdci", "a");
+
+        GelfTestSender.getMessages().clear();
+        logger.info(LOG_MESSAGE);
+        assertThat(GelfTestSender.getMessages()).hasSize(1);
+
+        gelfMessage = GelfTestSender.getMessages().get(0);
+        jsonObject = JsonUtil.parseToMap(gelfMessage.toJson(""));
+
+        assertThat(jsonObject.get("myMdcl")).isNull();
+        assertThat(jsonObject.get("myMdci")).isEqualTo(0);
+    }
+}