Include free-form message when encoding StructuredDataMessage to XML

log4j-api-test/src/test/java/org/apache/logging/log4j/message/StructuredDataMessageTest.java

@@ -64,6 +64,7 @@ void testMsgXml() {
         final String expected = "<StructuredData>\n"
                 + "<type>Alert</type>\n"
                 + "<id>MsgId@12345</id>\n"
+                + "<message>Test message {}</message>\n"
                 + "<Map>\n"
                 + "  <Entry key=\"memo\">This is a very long test memo to prevent regression of LOG4J2-114</Entry>\n"
                 + "  <Entry key=\"message\">Test message {}</Entry>\n"
@@ -73,12 +74,45 @@ void testMsgXml() {
         assertEquals(expected, result);
     }
 
+    @Test
+    void testMsgXmlIncludesConstructorMessage() {
+        // #4141: constructor message must appear (and be escaped) even when not put into the map
+        final StructuredDataMessage msg = new StructuredDataMessage("an id", "a <msg> & more", "a type");
+        final String result = msg.getFormattedMessage(new String[] {"XML"});
+        final String expected = "<StructuredData>\n"
+                + "<type>a type</type>\n"
+                + "<id>an id</id>\n"
+                + "<message>a &lt;msg&gt; &amp; more</message>\n"
+                + "<Map>\n"
+                + "</Map>\n"
+                + "</StructuredData>\n";
+        assertEquals(expected, result);
+    }
+
+    @Test
+    void testMsgXmlDistinguishesConstructorMessageFromMapEntry() {
+        // #4141: free-form message and a map entry keyed "message" are independent
+        final StructuredDataMessage msg = new StructuredDataMessage("an id", "a message", "a type");
+        msg.put("message", "foo");
+        final String result = msg.getFormattedMessage(new String[] {"XML"});
+        final String expected = "<StructuredData>\n"
+                + "<type>a type</type>\n"
+                + "<id>an id</id>\n"
+                + "<message>a message</message>\n"
+                + "<Map>\n"
+                + "  <Entry key=\"message\">foo</Entry>\n"
+                + "</Map>\n"
+                + "</StructuredData>\n";
+        assertEquals(expected, result);
+    }
+
     @Test
     void testXmlEncodingOfIdAndType1() {
         final String id = "i<&d>" + XmlFixture.TEXT;
         final String type = "t>yp<e&" + XmlFixture.TEXT;
+        // null message: keep this test focused on id/type escaping (and covers omission of <message>)
         final String actualXml =
-                new StructuredDataMessage(id, "discarded message", type).getFormattedMessage(new String[] {"XML"});
+                new StructuredDataMessage(id, null, type).getFormattedMessage(new String[] {"XML"});
         final String expectedXml = "<StructuredData>\n"
                 + "<type>t&gt;yp&lt;e&amp;" + XmlFixture.ENCODED_TEXT
                 + "</type>\n"
@@ -101,7 +135,7 @@ void testXmlEncodingOfIdAndType2() {
         final StructuredDataId id =
                 new StructuredDataId(idName, idEnterpriseNumber, idRequired, idOptional, Integer.MAX_VALUE);
         final String actualXml =
-                new StructuredDataMessage(id, "discarded message", type).getFormattedMessage(new String[] {"XML"});
+                new StructuredDataMessage(id, null, type).getFormattedMessage(new String[] {"XML"});
         final String expectedXml = "<StructuredData>\n"
                 + "<type>t&gt;yp&lt;e&amp;" + XmlFixture.ENCODED_TEXT
                 + "</type>\n"

log4j-api/src/main/java/org/apache/logging/log4j/message/StructuredDataMessage.java

@@ -373,6 +373,15 @@ private void asXml(final StructuredDataId structuredDataId, final StringBuilder
         StringBuilders.escapeXml(sb, start);
         sb.append("</id>\n");
 
+        // Encode message as its own element (distinct from a map entry keyed "message")
+        if (message != null) {
+            sb.append("<message>");
+            start = sb.length();
+            sb.append(message);
+            StringBuilders.escapeXml(sb, start);
+            sb.append("</message>\n");
+        }
+
         // Encode the rest
         super.asXml(sb);
 

src/changelog/.2.x.x/fix-StructuredDataMessage-XML-message.xml

@@ -0,0 +1,12 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<entry xmlns="https://logging.apache.org/xml/ns"
+       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+       xsi:schemaLocation="
+           https://logging.apache.org/xml/ns
+           https://logging.apache.org/xml/ns/log4j-changelog-0.xsd"
+       type="fixed">
+  <issue id="4141" link="https://github.com/apache/logging-log4j2/issues/4141"/>
+  <description format="asciidoc">
+    Include the free-form `message` field when encoding `StructuredDataMessage` to XML
+  </description>
+</entry>