Removes support for EventData

The `org.slf4j.ext.EventData` class was a primitive equivalent of
Log4j's `StructuredDataMessage`. QOS.CH published CVE-2018-8088 against
this class and removed it from `slf4j-ext` version 1.7.26.

For a long time we kept support code to convert `EventData` to its Log4j
equivalent for compatibility's sake: users that relied on this class
could still use Log4j Core, but the functionality was **automatically**
disabled once they upgraded `slf4j-ext`.

Since 5 years passed since `slfj4-ext` 1.7.26 was published, we can
safely assume that all the users upgraded the library and the support
code can be removed.

Author: ppkarwasz

log4j-parent/pom.xml

@@ -16,9 +16,7 @@
   ~ limitations under the License.
   -->
 <project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
-
   <modelVersion>4.0.0</modelVersion>
-
   <parent>
     <groupId>org.apache.logging.log4j</groupId>
     <artifactId>log4j-bom</artifactId>
@@ -140,8 +138,6 @@
     <pax-exam.version>4.13.5</pax-exam.version>
     <plexus-utils.version>3.5.1</plexus-utils.version>
     <slf4j.version>2.0.9</slf4j.version>
-    <!-- Last version before a breaking change -->
-    <slf4j-ext.version>1.7.25</slf4j-ext.version>
     <spring-boot.version>2.7.18</spring-boot.version>
     <spring-framework.version>5.3.31</spring-framework.version>
     <system-stubs.version>2.0.3</system-stubs.version>
@@ -956,7 +952,7 @@
       <dependency>
         <groupId>org.slf4j</groupId>
         <artifactId>slf4j-ext</artifactId>
-        <version>${slf4j-ext.version}</version>
+        <version>${slf4j.version}</version>
       </dependency>
 
       <dependency>

log4j-slf4j-impl/pom.xml

@@ -29,9 +29,6 @@
   <description>The Apache Log4j SLF4J API binding to Log4j 2 Core</description>
   <properties>
     <slf4j.version>1.7.36</slf4j.version>
-    <!-- Do not upgrade the SLF4J version. 1.7.26 broke backward compatibility. Users can update the version if
-      they do not require support for SLF4J's EventData -->
-    <slf4j-ext.version>1.7.25</slf4j-ext.version>
 
     <!--
       ~ OSGi and JPMS options
@@ -60,7 +57,7 @@
       <dependency>
         <groupId>org.slf4j</groupId>
         <artifactId>slf4j-ext</artifactId>
-        <version>${slf4j-ext.version}</version>
+        <version>${slf4j.version}</version>
         <optional>true</optional>
       </dependency>
     </dependencies>
@@ -80,11 +77,6 @@
       <groupId>org.slf4j</groupId>
       <artifactId>slf4j-api</artifactId>
     </dependency>
-    <dependency>
-      <groupId>org.slf4j</groupId>
-      <artifactId>slf4j-ext</artifactId>
-      <optional>true</optional>
-    </dependency>
     <dependency>
       <groupId>org.apache.logging.log4j</groupId>
       <artifactId>log4j-core</artifactId>
@@ -137,6 +129,11 @@
       <artifactId>junit-vintage-engine</artifactId>
       <scope>test</scope>
     </dependency>
+    <dependency>
+      <groupId>org.slf4j</groupId>
+      <artifactId>slf4j-ext</artifactId>
+      <scope>test</scope>
+    </dependency>
   </dependencies>
   <build>
     <plugins>

log4j-slf4j-impl/src/main/java/org/apache/logging/slf4j/EventDataConverter.java

@@ -39,18 +39,14 @@ public class Log4jLogger implements LocationAwareLogger, Serializable {
     public static final String FQCN = Log4jLogger.class.getName();
 
     private static final long serialVersionUID = 7869000638091304316L;
-    private static final Marker EVENT_MARKER = MarkerFactory.getMarker("EVENT");
-    private static final EventDataConverter CONVERTER = createConverter();
 
-    private final boolean eventLogger;
     private transient ExtendedLogger logger;
     private final String name;
     private transient Log4jMarkerFactory markerFactory;
 
     public Log4jLogger(final Log4jMarkerFactory markerFactory, final ExtendedLogger logger, final String name) {
         this.markerFactory = markerFactory;
         this.logger = logger;
-        this.eventLogger = "EventLogger".equals(name);
         this.name = name;
     }
 
@@ -370,10 +366,7 @@ public void log(
         }
         final Message msg;
         final Throwable actualThrowable;
-        if (CONVERTER != null && eventLogger && marker != null && marker.contains(EVENT_MARKER)) {
-            msg = CONVERTER.convertEvent(message, params, throwable);
-            actualThrowable = throwable != null ? throwable : msg.getThrowable();
-        } else if (params == null) {
+        if (params == null) {
             msg = new SimpleMessage(message);
             actualThrowable = throwable;
         } else {
@@ -407,15 +400,6 @@ private void writeObject(final ObjectOutputStream aOutputStream) throws IOExcept
         aOutputStream.defaultWriteObject();
     }
 
-    private static EventDataConverter createConverter() {
-        try {
-            LoaderUtil.loadClass("org.slf4j.ext.EventData");
-            return new EventDataConverter();
-        } catch (final ClassNotFoundException cnfe) {
-            return null;
-        }
-    }
-
     private static Level getLevel(final int i) {
         switch (i) {
             case TRACE_INT:

log4j-slf4j-impl/src/main/java/org/apache/logging/slf4j/Log4jLogger.java

@@ -21,7 +21,6 @@
 import static org.junit.Assert.assertTrue;
 
 import java.util.List;
-import java.util.Locale;
 import org.apache.logging.log4j.core.LogEvent;
 import org.apache.logging.log4j.core.test.appender.ListAppender;
 import org.apache.logging.log4j.core.test.junit.LoggerContextRule;
@@ -34,8 +33,6 @@
 import org.slf4j.LoggerFactory;
 import org.slf4j.MDC;
 import org.slf4j.Marker;
-import org.slf4j.ext.EventData;
-import org.slf4j.ext.EventLogger;
 import org.slf4j.ext.XLogger;
 import org.slf4j.ext.XLoggerFactory;
 import org.slf4j.spi.LocationAwareLogger;
@@ -140,30 +137,12 @@ public void testRootLogger() {
     public void doubleSubst() {
         logger.debug("Hello, {}", "Log4j {}");
         verify("List", "o.a.l.s.LoggerTest Hello, Log4j {} MDC{}" + Strings.LINE_SEPARATOR);
+        // XLogger 1.7.x performs substitution twice:
+        // https://jira.qos.ch/browse/SLF4J-421
         xlogger.debug("Hello, {}", "Log4j {}");
         verify("List", "o.a.l.s.LoggerTest Hello, Log4j Log4j {} MDC{}" + Strings.LINE_SEPARATOR);
     }
 
-    @Test
-    public void testEventLogger() {
-        MDC.put("loginId", "JohnDoe");
-        MDC.put("ipAddress", "192.168.0.120");
-        MDC.put("locale", Locale.US.getDisplayName());
-        final EventData data = new EventData();
-        data.setEventType("Transfer");
-        data.setEventId("Audit@18060");
-        data.setMessage("Transfer Complete");
-        data.put("ToAccount", "123456");
-        data.put("FromAccount", "123457");
-        data.put("Amount", "200.00");
-        EventLogger.logEvent(data);
-        MDC.clear();
-        verify(
-                "EventLogger",
-                "o.a.l.s.LoggerTest Transfer [Audit@18060 Amount=\"200.00\" FromAccount=\"123457\" ToAccount=\"123456\"] Transfer Complete"
-                        + Strings.LINE_SEPARATOR);
-    }
-
     @Test
     public void testThrowable() {
         final Throwable expected = new RuntimeException();
@@ -228,6 +207,5 @@ public void cleanup() {
         MDC.clear();
         ctx.getListAppender("List").clear();
         ctx.getListAppender("UnformattedList").clear();
-        ctx.getListAppender("EventLogger").clear();
     }
 }

log4j-slf4j-impl/src/test/java/org/apache/logging/slf4j/LoggerTest.java

@@ -23,6 +23,7 @@
     <version>${revision}</version>
     <relativePath>../log4j-parent</relativePath>
   </parent>
+
   <artifactId>log4j-slf4j2-impl</artifactId>
   <packaging>jar</packaging>
   <name>Apache Log4j SLF4J 2.0 Binding</name>
@@ -105,7 +106,6 @@
     <dependency>
       <groupId>org.slf4j</groupId>
       <artifactId>slf4j-ext</artifactId>
-      <version>${slf4j.version}</version>
       <scope>test</scope>
     </dependency>
   </dependencies>