Add tests for multiple URI configuration support

- Validate null/empty parameter handling
- Test single and multiple URI behavior
- Verify CompositeConfiguration creation
- Add changelog xml file

Author: yybmion

log4j-core-test/src/test/java/org/apache/logging/log4j/core/config/ConfigurationFactoryTest.java

@@ -19,14 +19,19 @@
 import static org.apache.logging.log4j.util.Unbox.box;
 import static org.junit.jupiter.api.Assertions.assertAll;
 import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertFalse;
 import static org.junit.jupiter.api.Assertions.assertInstanceOf;
 import static org.junit.jupiter.api.Assertions.assertNotNull;
 import static org.junit.jupiter.api.Assertions.assertThrows;
 import static org.junit.jupiter.api.Assertions.assertTrue;
 
 import java.io.IOException;
+import java.net.URI;
+import java.net.URL;
 import java.nio.file.Files;
 import java.nio.file.Path;
+import java.util.Arrays;
+import java.util.Collections;
 import java.util.Iterator;
 import java.util.List;
 import java.util.Map;
@@ -36,6 +41,7 @@
 import org.apache.logging.log4j.core.Logger;
 import org.apache.logging.log4j.core.LoggerContext;
 import org.apache.logging.log4j.core.appender.ConsoleAppender;
+import org.apache.logging.log4j.core.config.composite.CompositeConfiguration;
 import org.apache.logging.log4j.core.filter.ThreadContextMapFilter;
 import org.apache.logging.log4j.core.test.junit.LoggerContextSource;
 import org.apache.logging.log4j.test.junit.TempLoggingDir;
@@ -130,4 +136,63 @@ void properties(final LoggerContext context) throws IOException {
         final Path logFile = loggingPath.resolve("test-properties.log");
         checkFileLogger(context, logFile);
     }
+
+    @Test
+    void testGetConfigurationWithNullUris() {
+        final ConfigurationFactory factory = ConfigurationFactory.getInstance();
+        try (final LoggerContext context = new LoggerContext("test")) {
+            assertThrows(NullPointerException.class, () -> factory.getConfiguration(context, "test", (List<URI>) null));
+        }
+    }
+
+    @Test
+    void testGetConfigurationWithEmptyUris() {
+        final ConfigurationFactory factory = ConfigurationFactory.getInstance();
+        try (final LoggerContext context = new LoggerContext("test")) {
+            assertThrows(
+                    IllegalArgumentException.class,
+                    () -> factory.getConfiguration(context, "test", Collections.emptyList()));
+        }
+    }
+
+    @Test
+    void testGetConfigurationWithNullInList() {
+        final ConfigurationFactory factory = ConfigurationFactory.getInstance();
+        try (final LoggerContext context = new LoggerContext("test")) {
+            final List<URI> listWithNull = Collections.singletonList(null);
+            assertThrows(ConfigurationException.class, () -> factory.getConfiguration(context, "test", listWithNull));
+        }
+    }
+
+    @Test
+    void testGetConfigurationWithSingleUri() throws Exception {
+        final ConfigurationFactory factory = ConfigurationFactory.getInstance();
+        try (final LoggerContext context = new LoggerContext("test")) {
+            final URL resource = getClass().getResource("/log4j-test1.xml");
+            assertNotNull(resource);
+
+            final List<URI> singleUri = Collections.singletonList(resource.toURI());
+            final Configuration config = factory.getConfiguration(context, "test", singleUri);
+
+            assertNotNull(config);
+            assertFalse(config instanceof CompositeConfiguration);
+        }
+    }
+
+    @Test
+    void testGetConfigurationWithMultipleUris() throws Exception {
+        final ConfigurationFactory factory = ConfigurationFactory.getInstance();
+        try (final LoggerContext context = new LoggerContext("test")) {
+            final URL resource1 = getClass().getResource("/log4j-test1.xml");
+            final URL resource2 = getClass().getResource("/log4j-xinclude.xml");
+            assertNotNull(resource1);
+            assertNotNull(resource2);
+
+            final List<URI> multipleUris = Arrays.asList(resource1.toURI(), resource2.toURI());
+            final Configuration config = factory.getConfiguration(context, "test", multipleUris);
+
+            assertNotNull(config);
+            assertTrue(config instanceof CompositeConfiguration);
+        }
+    }
 }

log4j-core-test/src/test/java/org/apache/logging/log4j/core/config/builder/CustomConfigurationFactory.java

@@ -72,7 +72,7 @@ static Configuration addTestFixtures(final String name, final ConfigurationBuild
 
     @Override
     public Configuration getConfiguration(final LoggerContext loggerContext, final ConfigurationSource source) {
-        return getConfiguration(loggerContext, source.toString(), null);
+        return getConfiguration(loggerContext, source.toString(), (URI) null);
     }
 
     @Override

log4j-core/src/main/java/org/apache/logging/log4j/core/config/ConfigurationFactory.java

@@ -359,6 +359,11 @@ public Configuration getConfiguration(final LoggerContext loggerContext, final S
         final List<AbstractConfiguration> configurations = new ArrayList<>();
 
         for (final URI uri : uris) {
+
+            if (uri == null) {
+                throw new ConfigurationException("URI list contains null element");
+            }
+
             final Configuration config = getConfiguration(loggerContext, name, uri);
 
             if (config == null) {

log4j-core/src/main/java/org/apache/logging/log4j/core/config/json/package-info.java

@@ -18,7 +18,7 @@
  * Classes and interfaces supporting configuration of Log4j 2 with JSON.
  */
 @Export
-@Version("2.21.0")
+@Version("2.26.0")
 package org.apache.logging.log4j.core.config.json;
 
 import org.osgi.annotation.bundle.Export;

log4j-core/src/main/java/org/apache/logging/log4j/core/config/properties/package-info.java

@@ -18,7 +18,7 @@
  * Configuration using Properties files.
  */
 @Export
-@Version("2.21.0")
+@Version("2.26.0")
 package org.apache.logging.log4j.core.config.properties;
 
 import org.osgi.annotation.bundle.Export;

log4j-core/src/main/java/org/apache/logging/log4j/core/config/xml/package-info.java

@@ -18,7 +18,7 @@
  * Classes and interfaces supporting configuration of Log4j 2 with XML.
  */
 @Export
-@Version("2.21.0")
+@Version("2.26.0")
 package org.apache.logging.log4j.core.config.xml;
 
 import org.osgi.annotation.bundle.Export;

log4j-core/src/main/java/org/apache/logging/log4j/core/config/yaml/package-info.java

@@ -18,7 +18,7 @@
  * Classes and interfaces supporting configuration of Log4j 2 with YAML.
  */
 @Export
-@Version("2.21.0")
+@Version("2.26.0")
 package org.apache.logging.log4j.core.config.yaml;
 
 import org.osgi.annotation.bundle.Export;

src/changelog/.2.x.x/add_getConfiguration_method_for_mulitiple_URIs.xml

@@ -0,0 +1,13 @@
+<?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="added">
+  <issue id="3775" link="https://github.com/apache/logging-log4j2/issues/3775"/>
+  <issue id="3921" link="https://github.com/apache/logging-log4j2/pull/3921"/>
+  <description format="asciidoc">
+    Add a new `ConfigurationFactory::getConfiguration` method accepting multiple `URI`s
+  </description>
+</entry>