fix(logging): remove duplicate Commons Logging runtime binding

pom.xml

@@ -140,6 +140,12 @@
       <groupId>org.apache.pdfbox</groupId>
       <artifactId>pdfbox</artifactId>
       <version>${pdfbox.version}</version>
+      <exclusions>
+        <exclusion>
+          <groupId>commons-logging</groupId>
+          <artifactId>commons-logging</artifactId>
+        </exclusion>
+      </exclusions>
     </dependency>
 
     <dependency>

scripts/test_commons_logging_dependency_contract.py

@@ -0,0 +1,48 @@
+import re
+from pathlib import Path
+
+
+ROOT = Path(__file__).resolve().parents[1]
+POM = ROOT / "pom.xml"
+
+
+def _pom_text() -> str:
+    return POM.read_text(encoding="utf-8")
+
+
+def _dependency_block(pom: str, group_id: str, artifact_id: str) -> str:
+    pattern = re.compile(
+        r"<dependency>\s*"
+        rf"<groupId>{re.escape(group_id)}</groupId>\s*"
+        rf"<artifactId>{re.escape(artifact_id)}</artifactId>"
+        r".*?</dependency>",
+        re.DOTALL,
+    )
+    match = pattern.search(pom)
+    assert match is not None
+    return match.group(0)
+
+
+def test_pdfbox_excludes_standalone_commons_logging_provider() -> None:
+    pom = _pom_text()
+    pdfbox = _dependency_block(pom, "org.apache.pdfbox", "pdfbox")
+
+    exclusion = re.compile(
+        r"<exclusion>\s*"
+        r"<groupId>commons-logging</groupId>\s*"
+        r"<artifactId>commons-logging</artifactId>\s*"
+        r"</exclusion>"
+    )
+    assert exclusion.search(pdfbox) is not None
+
+
+def test_project_does_not_reintroduce_commons_logging_directly() -> None:
+    pom = _pom_text()
+
+    direct_commons_logging = re.compile(
+        r"<dependency>\s*"
+        r"<groupId>commons-logging</groupId>\s*"
+        r"<artifactId>commons-logging</artifactId>"
+    )
+    assert direct_commons_logging.search(pom) is None
+    _dependency_block(pom, "org.springframework.boot", "spring-boot-starter-log4j2")

src/test/java/com/clearfolio/viewer/config/CommonsLoggingRuntimeBindingTest.java

@@ -0,0 +1,35 @@
+package com.clearfolio.viewer.config;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+import java.net.URL;
+import java.util.Collections;
+import java.util.List;
+import org.junit.jupiter.api.Test;
+
+/**
+ * Verifies that the supported runtime contains exactly one Commons Logging API provider.
+ */
+final class CommonsLoggingRuntimeBindingTest {
+
+    @Test
+    void commonsLoggingApiIsProvidedOnlyBySpringJcl() throws Exception {
+        ClassLoader loader = Thread.currentThread().getContextClassLoader();
+        List<String> providers = Collections.list(
+                        loader.getResources("org/apache/commons/logging/LogFactory.class"))
+                .stream()
+                .map(URL::toExternalForm)
+                .sorted()
+                .toList();
+
+        assertEquals(
+                1,
+                providers.size(),
+                () -> "Expected one Commons Logging API provider but found: " + providers);
+        assertTrue(
+                providers.getFirst().contains("spring-jcl"),
+                () -> "Expected Spring's spring-jcl bridge to own Commons Logging, but found: "
+                        + providers.getFirst());
+    }
+}