Use slf4j adapters for logging.

- By introducing adapters for log4j and commons-logging and
- including the original log4j and commons-logging dependencies as provided
all logging should be redirected to slf4j and finally java.util.logging.

core/pom.xml

@@ -401,10 +401,6 @@ THE SOFTWARE.
           <groupId>org.springframework</groupId>
           <artifactId>spring-support</artifactId>
         </exclusion>
-        <exclusion>
-          <groupId>log4j</groupId>
-          <artifactId>log4j</artifactId>
-        </exclusion>
       </exclusions>
     </dependency>
     <dependency>
@@ -473,8 +469,8 @@ THE SOFTWARE.
       <version>1.1.0</version>
     </dependency>
     <dependency>
-      <groupId>commons-logging</groupId>
-      <artifactId>commons-logging</artifactId>
+      <groupId>org.slf4j</groupId>
+      <artifactId>jcl-over-slf4j</artifactId>
     </dependency>
     <dependency>
       <groupId>org.slf4j</groupId>

plugins/pom.xml

@@ -34,6 +34,8 @@
   <properties>
     <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
     <concurrency>2</concurrency> <!-- may use e.g. 2C for 2 × (number of cores) -->
+    <!-- same version as in org.jenkins-ci.main:pom -->
+    <slf4jVersion>1.7.7</slf4jVersion>
   </properties>
 
   <dependencies>
@@ -80,6 +82,32 @@
       <scope>provided</scope>
       <optional>true</optional><!-- no need to have this at runtime -->
     </dependency>
+    <!-- mark logging dependencies as provided by war -->
+    <dependency>
+      <groupId>org.slf4j</groupId>
+      <artifactId>slf4j-api</artifactId>
+      <version>${slf4jVersion}</version>
+      <scope>provided</scope>
+    </dependency>
+    <dependency>
+      <groupId>org.slf4j</groupId>
+      <artifactId>log4j-over-slf4j</artifactId>
+      <version>${slf4jVersion}</version>
+      <scope>provided</scope>
+    </dependency>
+    <dependency>
+      <groupId>org.slf4j</groupId>
+      <artifactId>jcl-over-slf4j</artifactId>
+      <version>${slf4jVersion}</version>
+      <scope>provided</scope>
+    </dependency>
+    <!-- make binding to java.util.logging available during tests -->
+    <dependency>
+      <groupId>org.slf4j</groupId>
+      <artifactId>slf4j-jdk14</artifactId>
+      <version>${slf4jVersion}</version>
+      <scope>test</scope>
+    </dependency>
   </dependencies>
 
   <build>

pom.xml

@@ -214,15 +214,22 @@ THE SOFTWARE.
         <artifactId>jcl-over-slf4j</artifactId>
         <version>${slf4jVersion}</version>
       </dependency>
+      <dependency>
+        <groupId>commons-logging</groupId>
+        <artifactId>commons-logging</artifactId>
+        <version>1.1.3</version>
+        <scope>provided</scope><!-- by jcl-over-slf4j -->
+      </dependency>
       <dependency>
         <groupId>org.slf4j</groupId>
         <artifactId>log4j-over-slf4j</artifactId>
         <version>${slf4jVersion}</version>
       </dependency>
       <dependency>
-        <groupId>commons-logging</groupId>
-        <artifactId>commons-logging</artifactId>
-        <version>1.1.3</version>
+        <groupId>log4j</groupId>
+        <artifactId>log4j</artifactId>
+        <version>1.2.17</version>
+        <scope>provided</scope><!-- by log4j-over-slf4j -->
       </dependency>
       <dependency>
         <groupId>org.samba.jcifs</groupId>
@@ -664,7 +671,6 @@ THE SOFTWARE.
                 <bannedDependencies>
                   <excludes>
                     <exclude>org.sonatype.sisu:sisu-guice</exclude>
-                    <exclude>log4j:log4j</exclude>
                   </excludes>
                 </bannedDependencies>
               </rules>