Based on #464. Avoid using null for class loader during lookups

Fall back to the class loader used to load JULI when the thread context
class loader is not set. In a normal Tomcat configuration, this will be
the system class loader.
Based on a pull request by jackshirazi.

Author: markt-asf

java/org/apache/juli/ClassLoaderLogManager.java

@@ -133,8 +133,7 @@ public synchronized boolean addLogger(final Logger logger) {
 
         final String loggerName = logger.getName();
 
-        ClassLoader classLoader =
-            Thread.currentThread().getContextClassLoader();
+        ClassLoader classLoader = getClassLoader();
         ClassLoaderLogInfo info = getClassLoaderInfo(classLoader);
         if (info.loggers.containsKey(loggerName)) {
             return false;
@@ -224,8 +223,7 @@ public synchronized boolean addLogger(final Logger logger) {
      */
     @Override
     public synchronized Logger getLogger(final String name) {
-        ClassLoader classLoader = Thread.currentThread()
-                .getContextClassLoader();
+        ClassLoader classLoader = getClassLoader();
         return getClassLoaderInfo(classLoader).loggers.get(name);
     }
 
@@ -236,8 +234,7 @@ public synchronized Logger getLogger(final String name) {
      */
     @Override
     public synchronized Enumeration<String> getLoggerNames() {
-        ClassLoader classLoader = Thread.currentThread()
-                .getContextClassLoader();
+        ClassLoader classLoader = getClassLoader();
         return Collections.enumeration(getClassLoaderInfo(classLoader).loggers.keySet());
     }
 
@@ -280,7 +277,7 @@ public String getProperty(String name) {
 
 
     private synchronized String findProperty(String name) {
-        ClassLoader classLoader = Thread.currentThread().getContextClassLoader();
+        ClassLoader classLoader = getClassLoader();
         ClassLoaderLogInfo info = getClassLoaderInfo(classLoader);
         String result = info.props.getProperty(name);
         // If the property was not found, and the current classloader had no
@@ -313,7 +310,7 @@ public void readConfiguration()
 
         checkAccess();
 
-        readConfiguration(Thread.currentThread().getContextClassLoader());
+        readConfiguration(getClassLoader());
 
     }
 
@@ -324,7 +321,7 @@ public void readConfiguration(InputStream is)
         checkAccess();
         reset();
 
-        readConfiguration(is, Thread.currentThread().getContextClassLoader());
+        readConfiguration(is, getClassLoader());
 
     }
 
@@ -337,7 +334,7 @@ public void reset() throws SecurityException {
             // because we have our own shutdown hook
             return;
         }
-        ClassLoader classLoader = thread.getContextClassLoader();
+        ClassLoader classLoader = getClassLoader();
         ClassLoaderLogInfo clLogInfo = getClassLoaderInfo(classLoader);
         resetLoggers(clLogInfo);
         // Do not call super.reset(). It should be a NO-OP as all loggers should
@@ -389,16 +386,17 @@ private void resetLoggers(ClassLoaderLogInfo clLogInfo) {
 
     /**
      * Retrieve the configuration associated with the specified classloader. If
-     * it does not exist, it will be created.
+     * it does not exist, it will be created. If no class loader is specified,
+     * the class loader used to load this class is used.
      *
-     * @param classLoader The classloader for which we will retrieve or build the
-     *                    configuration
+     * @param classLoader The class loader for which we will retrieve or build
+     *                    the configuration
      * @return the log configuration
      */
     protected synchronized ClassLoaderLogInfo getClassLoaderInfo(ClassLoader classLoader) {
 
         if (classLoader == null) {
-            classLoader = ClassLoader.getSystemClassLoader();
+            classLoader = this.getClass().getClassLoader();
         }
         ClassLoaderLogInfo info = classLoaderLoggers.get(classLoader);
         if (info == null) {
@@ -652,7 +650,7 @@ protected String replace(String str) {
 
 
     private String replaceWebApplicationProperties(String propName) {
-        ClassLoader cl = Thread.currentThread().getContextClassLoader();
+        ClassLoader cl = getClassLoader();
         if (cl instanceof WebappProperties) {
             WebappProperties wProps = (WebappProperties) cl;
             if ("classloader.webappName".equals(propName)) {
@@ -670,9 +668,28 @@ private String replaceWebApplicationProperties(String propName) {
     }
 
 
-    // ---------------------------------------------------- LogNode Inner Class
+    /**
+     * Obtain the class loader to use to lookup loggers, obtain configuration
+     * etc. The search order is:
+     * <ol>
+     * <li>Thread.currentThread().getContextClassLoader()</li>
+     * <li>The class laoder of this class</li>
+     * </ol>
+     *
+     * @return The class loader to use to lookup loggers, obtain configuration
+     *         etc.
+     */
+    static ClassLoader getClassLoader() {
+        ClassLoader result = Thread.currentThread().getContextClassLoader();
+        if (result == null) {
+            result = ClassLoaderLogManager.class.getClassLoader();
+        }
+        return result;
+    }
 
 
+    // ---------------------------------------------------- LogNode Inner Class
+
     protected static final class LogNode {
         Logger logger;
 

java/org/apache/juli/FileHandler.java

@@ -377,7 +377,7 @@ private void configure() {
 
         String className = this.getClass().getName(); //allow classes to override
 
-        ClassLoader cl = Thread.currentThread().getContextClassLoader();
+        ClassLoader cl = ClassLoaderLogManager.getClassLoader();
 
         // Retrieve configuration of logging file name
         if (rotatable == null) {

webapps/docs/changelog.xml

@@ -128,6 +128,12 @@
         <code>TomcatPrincipal</code> and <code>GenericPrincipal</code>.
         Patch provided by Carsten Klein. (michaelo)
       </add>
+      <fix>
+        <pr>464</pr>: Fall back to the class loader used to load JULI when the
+        thread context class loader is not set. In a normal Tomcat
+        configuration, this will be the system class loader. Based on a pull
+        request by jackshirazi. (markt)
+      </fix>
       <fix>
         <pr>469</pr>: Include the Jakarata Annotations API in the classes that
         Tomcat will not load from web applications. Pull request provided by