HV-2020 Use OSGi framework utils to get a classloader

and do not rely on a dependency to expressly

Author: marko-bekhta

engine/pom.xml

@@ -74,12 +74,6 @@
             <scope>provided</scope>
             <optional>true</optional>
         </dependency>
-        <dependency>
-            <groupId>org.glassfish.expressly</groupId>
-            <artifactId>expressly</artifactId>
-            <scope>provided</scope>
-            <optional>true</optional>
-        </dependency>
         <dependency>
             <groupId>org.jboss.logging</groupId>
             <artifactId>jboss-logging-annotations</artifactId>
@@ -125,6 +119,11 @@
         <!--
         Test dependencies
         -->
+        <dependency>
+            <groupId>org.glassfish.expressly</groupId>
+            <artifactId>expressly</artifactId>
+            <scope>test</scope>
+        </dependency>
         <dependency>
             <groupId>org.testng</groupId>
             <artifactId>testng</artifactId>

engine/src/main/java/org/hibernate/validator/messageinterpolation/ResourceBundleMessageInterpolator.java

@@ -5,6 +5,9 @@
 package org.hibernate.validator.messageinterpolation;
 
 import java.lang.invoke.MethodHandles;
+import java.lang.reflect.Array;
+import java.lang.reflect.InvocationTargetException;
+import java.lang.reflect.Method;
 import java.util.Collections;
 import java.util.Locale;
 import java.util.Set;
@@ -22,8 +25,6 @@
 import org.hibernate.validator.spi.messageinterpolation.LocaleResolver;
 import org.hibernate.validator.spi.resourceloading.ResourceBundleLocator;
 
-import com.sun.el.ExpressionFactoryImpl;
-
 /**
  * Resource bundle backed message interpolator.
  *
@@ -195,7 +196,10 @@ private static ExpressionFactory buildExpressionFactory() {
 
 			// Finally we try the CL of the EL implementation itself. This is necessary for OSGi now that the
 			// implementation is separated from the API.
-			SetContextClassLoader.action( ExpressionFactoryImpl.class.getClassLoader() );
+			// Instead of running this:
+			// SetContextClassLoader.action( ExpressionFactoryImpl.class.getClassLoader() );
+			// we do some reflection "magic" to not have a dependency on an implementation of the expression language:
+			SetContextClassLoader.action( classLoaderForExpressionFactory( originalContextClassLoader ) );
 			if ( canLoadExpressionFactory() ) {
 				ExpressionFactory expressionFactory = ELManager.getExpressionFactory();
 				LOG.debug( "Loaded expression factory via com.sun.el classloader" );
@@ -213,6 +217,41 @@ private static ExpressionFactory buildExpressionFactory() {
 		throw LOG.getUnableToInitializeELExpressionFactoryException( null );
 	}
 
+	/*
+	 * In an OSGi environment we won't have access to the classloader that is capable to instantiate the EL factory from the get-go.
+	 * Instead, we have to use the classloader that loaded some class from the EL implementation, e.g. ExpressionFactoryImpl.
+	 * To get that classloader we list all the OSGi bundles through the OSGi BundleContext and go bundle by bundle to find the one
+	 * that is able to load the ExpressionFactoryImpl class.
+	 *
+	 * We rely on reflection here as we do not have a dependency on OSGi in the engine module, and we do not want to add it!
+	 */
+	private static ClassLoader classLoaderForExpressionFactory(ClassLoader cl) throws Exception {
+		try {
+			Class<?> fu = cl.loadClass( "org.osgi.framework.FrameworkUtil" );
+			Method getBundle = fu.getMethod( "getBundle", Class.class );
+			Object currentBundle = getBundle.invoke( null, ResourceBundleMessageInterpolator.class );
+			if ( currentBundle != null ) {
+				Object context = cl.loadClass( "org.osgi.framework.Bundle" ).getMethod( "getBundleContext" ).invoke( currentBundle );
+				Object bundles = cl.loadClass( "org.osgi.framework.BundleContext" ).getMethod( "getBundles" ).invoke( context );
+				Method loadClass = cl.loadClass( "org.osgi.framework.Bundle" ).getMethod( "loadClass", String.class );
+				int n = Array.getLength( bundles );
+				for ( int i = 0; i < n; i++ ) {
+					try {
+						Object bundle = Array.get( bundles, i );
+						return ( (Class<?>) loadClass.invoke( bundle, "com.sun.el.ExpressionFactoryImpl" ) ).getClassLoader();
+					}
+					catch (Exception e) {
+						//
+					}
+				}
+			}
+		}
+		catch (ClassNotFoundException | NoSuchMethodException | IllegalAccessException | InvocationTargetException e) {
+			throw e;
+		}
+		return null;
+	}
+
 	/**
 	 * Instead of testing the different class loaders via {@link ELManager}, we directly access the
 	 * {@link ExpressionFactory}. This avoids issues with loading the {@code ELUtil} class (used by {@code ELManager})