support additional class loaders for savables (#2888)

* support additional class loaders for savables

* avoid allocating new empty lists per call

* ignore null classloaders

Author: riccardobl

jme3-core/src/main/java/com/jme3/asset/AssetManager.java

@@ -46,7 +46,7 @@
 import com.jme3.texture.plugins.TGALoader;
 import java.io.IOException;
 import java.io.InputStream;
-import java.util.ArrayList;
+import java.util.Collections;
 import java.util.EnumSet;
 import java.util.List;
 
@@ -122,7 +122,7 @@ public default void removeClassLoader(ClassLoader loader) {
      */
     @Deprecated
     public default List<ClassLoader> getClassLoaders() {
-        return new ArrayList<>();
+        return Collections.emptyList();
     }
 
     /**

jme3-core/src/main/java/com/jme3/export/SavableClassUtil.java

@@ -40,6 +40,7 @@
 import java.lang.reflect.Field;
 import java.lang.reflect.InvocationTargetException;
 import java.util.ArrayList;
+import java.util.Collection;
 import java.util.HashMap;
 import java.util.List;
 import java.util.logging.Level;
@@ -198,9 +199,13 @@ public static Savable fromName(String className)
      * @throws ClassNotFoundException thrown if the class name is not in the classpath.
      * @throws SecurityException thrown if the filter rejects the class name.
      */
-    public static Savable fromName(String className, SavableClassFilter classFilter)
-            throws ClassNotFoundException, IllegalAccessException,
-            InstantiationException, InvocationTargetException {
+    public static Savable fromName(String className, SavableClassFilter classFilter) 
+        throws ClassNotFoundException, IllegalAccessException, InstantiationException, InvocationTargetException {
+        return fromName(className, classFilter, null);
+    }
+
+    public static Savable fromName(String className, SavableClassFilter classFilter, Collection<ClassLoader> additionalClassLoaders) 
+        throws ClassNotFoundException, IllegalAccessException, InstantiationException, InvocationTargetException {
         className = remapClass(className);
         if (classFilter == null) {
             throw new NullPointerException("classFilter");
@@ -209,7 +214,7 @@ public static Savable fromName(String className, SavableClassFilter classFilter)
             throw new SecurityException("Savable class rejected by filter: " + className);
         }
 
-        Constructor noArgConstructor = findNoArgConstructor(className);
+        Constructor noArgConstructor = findNoArgConstructor(className, additionalClassLoaders);
         noArgConstructor.setAccessible(true);
         try {
             return (Savable) noArgConstructor.newInstance();
@@ -226,6 +231,7 @@ public static Savable fromName(String className, SavableClassFilter classFilter)
         }
     }
 
+
     /**
      * @deprecated use {@link #fromName(java.lang.String)} instead 
      */
@@ -240,6 +246,9 @@ public static Savable fromName(String className, List<ClassLoader> loaders) thro
         String newClassName = remapClass(className);
         synchronized (loaders) {
             for (ClassLoader classLoader : loaders) {
+                if (classLoader == null) {
+                    continue;
+                }
                 final Class<?> loadedClass;
                 try {
                     loadedClass = classLoader.loadClass(newClassName);
@@ -263,12 +272,35 @@ public static Savable fromName(String className, List<ClassLoader> loaders) thro
      * @return the pre-existing constructor (not null)
      */
     @SuppressWarnings("unchecked")
-    private static Constructor findNoArgConstructor(String className)
+    private static Constructor findNoArgConstructor(String className, Collection<ClassLoader> additionalClassLoaders)
             throws ClassNotFoundException, InstantiationException {
-        Class clazz = Class.forName(className);
+        Class clazz = null;
+        
+        try {
+            clazz = Class.forName(className);
+        } catch (ClassNotFoundException e) {
+            if (additionalClassLoaders != null) {
+                for (ClassLoader classLoader : additionalClassLoaders) {
+                    if (classLoader == null) {
+                        continue;
+                    }
+                    try {
+                        clazz = Class.forName(className, true, classLoader);
+                        break;
+                    } catch (ClassNotFoundException ex) {
+                        // ignore
+                    }
+                }
+            }
+            if (clazz == null) {
+                throw e;
+            }
+        }
+
         if (!SavableClassUtil.isImplementingSavable(clazz)) {
             throw new InstantiationException("Class " + className + " does not implement Savable.");
         }
+
         Constructor result;
         try {
             result = clazz.getDeclaredConstructor();

jme3-core/src/plugins/java/com/jme3/export/binary/BinaryImporter.java

@@ -399,7 +399,7 @@ public Savable readObject(int id) {
                 throw new IOException("Invalid J3O object data length: " + dataLength);
             }
 
-            Savable  out = SavableClassUtil.fromName(bco.className, classFilter);
+            Savable  out = SavableClassUtil.fromName(bco.className, classFilter, assetManager == null ? null : assetManager.getClassLoaders());
 
             BinaryInputCapsule cap = new BinaryInputCapsule(this, out, bco);
             cap.setContent(dataArray, loc, loc+dataLength);

jme3-plugins/src/xml/java/com/jme3/export/xml/DOMInputCapsule.java

@@ -34,6 +34,7 @@
 
 import com.jme3.export.InputCapsule;
 import com.jme3.export.Savable;
+import com.jme3.export.SavableClassFilter;
 import com.jme3.export.SavableClassUtil;
 import com.jme3.util.BufferUtils;
 import com.jme3.util.IntMap;
@@ -56,6 +57,7 @@
  */
 public class DOMInputCapsule implements InputCapsule {
     private static final Logger logger = Logger.getLogger(DOMInputCapsule.class .getName());
+    private SavableClassFilter classFilter = SavableClassFilter.ACCEPT_ALL;
 
     private Document doc;
     private Element currentElement;
@@ -85,6 +87,28 @@ public int getSavableVersion(Class<? extends Savable> desiredClass) {
         }
     }
 
+    /**
+     * Sets the policy used before this importer instantiates classes. 
+     * The default accepts all classes for backward compatibility.
+     * Use a restrictive filter when loading assets from untrusted sources.
+     *
+     * @param classFilter the filter to apply
+     */
+    public void setClassFilter(SavableClassFilter classFilter) {
+        if (classFilter == null) {
+            throw new NullPointerException("classFilter");
+        }
+        this.classFilter = classFilter;
+    }
+
+    /**
+     * @return the current class filter
+     */
+    public SavableClassFilter getClassFilter() {
+        return classFilter;
+    }
+
+
     private Element findChildElement(String name) {
         if (currentElement == null) {
             return null;
@@ -574,7 +598,7 @@ private Savable readSavableFromCurrentElement(Savable defVal) throws IOException
 
             Savable tmp = null;
             try {
-                tmp = SavableClassUtil.fromName(className);
+                tmp = SavableClassUtil.fromName(className, classFilter, importer.getAssetManager() == null ? null : importer.getAssetManager().getClassLoaders());
             } catch (ClassNotFoundException | IllegalAccessException | InstantiationException | InvocationTargetException e) {
                 throw new IOException(e);
             }