--- /dev/null
+/*
+ * Copyright (c) 2019 PANTHEON.tech, s.r.o. and others. All rights reserved.
+ *
+ * This program and the accompanying materials are made available under the
+ * terms of the Eclipse Public License v1.0 which accompanies this distribution,
+ * and is available at http://www.eclipse.org/legal/epl-v10.html
+ */
+package org.opendaylight.mdsal.binding.dom.codec.loader;
+
+import static com.google.common.base.Preconditions.checkArgument;
+import static com.google.common.base.Verify.verify;
+import static com.google.common.base.Verify.verifyNotNull;
+
+import com.google.common.annotations.Beta;
+import com.google.common.base.Strings;
+import java.io.IOException;
+import javassist.CannotCompileException;
+import javassist.ClassPool;
+import javassist.CtClass;
+import javassist.LoaderClassPath;
+import javassist.NotFoundException;
+import org.eclipse.jdt.annotation.NonNull;
+import org.opendaylight.mdsal.binding.spec.reflect.BindingReflections;
+
+/**
+ * A ClassLoader hosting types generated for a particular type. A root instance is attached to a
+ * BindingCodecContext instance, so any generated classes from it can be garbage-collected when the context
+ * is destroyed, as well as to prevent two contexts trampling over each other.
+ *
+ * <p>
+ * It semantically combines two class loaders: the class loader in which this class is loaded and the class loader in
+ * which a target Binding interface/class is loaded. This inherently supports multi-classloader environments -- the root
+ * instance has visibility only into codec classes and for each classloader we encounter when presented with a binding
+ * class we create a leaf instance and cache it in the root instance. Leaf instances are using the root loader as their
+ * parent, but consult the binding class's class loader if the root loader fails to load a particular class.
+ *
+ * <p>In single-classloader environments, obviously, the root loader can load all binding classes, and hence no leaf
+ * loader is created.
+ *
+ * <p>
+ * Each {@link CodecClassLoader} has a {@link ClassPool} attached to it and can perform operations on it. Leaf loaders
+ * specify the root loader's ClassPool as their parent, but are configured to lookup classes first in themselves.
+ *
+ * @author Robert Varga
+ */
+@Beta
+public abstract class CodecClassLoader extends ClassLoader {
+ /**
+ * A customizer allowing a generated class to be modified before it is loader.
+ */
+ @FunctionalInterface
+ public interface Customizer {
+ /**
+ * Customize a generated class before it is instantiated in the loader.
+ *
+ * @param loader CodecClassLoader which will hold the class. It can be used to lookup/instantiate other classes
+ * @param bindingClass Binding class for which the customized class is being generated
+ * @param generated The class being generated
+ * @throws CannotCompileException if the customizer cannot perform partial compilation
+ * @throws NotFoundException if the customizer cannot find a required class
+ * @throws IOException if the customizer cannot perform partial loading
+ */
+ void customize(@NonNull CodecClassLoader loader, @NonNull CtClass bindingClass, @NonNull CtClass generated)
+ throws CannotCompileException, NotFoundException, IOException;
+ }
+
+ static {
+ verify(ClassLoader.registerAsParallelCapable());
+ }
+
+ private final ClassPool classPool;
+
+ private CodecClassLoader(final ClassLoader parentLoader, final ClassPool parentPool) {
+ super(parentLoader);
+ this.classPool = new ClassPool(parentPool);
+ this.classPool.childFirstLookup = true;
+ this.classPool.appendClassPath(new LoaderClassPath(this));
+ }
+
+ CodecClassLoader() {
+ this(StaticClassPool.LOADER, StaticClassPool.POOL);
+ }
+
+ CodecClassLoader(final CodecClassLoader parent) {
+ this(parent, parent.classPool);
+ }
+
+ /**
+ * Turn a Class instance into a CtClass for referencing it in code generation. This method supports both
+ * generated- and non-generated classes.
+ *
+ * @param clazz Class to be looked up.
+ * @return A CtClass instance
+ * @throws NotFoundException if the class cannot be found
+ * @throws NullPointerException if {@code clazz} is null
+ */
+ public final @NonNull CtClass findClass(final @NonNull Class<?> clazz) throws NotFoundException {
+ return BindingReflections.isBindingClass(clazz) ? findClassLoader(clazz).getLocalFrozen(clazz.getName())
+ : StaticClassPool.findClass(clazz);
+ }
+
+ /**
+ * Create a new class by subclassing specified class and running a customizer on it. The name of the target class
+ * is formed through concatenation of the name of a {@code bindingInterface} and specified {@code suffix}
+ *
+ * @param superClass Superclass from which to derive
+ * @param bindingInterface Binding compile-time-generated interface
+ * @param suffix Suffix to use
+ * @param customizer Customizer to use to process the class
+ * @return A generated class object
+ * @throws CannotCompileException if the resulting generated class cannot be compiled or customized
+ * @throws NotFoundException if the binding interface cannot be found or the generated class cannot be customized
+ * @throws IOException if the generated class cannot be turned into bytecode or the generator fails with IOException
+ * @throws NullPointerException if any argument is null
+ */
+ public final Class<?> generateSubclass(final CtClass superClass, final Class<?> bindingInterface,
+ final String suffix, final Customizer customizer) throws CannotCompileException, IOException,
+ NotFoundException {
+ return findClassLoader(bindingInterface).doGenerateSubclass(superClass, bindingInterface, suffix, customizer);
+ }
+
+ final @NonNull CtClass getLocalFrozen(final String name) throws NotFoundException {
+ synchronized (getClassLoadingLock(name)) {
+ final CtClass result = classPool.get(name);
+ result.freeze();
+ return result;
+ }
+ }
+
+ abstract @NonNull CodecClassLoader findClassLoader(Class<?> bindingClass);
+
+ private Class<?> doGenerateSubclass(final CtClass superClass, final Class<?> bindingInterface, final String suffix,
+ final Customizer customizer) throws CannotCompileException, IOException, NotFoundException {
+ checkArgument(!superClass.isInterface(), "%s must not be an interface", superClass);
+ checkArgument(bindingInterface.isInterface(), "%s is not an interface", bindingInterface);
+ checkArgument(!Strings.isNullOrEmpty(suffix));
+
+ final String bindingName = bindingInterface.getName();
+ final String fqn = bindingName + "$$$" + suffix;
+ synchronized (getClassLoadingLock(fqn)) {
+ // Attempt to find a loaded class
+ final Class<?> loaded = findLoadedClass(fqn);
+ if (loaded != null) {
+ return loaded;
+ }
+
+ // Get the interface
+ final CtClass bindingCt = getLocalFrozen(bindingName);
+ try {
+ final byte[] byteCode;
+ final CtClass generated = verifyNotNull(classPool.makeClass(fqn, superClass));
+ try {
+ customizer.customize(this, bindingCt, generated);
+ final String ctName = generated.getName();
+ verify(fqn.equals(ctName), "Target class is %s returned result is %s", fqn, ctName);
+ byteCode = generated.toBytecode();
+ } finally {
+ // Always detach the result, as we will never use it again
+ generated.detach();
+ }
+
+ final Class<?> newClass = defineClass(fqn, byteCode, 0, byteCode.length);
+ resolveClass(newClass);
+ return newClass;
+ } finally {
+ // Binding interfaces are used only a few times, hence it does not make sense to cache them in the class
+ // pool.
+ // TODO: this hinders caching, hence we should re-think this
+ bindingCt.detach();
+ }
+ }
+ }
+}
Code Review / mdsal.git / blobdiff