alibaba/transmittable-thread-local

package com.alibaba.ttl.threadpool.agent;

import com.alibaba.ttl.threadpool.agent.logging.Logger;
import com.alibaba.ttl.threadpool.agent.transformlet.ClassInfo;
import com.alibaba.ttl.threadpool.agent.transformlet.TtlTransformlet;
import edu.umd.cs.findbugs.annotations.NonNull;
import edu.umd.cs.findbugs.annotations.Nullable;
import edu.umd.cs.findbugs.annotations.SuppressFBWarnings;

import java.lang.instrument.ClassFileTransformer;
import java.security.ProtectionDomain;
import java.util.ArrayList;
import java.util.List;

import static com.alibaba.ttl.threadpool.agent.transformlet.helper.TtlTransformletHelper.isClassUnderPackage;

/**
 * TTL {@link ClassFileTransformer} of Java Agent
 *
 * @author Jerry Lee (oldratlee at gmail dot com)
 * @see ClassFileTransformer
 * @see <a href="https://docs.oracle.com/en/java/javase/21/docs/api/java.instrument/java/lang/instrument/package-summary.html">The mechanism for instrumentation</a>
 * @since 0.9.0
 */
public class TtlTransformer implements ClassFileTransformer {
    private static final Logger logger = Logger.getLogger(TtlTransformer.class);

    /**
     * "<code>null</code> if no transform is performed",
     * see {@code @return} of {@link ClassFileTransformer#transform(ClassLoader, String, Class, ProtectionDomain, byte[])}
     */
    @SuppressFBWarnings({"EI_EXPOSE_REP"})
    // [ERROR] com.alibaba.ttl.threadpool.agent.TtlTransformer.transform(ClassLoader, String, Class, ProtectionDomain, byte[])
    //         may expose internal representation by returning TtlTransformer.NO_TRANSFORM
    // the value is null, so there is NO "EI_EXPOSE_REP" problem actually.
    private static final byte[] NO_TRANSFORM = null;

    private final TtlExtensionTransformletManager extensionTransformletManager;
    private final List<TtlTransformlet> transformletList = new ArrayList<>();
    private final boolean logClassTransform;

    TtlTransformer(List<? extends TtlTransformlet> transformletList, boolean logClassTransform) {
        extensionTransformletManager = new TtlExtensionTransformletManager();

        this.logClassTransform = logClassTransform;
        for (TtlTransformlet ttlTransformlet : transformletList) {
            this.transformletList.add(ttlTransformlet);
            logger.info("[TtlTransformer] add Transformlet " + ttlTransformlet.getClass().getName());
        }
    }

    /**
     * info about class loader: may be <code>null</code> if the bootstrap loader.
     * <p>
     * more info see {@link ClassFileTransformer#transform(java.lang.ClassLoader, java.lang.String, java.lang.Class, java.security.ProtectionDomain, byte[])}
     */
    @Override
    public final byte[] transform(@Nullable final ClassLoader loader, @Nullable final String classFile, final Class<?> classBeingRedefined,
                                  final ProtectionDomain protectionDomain, @NonNull final byte[] classFileBuffer) {
        try {
            // Lambda has no class file, no need to transform, just return.
            if (classFile == null) return NO_TRANSFORM;

            final ClassInfo classInfo = new ClassInfo(classFile, classFileBuffer, loader);
            if (isClassUnderPackage(classInfo.getClassName(), "com.alibaba.ttl")) return NO_TRANSFORM;
            if (isClassUnderPackage(classInfo.getClassName(), "java.lang")) return NO_TRANSFORM;

            if (logClassTransform)
                logger.info("[TtlTransformer] transforming " + classInfo.getClassName()
                        + " from classloader " + classInfo.getClassLoader()
                        + " at location " + classInfo.getLocationUrl());

            extensionTransformletManager.collectExtensionTransformlet(classInfo);

            for (TtlTransformlet transformlet : transformletList) {
                transformlet.doTransform(classInfo);
                if (classInfo.isModified()) {
                    logger.info("[TtlTransformer] " + transformlet.getClass().getName() + " transformed " + classInfo.getClassName()
                            + " from classloader " + classInfo.getClassLoader()
                            + " at location " + classInfo.getLocationUrl());
                    return classInfo.getCtClass().toBytecode();
                }
            }

            final String transformlet = extensionTransformletManager.extensionTransformletDoTransform(classInfo);
            if (classInfo.isModified()) {
                logger.info("[TtlTransformer] " + transformlet + " transformed " + classInfo.getClassName()
                        + " from classloader " + classInfo.getClassLoader()
                        + " at location " + classInfo.getLocationUrl());
                return classInfo.getCtClass().toBytecode();
            }
        } catch (Throwable t) {
            String msg = "[TtlTransformer] fail to transform class " + classFile + ", cause: " + t.toString();
            logger.error(msg, t);
            throw new IllegalStateException(msg, t);
        }

        return NO_TRANSFORM;
    }
}