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Inspect and record the execution of Java for use with App Land
package com.appland.appmap.transform;
import java.io.ByteArrayInputStream;
import java.lang.instrument.IllegalClassFormatException;
import java.security.ProtectionDomain;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Comparator;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Objects;
import java.util.stream.Collectors;
import java.util.stream.Stream;
import org.reflections.Reflections;
import org.reflections.scanners.SubTypesScanner;
import org.reflections.util.ClasspathHelper;
import org.reflections.util.ConfigurationBuilder;
import org.reflections.util.FilterBuilder;
import org.tinylog.TaggedLogger;
import com.appland.appmap.config.AppMapConfig;
import com.appland.appmap.config.Properties;
import com.appland.appmap.output.v1.NoSourceAvailableException;
import com.appland.appmap.transform.annotations.Hook;
import com.appland.appmap.transform.annotations.HookSite;
import com.appland.appmap.transform.annotations.HookValidationException;
import com.appland.appmap.util.AppMapBehavior;
import com.appland.appmap.util.Logger;
import javassist.ClassPool;
import javassist.CtBehavior;
import javassist.CtClass;
import javassist.CtMethod;
import javassist.LoaderClassPath;
import javassist.Modifier;
import javassist.NotFoundException;
import javassist.bytecode.Descriptor;
/**
* The ClassFileTransformer is responsible for loading and caching hooks during {@link com.appland.appmap.Agent}
* statup. The {@link ClassFileTransformer#transform} method is used by the Instrumentation API to
* modify class bytecode at load time. When a class is loaded, this class will attempt to apply
* hooks to each behavior declared by that class.
*/
public class ClassFileTransformer implements java.lang.instrument.ClassFileTransformer {
private static final TaggedLogger logger = AppMapConfig.getLogger(null);
private static String tracePrefix = Properties.DebugClassPrefix;
private static final List unkeyedHooks = new ArrayList<>();
private static final Map> keyedHooks = new HashMap<>();
/**
* Default constructor. Caches hooks for future class transforms.
*/
public ClassFileTransformer() {
super();
Reflections reflections = new Reflections(new ConfigurationBuilder()
.setUrls(ClasspathHelper.forPackage("com.appland.appmap.process"))
.setScanners(new SubTypesScanner(false))
.filterInputsBy(new FilterBuilder().includePackage("com.appland.appmap.process")));
ClassPool classPool = ClassPool.getDefault();
for (Class classType : reflections.getSubTypesOf(Object.class)) {
try {
CtClass ctClass = classPool.get(classType.getName());
processClass(ctClass);
ctClass.detach();
} catch (NotFoundException e) {
Logger.printf("failed to find %s in class pool", classType.getName());
Logger.println(e);
}
}
}
private void addHook(Hook hook) {
if (hook == null) {
return;
}
String key = hook.getKey();
logger.trace("{}: {}", key, hook);
if (key == null) {
unkeyedHooks.add(hook);
} else {
List matchingKeyedHooks = keyedHooks.computeIfAbsent(key, k -> new ArrayList<>());
matchingKeyedHooks.add(hook);
}
}
private List getHooks(String methodId) {
List matchingKeyedHooks = keyedHooks.get(methodId);
if (matchingKeyedHooks == null) {
matchingKeyedHooks = new ArrayList();
}
return Stream.of(matchingKeyedHooks, unkeyedHooks)
.flatMap(Collection::stream)
.sorted(Comparator.comparingInt(Hook::getPosition))
.collect(Collectors.toList());
}
private void processClass(CtClass ctClass) {
boolean traceClass = tracePrefix == null || ctClass.getName().startsWith(tracePrefix);
if (traceClass) {
logger.trace(() -> ctClass.getName());
}
for (CtBehavior behavior : ctClass.getDeclaredBehaviors()) {
if (traceClass) {
logger.trace(() -> behavior.getLongName());
}
Hook hook = Hook.from(behavior);
if (hook == null) {
if (traceClass) {
logger.trace("{}, no hooks", () -> behavior.getLongName());
}
continue;
}
ctClass.defrost();
try {
hook.validate();
} catch (HookValidationException e) {
logger.debug(e, "failed to validate hook");
continue;
}
this.addHook(hook);
if (traceClass) {
logger.trace("registered hook {}", hook);
}
}
}
private boolean applyHooks(CtBehavior behavior) {
boolean traceClass = tracePrefix == null || behavior.getDeclaringClass().getName().startsWith(tracePrefix);
try {
final List hookSites = this.getHooks(behavior.getName())
.stream()
.map(hook -> hook.prepare(behavior))
.filter(Objects::nonNull)
.collect(Collectors.toList());
if (hookSites.size() < 1) {
if (traceClass) {
logger.trace("no hook sites");
}
return false;
}
Hook.apply(behavior, hookSites);
if (logger.isDebugEnabled()) {
for (HookSite hookSite : hookSites) {
final Hook hook = hookSite.getHook();
String className = behavior.getDeclaringClass().getName();
if (tracePrefix != null && !className.startsWith(tracePrefix)) {
continue;
}
if (traceClass) {
logger.debug("hooked {}.{}{} on ({},{}) with {}",
className,
behavior.getName(),
behavior.getMethodInfo().getDescriptor(),
hook.getMethodEvent().getEventString(),
hook.getPosition(),
hook);
}
}
}
return true;
} catch (NoSourceAvailableException e) {
Logger.println(e);
}
return false;
}
@Override
public byte[] transform(ClassLoader loader,
String className,
Class redefiningClass,
ProtectionDomain domain,
byte[] bytes) throws IllegalClassFormatException {
ClassPool classPool = new ClassPool();
try {
// Anonymous classes created by sun.misc.Unsafe.defineAnonymousClass don't
// have names.
if (className == null) {
return null;
}
className = className.replaceAll("/", ".");
boolean traceClass = tracePrefix == null || className.startsWith(tracePrefix);
if (traceClass) {
logger.trace("className: {}, classPool: {}", className, classPool);
}
classPool.appendClassPath(new LoaderClassPath(loader));
CtClass ctClass;
try {
ctClass = classPool.makeClass(new ByteArrayInputStream(bytes));
} catch (RuntimeException e) {
// The class is frozen
// We can defrost it and apply our changes, though in practice I've observed this to be
// unstable. Particularly, exceptions thrown from the Groovy runtime due to missing methods.
// There's likely a way to do this safely, but further investigation is needed.
//
// ctClass = classPool.get(className.replace('/', '.'));
// ctClass.defrost();
//
// For now, just skip this class
logger.warn(e, "makeClass failed");
return null;
}
if (ctClass.isInterface()) {
if (traceClass) {
logger.trace("{} is an interface", className);
}
return null;
}
boolean hookApplied = false;
for (CtBehavior behavior : ctClass.getDeclaredBehaviors()) {
if (traceClass) {
logger.trace("behavior: {} ", behavior.getLongName());
}
if (ignoreMethod(behavior)) {
if (traceClass) {
logger.trace("ignored");
}
continue;
}
if (this.applyHooks(behavior)) {
hookApplied = true;
}
}
if (hookApplied) {
if (traceClass) {
logger.trace("hooks applied to {}", className);
}
return ctClass.toBytecode();
}
if (traceClass) {
logger.trace("no hooks applied to {}", className);
}
} catch (Throwable t) {
// Don't allow this exception to propagate out of this method, because it will
// be swallowed
// by sun.instrument.TransformerManager.
logger.warn(t);
}
return null;
}
private boolean ignoreMethod(CtBehavior behavior) {
if (!(behavior instanceof CtMethod)) {
return false;
}
if ((behavior.getModifiers() & Modifier.ABSTRACT) != 0) {
return true;
}
CtMethod method = (CtMethod) behavior;
try {
return behavior.getMethodInfo2().isConstructor() ||
behavior.getMethodInfo2().isStaticInitializer() ||
isGetter(method) ||
isSetter(method) ||
isIgnoredInstanceMethod(method);
} catch (NotFoundException e) {
Logger.println(e);
return true;
}
}
private boolean isIgnoredInstanceMethod(CtMethod method) {
final int mods = method.getModifiers();
if ( Modifier.isStatic(mods) || !new AppMapBehavior(method).isRecordable()) {
return false;
}
final String methodName = method.getName();
return
methodName.equals("equals") ||
methodName.equals("hashCode") ||
methodName.equals("iterator") ||
methodName.equals("toString");
}
public static boolean isGetter(CtMethod method) throws NotFoundException {
// KEG I'm getting exceptions like this when trying to use method.getReturnType():
//
// com.appland.shade.javassist.NotFoundException: java.lang.String
//
// The descriptor is used under the hood by javassist, and it provides
// what we need, albeit in a cryptic format.
String descriptor = method.getMethodInfo().getDescriptor();
String methodName = method.getName();
if (new AppMapBehavior(method).isRecordable() &&
Descriptor.numOfParameters(descriptor) == 0) {
if (methodName.matches("^get[A-Z].*") &&
!descriptor.matches("\\)V$")) /* void */
return true;
if (methodName.matches("^is[A-Z].*") &&
descriptor.matches("\\)Z$")) /* boolean */
return true;
/* boolean */
return methodName.matches("^has[A-Z].*") &&
descriptor.matches("\\)Z$");
}
return false;
}
public static boolean isSetter(CtMethod method) throws NotFoundException {
String descriptor = method.getMethodInfo().getDescriptor();
return new AppMapBehavior(method).isRecordable() &&
descriptor.matches("\\)V$") /* void */ &&
Descriptor.numOfParameters(descriptor) == 1 &&
method.getName().matches("^set[A-Z].*");
}
}