net.bytebuddy.dynamic.scaffold.inline.ClassFileLocator Maven / Gradle / Ivy
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Byte Buddy is a Java library for creating Java classes at run time.
This artifact is a build of Byte Buddy with all ASM dependencies repackaged into its own name space.
package net.bytebuddy.dynamic.scaffold.inline;
import net.bytebuddy.instrumentation.type.TypeDescription;
import net.bytebuddy.utility.StreamDrainer;
import java.io.IOException;
import java.io.InputStream;
import java.lang.instrument.ClassFileTransformer;
import java.lang.instrument.IllegalClassFormatException;
import java.lang.instrument.Instrumentation;
import java.security.ProtectionDomain;
import java.util.Arrays;
import static net.bytebuddy.utility.ByteBuddyCommons.nonNull;
/**
* Locates a class file or its byte array representation when it is given its type description.
*/
public interface ClassFileLocator {
/**
* The file extension for a Java class file.
*/
static final String CLASS_FILE_EXTENSION = ".class";
/**
* Locates the class file for a given type and returns the binary data of the class file.
*
* @param typeDescription The description of the type for which a class file is to be located.
* @return Any binary representation of the type which might be illegal.
* @throws java.io.IOException If reading a class file causes an error.
*/
TypeDescription.BinaryRepresentation classFileFor(TypeDescription typeDescription) throws IOException;
/**
* Default implementations for a {@link net.bytebuddy.dynamic.scaffold.inline.ClassFileLocator}.
*/
static enum Default implements ClassFileLocator {
/**
* Locates a class file from the class path.
*/
CLASS_PATH {
@Override
public TypeDescription.BinaryRepresentation classFileFor(TypeDescription typeDescription) throws IOException {
InputStream inputStream = ClassLoader.getSystemResourceAsStream(typeDescription.getInternalName() + CLASS_FILE_EXTENSION);
if (inputStream != null) {
try {
return new TypeDescription.BinaryRepresentation.Explicit(new StreamDrainer().drain(inputStream));
} finally {
inputStream.close();
}
} else {
return TypeDescription.BinaryRepresentation.Illegal.INSTANCE;
}
}
},
/**
* Locates a class file a type description's attached description.
*/
ATTACHED {
@Override
public TypeDescription.BinaryRepresentation classFileFor(TypeDescription typeDescription) {
return typeDescription.toBinary();
}
}
}
/**
* A Java agent that allows the location of class files by emulating a retransformation. Note that this class file
* locator causes a class to be loaded in order to look up its class file. Also, this locator does deliberately not
* support the look-up of classes that represent lambda expressions.
*/
static class AgentBased implements ClassFileLocator {
/**
* The name of the Byte Buddy agent class.
*/
private static final String BYTE_BUDDY_AGENT_TYPE = "net.bytebuddy.agent.ByteBuddyAgent";
/**
* The name of the {@code ByteBuddyAgent} class's method for obtaining an instrumentation.
*/
private static final String GET_INSTRUMENTATION_METHOD = "getInstrumentation";
/**
* Base for access to a reflective member to make the code more readable.
*/
private static final Object STATIC_METHOD = null;
/**
* The instrumentation instance to use for looking up the binary format of a type.
*/
private final Instrumentation instrumentation;
/**
* The class loader which is expected to load a class of a given binary format.
*/
private final ClassLoader classLoader;
/**
* Creates an agent-based class file locator.
*
* @param instrumentation The instrumentation to use for looking up a class file implementation.
* @param classLoader The class loader that is expected to load the looked-up a class.
*/
public AgentBased(Instrumentation instrumentation, ClassLoader classLoader) {
if (!instrumentation.isRetransformClassesSupported()) {
throw new IllegalArgumentException(instrumentation + " does not support retransformation");
}
this.instrumentation = instrumentation;
this.classLoader = nonNull(classLoader);
}
/**
* Returns an agent-based class file locator for the given class loader and an already installed
* Byte Buddy agent.
*
* @param classLoader The class loader that is expected to load the looked-up a class.
* @return A class file locator for the given class loader based on a Byte Buddy agent.
*/
public static ClassFileLocator fromInstalledAgent(ClassLoader classLoader) {
try {
return new AgentBased((Instrumentation) ClassLoader.getSystemClassLoader()
.loadClass(BYTE_BUDDY_AGENT_TYPE)
.getDeclaredMethod(GET_INSTRUMENTATION_METHOD)
.invoke(STATIC_METHOD), classLoader);
} catch (Exception e) {
throw new IllegalStateException("The Byte Buddy agent is not installed or not accessible", e);
}
}
@Override
public TypeDescription.BinaryRepresentation classFileFor(TypeDescription typeDescription) {
try {
ExtractionClassFileTransformer classFileTransformer = new ExtractionClassFileTransformer(classLoader, typeDescription);
try {
instrumentation.addTransformer(classFileTransformer, true);
instrumentation.retransformClasses(classLoader.loadClass(typeDescription.getName()));
byte[] binaryRepresentation = classFileTransformer.getClassFile();
return binaryRepresentation == null
? TypeDescription.BinaryRepresentation.Illegal.INSTANCE
: new TypeDescription.BinaryRepresentation.Explicit(binaryRepresentation);
} finally {
instrumentation.removeTransformer(classFileTransformer);
}
} catch (Exception ignored) {
return null;
}
}
@Override
public boolean equals(Object other) {
return this == other || !(other == null || getClass() != other.getClass())
&& classLoader.equals(((AgentBased) other).classLoader)
&& instrumentation.equals(((AgentBased) other).instrumentation);
}
@Override
public int hashCode() {
return 31 * instrumentation.hashCode() + classLoader.hashCode();
}
@Override
public String toString() {
return "ClassFileLocator.AgentBased{" +
"instrumentation=" + instrumentation +
", classLoader=" + classLoader +
'}';
}
/**
* A non-operational class file transformer that remembers the binary format of a given class.
*/
protected static class ExtractionClassFileTransformer implements ClassFileTransformer {
/**
* The class loader that is expected to have loaded the looked-up a class.
*/
private final ClassLoader classLoader;
/**
* A description of the type to look up.
*/
private final TypeDescription typeDescription;
/**
* The binary representation of the looked-up class.
*/
private volatile byte[] classFile;
/**
* Creates a class file transformer for the purpose of extraction.
*
* @param classLoader The class loader that is expected to have loaded the looked-up a class.
* @param typeDescription A description of the type to look up.
*/
protected ExtractionClassFileTransformer(ClassLoader classLoader, TypeDescription typeDescription) {
this.classLoader = classLoader;
this.typeDescription = typeDescription;
}
@Override
public byte[] transform(ClassLoader classLoader,
String internalName,
Class redefinedType,
ProtectionDomain protectionDomain,
byte[] classFile) throws IllegalClassFormatException {
if (isChild(classLoader) && typeDescription.represents(redefinedType)) {
this.classFile = classFile;
}
return classFile;
}
/**
* Checks if the given class loader is a child of the specified class loader.
*
* @param classLoader The class loader that loaded the retransformed class.
* @return {@code true} if te given class loader is a child of the specified class loader.
*/
private boolean isChild(ClassLoader classLoader) {
if (this.classLoader == null) {
return true; // The bootstrap class loader is any class loader's parent.
}
do {
if (classLoader == this.classLoader) {
return true;
}
} while ((classLoader = classLoader.getParent()) != null);
return false;
}
/**
* Returns the binary representation of the class file that was looked up.
*
* @return The binary representation of the class file or {@code null} if no such class file could
* be located.
*/
protected byte[] getClassFile() {
return classFile;
}
@Override
public String toString() {
return "ClassFileLocator.AgentBased.ExtractionClassFileTransformer{" +
"classLoader=" + classLoader +
", typeDescription=" + typeDescription +
", classFile=" + Arrays.toString(classFile) +
'}';
}
}
}
/**
* A compound {@link net.bytebuddy.dynamic.scaffold.inline.ClassFileLocator} that chains several locators.
* Any class file locator is queried in the supplied order until one locator is able to provide an input
* stream of the class file.
*/
static class Compound implements ClassFileLocator {
/**
* The {@link net.bytebuddy.dynamic.scaffold.inline.ClassFileLocator}s which are represented by this compound
* class file locator in the order of their application.
*/
private final ClassFileLocator[] classFileLocator;
/**
* Creates a new compound class file locator.
*
* @param classFileLocator The {@link net.bytebuddy.dynamic.scaffold.inline.ClassFileLocator}s to be
* represented by this compound class file locator in the order of their application.
*/
public Compound(ClassFileLocator... classFileLocator) {
this.classFileLocator = classFileLocator;
}
/**
* Creates a default class file locator by chaining the
* {@link net.bytebuddy.dynamic.scaffold.inline.ClassFileLocator.Default#ATTACHED} and the
* {@link net.bytebuddy.dynamic.scaffold.inline.ClassFileLocator.Default#CLASS_PATH} class file locator.
*
* @return A default class file locator.
*/
public static ClassFileLocator makeDefault() {
return new Compound(Default.ATTACHED, Default.CLASS_PATH);
}
@Override
public TypeDescription.BinaryRepresentation classFileFor(TypeDescription typeDescription) throws IOException {
for (ClassFileLocator classFileLocator : this.classFileLocator) {
TypeDescription.BinaryRepresentation binaryRepresentation = classFileLocator.classFileFor(typeDescription);
if (binaryRepresentation.isValid()) {
return binaryRepresentation;
}
}
return null;
}
@Override
public boolean equals(Object other) {
return this == other || !(other == null || getClass() != other.getClass())
&& Arrays.equals(classFileLocator, ((Compound) other).classFileLocator);
}
@Override
public int hashCode() {
return Arrays.hashCode(classFileLocator);
}
@Override
public String toString() {
return "ClassFileLocator.Compound{classFileLocator=" + Arrays.toString(classFileLocator) + '}';
}
}
}
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