com.github.dmgcodevil.jmspy.agent.Agent Maven / Gradle / Ivy
Go to download
Show more of this group Show more artifacts with this name
Show all versions of jmspy-agent Show documentation
Show all versions of jmspy-agent Show documentation
Library to record method invocations
package com.github.dmgcodevil.jmspy.agent;
import org.objectweb.asm.ClassAdapter;
import org.objectweb.asm.ClassReader;
import org.objectweb.asm.ClassVisitor;
import org.objectweb.asm.ClassWriter;
import org.objectweb.asm.MethodVisitor;
import org.objectweb.asm.Opcodes;
import org.objectweb.asm.Type;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import java.lang.instrument.ClassFileTransformer;
import java.lang.instrument.IllegalClassFormatException;
import java.lang.instrument.Instrumentation;
import java.security.ProtectionDomain;
import java.util.Collections;
import java.util.Set;
/**
* Jmspy Agent transforms classes to make it possible to create CGLIB proxies
* for final classes, classes without default constructor and etc.
*
* @author dmgcodevil
*/
public class Agent {
private static final Logger LOGGER = LoggerFactory.getLogger(Agent.class);
/**
* Premain method is required to apply agent.
*
* @param agentArgs the arguments for the agent. Whole string follows after '=' is considered as single parameter
* or property from the property file.
*
* Examples:
* javaagent parameter:
* -javaagent:jmspy-core/lib/jmspy-agent.jar=com.github.dmgcodevil.jmspy.example.Candidate.class,com.github.dmgcodevil.jmspy.test.data
*
* property file that should be placed at top project level for example:
* 'src/main/resources\jmspy_agent.properties'
* or
* 'src/test/resources\jmspy_agent.properties'
* Property name is "instrumentedResources", for instance: instrumentedResources=com.github.dmgcodevil.jmspy.example.Candidate.class
*
* Arguments allows specify concrete classes that should be instrumented or whole packages.
* The agent expects argument string in the next format:
* [ {canonicalClassName}.class, {package}, {canonicalClassName}.class, ... ]
* thus it's possible to specify classes or packages as much as required
* There are several significant notes:
* 1. If agentArgs/property file weren't specified (nonexistent property file or empty string)
* then all classes will be transformed if need be.
* 2. Classes and packages must be separated using ',' sign
* 3. Class name must end with '.class' suffix, otherwise it will be considered as a package name
*
* Preferred to use packages names in a agentArgs instead of specifying concrete classes names
* instead of cases when you know exactly a class name at runtime,
* because it's possible that nested or anonymous classes that have class name like 'com/site/project/URLClassPath$FileLoader$1'
* will not be transformed, in this case better specify package name as 'com.site.project'
* @param inst the instrumentation instance
*/
public static void premain(String agentArgs, Instrumentation inst) {
inst.addTransformer(new JmspyClassFileTransformer(new JmspyAgentConfig(agentArgs)));
}
/**
* Creates default constructor.
*
* @param classWriter the class writer
*/
private static void createDefaultConstructor(ClassWriter classWriter) {
// constructor
MethodVisitor mv = classWriter.visitMethod(Opcodes.ACC_PUBLIC, "", "()V", null, null);
mv.visitMaxs(2, 1);
mv.visitVarInsn(Opcodes.ALOAD, 0); // push `this` to the operand stack
mv.visitMethodInsn(Opcodes.INVOKESPECIAL, Type.getInternalName(Object.class), "", "()V"); // call the constructor of super class
mv.visitInsn(Opcodes.RETURN);
mv.visitEnd();
}
private static class ClassInfoReader extends IdleClassVisitor {
private static final String DEFAULT_CONSTRUCTOR_SIGNATURE = "()V";
private boolean defaultConstructor;
@Override
public MethodVisitor visitMethod(int access, String name, String desc, String signature, String[] exceptions) {
if (DEFAULT_CONSTRUCTOR_SIGNATURE.equals(name + desc)) {
defaultConstructor = true;
}
return super.visitMethod(access, name, desc, signature, exceptions);
}
public boolean isDefaultConstructor() {
return defaultConstructor;
}
}
private static class JmspyClassFileTransformer implements ClassFileTransformer {
//no transform is performed
private static final byte[] NO_TRANSFORM = null;
private Set instrumentedPackages = Collections.emptySet();
private Set instrumentedClasses = Collections.emptySet();
private JmspyClassFileTransformer(JmspyAgentConfig agentConfig) {
instrumentedClasses = agentConfig.getInstrumentedClasses();
instrumentedPackages = agentConfig.getInstrumentedPackages();
}
private boolean isInstrumented(String className) {
// if no arrgs were passed to agent then all classes must be instrumented
if (instrumentedClasses.isEmpty() && instrumentedPackages.isEmpty()) {
return true;
}
if (instrumentedClasses.contains(className)) {
return true;
}
for (String instrumentedPkg : instrumentedPackages) {
if (className.startsWith(instrumentedPkg)) {
return true;
}
}
return false;
}
@Override
public byte[] transform(ClassLoader classLoader, String className, Class aClass,
ProtectionDomain protectionDomain, byte[] bytes)
throws IllegalClassFormatException {
if (isInstrumented(className)) {
try {
ClassReader classReader = new ClassReader(bytes);
ClassWriter classWriter = new ClassWriter(0);
// read class info
ClassInfoReader classInfoReader = new ClassInfoReader();
classReader.accept(classInfoReader, 0);
if (!classInfoReader.isDefaultConstructor()) {
createDefaultConstructor(classWriter);
}
ClassVisitor classVisitor = new ClassAdapter(classWriter) {
@Override
public void visit(int version, int access, String name, String signature, String superName,
String[] interfaces) {
int removeFinal = access & (~Opcodes.ACC_FINAL);
super.visit(version, removeFinal, name, signature, superName, interfaces);
}
@Override
public MethodVisitor visitMethod(int access, String name, String desc, String signature,
String[] exceptions) {
int removeFinal = access & (~Opcodes.ACC_FINAL);
return super.visitMethod(removeFinal, name, desc, signature, exceptions);
}
};
classReader.accept(classVisitor, 0);
return classWriter.toByteArray();
} catch (Throwable e) {
// do nothing, just log error
LOGGER.error("failed transform class. message: '{}'", e.getMessage());
}
}
return NO_TRANSFORM;
}
}
}