Agent agentmain+ASM记录方法运行时参数信息
agentmain提供了运行时修改指定进程中字节码的能力，配合ASM框架，达到随时修改字节码的效果。
agentmain方法：
public static void agentmain(String agentArgs, Instrumentation inst){
System.out.println("Agent Main called");
inst.addTransformer(new TimeTransformer(),true);
inst.addTransformer(new LogTransformer(),true);
Class[] cs =inst.getAllLoadedClasses();
if (cs!=null){
for (Class c: cs) {
if (c.isInterface() ||c.isAnnotation() ||c.isArray() ||c.isEnum()){
continue;
}
if (c.getName().contains(paths)) {
try {
System.out.println(c.getName());
inst.retransformClasses(c);
} catch (UnmodifiableClassException e) {
System.err.println(c.getName());
e.printStackTrace();
}
}
}
}
}
启动方法，用于连接指定进程，Main是这里测试目标的进程名，如果是tomcat项目，那么名字可能是Bootstrap，具体名字使用jps工具查看。
public static void main( String[] args ) throws IOException, AttachNotSupportedException, AgentLoadException, AgentInitializationException {
List list = VirtualMachine.list();
for (VirtualMachineDescriptor vmd : list) {
if (vmd.displayName().endsWith("Main")) {
VirtualMachine virtualMachine = VirtualMachine.attach(vmd.id());
virtualMachine.loadAgent("D:\\项目\\bytecode\\target\\bytecode-1.0-SNAPSHOT.jar");
System.out.println("ok");
virtualMachine.detach();
}
}
}
转换器LogTransformer ：
public class LogTransformer implements ClassFileTransformer {
@Override
public byte[] transform(ClassLoader loader, String className, Class classBeingRedefined, ProtectionDomain protectionDomain, byte[] classfileBuffer) throws IllegalClassFormatException {
LogAdapter logAdapter=new LogAdapter();
return logAdapter.addLog(classfileBuffer);
}
}
实际作用类：
这里使用asm的treeApi修改类。参数信息直接打印在控制台的，事实上，可以把它输出到任意位置。
package com.runtime.bytecode.adapter;
import com.runtime.bytecode.UdAgent;
import org.objectweb.asm.ClassReader;
import org.objectweb.asm.ClassWriter;
import org.objectweb.asm.Opcodes;
import org.objectweb.asm.tree.*;
import static java.lang.System.out;
/**
* Created by lenovo on 2018/11/20.
*/
public class LogAdapter implements Opcodes {
public static boolean debug=false;
public byte[] addLog(byte[] sourceCodes) {
ClassReader cr = new ClassReader(sourceCodes);
ClassNode cn = new ClassNode();
cr.accept(cn, ClassReader.EXPAND_FRAMES);
int access = cn.access;
if (debug)
out.println(cn.name);
if ((access & ACC_INTERFACE) == 0 && cn.name.replace('/','.').contains(UdAgent.paths)) {//不处理接口
if (debug)
out.println(cn.name+"-进入if条件，即将处理methods对象");
//不修改接口
cn.methods.forEach(mn -> {
if ((mn.access & ACC_ABSTRACT) == 0 && !mn.name.equals("") && !mn.name.equals("")) {
//不修改抽象方法,静态初始化方法或者无参构造方法
if (mn.instructions != null && mn.instructions.size() > 0) {
if (debug){
out.println("方法"+mn.name+"指令数为："+mn.instructions.size());
}
String methodDescriptor = mn.desc;//方法描述符
boolean isStaticMethod = (mn.access & ACC_STATIC) != 0;
//方法本身有指令。不修改空方法
AbstractInsnNode insnNode = mn.instructions.getFirst();
int argumentsSize=0;
//methodnodes尚未发现新增局部变量的方法，因为新增局部变量需要遍历修改后续所有的字节码指令
while (insnNode != null) {
int opcode = insnNode.getOpcode();
if ((opcode >= IRETURN && opcode <= RETURN) || opcode == ATHROW) {
InsnList insnList = new InsnList();
insnList.add(new FieldInsnNode(GETSTATIC, "java/lang/System", "out", "Ljava/io/PrintStream;"));
insnList.add(new TypeInsnNode(NEW, "java/lang/StringBuilder"));
insnList.add(new InsnNode(DUP));
insnList.add(new MethodInsnNode(INVOKESPECIAL, "java/lang/StringBuilder", "", "()V", false));
int currentOffset = 1;
int currentSlot = 1;
if (isStaticMethod) {
currentSlot = 0;//静态方法没有this
}
char currentChar;
for (currentChar = methodDescriptor.charAt(currentOffset); currentChar != 41; currentChar = methodDescriptor.charAt(currentOffset)) {
//判断当前参数是什么类型
switch (currentChar) {
case 68:
insnList.add(new VarInsnNode(DLOAD, currentSlot));
insnList.add(new MethodInsnNode(INVOKEVIRTUAL, "java/lang/StringBuilder", "append", "(D)Ljava/lang/StringBuilder;", false));
currentSlot += 2;
currentOffset+=1;
break;
case 74:
insnList.add(new VarInsnNode(LLOAD, currentSlot));
insnList.add(new MethodInsnNode(INVOKEVIRTUAL, "java/lang/StringBuilder", "append", "(J)Ljava/lang/StringBuilder;", false));
currentSlot += 2;
currentOffset+=1;
break;
case 91://数组类型
case 76://引用类型
while (methodDescriptor.charAt(currentOffset) == 91) {
++currentOffset;
}
if(methodDescriptor.charAt(currentOffset++) == 76) {//以L开头
while(methodDescriptor.charAt(currentOffset++) != 59) {
}
}
insnList.add(new VarInsnNode(ALOAD, currentSlot));
insnList.add(new MethodInsnNode(INVOKEVIRTUAL, "java/lang/Object", "toString", "()Ljava/lang/String;", false));
insnList.add(new MethodInsnNode(INVOKEVIRTUAL, "java/lang/StringBuilder", "append", "(Ljava/lang/String;)Ljava/lang/StringBuilder;", false));
currentSlot+=1;
break;
case 65:
case 66:
case 73:
insnList.add(new VarInsnNode(ILOAD, currentSlot));
insnList.add(new MethodInsnNode(INVOKEVIRTUAL, "java/lang/StringBuilder", "append", "(I)Ljava/lang/StringBuilder;", false));
currentSlot+=1;
currentOffset+=1;
break;
case 70:
insnList.add(new VarInsnNode(FLOAD, currentSlot));
insnList.add(new MethodInsnNode(INVOKEVIRTUAL, "java/lang/StringBuilder", "append", "(F)Ljava/lang/StringBuilder;", false));
currentSlot+=1;
currentOffset+=1;
break;
}
++argumentsSize;
insnList.add(new LdcInsnNode(" | "));
insnList.add(new MethodInsnNode(INVOKEVIRTUAL, "java/lang/StringBuilder", "append", "(Ljava/lang/String;)Ljava/lang/StringBuilder;", false));
}
insnList.add(new MethodInsnNode(INVOKEVIRTUAL, "java/lang/StringBuilder", "toString", "()Ljava/lang/String;", false));
insnList.add(new MethodInsnNode(INVOKEVIRTUAL, "java/io/PrintStream", "println", "(Ljava/lang/String;)V", false));
if (argumentsSize>0) {
mn.instructions.insertBefore(insnNode, insnList);
}
if (debug){
out.println("方法"+mn.name+"指令数为："+mn.instructions.size()+"，成功添加指令");
}
}
insnNode=insnNode.getNext();
}
if (argumentsSize>0)
mn.maxStack+=4;
}
}
});
}
ClassWriter cw = new ClassWriter(ClassWriter.COMPUTE_MAXS);
cn.accept(cw);
return cw.toByteArray();
}
}