目标
-
之前的Arthas里的字节码增强，是通过asm来处理的，代码逻辑不好修改，理解困难
-
基于ASM提供更高层的字节码处理能力，面向诊断/APM领域，不是通用的字节码库
-
ByteKit期望能提供一套简洁的API，让开发人员可以比较轻松的完成字节码增强
对比
| 功能 | 函数Enter/Exit注入点 | 绑定数据 | inline | 防止重复增强 | 避免装箱/拆箱开销 | origin调用替换 | @ExceptionHandler |
|---|---|---|---|---|---|---|---|
| ByteKit | @AtEnter @AtExit @AtExceptionExit @AtFieldAccess @AtInvoke@AtInvokeException@AtLine@AtSyncEnter@AtSyncExit@AtThrow |
this/args/return/throw field locals 子调用入参/返回值/子调用异常 line number |
✓ | ✓ | ✓ | ✓ | ✓ |
| ByteBuddy | OnMethodEnter@OnMethodExit@OnMethodExit#onThrowable() |
this/args/return/throw field locals |
✓ | ✗ | ✓ | ✓ | ✓ |
| 传统AOP | EnterExitException |
this/args/return/throw | ✗ | ✗ | ✗ | ✗ | ✗ |
特性
1. 丰富的注入点支持
@AtEnter 函数入口 @AtExit 函数退出 @AtExceptionExit 函数抛出异常 @AtFieldAccess 访问field @AtInvoke 在method里的子函数调用 @AtInvokeException 在method里的子函数调用抛出异常 @AtLine 在指定行号 @AtSyncEnter 进入同步块，比如synchronized块 @AtSyncExit 退出同步块 @AtThrow 代码里显式throw异常点
2. 动态的Binding
@Binding.This this对象
@Binding.Class Class对象
@Binding.Method 函数调用的 Method 对象
@Binding.MethodName 函数的名字
@Binding.MethodDesc 函数的desc
@Binding.Return 函数调用的返回值
@Binding.Throwable 函数里抛出的异常
@Binding.Args 函数调用的入参
@Binding.ArgNames 函数调用的入参的名字
@Binding.LocalVars 局部变量
@Binding.LocalVarNames 局部变量的名字
@Binding.Field field对象属性字段
@Binding.InvokeArgs method里的子函数调用的入参
@Binding.InvokeReturn method里的子函数调用的返回值
@Binding.InvokeMethodName method里的子函数调用的名字
@Binding.InvokeMethodOwner method里的子函数调用的类名
@Binding.InvokeMethodDeclaration method里的子函数调用的desc
@Binding.Line 行号
@Binding.Monitor 同步块里监控的对象
3. 可编程的异常处理
@ExceptionHandler 在插入的增强代码，可以用try/catch块包围起来
4. inline支持
增强的代码 和 异常处理代码都可以通过 inline技术内联到原来的类里，达到最理想的增强效果。
5. invokeOrigin 技术
通常，我们要增强一个类，就想要办法在函数前后插入一个static的回调函数，但这样子局限太大。
那么有没有更灵活的方式呢？
比如有一个 hello() 函数：
public String hello(String str) {
return "hello " + str;
}
我们想对它做增强，那么可以编写下面的代码：
public String hello(String str) {
System.out.println("before");
Object value = InstrumentApi.invokeOrigin();
System.out.println("after, result: " + value);
return object;
}
增强后的结果是：
public String hello(String str) {
System.out.println("before");
Object value = "hello " + str;
System.out.println("after, result: " + value);
return object;
}
这种方式可以随意插入代码，非常灵活。
参考增强Dubbo Filter的示例：
package com.alibaba.bytekit.asm.inst;
import org.apache.dubbo.rpc.Invocation;
import org.apache.dubbo.rpc.Invoker;
import org.apache.dubbo.rpc.Result;
import org.apache.dubbo.rpc.RpcException;
import com.alibaba.bytekit.agent.inst.Instrument;
import com.alibaba.bytekit.agent.inst.InstrumentApi;
/**
* @see org.apache.dubbo.rpc.Filter
* @author hengyunabc 2020-11-26
*
*/
@Instrument(Interface = "org.apache.dubbo.rpc.Filter")
public abstract class DubboFilter_APM {
public Result invoke(Invoker<?> invoker, Invocation invocation) throws RpcException {
DubboUtils.print(invoker);
System.err.println("invoker class: " + this.getClass().getName());
Result result = InstrumentApi.invokeOrigin();
return result;
}
}
示例
以ByteKitDemo.java为例说明。
package com.example;
import java.util.List;
import java.util.concurrent.TimeUnit;
import com.alibaba.deps.org.objectweb.asm.tree.ClassNode;
import com.alibaba.deps.org.objectweb.asm.tree.MethodNode;
import com.alibaba.bytekit.asm.MethodProcessor;
import com.alibaba.bytekit.asm.binding.Binding;
import com.alibaba.bytekit.asm.interceptor.InterceptorProcessor;
import com.alibaba.bytekit.asm.interceptor.annotation.AtEnter;
import com.alibaba.bytekit.asm.interceptor.annotation.AtExceptionExit;
import com.alibaba.bytekit.asm.interceptor.annotation.AtExit;
import com.alibaba.bytekit.asm.interceptor.annotation.ExceptionHandler;
import com.alibaba.bytekit.asm.interceptor.parser.DefaultInterceptorClassParser;
import com.alibaba.bytekit.utils.AgentUtils;
import com.alibaba.bytekit.utils.AsmUtils;
import com.alibaba.bytekit.utils.Decompiler;
/**
*
* @author hengyunabc 2020-05-21
*
*/
public class ByteKitDemo {
public static class Sample {
private int exceptionCount = 0;
public String hello(String str, boolean exception) {
if (exception) {
exceptionCount++;
throw new RuntimeException("test exception, str: " + str);
}
return "hello " + str;
}
}
public static class PrintExceptionSuppressHandler {
@ExceptionHandler(inline = true)
public static void onSuppress(@Binding.Throwable Throwable e, @Binding.Class Object clazz) {
System.out.println("exception handler: " + clazz);
e.printStackTrace();
}
}
public static class SampleInterceptor {
@AtEnter(inline = true, suppress = RuntimeException.class, suppressHandler = PrintExceptionSuppressHandler.class)
public static void atEnter(@Binding.This Object object,
@Binding.Class Object clazz,
@Binding.Args Object[] args,
@Binding.MethodName String methodName,
@Binding.MethodDesc String methodDesc) {
System.out.println("atEnter, args[0]: " + args[0]);
}
@AtExit(inline = true)
public static void atExit(@Binding.Return Object returnObject) {
System.out.println("atExit, returnObject: " + returnObject);
}
@AtExceptionExit(inline = true, onException = RuntimeException.class)
public static void atExceptionExit(@Binding.Throwable RuntimeException ex,
@Binding.Field(name = "exceptionCount") int exceptionCount) {
System.out.println("atExceptionExit, ex: " + ex.getMessage() + ", field exceptionCount: " + exceptionCount);
}
}
public static void main(String[] args) throws Exception {
AgentUtils.install();
// 启动Sample，不断执行
final Sample sample = new Sample();
Thread t = new Thread(new Runnable() {
@Override
public void run() {
for (int i = 0; i < 100; ++i) {
try {
TimeUnit.SECONDS.sleep(3);
String result = sample.hello("" + i, (i % 3) == 0);
System.out.println("call hello result: " + result);
} catch (Throwable e) {
// ignore
System.out.println("call hello exception: " + e.getMessage());
}
}
}
});
t.start();
// 解析定义的 Interceptor类 和相关的注解
DefaultInterceptorClassParser interceptorClassParser = new DefaultInterceptorClassParser();
List<InterceptorProcessor> processors = interceptorClassParser.parse(SampleInterceptor.class);
// 加载字节码
ClassNode classNode = AsmUtils.loadClass(Sample.class);
// 对加载到的字节码做增强处理
for (MethodNode methodNode : classNode.methods) {
if (methodNode.name.equals("hello")) {
MethodProcessor methodProcessor = new MethodProcessor(classNode, methodNode);
for (InterceptorProcessor interceptor : processors) {
interceptor.process(methodProcessor);
}
}
}
// 获取增强后的字节码
byte[] bytes = AsmUtils.toBytes(classNode);
// 查看反编译结果
System.out.println(Decompiler.decompile(bytes));
// 等待，查看未增强里的输出结果
TimeUnit.SECONDS.sleep(10);
// 通过 reTransform 增强类
AgentUtils.reTransform(Sample.class, bytes);
System.in.read();
}
}
1. 定义注入点和Binding数据
-
在下面的 SampleInterceptor 时定义了要注入 @AtEnter/@AtExit/@AtExceptionExit 三个地方，
-
用@Binding绑定了不同的数据
-
在@AtEnter里配置了 inline = true，则说明插入的SampleInterceptor#atEnter函数本身会被inline掉
-
配置了 suppress = RuntimeException.class 和 suppressHandler = PrintExceptionSuppressHandler.class，说明插入的代码会被 try/catch 包围
public static class SampleInterceptor {
@AtEnter(inline = true, suppress = RuntimeException.class, suppressHandler = PrintExceptionSuppressHandler.class)
public static void atEnter(@Binding.This Object object,
@Binding.Class Object clazz,
@Binding.Args Object[] args,
@Binding.MethodName String methodName,
@Binding.MethodDesc String methodDesc) {
System.out.println("atEnter, args[0]: " + args[0]);
}
@AtExit(inline = true)
public static void atExit(@Binding.Return Object returnObject) {
System.out.println("atExit, returnObject: " + returnObject);
}
@AtExceptionExit(inline = true, onException = RuntimeException.class)
public static void atExceptionExit(@Binding.Throwable RuntimeException ex,
@Binding.Field(name = "exceptionCount") int exceptionCount) {
System.out.println("atExceptionExit, ex: " + ex.getMessage() + ", field exceptionCount: " + exceptionCount);
}
}
2. @ExceptionHandler
在上面的 @AtEnter配置里，生成的代码会被 try/catch 包围，那么具体的内容是在PrintExceptionSuppressHandler里
public static class PrintExceptionSuppressHandler {
@ExceptionHandler(inline = true)
public static void onSuppress(@Binding.Throwable Throwable e, @Binding.Class Object clazz) {
System.out.println("exception handler: " + clazz);
e.printStackTrace();
}
}
3. 查看反编译结果
原始的Sample类是：
public static class Sample {
private int exceptionCount = 0;
public String hello(String str, boolean exception) {
if (exception) {
exceptionCount++;
throw new RuntimeException("test exception, str: " + str);
}
return "hello " + str;
}
}
增强后的字节码，再反编译：
package com.example;
public static class ByteKitDemo.Sample {
private int exceptionCount = 0;
public String hello(String string, boolean bl) {
try {
String string2 = "(Ljava/lang/String;Z)Ljava/lang/String;";
String string3 = "hello";
Object[] arrobject = new Object[]{string, new Boolean(bl)};
Class<ByteKitDemo.Sample> class_ = ByteKitDemo.Sample.class;
ByteKitDemo.Sample sample = this;
System.out.println("atEnter, args[0]: " + arrobject[0]);
}
catch (RuntimeException runtimeException) {
Class<ByteKitDemo.Sample> class_ = ByteKitDemo.Sample.class;
RuntimeException runtimeException2 = runtimeException;
System.out.println("exception handler: " + class_);
runtimeException2.printStackTrace();
}
try {
String string4;
void str;
void exception;
if (exception != false) {
++this.exceptionCount;
throw new RuntimeException("test exception, str: " + (String)str);
}
String string5 = string4 = "hello " + (String)str;
System.out.println("atExit, returnObject: " + string5);
return string4;
}
catch (RuntimeException runtimeException) {
int n = this.exceptionCount;
RuntimeException runtimeException3 = runtimeException;
System.out.println("atExceptionExit, ex: " + runtimeException3.getMessage() + ", field exceptionCount: " + n);
throw runtimeException;
}
}
}
开发相关
deploy到远程仓库：
mvn clean deploy -DskipTests -P release
参考资料
https://github.com/alibaba/bytekit
