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https://github.com/alibaba/bytekit
Java Bytecode Kit
https://github.com/alibaba/bytekit
Last synced: about 2 months ago
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Java Bytecode Kit
- Host: GitHub
- URL: https://github.com/alibaba/bytekit
- Owner: alibaba
- License: apache-2.0
- Created: 2020-10-21T03:20:13.000Z (about 4 years ago)
- Default Branch: master
- Last Pushed: 2024-09-12T16:35:31.000Z (3 months ago)
- Last Synced: 2024-09-13T05:37:57.356Z (3 months ago)
- Language: Java
- Size: 264 KB
- Stars: 465
- Watchers: 16
- Forks: 107
- Open Issues: 17
-
Metadata Files:
- Readme: README.md
- License: LICENSE.txt
Awesome Lists containing this project
- awesome - alibaba/bytekit - Java Bytecode Kit (Java)
README
## ByteKit
[](https://search.maven.org/search?q=g:com.alibaba%20AND%20a:bytekit*)
[](http://isitmaintained.com/project/alibaba/bytekit "Average time to resolve an issue")
[](http://isitmaintained.com/project/alibaba/bytekit "Percentage of issues still open")
bytecode kit for java.
## 目标
1. 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
1. 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
1. 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 | `Enter`
`Exit`
`Exception` |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：
```java
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：
```java
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：
```java
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： [[查看源文件](bytekit-core/src/test/java/com/alibaba/bytekit/asm/inst/DubboFilter_APM.java)]
## 示例
以`ByteKitDemo.java`为例说明，[[查看源文件](bytekit-core/src/test/java/com/example/ByteKitDemo.java)]。
### 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
```java
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
```java
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：
```java
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：
```java
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 class_ = ByteKitDemo.Sample.class;
ByteKitDemo.Sample sample = this;
System.out.println("atEnter, args[0]: " + arrobject[0]);
}
catch (RuntimeException runtimeException) {
Class 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：
```bash
mvn clean deploy -DskipTests -P release
```
## License
Apache License V2