Basic-Javaagent

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man java

 -javaagent:jarpath[=options]

Loads the specified Java programming language agent. For more information about instrumenting Java applications, see the java.lang.instrument package description in the Java API documentation at http://docs.oracle.com/javase/8/docs/api/java/lang/instrument/package-summary.html
文档说明部分介绍了基本概念

Provides services that allow Java programming language agents to instrument programs running on the JVM.

四步快速入门：

  1. Implement a static premain (as an analogy to main) method, like this:
import java.lang.instrument.Instrumentation;
class Example {
    public static void premain(String args, Instrumentation inst) {
        ...
    }
}
  1. Create a manifest file (say, manifest.txt) marking this class for pre-main execution. Its contents are:
Premain-Class: Example
  1. Compile the class and package this class into a JAR archive:
javac Example.java
jar cmf manifest.txt yourAwesomeAgent.jar *.class
  1. Execute your JVM with -javaagent parameter, like this:
java -javaagent:yourAwesomeAgent.jar -jar yourApp.jar

Guide to Java Instrumentation 这个baeldung.com站点的google搜索权重很高，一般的Java相关的各种Guide都可以在这里看到。

编译完执行java -javaagent:core-java-jvm.jar -jar core-java-jvm.jar StartMyAtmApplication 15000 2 3出来下面的log表示上面的文章实现了Java Instrumentation的效果。

E:\>java -javaagent:core-java-jvm.jar -jar core-java-jvm.jar StartMyAtmApplication 15000 2 3
17:48:09.109 [main] INFO com.baeldung.instrumentation.agent.MyInstrumentationAgent - [Agent] In premain method
17:48:09.113 [main] INFO com.baeldung.instrumentation.agent.AtmTransformer - [Agent] Transforming class MyAtm
StartMyAtmApplication
17:48:09.212 [main] INFO com.baeldung.instrumentation.application.MyAtmApplication - [Application] Starting ATM application
17:48:11.213 [main] INFO com.baeldung.instrumentation.application.MyAtm - [Application] Successful Withdrawal of [2] units!
17:48:11.219 [main] INFO com.baeldung.instrumentation.application.MyAtm - [Application] Withdrawal operation completed in:2 seconds!
17:48:28.221 [main] INFO com.baeldung.instrumentation.application.MyAtm - [Application] Successful Withdrawal of [3] units!
17:48:28.221 [main] INFO com.baeldung.instrumentation.application.MyAtm - [Application] Withdrawal operation completed in:2 seconds!

https://www.jacoco.org/jacoco/ https://github.com/jacoco/jacoco
测acoco 插桩的不同形式总结和踩坑记录

 
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