基于JavaAgent的全链路监控二《通过字节码增加监控执行耗时》

itstack-demo-agent-02
├── pom.xml
└── src
    ├── main
    │   ├── java
    │   │   └── org.itstack.demo.agent
    │   │       ├── MyAgent.java
    │   │	    └── MyMonitorTransformer.java
    │	└── resources
    │       └── META-INF
    │           └── MANIFEST.MF 	
    └── test
         └── java
             └── org.itstack.demo.test
                 └── ApiTest.java

/**
 * 博客：http://itstack.org
 * 论坛：http://bugstack.cn
 * 公众号：bugstack虫洞栈  ｛获取学习源码｝
 * create by fuzhengwei on 2019
 */
public class MyAgent {

    //JVM 首先尝试在代理类上调用以下方法
    public static void premain(String agentArgs, Instrumentation inst) {
        System.out.println("this is my agent：" + agentArgs);
        MyMonitorTransformer monitor = new MyMonitorTransformer();
        inst.addTransformer(monitor);
    }

    //如果代理类没有实现上面的方法，那么 JVM 将尝试调用该方法
    public static void premain(String agentArgs) {
    }

}

/**
 * 博客：http://itstack.org
 * 论坛：http://bugstack.cn
 * 公众号：bugstack虫洞栈  ｛获取学习源码｝
 * create by fuzhengwei on 2019
 */
public class MyMonitorTransformer implements ClassFileTransformer {

    private static final Set<String> classNameSet = new HashSet<>();

    static {
        classNameSet.add("org.itstack.demo.test.ApiTest");
    }

    @Override
    public byte[] transform(ClassLoader loader, String className, Class<?> classBeingRedefined, ProtectionDomain protectionDomain, byte[] classfileBuffer) {
        try {
            String currentClassName = className.replaceAll("/", ".");
            if (!classNameSet.contains(currentClassName)) { // 提升classNameSet中含有的类
                return null;
            }
            System.out.println("transform: [" + currentClassName + "]");

            CtClass ctClass = ClassPool.getDefault().get(currentClassName);
            CtBehavior[] methods = ctClass.getDeclaredBehaviors();
            for (CtBehavior method : methods) {
                enhanceMethod(method);
            }
            return ctClass.toBytecode();
        } catch (Exception e) {
            e.printStackTrace();
        }
        
        return null;

    }


    private void enhanceMethod(CtBehavior method) throws Exception {
        if (method.isEmpty()) {
            return;
        }
        String methodName = method.getName();
        if ("main".equalsIgnoreCase(methodName)) {
            return;
        }

        final StringBuilder source = new StringBuilder();
        // 前置增强: 打入时间戳
        // 保留原有的代码处理逻辑
        source.append("{")
                .append("long start = System.nanoTime();\n") //前置增强: 打入时间戳
                .append("$_ = $proceed($$);\n")              //调用原有代码，类似于method();($$)表示所有的参数
                .append("System.out.print(\"method:[")
                .append(methodName).append("]\");").append("\n")
                .append("System.out.println(\" cost:[\" +(System.nanoTime() - start)+ \"ns]\");") // 后置增强，计算输出方法执行耗时
                .append("}");

        ExprEditor editor = new ExprEditor() {
            @Override
            public void edit(MethodCall methodCall) throws CannotCompileException {
                methodCall.replace(source.toString());
            }
        };
        method.instrument(editor);
    }

}

/**
 * 博客：http://itstack.org
 * 论坛：http://bugstack.cn
 * 公众号：bugstack虫洞栈  ｛获取学习源码｝
 * create by fuzhengwei on 2019
 *
 * VM options：
 * -javaagent:E:\itstack\GIT\itstack.org\itstack-demo-agent\itstack-demo-agent-02\target\itstack-demo-agent-02-1.0.0-SNAPSHOT.jar=testargs
 *
 */
public class ApiTest {

    public static void main(String[] args) {
        ApiTest apiTest = new ApiTest();
        apiTest.echoHi();
    }

    private void echoHi(){
        System.out.println("hi agent");
    }

}

this is my agent：testargs
transform: [org.itstack.demo.test.ApiTest]
hi agent
method:[echoHi] cost:[294845ns]