1.概述
上一篇文章：【字节码】javaagent 入门 案例 最简单的案例
转载：https://github.com/fuzhengwei/itstack-demo-bytecode
在第二章中我们已经可以监控方法执行耗时，虽然它能完成我们一些基本需要，但是为了增强代码的扩展性，我们需要使用字节码操作工具ByteBuddy来帮助我们实现更完善的监控程序。
Byte Buddy is a code generation and manipulation library for creating and modifying Java classes during the runtime of a Java application and without the help of a compiler. Other than the code generation utilities that ship with the Java Class Library, Byte Buddy allows the creation of arbitrary classes and is not limited to implementing interfaces for the creation of runtime proxies. Furthermore, Byte Buddy offers a convenient API for changing classes either manually, using a Java agent or during a build.
MethodCostTime
import net.bytebuddy.asm.Advice;
import net.bytebuddy.implementation.bind.annotation.RuntimeType;
import net.bytebuddy.implementation.bind.annotation.SuperCall;
import java.lang.reflect.Method;
import java.util.concurrent.Callable;
public class MethodCostTime {
@RuntimeType
public static Object intercept(@Advice.Origin Method method, @SuperCall Callable<?> callable) throws Exception {
long start = System.currentTimeMillis();
try {
// 原有函数执行
return callable.call();
} finally {
System.out.println(method + " 方法耗时： " + (System.currentTimeMillis() - start) + "ms");
}
}
}
MyPreMainAgent
package com.javaagent.bytebuddy;
import net.bytebuddy.agent.builder.AgentBuilder;
import net.bytebuddy.description.type.TypeDescription;
import net.bytebuddy.dynamic.DynamicType;
import net.bytebuddy.implementation.MethodDelegation;
import net.bytebuddy.matcher.ElementMatchers;
import net.bytebuddy.utility.JavaModule;
import java.lang.instrument.Instrumentation;
public class MyPreMainAgent {
//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);
AgentBuilder.Transformer transformer = ((builder, typeDescription, classLoader, javaModule) -> {
DynamicType.Builder.MethodDefinition.ReceiverTypeDefinition<?> receiverTypeDefinition
= builder.method(ElementMatchers.any())// 拦截任意方法
.intercept(MethodDelegation.to(MethodCostTime.class)); // 委托
return receiverTypeDefinition;
});
AgentBuilder.Listener listener = new AgentBuilder.Listener() {
@Override
public void onDiscovery(String s, ClassLoader classLoader, JavaModule javaModule, boolean b) {
}
@Override
public void onTransformation(TypeDescription typeDescription, ClassLoader classLoader, JavaModule javaModule, boolean b, DynamicType dynamicType) {
}
@Override
public void onIgnored(TypeDescription typeDescription, ClassLoader classLoader, JavaModule javaModule, boolean b) {
}
@Override
public void onError(String s, ClassLoader classLoader, JavaModule javaModule, boolean b, Throwable throwable) {
}
@Override
public void onComplete(String s, ClassLoader classLoader, JavaModule javaModule, boolean b) {
}
};
new AgentBuilder
.Default()
.type(ElementMatchers.nameStartsWith("com.bytebuddy.service.demo4")) // 指定需要拦截的类
.transform(transformer)
.with(listener)
.installOn(inst);
}
//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) {
}
}
MethodCostAgentTest
public class MethodCostAgentTest {
public static void main(String[] args) throws InterruptedException {
MethodCostAgentTest apiTest = new MethodCostAgentTest();
apiTest.echoHi();
}
private void echoHi() throws InterruptedException {
System.out.println("hi agent");
Thread.sleep((long) (Math.random() * 500));
}
}
maven设置如下
<properties>
<asm.version>9.0</asm.version>
<slf4j-api.version>1.7.28</slf4j-api.version>
<byte-buddy.version>1.12.11</byte-buddy.version>
<fastjson.version>1.2.76</fastjson.version>
<lombok.version>1.18.16</lombok.version>
</properties>
<dependencies>
<!-- 日志 相关 -->
<dependency>
<groupId>org.slf4j</groupId>
<artifactId>slf4j-api</artifactId>
<version>${
slf4j-api.version}</version>
</dependency>
<dependency>
<groupId>org.slf4j</groupId>
<artifactId>slf4j-log4j12</artifactId>
<version>${
slf4j-api.version}</version>
</dependency>
<dependency>
<groupId>com.alibaba</groupId>
<artifactId>fastjson</artifactId>
<version>${
fastjson.version}</version>
</dependency>
<dependency>
<groupId>org.projectlombok</groupId>
<artifactId>lombok</artifactId>
<version>${
lombok.version}</version>
</dependency>
<dependency>
<groupId>net.bytebuddy</groupId>
<artifactId>byte-buddy</artifactId>
<version>${
byte-buddy.version}</version>
</dependency>
<dependency>
<groupId>net.bytebuddy</groupId>
<artifactId>byte-buddy-agent</artifactId>
<version>${
byte-buddy.version}</version>
</dependency>
<dependency>
<groupId>com.bytebuddy</groupId>
<artifactId>byte-buddy-commons</artifactId>
<version>1.0-SNAPSHOT</version>
</dependency>
</dependencies>
<build>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
<configuration>
<source>1.8</source>
<target>1.8</target>
<encoding>utf-8</encoding>
</configuration>
</plugin>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-jar-plugin</artifactId>
<configuration>
<archive>
<manifestEntries>
<addClasspath>true</addClasspath>
<Premain-Class>com.javaagent.bytebuddy.MyPreMainAgent</Premain-Class>
<addDefaultImplementationEntries>true</addDefaultImplementationEntries>
<addDefaultSpecificationEntries>true</addDefaultSpecificationEntries>
</manifestEntries>
</archive>
</configuration>
</plugin>
</plugins>
</build>
打包如下
byte-buddy-v1x-javaagent-demo3]$ mvn clean package -DskipTests
设置参数 -javaagent:/Users/lcc/IdeaProjects/lcc_work/test-byte-buddy/byte-buddy-v1x-javaagent-demo3/target/byte-buddy-v1x-javaagent-demo3-1.0-SNAPSHOT.jar=testargs
运行结果如下
this is my agent：testargs
hi agent
private void org.itstack.demo.test.ApiTest.echoHi() throws java.lang.InterruptedException 方法耗时： 329ms
public static void org.itstack.demo.test.ApiTest.main(java.lang.String[]) throws java.lang.InterruptedException 方法耗时： 329ms
Process finished with exit code 0