java agent开发
java agent介绍
java agent是jvm插件或者叫做代理，她是运行在main方法之前，她内定的方法名称叫premain。
java agent 概述
接下来我们进行开发
实现premain方法
package org.xxz; public class AgentMain { public static void premain(String args, Instrumentation inst) { System.out.println('hello java agent'); } }上面的这段代码就完成了java agent的第一步了
打包
这里我们使用maven的方式进行打包，请看下面的配置文件
<build> <finalName>java-agentfinalName> <plugins> <plugin> <groupId>org.apache.maven.pluginsgroupId> <artifactId>maven-compiler-pluginartifactId> <configuration> <source>1.8source> <target>1.8target> <encoding>utf-8encoding> configuration> plugin> <plugin> <groupId>org.apache.maven.pluginsgroupId> <artifactId>maven-assembly-pluginartifactId> <version>3.0.0version> <configuration> <archive> <manifest> <addClasspath>trueaddClasspath> manifest> <manifestEntries> <Premain-Class>org.xxz.AgentMainPremain-Class> manifestEntries> archive> <descriptorRefs> <descriptorRef>jar-with-dependenciesdescriptorRef> descriptorRefs> configuration> <executions> <execution> <id>make-assemblyid> <phase>packagephase> <goals> <goal>singlegoal> goals> execution> executions> plugin> plugins> build>使用java agent
新建一个maven工程，打包然后运行
java -jar demo.jar -javaagent:/apps/java-agent.jar执行上面的运行命令后，在我们控制台输出时就会看到hello java agent的字样哦！！！
看到这里就结束了吗？没有哦，我们来看一个小例子。。。。。。。
新建maven工程
java-agent
--src
--main
--java
--org.xxz
--AgentMain.java
--TimeInterceptor.java
--TraceTime.java
--resource
--test
--pom.xml首先看看我们的pom.xml是如何配置的
<project xmlns="http://maven.apache.org/POM/4.0.0"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0modelVersion>
<groupId>org.xxzgroupId>
<artifactId>java-agentartifactId>
<version>1.0version>
<properties>
<bytebuddy.version>1.8.0bytebuddy.version>
<slf4j.version>1.7.25slf4j.version>
properties>
<dependencies>
<dependency>
<groupId>net.bytebuddygroupId>
<artifactId>byte-buddyartifactId>
<version>${bytebuddy.version}version>
dependency>
<dependency>
<groupId>org.slf4jgroupId>
<artifactId>slf4j-apiartifactId>
<version>${slf4j.version}version>
dependency>
dependencies>
<build>
<plugins>
<plugin>
<groupId>org.apache.maven.pluginsgroupId>
<artifactId>maven-compiler-pluginartifactId>
<configuration>
<source>1.8source>
<target>1.8target>
<encoding>utf-8encoding>
configuration>
plugin>
<plugin>
<groupId>org.apache.maven.pluginsgroupId>
<artifactId>maven-assembly-pluginartifactId>
<version>3.0.0version>
<configuration>
<archive>
<manifest>
<addClasspath>trueaddClasspath>
manifest>
<manifestEntries>
<Premain-Class>org.xxz.AgentMainPremain-Class>
manifestEntries>
archive>
<descriptorRefs>
<descriptorRef>jar-with-dependenciesdescriptorRef>
descriptorRefs>
configuration>
<executions>
<execution>
<id>make-assemblyid>
<phase>packagephase>
<goals>
<goal>singlegoal>
goals>
execution>
executions>
plugin>
plugins>
build>
project>这里我们使用了bytebuddy，不懂得看官可以上官方网站瞧瞧http://bytebuddy.net/
再来看看我们得AgentMain.java
package org.xxz;
import net.bytebuddy.agent.builder.AgentBuilder;
import net.bytebuddy.description.method.MethodDescription;
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;
/**
* @author tt
*/
public class AgentMain {
public static void premain(String args, Instrumentation inst) {
AgentBuilder.Transformer transformer = new AgentBuilder.Transformer() {
@Override
public DynamicType.Builder transform(DynamicType.Builder builder,
TypeDescription typeDescription,
ClassLoader classLoader,
JavaModule javaModule) {
return builder
.method(ElementMatchers.any()) // 拦截任意方法
.intercept(MethodDelegation.to(TimeInterceptor.class)); // 委托
}
};
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("org.xxz"))// 指定需要拦截的类
.transform(transformer)
.with(listener)
.installOn(inst);
}
}这里我们看看我们得TimeInterceptor.java
package org.xxz;
import net.bytebuddy.implementation.bind.annotation.Origin;
import net.bytebuddy.implementation.bind.annotation.RuntimeType;
import net.bytebuddy.implementation.bind.annotation.SuperCall;
import java.lang.reflect.Method;
import java.util.concurrent.Callable;
/**
* @author tt
*/
public class TimeInterceptor {
@RuntimeType
public static Object interceptor(@Origin Class clazz,
@Origin Method method,
@SuperCall Callable callable) throws Exception {
TraceTime traceTime = method.getAnnotation(TraceTime.class);
if (traceTime == null) {
return callable.call();
}
long start = System.currentTimeMillis();
try {
// 原有函数执行
return callable.call();
} finally {
System.out.println(clazz.getSimpleName() + "#" + method.getName() + " cost " + (System.currentTimeMillis() - start) + "ms");
}
}
}最后就是我们得注解了TraceTime.java
package org.xxz;
import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
/**
* @author tt
*/
@Target(ElementType.METHOD)
@Retention(RetentionPolicy.RUNTIME)
public @interface TraceTime {
}
到这里我们得java-agent就开发完成了。。。。。是不是很简单啊。。。。
接下来，我们看看使用方式咯。。。。。
java-agent-test
--src
--main
--java
--org.xxz
--test
--AgentMainTest.java
--Demo.java
--TraceTime.java
--resource
--test
--pom.xml依旧先看我们得pom文件
"1.0" encoding="UTF-8"?>
"http://maven.apache.org/POM/4.0.0"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
4.0.0
org.xxz
java-agent-test
1.0
org.apache.maven.plugins
maven-compiler-plugin
1.8
1.8
utf-8
这里的pom文件上面的简单多了。
看看我们的测试类AgentMainTest.java
package org.xxz.test;
/**
* @author tt
*/
public class AgentMainTest {
public static void main(String[] args) throws Exception {
Demo demo = new Demo();
demo.print("agent");
}
}看看我们的Demo.java
package org.xxz.test;
import org.xxz.TraceTime;
/**
* @author tt
*/
public class Demo {
@TraceTime
public void print(String string) throws InterruptedException {
Thread.sleep(100L);
System.out.println("hello " + string);
}
}这里还少了一个TraceTime.java，把上面的拷贝过来哦。。。。注意包的结构要一样哦。。。。。
上面介绍了如何命令行使用java-agent.jar，这里我们介绍如何再IDE中使用，要上图了哦。。。。。
好了，今天的文章到这里就结束了。。。
最后还来一张运行结果吧。。。。
原文地址：https://blog.uyiplus.com/2018/java-agent-01/