java agent開發(fā)

java agent介紹

java agent是jvm插件或者叫做代理吮蛹，她是運行在main方法之前豁生，她內(nèi)定的方法名稱叫premain。

java agent 概述

https://ws1.sinaimg.cn/large/afc434bdly1fplw4dc0lzj20j70ch74u.jpg

接下來我們進(jìn)行開發(fā)

實現(xiàn)premain方法

package org.xxz;

public class AgentMain {
  public static void premain(String args, Instrumentation inst) {
    System.out.println('hello java agent');
  }
}

上面的這段代碼就完成了java agent的第一步了

打包

這里我們使用maven的方式進(jìn)行打包肖粮，請看下面的配置文件

<build>
        <finalName>java-agent</finalName>
        <plugins>
         <plugin>
             <groupId>org.apache.maven.plugins</groupId>
             <artifactId>maven-compiler-plugin</artifactId>
             <version>3.8.1</version>
             <configuration>
                 <source>${maven.compiler.source}</source>
                 <target>${maven.compiler.target}</target>
                 <encoding>utf-8</encoding>
             </configuration>
         </plugin>
         <plugin>
             <groupId>org.apache.maven.plugins</groupId>
             <artifactId>maven-assembly-plugin</artifactId>
             <version>3.0.0</version>
             <configuration>
                 <archive>
                     <manifest>
                         <addDefaultImplementationEntries>true</addDefaultImplementationEntries>
                         <addDefaultSpecificationEntries>true</addDefaultSpecificationEntries>
                     </manifest>
                     <manifestEntries>
                         <Premain-Class>org.xxz.AgentMain</Premain-Class>
                         <Can-Redefine-Classes>true</Can-Redefine-Classes>
                         <Can-Retransform-Classes>true</Can-Retransform-Classes>
                     </manifestEntries>
                 </archive>
                 <descriptorRefs>
                     <descriptorRef>jar-with-dependencies</descriptorRef>
                 </descriptorRefs>
             </configuration>
             <executions>
                 <execution>
                     <id>make-assembly</id>
                     <phase>package</phase>
                     <goals>
                         <goal>single</goal>
                     </goals>
                 </execution>
             </executions>
         </plugin>
     </plugins>
    </build>

使用java agent

新建一個maven工程砂蔽，打包然后運行
```
java -jar demo.jar -javaagent:/apps/java-agent.jar
```
執(zhí)行上面的運行命令后，在我們控制臺輸出時就會看到hello java agent的字樣哦Ａ髀搿Ｓ止佟！

看到這里就結(jié)束了嗎漫试？沒有哦六敬，我們來看一個小例子。驾荣。外构。。秘车。典勇。。

新建maven工程

java-agent
--src
    --main
        --java
            --org.xxz
                --AgentMain.java
                --TimeInterceptor.java
                --TraceTime.java
        --resource
    --test
--pom.xml

首先看看我們的pom.xml是如何配置的

<?xml version="1.0" encoding="UTF-8"?>
<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>4.0.0</modelVersion>

    <groupId>org.xxz</groupId>
    <artifactId>java-agent</artifactId>
    <version>1.0</version>

    <properties>
        <bytebuddy.version>1.8.0</bytebuddy.version>
        <slf4j.version>1.7.25</slf4j.version>
    </properties>

    <dependencies>
        <dependency>
            <groupId>net.bytebuddy</groupId>
            <artifactId>byte-buddy</artifactId>
            <version>${bytebuddy.version}</version>
        </dependency>
        <dependency>
            <groupId>org.slf4j</groupId>
            <artifactId>slf4j-api</artifactId>
            <version>${slf4j.version}</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-assembly-plugin</artifactId>
                <version>3.0.0</version>
                <configuration>
                    <archive>
                        <manifest>
                            <addClasspath>true</addClasspath>
                        </manifest>
                        <manifestEntries>
                            <Premain-Class>org.xxz.AgentMain</Premain-Class>
                        </manifestEntries>
                    </archive>
                    <descriptorRefs>
                        <descriptorRef>jar-with-dependencies</descriptorRef>
                    </descriptorRefs>
                </configuration>
                <executions>
                    <execution>
                        <id>make-assembly</id>
                        <phase>package</phase>
                        <goals>
                            <goal>single</goal>
                        </goals>
                    </execution>
                </executions>
            </plugin>
        </plugins>
    </build>
</project>

這里我們使用了bytebuddy叮趴，不懂得看官可以上官方網(wǎng)站瞧瞧http://bytebuddy.net/

再來看看我們得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()) // 攔截任意方法
                        .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"))// 指定需要攔截的類
                .transform(transformer)
                .with(listener)
                .installOn(inst);

    }

}

這里我們看看我們得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,
                                     @This Object target,
                                     @Origin Method method,
                                     @AllArguments Object[] args,
                                     @Super Object delegate,
                                     @SuperCall Callable<?> callable) throws Exception {

        TraceTime traceTime = method.getAnnotation(TraceTime.class);

        if (traceTime == null) {
            return callable.call();
        }

        long start = System.currentTimeMillis();
        try {
            // 原有函數(shù)執(zhí)行
            return callable.call();
        } finally {
            System.out.println(clazz.getSimpleName() + "#" + method.getName() + " cost " + (System.currentTimeMillis() - start) + "ms");
        }
    }

}

最后就是我們得注解了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 {
}

到這里我們得java-agent就開發(fā)完成了割笙。。。伤溉。般码。是不是很簡單啊。乱顾。板祝。。

接下來走净，我們看看使用方式咯券时。。伏伯。橘洞。。

java-agent-test
--src
    --main
        --java
            --org.xxz
                --test
                    --AgentMainTest.java
                    --Demo.java
                --TraceTime.java
        --resource
    --test
--pom.xml

依舊先看我們得pom文件

<?xml version="1.0" encoding="UTF-8"?>
<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>4.0.0</modelVersion>

    <groupId>org.xxz</groupId>
    <artifactId>java-agent-test</artifactId>
    <version>1.0</version>

    <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>
        </plugins>
    </build>
</project>

這里的pom文件上面的簡單多了说搅。

看看我們的測試類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");
    }
}

看看我們的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);
    }
}

這里還少了一個TraceTime.java炸枣，把上面的拷貝過來哦。弄唧。适肠。。注意包的結(jié)構(gòu)要一樣哦候引。侯养。。背伴。沸毁。

上面介紹了如何命令行使用java-agent.jar，這里我們介紹如何再IDE中使用傻寂，要上圖了哦。携兵。疾掰。。徐紧。

image

好了静檬，今天的文章到這里就結(jié)束了。并级。拂檩。

最后還來一張運行結(jié)果吧。嘲碧。稻励。。

image

原文地址：https://blog.uyiplus.com/2018/java-agent-01/