Fake time java agent

FtmAgent.java

package com.zyh.ftmagent;

import java.lang.instrument.Instrumentation;
import java.lang.instrument.UnmodifiableClassException;

public class FtmAgent {
	public static void premain(String agentArgs, Instrumentation inst)
			throws ClassNotFoundException, UnmodifiableClassException{
			inst.addTransformer(new TimeTransformer());
		}
}

MANIFEST.MF

Manifest-Version: 1.0
Premain-Class: com.zyh.ftmagent.FtmAgent
Boot-Class-Path: javassist-3.22.0-CR1.jar

MyDate.java

package com.zyh.ftmagent;

import java.util.Date;

public class MyDate extends Date {
	private static final long serialVersionUID = 1L;

	public MyDate(){
		super(MySystemTime.currentTimeMillis());
	}
}

MySystemTime.java

package com.zyh.ftmagent;

public class MySystemTime {
	//默认为当前时间
	private static final Long INIT_VALUE = 0l;

	private static ThreadLocal<Long> timeDiff = new ThreadLocal<Long>() {
		@Override
		protected Long initialValue() {
			return INIT_VALUE;
		}
	};

	public static long currentTimeMillis() {
		return System.currentTimeMillis() - timeDiff.get();
	}

	public static long nanoTime() {
		return System.nanoTime() - timeDiff.get() * 1000;
	}

	/**
	 * 设置距离当前的时间，为正表示后退多少ms
	 * 
	 * @param diff
	 */
	public static void setTimeDiff(long diff) {
		timeDiff.set(diff);
	}
}

MyTestClass.java

package com.zyh.test;

import java.text.SimpleDateFormat;
import java.util.Date;

public class MyTestClass {
	public void dateTest() {
		long stTime = System.currentTimeMillis();
		System.out.println("Now CurrentTimeMillis 1:" + stTime);
		long nt = System.nanoTime();
		System.out.println("Now nanoTime:" + nt);
		System.out.println("Now CurrentTImeMillis 2:" + System.currentTimeMillis());
		Date ct = new Date();
		SimpleDateFormat sdf = new SimpleDateFormat("yyyyMMdd HH:mm:ss");
		String rslt = sdf.format(ct);
		System.out.println("Now Date:" + rslt);
		System.out.println("now Date2:" + sdf.format(new Date()));
		Date ct2 = new Date(System.currentTimeMillis());
		System.out.println("Now Date3:" + ct2);
	}
}

pom.xml

<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>com.zyh</groupId>
	<artifactId>ftmagent</artifactId>
	<version>0.0.1-SNAPSHOT</version>
	<packaging>jar</packaging>

	<name>ftmagent</name>
	<url>http://maven.apache.org</url>

	<properties>
		<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
	</properties>

	<dependencies>
		<dependency>
			<groupId>junit</groupId>
			<artifactId>junit</artifactId>
			<version>4.12</version>
			<scope>test</scope>
		</dependency>
		<!-- https://mvnrepository.com/artifact/org.javassist/javassist -->
		<dependency>
			<groupId>org.javassist</groupId>
			<artifactId>javassist</artifactId>
			<version>3.22.0-CR1</version>
		</dependency>
	</dependencies>
</project>

run-test.sh

java -javaagent=ftm-agent.jar -jar ftm-test.jar

TestMain.java

package com.zyh.test;

import java.text.SimpleDateFormat;
import java.util.Date;

import com.zyh.ftmagent.MySystemTime;

public class TestMain {
	  public static void main( String[] args ) throws Exception  {
		  	System.out.println("Real Time:" +System.currentTimeMillis());
		  	SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
		  	System.out.println("Real Date2:" + sdf.format(new Date()));
		  	MySystemTime.setTimeDiff(3000l);//时钟回拨3s
	        MyTestClass testClass = new MyTestClass();
	        testClass.dateTest();
	    }
}

TimeTransformer.java

package com.zyh.ftmagent;

import java.lang.instrument.ClassFileTransformer;
import java.lang.instrument.IllegalClassFormatException;
import java.security.ProtectionDomain;

import javassist.CannotCompileException;
import javassist.ClassPool;
import javassist.CtBehavior;
import javassist.CtClass;
import javassist.NotFoundException;
import javassist.expr.ExprEditor;
import javassist.expr.MethodCall;
import javassist.expr.NewExpr;

public class TimeTransformer implements ClassFileTransformer {

	public byte[] transform(ClassLoader loader, String className, Class<?> classBeingRedefined,
			ProtectionDomain protectionDomain, byte[] classfileBuffer) throws IllegalClassFormatException {
		// 仅对于com.zyh.test包下的类进行替换
		if (className.startsWith("com/zyh/test")) {
			byte[] transformed = null;
			System.out.println("Transforming " + className);
			ClassPool pool = ClassPool.getDefault();
			CtClass cl = null;
			try {
				cl = pool.makeClass(new java.io.ByteArrayInputStream(classfileBuffer));
				if (cl.isInterface() == false) {
					CtBehavior[] methods = cl.getDeclaredBehaviors();
					for (int i = 0; i < methods.length; i++) {
						if (methods[i].isEmpty() == false) {
							doMethod(methods[i]);
						}
					}
					transformed = cl.toBytecode();
				}
			} catch (Exception e) {
				System.err.println("Could not instrument  " + className + ",  exception : " + e.getMessage());
			} finally {
				if (cl != null) {
					cl.detach();
				}
			}
			return transformed;
		}
		return null;
	}

	private void doMethod(CtBehavior method) throws NotFoundException, CannotCompileException {
		// 修改方法体的定义
		method.instrument(new ExprEditor() {

			// 修改一般的方法调用语句
			public void edit(MethodCall m) throws CannotCompileException {
				try {
					if (m.getClassName().equals("java.lang.System")) {
						if (m.getMethodName().equals("nanoTime")) {
							m.replace("{long rslt = com.zyh.ftmagent.MySystemTime#nanoTime(); $_ = ($r)rslt; }");
						} else if (m.getMethodName().equals("currentTimeMillis")) {
							m.replace(
									"{long rslt = com.zyh.ftmagent.MySystemTime#currentTimeMillis(); $_ = ($r)rslt; }");
						}
					}
				} catch (Exception ex) {
					ex.printStackTrace();
					throw new RuntimeException(ex);
				}
			}

			// 修改new Date()这种格式的代码，替换其中的class类
			public void edit(NewExpr e) throws CannotCompileException {
				try {
					if (e.getClassName().equals("java.util.Date")) {
						e.replace("{$_ = new com.zyh.ftmagent.MyDate();}");
					}
				} catch (Exception ex) {
					ex.printStackTrace();
					throw new RuntimeException(ex);
				}
			}
		});
	}
}