ByteBuddy
一路上看见晦涩难懂的ASM，小巧可人的Javassist。直到遇见了ByteBuddy才知世上竟有如此的冷艳简洁。
JavaAgent
从Jdk1.5开始Java开始支持Java Agent特性，可以通过premain方法，在Class字节码加载进虚拟机之前对底层的字节码进行修改。从而达到可以自定义特性的功能。给Aop的实现提供了一种更加简洁的方式。
ByteBuddy
字节码修改工具貌似从Java的诞生就一直存在，一开始的ASM，后来可以通过人类可以理解的方式修改字节码的Javassist，到现在的ByteBuddy，甚至不需要了解Class文件的构成就可以修改字节码，实现自己需求，简直神器。对于Class文件结构构成不在此赘述，有兴趣可以去之前摹写的一个加载Class文件的工具了解一下GOM，ByteBuddy官方地址。
通过ByteBuddy修改字节码，计算方法耗时
直接上代码
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| package com.langel.anal.agent;
import com.langel.anal.agent.constant.Const;
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;
public class AnalAgent {
public static void premain(String agentOps, Instrumentation inst) {
System.out.println(Const.LOG_PREFIX + "This is an perform monitor agent.");
new Param(agentOps);
Param.print();
AgentBuilder.Transformer transformer = new AgentBuilder.Transformer() {
@Override
public DynamicType.Builder<?> transform(DynamicType.Builder<?> builder,
TypeDescription typeDescription,
ClassLoader classLoader) {
return builder
.method(ElementMatchers.<MethodDescription>any())
.intercept(MethodDelegation.to(TimeInterceptor.class));
}
};
AgentBuilder.Listener listener = new AgentBuilder.Listener() {
@Override
public void onTransformation(TypeDescription typeDescription, ClassLoader classLoader, JavaModule module, DynamicType dynamicType) {
}
@Override
public void onIgnored(TypeDescription typeDescription, ClassLoader classLoader, JavaModule module) {
}
@Override
public void onError(String typeName, ClassLoader classLoader, JavaModule module, Throwable throwable) {
}
@Override
public void onComplete(String typeName, ClassLoader classLoader, JavaModule module) {
}
};
String packagePrefix = Param.get("prefix") == null ? "com" : Param.get("prefix");
new AgentBuilder
.Default()
.type(ElementMatchers.nameStartsWith(packagePrefix)
.and(ElementMatchers.not(ElementMatchers.isAnnotation()))
.and(ElementMatchers.not(ElementMatchers.isInterface()))
.and(ElementMatchers.not(ElementMatchers.isEnum())))
.transform(transformer)
.with(listener)
.installOn(inst);
}
}
|
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| package com.langel.anal.agent;
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.time.format.DateTimeFormatter;
import java.util.concurrent.Callable;
public class TimeInterceptor {
@RuntimeType
public static Object intercept(@Origin Method method,
@SuperCall Callable<?> callable) throws Exception {
String methodName = method.getName();
if (methodName.startsWith("equals")
|| methodName.startsWith("hashCode")
|| methodName.startsWith("toString")) {
return callable.call();
}
DateTimeFormatter formatter = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss.SSS");
long start = System.currentTimeMillis();
try {
return callable.call();
} finally {
Long elpse = System.currentTimeMillis() - start;
LogCachePool.putInstant(method.getDeclaringClass().getName(), methodName, elpse);
}
}
}
|
然后在JVMOptions加入下面配置
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| -javaagent:/Users/rick/Workspaces/sourcecode/anal/target/anal-agent.jar=file=log.txt,prefix=com.langel.kmp
|
这只是ByteBuddy 的API的一个简单使用。更多特性值得去探索
测试
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| package com.langel.kmp;
import com.langel.util.PrintUtils;
public class KMP {
private static final String searchStr = "bacbababadababacambabacaddababacasdsd";
private static final String ptrStr = "ababaca";
private static int[] calNext(String pStr) {
int[] next = new int[pStr.length()];
next[0] = -1;
int k = -1;
for (int i = 1; i < next.length; i++) {
while (k > -1 && pStr.charAt(i) != pStr.charAt(k + 1)) {
k = next[k];
}
if (pStr.charAt(k + 1) == pStr.charAt(i)) {
next[i] = k = k + 1;
}
}
return next;
}
private static int search(String sStr, String pStr) {
int[] next = calNext(pStr);
PrintUtils.println(next);
int k = -1;
for (int i = 0; i < sStr.length(); i++) {
while (k > -1 && sStr.charAt(i) != pStr.charAt(k + 1)) {
k = next[k];
System.out.println(k);
}
if (pStr.charAt(k + 1) == sStr.charAt(i)) {
k = k + 1;
System.out.println("k + 1 : " + k);
}
if (k == pStr.length() - 1) {
return i - pStr.length() + 1;
}
System.out.println();
}
return -1;
}
public static void main(String[] args) throws InterruptedException {
for (int idx = 0; idx < 1000; idx++) {
Thread.sleep(1000);
System.out.println(search(searchStr, ptrStr));
}
}
}
|
日志
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| Anal monitor : time - 2019-07-11T01:14:30.785
com.langel.kmp.KMP
-- search : 27ms
-- calNext : 0ms
|