使用javassist更改代码无效(MethodCall)
我有一个简单的功能:使用javassist更改代码无效(MethodCall),java,javassist,java-assist,Java,Javassist,Java Assist,我有一个简单的功能: public int id() { return 0; } void test() { int a = id(); int b = id(); int c = id(); int d = id(); int e = id(); int f = id(); System.out.println(a+" "+b+" "+c+" "+d+" "+e+" "+f); } 我有这个测试功能: public int
public int id() {
return 0;
}
void test() {
int a = id();
int b = id();
int c = id();
int d = id();
int e = id();
int f = id();
System.out.println(a+" "+b+" "+c+" "+d+" "+e+" "+f);
}
我有这个测试功能:
public int id() {
return 0;
}
void test() {
int a = id();
int b = id();
int c = id();
int d = id();
int e = id();
int f = id();
System.out.println(a+" "+b+" "+c+" "+d+" "+e+" "+f);
}
我希望输出是1,2,3,4,5,6
现在我在CtMethod
上调用instrument
,它工作正常
call to id! on line: 57
call to id! on line: 58
call to id! on line: 59
call to id! on line: 60
call to id! on line: 61
call to id! on line: 62
但最终,所有的转换都没有任何效果。
我不知道该怎么办,因为信息太少了
以下是完整的代码:
package doeke.method\u call\u test;
导入java.lang.instrument.Instrumentation;
导入javassist.CannotCompileException;
导入javassist.ClassPool;
导入javassist.CtClass;
导入javassist.CtMethod;
导入javassist.expr.ExprEditor;
导入javassist.expr.MethodCall;
公共类方法调用测试{
静态int-id=1;
公共静态无效预输入(字符串代理、仪器仪表){
试一试{
ClassPool ClassPool=ClassPool.getDefault();
CtClass-CtClass=classPool.getCtClass(“doeke.method\u call\u test.MethodCallTest”);
CtMethod[]methods=ctClass.getDeclaredMethods();
用于(CTCM方法:方法){
厘米仪器(
新ExprEditor(){
public void edit(MethodCall m)抛出CannotCompileException{
if(m.getMethodName().equals(“id”)){
//m.replace(“{$\=“+id+”;}”);
m、 替换(“$\”=1;System.out.println(\“hello?\”);”;
System.out.println(“在线调用id:+m.getLineNumber());
id++;
}
}
}
);
}
inst.retransformClasses(MethodCallTest.class);
}
捕获(例外e){
e、 printStackTrace();
}
}
公共静态void main(字符串[]args){
MethodCallTest mct=新的MethodCallTest();
mct.test();
}
无效测试(){
int a=id();
int b=id();
int c=id();
int d=id();
int e=id();
int f=id();
系统输出打印项次(a+“”+b+“”+c+“”+d+“”+e+“”+f);
}
公共int id(){
返回0;
}
}
不确定如何运行代码,因为通常需要在命令行上使用javaagent启动JVM来注入实例。在下面的示例中,我使用在运行时获取Instrumentation实例
您还必须创建一个返回已修改类的字节码的,您可以通过调用CtClass.toByteCode()
下面的代码打印此输出:
call to id! on line: 84
call to id! on line: 85
call to id! on line: 86
call to id! on line: 87
call to id! on line: 88
call to id! on line: 89
Transforming [doeke/method_call_test/MethodCallTest]
hello?
hello?
hello?
hello?
hello?
hello?
1 1 1 1 1 1
基本代码:
package doeke.method_call_test;
import java.lang.instrument.ClassFileTransformer;
import java.lang.instrument.IllegalClassFormatException;
import java.lang.instrument.Instrumentation;
import java.security.ProtectionDomain;
import javassist.CannotCompileException;
import javassist.ClassPool;
import javassist.CtClass;
import javassist.CtMethod;
import javassist.expr.ExprEditor;
import javassist.expr.MethodCall;
import net.bytebuddy.agent.ByteBuddyAgent;
public class MethodCallTest {
static int id = 1;
public static void premain(String agentArgs, Instrumentation inst) {
try {
ClassPool classPool = ClassPool.getDefault();
CtClass ctClass = classPool.getCtClass("doeke.method_call_test.MethodCallTest");
CtMethod[] methods = ctClass.getDeclaredMethods();
for (CtMethod cm : methods) {
cm.instrument(
new ExprEditor() {
public void edit(MethodCall m) throws CannotCompileException {
if (m.getMethodName().equals("id")) {
// m.replace("{ $_ = "+id+"; }");
m.replace("$_ = 1; System.out.println(\"hello?\");");
System.out.println("call to id! on line: "+m.getLineNumber());
id++;
}
}
}
);
}
final byte[] byteCode = ctClass.toBytecode();
final String rezName = MethodCallTest.class.getName().replace('.', '/');
final ClassFileTransformer transformer = new ClassFileTransformer() {
@Override
public byte[] transform(ClassLoader loader, String className, Class<?> classBeingRedefined,
ProtectionDomain protectionDomain, byte[] classfileBuffer) throws IllegalClassFormatException {
if (rezName.equals(className)) {
System.out.println("Transforming [" + className + "]");
return byteCode;
}
return null;
}
};
inst.addTransformer(transformer, true);
try {
inst.retransformClasses(MethodCallTest.class);
} finally {
inst.removeTransformer(transformer);
}
}
catch (Exception e) {
e.printStackTrace();
}
}
public static void main(String[] args) {
MethodCallTest mct = new MethodCallTest();
Instrumentation inst = ByteBuddyAgent.install();
MethodCallTest.premain("", inst);
mct.test();
}
void test() {
int a = id();
int b = id();
int c = id();
int d = id();
int e = id();
int f = id();
System.out.println(a+" "+b+" "+c+" "+d+" "+e+" "+f);
}
public int id() {
return 0;
}
}
package doeke.method\u call\u test;
导入java.lang.instrument.ClassFileTransformer;
导入java.lang.instrument.IllegalClassFormatException;
导入java.lang.instrument.Instrumentation;
导入java.security.ProtectionDomain;
导入javassist.CannotCompileException;
导入javassist.ClassPool;
导入javassist.CtClass;
导入javassist.CtMethod;
导入javassist.expr.ExprEditor;
导入javassist.expr.MethodCall;
导入net.bytebuddy.agent.bytebuddy代理;
公共类方法调用测试{
静态int-id=1;
公共静态无效预输入(字符串代理、仪器仪表){
试一试{
ClassPool ClassPool=ClassPool.getDefault();
CtClass-CtClass=classPool.getCtClass(“doeke.method\u call\u test.MethodCallTest”);
CtMethod[]methods=ctClass.getDeclaredMethods();
用于(CTCM方法:方法){
厘米仪器(
新ExprEditor(){
public void edit(MethodCall m)抛出CannotCompileException{
if(m.getMethodName().equals(“id”)){
//m.replace(“{$\=“+id+”;}”);
m、 替换(“$\”=1;System.out.println(\“hello?\”);”;
System.out.println(“在线调用id:+m.getLineNumber());
id++;
}
}
}
);
}
最后一个字节[]字节码=ctClass.toBytecode();
最后一个字符串rezName=MethodCallTest.class.getName().replace('.','/');
最终ClassFileTransformer transformer=新ClassFileTransformer(){
@凌驾
公共字节[]转换(类加载器、字符串类名、类被重新定义、,
ProtectionDomain ProtectionDomain,字节[]classfileBuffer)引发IllegalClassFormatException{
if(rezName.equals(className)){
System.out.println(“转换[“+className+”]);
返回字节码;
}
返回null;
}
};
仪器添加变压器(变压器,真实);
试一试{
inst.retransformClasses(MethodCallTest.class);
}最后{
仪表拆卸变压器(变压器);
}
}
捕获(例外e){
e、 printStackTrace();
}
}
公共静态void main(字符串[]args){
MethodCallTest mct=新的MethodCallTest();
Instrumentation inst=ByteBuddyAgent.install();
方法:普莱曼试验(“,inst);
mct.test();
}
无效测试(){
int a=id();
int b=id();
int c=id();
int d=id();
int e=id();
int f=id();
系统输出打印项次(a+“”+b+“”+c+“”+d+“”+e+“”+f);
}
公共int id(){
返回0;
}
}