bytebuddy使用

测试类

package org.example.bytebuddy;

public class Log {

    public void print(String message){
        System.out.println(message);
    }
}

复写class并拦截请求

package org.example;

import net.bytebuddy.agent.ByteBuddyAgent;
import net.bytebuddy.agent.builder.AgentBuilder;
import net.bytebuddy.implementation.MethodDelegation;
import net.bytebuddy.implementation.bind.annotation.AllArguments;
import net.bytebuddy.implementation.bind.annotation.RuntimeType;
import net.bytebuddy.implementation.bind.annotation.SuperCall;
import net.bytebuddy.matcher.ElementMatchers;
import org.example.bytebuddy.Log;

import java.lang.instrument.Instrumentation;
import java.util.concurrent.Callable;

public class Main {
    static {
        Instrumentation instrumentation = ByteBuddyAgent.install();
//         new ByteBuddy().redefine(Log.class).method(ElementMatchers.named("print")
//                         .and(ElementMatchers.takesArgument(0,String.class)))
//                 .intercept(MethodDelegation.to(LogDelegate.class))
//                 .make()
//                 .load(Log.class.getClassLoader(), ClassReloadingStrategy.fromInstalledAgent());
        // REBASE  复制后修改 允许新增、删除方法 性能较低  REDEFINITION 直接修改 不允许新增、删除方法 性能高
        new AgentBuilder.Default().with(AgentBuilder.TypeStrategy.Default.REDEFINE)
                .with(AgentBuilder.RedefinitionStrategy.REDEFINITION).type(ElementMatchers.named("org.example.bytebuddy.Log"))
                .transform((builder, typeDescription, classLoader,
                            javaModule, protectionDomain) ->
                    builder.method(ElementMatchers.named("print").and(ElementMatchers.takesArgument(0,String.class))
                    .and(ElementMatchers.returns(void.class))).intercept(
                    MethodDelegation.to(LogDelegate.class)
            )
        ).installOn(instrumentation);
    }
    public static void main(String[] args) {

        new Log().print("Hello World");

        new Log().print("haha");
    }

    public static class LogDelegate{
        @RuntimeType
        public static void intercept(@AllArguments Object[] args, @SuperCall Callable<Void> superCall) {
            String arg = (String) args[0];
            System.out.println("hello" + arg);
            try {
                superCall.call();
            } catch (Exception e) {
                throw new RuntimeException(e);
            }
        }
    }
}