&引用；java.lang.VerifyError“；使用仪器时，添加变压器（变压器，正确）；

我想将代理附加到进程并修改vm中的类代码。当我添加transformer并调用RetransformClass时，它抛出

java.lang.VerifyError

。代理正在处理中，请在main中调用attach

主要内容：

代理人：

public static void attach() throws IOException, AttachNotSupportedException, AgentLoadException, AgentInitializationException, URISyntaxException {
    int processID = getProcessID();
    VirtualMachine vm = VirtualMachine.attach(String.valueOf(processID));
    String filePath = Agent.class.getProtectionDomain().getCodeSource().getLocation().toURI().getPath();
    File file = new File(filePath);
    vm.loadAgent(file.getPath());
}

public static int getProcessID() {
    RuntimeMXBean runtimeMXBean = ManagementFactory.getRuntimeMXBean();
    return Integer.valueOf(runtimeMXBean.getName().split("@")[0]);
}

public static void agentmain(String agentArgs, Instrumentation instrumentation) throws Throwable {
    Agent.instrumentation = instrumentation;
}

public static void premain(String agentArgs, Instrumentation instrumentation) throws Throwable {
    Agent.instrumentation = instrumentation;
}

public static void modify(String className) {
    Arrays.stream(instrumentation.getAllLoadedClasses()).forEach((aClass) -> {
        if (className.equals(aClass.getName())) {
            ClassFileTransformer transformer = new ToStringTransformer();
            instrumentation.addTransformer(transformer, true);

            try {
                instrumentation.retransformClasses(new Class[]{aClass});
                instrumentation.removeTransformer(transformer);
            } catch (UnmodifiableClassException var4) {
                var4.printStackTrace();
            }
        }

    });
}

串级变压器

public class ToStringTransformer implements ClassFileTransformer {
    public ToStringTransformer() {
    }

    public byte[] transform(ClassLoader loader, String className, Class<?> classBeingRedefined, ProtectionDomain protectionDomain, byte[] classfileBuffer) throws IllegalClassFormatException {
        String compareClass = className.replace('/', '.');
        System.out.println("transformer..." + compareClass);
        if (loader == null) {
            return classfileBuffer;
        } else {
            try {
                ClassPool classPool = ClassPool.getDefault();
                classPool.appendClassPath(Agent.class.getProtectionDomain().getCodeSource().getLocation().toURI().getPath());
                CtClass ctClass = classPool.get(compareClass);
                CtMethod ctMethod = ctClass.getDeclaredMethod("toString");
                ctMethod.setBody("return true;");
                ctClass.writeFile();
                return ctClass.toBytecode();
            } catch (Exception var10) {
                var10.printStackTrace();
                return new byte[0];
            }
        }
    }
}

---

在

ToStringTransformer

中，您有以下代码：

CtMethod ctMethod = ctClass.getDeclaredMethod("toString");
ctMethod.setBody("return true;");
ctClass.writeFile();

toString

返回一个

字符串

，但在这里，您试图通过

返回true使其返回一个
布尔值
。当您尝试加载修改后的类时，这将抛出一个
VerifyError
，因为堆栈上的返回值（
true
）将与
toString
方法（
String
）的返回值不匹配

transformer...com.tostring.agent.Order
transformer...java.lang.VerifyError Exception in thread "main"
transformer...java.lang.Throwable$WrappedPrintStream
transformer...java.lang.Throwable$PrintStreamOrWriter
transformer...java.util.IdentityHashMap
transformer...java.util.IdentityHashMap$KeySet java.lang.VerifyError
    at sun.instrument.InstrumentationImpl.retransformClasses0(Native Method) 
    at sun.instrument.InstrumentationImpl.retransformClasses(InstrumentationImpl.java:144) 
    at com.tostring.agent.Agent.lambda$modify$0(Agent.java:65) 
    at java.util.Spliterators$ArraySpliterator.forEachRemaining(Spliterators.java:948) 
    at java.util.stream.ReferencePipeline$Head.forEach(ReferencePipeline.java:580) 
    at com.tostring.agent.Agent.modify(Agent.java:60) 
    at com.generate.perdicition.PredictionExcel.main(PredictionExcel.java:53)
transformer...java.lang.Shutdown transformer...java.lang.Shutdown$Lock

CtMethod ctMethod = ctClass.getDeclaredMethod("toString");
ctMethod.setBody("return true;");
ctClass.writeFile();