RetransformClassesZeroLength.java

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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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/**
 * @test
 * @bug 8198393
 * @summary Instrumentation.retransformClasses(new Class[0]) should be NOP
 * @requires vm.jvmti
 * @library /test/lib
 * @modules java.instrument
 * @compile RetransformClassesZeroLength.java
 * @run driver RetransformClassesZeroLength
 */

import java.lang.instrument.ClassFileTransformer;
import java.lang.instrument.IllegalClassFormatException;
import java.lang.instrument.Instrumentation;
import java.lang.instrument.UnmodifiableClassException;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.security.ProtectionDomain;

import jdk.test.lib.process.ProcessTools;
import jdk.test.lib.helpers.ClassFileInstaller;

public class RetransformClassesZeroLength {

    private static String manifest =
            "Premain-Class: " + RetransformClassesZeroLength.Agent.class.getName() + "\n"
            + "Can-Retransform-Classes: true\n";

    private static String CP = System.getProperty("test.classes");

    public static void main(String args[]) throws Throwable {
        String agentJar = buildAgent();
        ProcessTools.executeProcess(
                ProcessTools.createJavaProcessBuilder(
                        "-javaagent:" + agentJar,
                        "-version")
        ).shouldHaveExitValue(0);
    }

    private static String buildAgent() throws Exception {
        Path jar = Files.createTempFile(Paths.get("."), null, ".jar");
        String jarPath = jar.toAbsolutePath().toString();
        ClassFileInstaller.writeJar(jarPath,
                ClassFileInstaller.Manifest.fromString(manifest),
                RetransformClassesZeroLength.class.getName());
        return jarPath;
    }


    public static class Agent implements ClassFileTransformer {
        public static void premain(String args, Instrumentation inst) {
            inst.addTransformer(new NoOpTransformer());
            try {
                inst.retransformClasses(new Class[0]);
            } catch (UnmodifiableClassException ex) {
                throw new AssertionError(ex);
            }
        }
    }

    private static class NoOpTransformer implements ClassFileTransformer {
        @Override
        public byte[] transform(ClassLoader loader,
                                String className,
                                Class<?> classBeingRedefined,
                                ProtectionDomain protectionDomain,
                                byte[] classfileBuffer
                                ) throws IllegalClassFormatException {
            return null;    // no transform
        }
    }
}