jdk 9b112 上的 javassist 问题

Question

我正在将项目迁移到 java 9，它也使用 javassist 生成运行时代码。我的一项测试在 jdk 9b112 上失败，而在 jdk 8u77.

上通过

import static javassist.CtClass.voidType;

import java.lang.reflect.Method;
import java.lang.reflect.Modifier;
import java.util.HashMap;
import java.util.Map;

import org.junit.Test;

import javassist.ClassClassPath;
import javassist.ClassPool;
import javassist.CtClass;
import javassist.CtField;
import javassist.CtMethod;
import javassist.CtNewMethod;

public class MyTests {

    public static class MyObject {
        protected Object field;
        Object getField() {return field;}
        public void setField(Object field) {}
    }

    @Test
    public void test() throws InstantiationException, IllegalAccessException {
        Class<? extends MyObject> clazz = compile(MyObject.class);
        clazz.newInstance().setField(null);
    }

    /** Compile a transfer class */
    public static synchronized Class<? extends MyObject> compile(Class<?> targetClass) {

        // Determine class setters
        Map<String, Method> setters = extractSetters(targetClass);

        ClassPool classPool = ClassPool.getDefault();
        classPool.insertClassPath(new ClassClassPath(targetClass));

        try {

            // Compile a new transfer class on the fly
            CtClass baseClass = classPool.get(MyObject.class.getName());
            CtClass proxyClass = classPool.makeClass(targetClass.getName() + "_Modified", baseClass);

            for(Method originalSetter : setters.values()) {
                // Create a field to hold the attribute
                Class<?> fieldClass = originalSetter.getParameterTypes()[0];
                CtClass fieldType = classPool.get(fieldClass.getName());
                String fieldName = originalSetter.getName().substring(3);
                CtField field = new CtField(fieldType, fieldName, proxyClass);
                proxyClass.addField(field);

                // Create a setter method to set that field
                CtClass[] parameters = new CtClass[] { fieldType };
                String setterBody = "{ System.out.println(\"Hello World\"); }";
                CtMethod setter = CtNewMethod.make(voidType, originalSetter.getName(), parameters, new CtClass[0], setterBody, proxyClass);
                proxyClass.addMethod(setter);
            }

            Class<? extends MyObject> javaClass = proxyClass.toClass(targetClass.getClassLoader(), targetClass.getProtectionDomain());

            return javaClass;

        } catch(Exception e) {
            throw new RuntimeException("Failure during transfer compilation for " + targetClass, e);
        }
    }


    /** Extract setter methods from a class */
    public static Map<String, Method> extractSetters(Class<?> cls) {

        Map<String, Method> setters = new HashMap<String, Method>();
        for(Method method : cls.getMethods()) {
            // Lookup setter methods
            if(method.getName().startsWith("set")) {
                // Only public setters
                int modifiers = method.getModifiers();
                if(Modifier.isPublic(modifiers)) {
                    Class<?>[] exceptions = method.getExceptionTypes();
                    Class<?>[] parameters = method.getParameterTypes();
                    Class<?> returnType = method.getReturnType();
                    if(exceptions.length <= 0 && parameters.length == 1 && "void".equals(returnType.getName())) {
                        setters.put(method.getName(), method);
                    }
                }
            }
        }
        return setters;
    }
}

在 jdk 8u77 上，compile() 函数 returns 成功并且 "Hello world" 被打印到控制台。在 jdk 9b112，我遇到了这个异常

java.lang.RuntimeException: Failure during transfer compilation for class MyTests$MyObject
    at MyTests.compile(MyTests.java:68)
    at MyTests.test(MyTests.java:29)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(java.base@9-ea/Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(java.base@9-ea/NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(java.base@9-ea/DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(java.base@9-ea/Method.java:531)
    at org.junit.runners.model.FrameworkMethod.runReflectiveCall(FrameworkMethod.java:47)
    at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
    at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:44)
    at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
    at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:271)
    at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:70)
    at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:50)
    at org.junit.runners.ParentRunner.run(ParentRunner.java:238)
    at org.junit.runners.ParentRunner.schedule(ParentRunner.java:63)
    at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:236)
    at org.junit.runners.ParentRunner.access[=12=]0(ParentRunner.java:53)
    at org.junit.runners.ParentRunner.evaluate(ParentRunner.java:229)
    at org.junit.runners.ParentRunner.run(ParentRunner.java:309)
    at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:86)
    at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:38)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:459)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:670)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:382)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:192)
Caused by: javassist.NotFoundException: java.lang.Object
    at javassist.ClassPool.get(ClassPool.java:450)
    at MyTests.compile(MyTests.java:51)
    ... 24 more

我在 Internet 上搜索了这个问题，甚至在 javassist 的错误跟踪器中也没有发现相关问题。

Answer 1

Javassist 3.22.0-GA 似乎已修复此问题，现在在其发行说明中读取 -

Compatible with Java 9.

您可以使用相同的方式

Maven

<dependency>
    <groupId>org.javassist</groupId>
    <artifactId>javassist</artifactId>
    <version>3.22.0-GA</version>
</dependency>

Gradle

compile 'org.javassist:javassist:3.22.0-GA'

SBT

libraryDependencies += "org.javassist" % "javassist" % "3.22.0-GA"

PS：我也在使用 JDK 的 9.0.1 版本。

jdk 9b112 上的 javassist 问题

Issue with javassist on jdk 9b112

java

javassist

java-9