我正在将一个项目迁移到 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，该compile()函数成功返回，并且“Hello world”被打印到控制台。在 jdk 9b112 上，我得到了这个异常
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$1.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$3.run(ParentRunner.java:238)
at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:63)
at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:236)
at org.junit.runners.ParentRunner.access$000(ParentRunner.java:53)
at org.junit.runners.ParentRunner$2.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
我在互联网上搜索过这个问题，即使在 javassist 的错误跟踪器中也没有发现相关问题。