public static Method getClassMethod(
String classInternalName, String methodName, String methodDesc) {
checkArgNotNull(classInternalName, "classInternalName");
checkArgNotNull(methodName, "methodName");
checkArgNotNull(methodDesc, "methodDesc");
Class<?> clazz = getClassForInternalName(classInternalName);
Type[] types = Type.getArgumentTypes(methodDesc);
Class<?>[] argTypes = new Class<?>[types.length];
for (int i = 0; i < types.length; i++) {
argTypes[i] = getClassForType(types[i]);
}
Class<?> current = clazz;
while (true) {
try {
return current.getDeclaredMethod(methodName, argTypes);
} catch (NoSuchMethodException e) {
current = current.getSuperclass();
if (Object.class.equals(current)) {
throw new RuntimeException(
"Method '"
+ methodName
+ "' with descriptor '"
+ methodDesc
+ "' not found in '"
+ clazz
+ "\' or any superclass",
e);
}
}
}
}
public static Constructor getClassConstructor(String classInternalName, String constructorDesc) {
checkArgNotNull(classInternalName, "classInternalName");
checkArgNotNull(constructorDesc, "constructorDesc");
Class<?> clazz = getClassForInternalName(classInternalName);
Type[] types = Type.getArgumentTypes(constructorDesc);
Class<?>[] argTypes = new Class<?>[types.length];
for (int i = 0; i < types.length; i++) {
argTypes[i] = getClassForType(types[i]);
}
try {
return clazz.getDeclaredConstructor(argTypes);
} catch (NoSuchMethodException e) {
throw new RuntimeException(
"Constructor with descriptor '" + constructorDesc + "' not found in '" + clazz, e);
}
}
public static Field getClassField(String classInternalName, String fieldName) {
checkArgNotNull(classInternalName, "classInternalName");
checkArgNotNull(fieldName, "fieldName");
Class<?> clazz = getClassForInternalName(classInternalName);
Class<?> current = clazz;
while (true) {
try {
return current.getDeclaredField(fieldName);
} catch (NoSuchFieldException e) {
current = current.getSuperclass();
if (Object.class.equals(current)) {
throw new RuntimeException(
"Field '" + fieldName + "' not found in '" + clazz + "\' or any superclass", e);
}
}
}
}
/**
* Returns the class with the given name if it has already been loaded by the given class loader.
* Otherwise the method returns null.
*
* @param className the full name of the class to be loaded
* @param classLoader the class loader to use
* @return the class instance or null
*/
public static Class<?> findLoadedClass(String className, ClassLoader classLoader) {
checkArgNotNull(className, "className");
checkArgNotNull(classLoader, "classLoader");
try {
Class<?> classLoaderBaseClass = Class.forName("java.lang.ClassLoader");
Method findLoadedClassMethod =
classLoaderBaseClass.getDeclaredMethod("findLoadedClass", String.class);
// protected method invocation
findLoadedClassMethod.setAccessible(true);
try {
return (Class<?>) findLoadedClassMethod.invoke(classLoader, className);
} finally {
findLoadedClassMethod.setAccessible(false);
}
} catch (Exception e) {
throw new RuntimeException(
"Could not determine whether class '" + className + "' has already been loaded", e);
}
}
/**
* Loads the class defined with the given name and bytecode using the given class loader. Since
* package and class idendity includes the ClassLoader instance used to load a class we use
* reflection on the given class loader to define generated classes. If we used our own class
* loader (in order to be able to access the protected "defineClass" method) we would likely still
* be able to load generated classes, however, they would not have access to package-private
* classes and members of their super classes.
*
* @param className the full name of the class to be loaded
* @param code the bytecode of the class to load
* @param classLoader the class loader to use
* @return the class instance
*/
public static Class<?> loadClass(String className, byte[] code, ClassLoader classLoader) {
checkArgNotNull(className, "className");
checkArgNotNull(code, "code");
checkArgNotNull(classLoader, "classLoader");
try {
Class<?> classLoaderBaseClass = Class.forName("java.lang.ClassLoader");
Method defineClassMethod =
classLoaderBaseClass.getDeclaredMethod(
"defineClass", String.class, byte[].class, int.class, int.class);
// protected method invocation
defineClassMethod.setAccessible(true);
try {
return (Class<?>) defineClassMethod.invoke(classLoader, className, code, 0, code.length);
} finally {
defineClassMethod.setAccessible(false);
}
} catch (Exception e) {
throw new RuntimeException("Could not load class '" + className + '\'', e);
}
}
public static ClassReader createClassReader(Class<?> clazz) throws IOException {
checkArgNotNull(clazz, "clazz");
String classFilename = clazz.getName().replace('.', '/') + ".class";
InputStream inputStream = clazz.getClassLoader().getResourceAsStream(classFilename);
return new ClassReader(inputStream);
}
/**
* Determines whether the class with the given descriptor is assignable to the given type.
*
* @param classInternalName the class descriptor
* @param type the type
* @return true if the class with the given descriptor is assignable to the given type
*/
public static boolean isAssignableTo(String classInternalName, Class<?> type) {
checkArgNotNull(classInternalName, "classInternalName");
checkArgNotNull(type, "type");
return type.isAssignableFrom(getClassForInternalName(classInternalName));
}