com.google.common.reflect.Reflection Maven / Gradle / Ivy
/*
* Copyright (C) 2005 The Guava Authors
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.google.common.reflect;
import static com.google.common.base.Preconditions.checkArgument;
import static com.google.common.base.Preconditions.checkNotNull;
import com.google.common.annotations.Beta;
import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Proxy;
/**
* Static utilities relating to Java reflection.
*
* @since 12.0
*/
@Beta
public final class Reflection {
/**
* Returns the package name of {@code clazz} according to the Java Language Specification (section
* 6.7). Unlike {@link Class#getPackage}, this method only parses the class name, without
* attempting to define the {@link Package} and hence load files.
*/
public static String getPackageName(Class clazz) {
return getPackageName(clazz.getName());
}
/**
* Returns the package name of {@code classFullName} according to the Java Language Specification
* (section 6.7). Unlike {@link Class#getPackage}, this method only parses the class name, without
* attempting to define the {@link Package} and hence load files.
*/
public static String getPackageName(String classFullName) {
int lastDot = classFullName.lastIndexOf('.');
return (lastDot < 0) ? "" : classFullName.substring(0, lastDot);
}
/**
* Ensures that the given classes are initialized, as described in
*
* JLS Section 12.4.2.
*
* WARNING: Normally it's a smell if a class needs to be explicitly initialized, because static
* state hurts system maintainability and testability. In cases when you have no choice while
* inter-operating with a legacy framework, this method helps to keep the code less ugly.
*
* @throws ExceptionInInitializerError if an exception is thrown during
* initialization of a class
*/
public static void initialize(Class... classes) {
for (Class clazz : classes) {
try {
Class.forName(clazz.getName(), true, clazz.getClassLoader());
} catch (ClassNotFoundException e) {
throw new AssertionError(e);
}
}
}
/**
* Returns a proxy instance that implements {@code interfaceType} by
* dispatching method invocations to {@code handler}. The class loader of
* {@code interfaceType} will be used to define the proxy class. To implement
* multiple interfaces or specify a class loader, use
* {@link Proxy#newProxyInstance}.
*
* @throws IllegalArgumentException if {@code interfaceType} does not specify
* the type of a Java interface
*/
public static T newProxy(
Class interfaceType, InvocationHandler handler) {
checkNotNull(handler);
checkArgument(interfaceType.isInterface(), "%s is not an interface", interfaceType);
Object object = Proxy.newProxyInstance(
interfaceType.getClassLoader(),
new Class[] { interfaceType },
handler);
return interfaceType.cast(object);
}
private Reflection() {}
}