org.robobinding.util.ConstructorUtils Maven / Gradle / Ivy
/*
* NOTICE: THE FILE HAS BEEN MODIFIED TO SUIT THE NEEDS OF THE PROJECT.
*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You 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 org.robobinding.util;
import java.lang.reflect.Constructor;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Modifier;
/**
* Migrated some of methods from
* {@link org.apache.commons.lang3.reflect.ConstructorUtils}.
*
* @since 1.0
* @version $Revision: 1.0 $
* @author Cheng Wei
*/
public class ConstructorUtils {
private ConstructorUtils() {
}
/**
*
* Returns a new instance of the specified class inferring the right
* constructor from the types of the arguments.
*
*
*
* This locates and calls a constructor. The constructor signature must
* match the argument types by assignment compatibility.
*
*
* @param
* the type to be constructed
* @param cls
* the class to be constructed, not null
* @param args
* the array of arguments, null treated as empty
* @return new instance of cls, not null
*
* @throws NoSuchMethodException
* if a matching constructor cannot be found
* @throws IllegalAccessException
* if invocation is not permitted by security
* @throws InvocationTargetException
* if an error occurs on invocation
* @throws InstantiationException
* if an error occurs on instantiation
* @see #invokeConstructor(java.lang.Class, java.lang.Object[],
* java.lang.Class[])
*/
public static T invokeConstructor(final Class cls, Object... args) throws NoSuchMethodException, IllegalAccessException, InvocationTargetException,
InstantiationException {
if (args == null) {
args = ArrayUtils.EMPTY_OBJECT_ARRAY;
}
final Class[] parameterTypes = ClassUtils.toClass(args);
return invokeConstructor(cls, args, parameterTypes);
}
/**
*
* Returns a new instance of the specified class choosing the right
* constructor from the list of parameter types.
*
*
*
* This locates and calls a constructor. The constructor signature must
* match the parameter types by assignment compatibility.
*
*
* @param
* the type to be constructed
* @param cls
* the class to be constructed, not null
* @param args
* the array of arguments, null treated as empty
* @param parameterTypes
* the array of parameter types, null treated as empty
* @return new instance of cls, not null
*
* @throws NoSuchMethodException
* if a matching constructor cannot be found
* @throws IllegalAccessException
* if invocation is not permitted by security
* @throws InvocationTargetException
* if an error occurs on invocation
* @throws InstantiationException
* if an error occurs on instantiation
* @see Constructor#newInstance
*/
public static T invokeConstructor(final Class cls, Object[] args, Class[] parameterTypes) throws NoSuchMethodException, IllegalAccessException,
InvocationTargetException, InstantiationException {
if (parameterTypes == null) {
parameterTypes = ArrayUtils.EMPTY_CLASS_ARRAY;
}
if (args == null) {
args = ArrayUtils.EMPTY_OBJECT_ARRAY;
}
final Constructor ctor = getMatchingAccessibleConstructor(cls, parameterTypes);
if (ctor == null) {
throw new NoSuchMethodException("No such accessible constructor on object: " + cls.getName());
}
return ctor.newInstance(args);
}
// -----------------------------------------------------------------------
/**
*
* Finds a constructor given a class and signature, checking accessibility.
*
*
*
* This finds the constructor and ensures that it is accessible. The
* constructor signature must match the parameter types exactly.
*
*
* @param
* the constructor type
* @param cls
* the class to find a constructor for, not null
* @param parameterTypes
* the array of parameter types, null treated as empty
* @return the constructor, null if no matching accessible constructor found
* @see Class#getConstructor
* @see #getAccessibleConstructor(java.lang.reflect.Constructor)
*/
public static Constructor getAccessibleConstructor(final Class cls, final Class... parameterTypes) {
try {
return getAccessibleConstructor(cls.getConstructor(parameterTypes));
} catch (final NoSuchMethodException e) {
return null;
}
}
/**
*
* Checks if the specified constructor is accessible.
*
*
*
* This simply ensures that the constructor is accessible.
*
*
* @param
* the constructor type
* @param ctor
* the prototype constructor object, not null
* @return the constructor, null if no matching accessible constructor found
* @see java.lang.SecurityManager
*/
public static Constructor getAccessibleConstructor(final Constructor ctor) {
return MemberUtils.isAccessible(ctor) && Modifier.isPublic(ctor.getDeclaringClass().getModifiers()) ? ctor : null;
}
/**
*
* Finds an accessible constructor with compatible parameters.
*
*
*
* This checks all the constructor and finds one with compatible parameters
* This requires that every parameter is assignable from the given parameter
* types. This is a more flexible search than the normal exact matching
* algorithm.
*
*
*
* First it checks if there is a constructor matching the exact signature.
* If not then all the constructors of the class are checked to see if their
* signatures are assignment compatible with the parameter types. The first
* assignment compatible matching constructor is returned.
*
*
* @param
* the constructor type
* @param cls
* the class to find a constructor for, not null
* @param parameterTypes
* find method with compatible parameters
* @return the constructor, null if no matching accessible constructor found
*/
public static Constructor getMatchingAccessibleConstructor(final Class cls, final Class... parameterTypes) {
// see if we can find the constructor directly
// most of the time this works and it's much faster
try {
final Constructor ctor = cls.getConstructor(parameterTypes);
MemberUtils.setAccessibleWorkaround(ctor);
return ctor;
} catch (final NoSuchMethodException e) { // NOPMD - Swallow
}
Constructor result = null;
/*
* (1) Class.getConstructors() is documented to return Constructor so
* as long as the array is not subsequently modified, everything's fine.
*/
final Constructor[] ctors = cls.getConstructors();
// return best match:
for (Constructor ctor : ctors) {
// compare parameters
if (ClassUtils.isAssignable(parameterTypes, ctor.getParameterTypes(), true)) {
// get accessible version of constructor
ctor = getAccessibleConstructor(ctor);
if (ctor != null) {
MemberUtils.setAccessibleWorkaround(ctor);
if (result == null || MemberUtils.compareParameterTypes(ctor.getParameterTypes(), result.getParameterTypes(), parameterTypes) < 0) {
// temporary variable for annotation, see comment above
// (1)
@SuppressWarnings("unchecked")
final Constructor constructor = (Constructor) ctor;
result = constructor;
}
}
}
}
return result;
}
}
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