com.netflix.iep.service.DefaultClassFactory Maven / Gradle / Ivy
/*
* Copyright 2014-2024 Netflix, Inc.
*
* 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.netflix.iep.service;
import java.lang.reflect.Constructor;
import java.lang.reflect.Type;
import java.util.function.Function;
/**
* Simple implementation of ClassInstanceFactory that works for classes that have a no-argument
* constructor or a single constructor with explicit bindings provided.
*/
public class DefaultClassFactory implements ClassFactory {
private final Function bindings;
public DefaultClassFactory() {
this(c -> null);
}
public DefaultClassFactory(Function bindings) {
this.bindings = bindings;
}
@SuppressWarnings("unchecked")
@Override public T newInstance(Type type, Function overrides)
throws CreationException {
Class cls = (Class) type;
Constructor[] constructors = cls.getDeclaredConstructors();
if (constructors.length == 1) {
Constructor c = constructors[0];
return newInstance(cls, c, c.getGenericParameterTypes(), overrides);
} else {
for (Constructor c : constructors) {
Type[] ptypes = c.getGenericParameterTypes();
if (ptypes.length == 0) {
return newInstance(cls, c, ptypes, overrides);
}
}
throw new CreationException("class " + cls.getCanonicalName() +
" has more than one constructor and does not have a no-argument constructor");
}
}
@SuppressWarnings("unchecked")
private T newInstance(
Type type,
Constructor c,
Type[] ptypes,
Function overrides) throws CreationException {
try {
c.setAccessible(true);
if (ptypes.length == 0) {
return (T) c.newInstance();
} else {
Object[] pvalues = new Object[ptypes.length];
for (int i = 0; i < ptypes.length; ++i) {
pvalues[i] = overrides.apply(ptypes[i]);
if (pvalues[i] == null) {
pvalues[i] = bindings.apply(ptypes[i]);
}
}
return (T) c.newInstance(pvalues);
}
} catch (Exception e) {
throw new CreationException(type, e);
}
}
}