spring NullBean 源码
spring NullBean 代码
文件路径：/spring-beans/src/main/java/org/springframework/beans/factory/support/NullBean.java
/*
* Copyright 2002-2017 the original author or 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
*
* https://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.springframework.beans.factory.support;
import org.springframework.beans.factory.FactoryBean;
import org.springframework.lang.Nullable;
/**
* Internal representation of a null bean instance, e.g. for a {@code null} value
* returned from {@link FactoryBean#getObject()} or from a factory method.
*
* <p>Each such null bean is represented by a dedicated {@code NullBean} instance
* which are not equal to each other, uniquely differentiating each bean as returned
* from all variants of {@link org.springframework.beans.factory.BeanFactory#getBean}.
* However, each such instance will return {@code true} for {@code #equals(null)}
* and returns "null" from {@code #toString()}, which is how they can be tested
* externally (since this class itself is not public).
*
* @author Juergen Hoeller
* @since 5.0
*/
final class NullBean {
NullBean() {
}
@Override
public boolean equals(@Nullable Object obj) {
return (this == obj || obj == null);
}
@Override
public int hashCode() {
return NullBean.class.hashCode();
}
@Override
public String toString() {
return "null";
}
}
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