@Lazy注解用于标识 bean 是否需要延迟加载：
代码语言：javascript复制@Target({ElementType.TYPE, ElementType.METHOD, ElementType.CONSTRUCTOR, ElementType.PARAMETER, ElementType.FIELD})
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface Lazy {
/**
* Whether lazy initialization should occur.
*/
boolean value() default true;
}只有一个参数，默认是true，也就是说只要加了这个注解就会延迟加载。 @Lazy注解则必须在第一次调用的时候才会加载。 @Lazy注解注解的作用主要是减少springIOC容器启动的加载时间。
@Lazy注解可以用来解决 Requested bean is currently in creation 的问题 （https://www.cnblogs.com/zjhgx/p/12158698.html）。
完整源码如下：
代码语言：javascript复制/*
* Copyright 2002-2013 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.context.annotation;
import java.lang.annotation.Documented;
import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
/**
* Indicates whether a bean is to be lazily initialized.
*
* <p>May be used on any class directly or indirectly annotated with {@link
* org.springframework.stereotype.Component @Component} or on methods annotated with
* {@link Bean @Bean}.
*
* <p>If this annotation is not present on a {@code @Component} or {@code @Bean} definition,
* eager initialization will occur. If present and set to {@code true}, the {@code @Bean} or
* {@code @Component} will not be initialized until referenced by another bean or explicitly
* retrieved from the enclosing {@link org.springframework.beans.factory.BeanFactory
* BeanFactory}. If present and set to {@code false}, the bean will be instantiated on
* startup by bean factories that perform eager initialization of singletons.
*
* <p>If Lazy is present on a {@link Configuration @Configuration} class, this
* indicates that all {@code @Bean} methods within that {@code @Configuration}
* should be lazily initialized. If {@code @Lazy} is present and false on a {@code @Bean}
* method within a {@code @Lazy}-annotated {@code @Configuration} class, this indicates
* overriding the 'default lazy' behavior and that the bean should be eagerly initialized.
*
* <p>In addition to its role for component initialization, this annotation may also be placed
* on injection points marked with {@link org.springframework.beans.factory.annotation.Autowired}
* or {@link javax.inject.Inject}: In that context, it leads to the creation of a
* lazy-resolution proxy for all affected dependencies, as an alternative to using
* {@link org.springframework.beans.factory.ObjectFactory} or {@link javax.inject.Provider}.
*
* @author Chris Beams
* @author Juergen Hoeller
* @since 3.0
* @see Primary
* @see Bean
* @see Configuration
* @see org.springframework.stereotype.Component
*/
@Target({ElementType.TYPE, ElementType.METHOD, ElementType.CONSTRUCTOR, ElementType.PARAMETER, ElementType.FIELD})
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface Lazy {
/**
* Whether lazy initialization should occur.
*/
boolean value() default true;
}
