在Spring上下文中，初始化和实例化是否相同？

Question

In programming parlance, String str = new String(); // instantiation str = "hello"; // initialization

Now, in Spring, there is concept of lazy initialization. Does that mean they the object is lazily instantiated or is lazily initialized?

Or, is it that the name lazy-init attribute or @lazy annotation are misleading in that it actually lazily instantiates?

PS I understand from 4.3 onwards, @lazy can be used for both lazy initialization and also for lazy dependency resolution.

Answer 1

With regards to your example

String str = new String();
str = "hello";

Involves both Instantiation and Initialization. First line instantiates a String and initializes it with an empty string meaning if you do a System.out.println you will see empty not a null .

Second line instantiates a String constant in String pool and initializes str with that value.

For your question of Spring Lazy Initialization, Spring Context uses lazy initialization to speed up start up timing. In Spring a Bean in is initialized only when it is first requested from the Spring context. Remember Initialization will always happen after Instantiation.

Answer 2

According to this (Spring documentation), @Lazy involves delaying both the instantiation and initizlization of the bean:

By default, ApplicationContext implementations eagerly create and configure all singleton beans as part of the initialization process. Generally, this pre-instantiation is desirable, because errors in the configuration or surrounding environment are discovered immediately, as opposed to hours or even days later. When this behavior is not desirable, you can prevent pre-instantiation of a singleton bean by marking the bean definition as lazy-initialized. A lazy-initialized bean tells the IoC container to create a bean instance when it is first requested, rather than at startup.