@Lazy批注和< bean />的lazy-init属性有什么区别？标签？ [英] What's the difference between @Lazy annotation and lazy-init attribute of <bean/> tag?

问题描述

据我了解，标签的@Lazy批注和lazy-init属性应具有相同的功能。但是，当我开发以下代码时，它表现出独特的行为。
在以下代码中，我期望：-（循环依赖项错误）

As per my understanding, @Lazy annotation and lazy-init attribute of tag should have the same functionality. But when I developed the following code, it's showing distinct behaviours. In the following code, I was expecting :- (Circular Dependency Error)

org.springframework.beans.factory.BeanCurrentlyInCreationException

org.springframework.beans.factory.BeanCurrentlyInCreationException

我已经使用@Lazy注释附加了代码，按照我的期望，它不应允许循环依赖。

I have attached code using @Lazy annotation, as per my expectations it should not allow Circular Dependency.

@Component
public class A {
   private B b;
   @Autowired
   public A(@Lazy B b) {
         System.out.println("A.A() - 1-param Constructor");
         this.b = b;
   }    
}

@Component
public class B {
   private A a;
   @Autowired
   public B(A a) {
         System.out.println("B.B() - 1-param Constructor");
         this.a = a;
   }        
} 

主要类别：

public class AnnotationApp{
    public static void main(String[] args){
         ApplicationContext ctx = new ClassPathXmlApplicationContext("com/ry/cfgs/annotationAppContext.xml"); 
         B objB = ctx.getBean("b", B.class); 
         A objA = ctx.getBean("a", A.class);
    }
}

Spring配置文件：

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:context="http://www.springframework.org/schema/context" xsi:schemaLocation="http://www.springframework.org/schema/beans 
http://www.springframework.org/schema/beans/spring-beans.xsd http://www.springframework.org/schema/context 
http://www.springframework.org/schema/context/spring-context-4.3.xsd">

     <context:component-scan base-package="com.ry.beans.annotation"></context:component-scan>

</beans>

输出：-

AA（）-1参数构造函数

A.A() - 1-param Constructor

BB（）-1参数构造函数

B.B() - 1-param Constructor

需要解释，为什么会这样？

推荐答案

来自 Spring框架文档：

...您还可以将 @Lazy 注释放置在标记为
且带有 @Autowired 或 @Inject 。在这种情况下，它会导致注入
的惰性解析代理。

... you can also place the @Lazy annotation on injection points marked with @Autowired or @Inject. In this context, it leads to the injection of a lazy-resolution proxy.

因此，在以下代码中：

So, in the following code:

@Autowired
public A(@Lazy B b) {
    // ...
}

b （

现在，如果您将代码更改为以下内容，则只需在 上自动连接）。

Now, if you change your code to the following:

@Autowired
public A(@Lazy B b) {
    System.out.println("A.A() - 1-param Constructor");
    System.out.println(b.toString());
    this.b = b;
}

您将看到 org.springframework.beans。抛出了factory.BeanCurrentlyInCreationException 。

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