为什么Spring bean是单例作用域? [英] Why Spring bean is singleton scope?

问题描述

我正在使用Hibernet和Spring，它运行的很好..但是我有一些疑问

I am working with Hibernet and Spring it's going good..but I have some doubts

1)为什么默认情况下spring范围是单例的?是否有任何原因

1) why spring scope is singleton by default?Is there any reason for that

2)我可以在Hibernate实体中写final变量吗? 示例:

2) Can I write final varible in Hibernate entity? Example :

@Entity
public class Emp {
  @Id
  private Long id;
  final private String panNo;
}

我可以像上面一样写

3)静态变量可以Searlizable吗?

3) static varibles can Searlizable?

推荐答案

无状态bean规则:)如果您不打算将状态数据保存在bean中，则每个bean仅具有一个实例就足够了.您还应该记住，这不是JVM单例，而是Spring单例.因此，您不必仅提供私有构造函数和任何getInstance()方法.

Stateless beans rules :) If you're not going to hold state data in beans then it's enough to have only one instance of each bean. You should also remember that it's not JVM singletons - just Spring singletons. So you don't have to provide only private constructor and any getInstance() methods.

Spring文档中的语录:

Quote from Spring documentation:

当一个bean是单例时，只有一个bean的共享实例 被管理，并且所有对具有一个或多个id的bean的请求均与该 bean定义将导致一个特定的bean实例被 返回.

When a bean is a singleton, only one shared instance of the bean will be managed and all requests for beans with an id or ids matching that bean definition will result in that one specific bean instance being returned.

仅当必须保留一些会话详细信息时，才应使用例如会话范围.

Only when you have to keep some session details you should use for example session scope.

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