Spring Bean Scopes

Question

Can someone explain what the scopes are in Spring beans I ve always just used  prototype  but are there other parameters I can put in place of that   Example of what I m talking about   lt bean id  customerInfoController  class  com action Controller  scope  prototype  gt       lt property name  accountDao  ref  accountDao   gt       lt property name  utilityDao  ref  utilityDao   gt       lt property name  account usageDao  ref  account usageDao   gt     lt  bean gt

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Also websocket scope is added   Scopes a single bean definition to the lifecycle of a WebSocket  Only valid in the context of a web-aware Spring ApplicationContext   As the per the content of the documentation  there is also thread scope  that is not registered by default

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A short example what is the difference between  Scope  singleton    default  and  Scope  prototype     DAO class   package com example demo   public class Manager       private String name       public String getName             return name             public void setName String name            this name   name            Configuration    Configuration public class AppConfiguration        Bean      Scope  singleton       public Manager getManager            return new Manager              and MainApp    SpringBootApplication public class DemoApplication        public static void main String   args            SpringApplication run DemoApplication class  args           AnnotationConfigApplicationContext context   new AnnotationConfigApplicationContext            context scan  com example demo            context refresh             Manager firstManager   context getBean Manager class           firstManager setName  Karol             Manager secondManager   context getBean Manager class           System out println secondManager getName                In this example the result is  Karol even if we set this name only for firstManager object  It s because Spring IoC container created one instance of object  However when we change scope to  Scope  prototype   in Configuration class then result is  null because Spring IoC container creates a new bean instance of the object when request for that bean is made

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The Spring documentation describes the following standard scopes   singleton   Default  Scopes a single bean definition to a single object instance per Spring IoC container  prototype  Scopes a single bean definition to any number of object instances  request  Scopes a single bean definition to the lifecycle of a single HTTP request  that is  each HTTP request has its own instance of a bean created off the back of a single bean definition  Only valid in the context of a web-aware Spring ApplicationContext  session  Scopes a single bean definition to the lifecycle of an HTTP Session  Only valid in the context of a web-aware Spring ApplicationContext  global session  Scopes a single bean definition to the lifecycle of a global HTTP Session  Typically only valid when used in a portlet context  Only valid in the context of a web-aware Spring ApplicationContext   Additional custom scopes can also be created and configured using a CustomScopeConfigurer  An example would be the flow scope added by Spring Webflow  By the way  you argues that you always used prototype what I find strange  The standard scope is singleton and in the application I develop  I rarely need the prototype scope  You should maybe take a look at this

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According to the documentation of Spring-Cloud-Config there is one extra scope next to the existing five  It is  RefreshScope   This is the short description of RefreshScope      When there is a configuration change  a Spring  Bean that is marked as    RefreshScope gets special treatment  This feature addresses the   problem of stateful beans that only get their configuration injected   when they are initialized  For instance  if a DataSource has open   connections when the database URL is changed via the Environment  you   probably want the holders of those connections to be able to complete   what they are doing  Then  the next time something borrows a   connection from the pool  it gets one with the new URL       Sometimes  it might even be mandatory to apply the  RefreshScope   annotation on some beans which can be only initialized once  If a bean   is  immutable   you will have to either annotate the bean with    RefreshScope or specify the classname under the property key   spring cloud refresh extra-refreshable       Refresh scope beans are lazy proxies that initialize when they are   used  that is  when a method is called   and the scope acts as a cache   of initialized values  To force a bean to re-initialize on the next   method call  you must invalidate its cache entry       The RefreshScope is a bean in the context and has a public   refreshAll   method to refresh all beans in the scope by clearing the   target cache  The  refresh endpoint exposes this functionality  over   HTTP or JMX   To refresh an individual bean by name  there is also a   refresh String  method

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Detailed explanation for each scope can be found here in Spring bean scopes  Below is the summary  Singleton -   Default  Scopes a single bean definition to a single object instance per Spring IoC container   prototype - Scopes a single bean definition to any number of object instances   request - Scopes a single bean definition to the lifecycle of a single HTTP request  that is  each HTTP request has its own instance of a bean created off the back of a single bean definition  Only valid in the context of a web-aware Spring ApplicationContext   session - Scopes a single bean definition to the lifecycle of an HTTP Session  Only valid in the context of a web-aware Spring ApplicationContext   global session - Scopes a single bean definition to the lifecycle of a global HTTP Session  Typically only valid when used in a portlet context  Only valid in the context of a web-aware Spring ApplicationContext

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From the spring specs  there are five types of bean scopes supported       1  singleton default        Scopes a single bean definition to a single object instance per Spring   IoC container       2  prototype      Scopes a single bean definition to any number of object instances       3  request      Scopes a single bean definition to the lifecycle of a single HTTP   request  that is each and every HTTP request will have its own   instance of a bean created off the back of a single bean definition    Only valid in the context of a web-aware Spring ApplicationContext       4  session      Scopes a single bean definition to the lifecycle of a HTTP Session    Only valid in the context of a web-aware Spring ApplicationContext       5  global session      Scopes a single bean definition to the lifecycle of a global HTTP   Session  Typically only valid when used in a portlet context  Only   valid in the context of a web-aware Spring ApplicationContext     default means when no scope is explicitly provided in the  lt bean   gt  tag  read more about them here  http   static springsource org spring docs 3 0 0 M3 reference html ch04s04 html

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Just want to update  that in Spring 5  as mentioned in Spring docs  Spring supports 6 scopes  four of which are available only if you use a web-aware ApplicationContext      singleton  Default  Scopes a single bean definition to a single object instance per Spring IoC container       prototype   Scopes a single bean definition to any number of object instances       request   Scopes a single bean definition to the lifecycle of a single HTTP request  that is  each HTTP request has its own instance of a bean created off the back of a single bean definition  Only valid in the context of a web-aware Spring ApplicationContext       session   Scopes a single bean definition to the lifecycle of an HTTP Session  Only valid in the context of a web-aware Spring ApplicationContext       application   Scopes a single bean definition to the lifecycle of a ServletContext  Only valid in the context of a web-aware Spring ApplicationContext       websocket   Scopes a single bean definition to the lifecycle of a WebSocket  Only valid in the context of a web-aware Spring ApplicationContext

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In Spring  bean scope is used to decide which type of bean instance should be returned from Spring container back to the caller  5 types of bean scopes are supported    Singleton   It returns a single bean instance per Spring IoC container This single instance is stored in a cache of such singleton beans  and all subsequent requests and references for that named bean return the cached object If no bean scope is specified in bean configuration file  default to singleton    Prototype   It returns a new bean instance each time when requested  It does not store any cache version like singleton    Request   It returns a single bean instance per HTTP request    Session   It returns a single bean instance per HTTP session  User level session    GlobalSession   It returns a single bean instance per global HTTP session  It is only valid in the context of a web-aware Spring ApplicationContext  Application level session     In most cases  you may only deal with the Spring   s core scope     singleton and prototype  and the default scope is singleton

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About prototype bean s        The client code must clean up prototype-scoped objects and release   expensive resources that the prototype bean s  are holding  To get the   Spring container to release resources held by prototype-scoped beans    try using a custom bean post-processor  which holds a reference to   beans that need to be cleaned up    ref   https   docs spring io spring docs 3 0 0 M3 reference html ch04s04 html beans-factory-scopes-prototype

[java] Spring Bean Scopes

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