How to define a List bean in Spring

Question

I m using Spring to define stages in my application  It s configured that the necessary class  here called Configurator  is injected with the stages  Now I need the List of Stages in another class  named LoginBean  The Configurator doesn t offer access to his List of Stages   I cannot change the class Configurator   My Idea  Define a new bean called Stages and inject it to Configurator and LoginBean  My problem with this idea is that I don t know how to transform this property    lt property     gt     lt list gt       lt bean      gt     lt  bean gt       lt bean      gt     lt  bean gt       lt bean      gt     lt  bean gt     lt  list gt   lt  property gt    into a bean   Something like this does not work    lt bean id  stages  class  java util ArrayList  gt    Can anybody help me with this

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lt bean id  student1  class  com spring assin2 Student  gt     lt property name  name  value  ram  gt  lt  property gt     lt property name  id  value  1  gt  lt  property gt    lt property name  listTest  gt           lt list value-type  java util List  gt               lt ref bean  test1   gt               lt ref bean  test2   gt           lt  list gt       lt  property gt   lt  bean gt      define those beans test1 test2  afterwards

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I think you may be looking for org springframework beans factory config ListFactoryBean   You declare a ListFactoryBean instance  providing the list to be instantiated as a property withe a  lt list gt  element as its value  and give the bean an id attribute   Then  each time you use the declared id as a ref or similar in some other bean declaration  a new copy of the list is instantiated   You can also specify the List class to be used

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Import the spring util namespace  Then you can define a list bean as follows    lt  xml version  1 0  encoding  UTF-8   gt   lt beans xmlns  http   www springframework org schema beans  xmlns xsi  http   www w3 org 2001 XMLSchema-instance  xmlns util  http   www springframework org schema util  xsi schemaLocation  http   www springframework org schema beans                     http   www springframework org schema beans spring-beans-3 0 xsd                     http   www springframework org schema util                     http   www springframework org schema util spring-util-2 5 xsd  gt     lt util list id  myList  value-type  java lang String  gt       lt value gt foo lt  value gt       lt value gt bar lt  value gt   lt  util list gt      The value-type is the generics type to be used  and is optional  You can also specify the list implementation class using the attribute list-class

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Inject list of strings   Suppose you have Countries model class that take list of strings like below   public class Countries       private List lt String gt  countries       public List lt String gt  getCountries             return countries                public void setCountries List lt String gt  countries            this countries   countries             Following xml definition define a bean and inject list of countries    lt bean id  demoCountryCapitals  name  demoCountryCapitals  class  com sample pojo Countries  gt      lt property name  countries  gt         lt list gt            lt value gt Iceland lt  value gt            lt value gt India lt  value gt            lt value gt Sri Lanka lt  value gt            lt value gt Russia lt  value gt         lt  list gt      lt  property gt   lt  bean gt    Reference link  Inject list of Pojos  Suppose if you have model class like below   public class Country       private String name      private String capital                          public class Countries       private List lt Country gt  favoriteCountries       public List lt Country gt  getFavoriteCountries             return favoriteCountries             public void setFavoriteCountries List lt Country gt  favoriteCountries            this favoriteCountries   favoriteCountries             Bean Definitions     lt bean id  india  class  com sample pojo Country  gt     lt property name  name  value  India    gt     lt property name  capital  value  New Delhi    gt    lt  bean gt     lt bean id  russia  class  com sample pojo Country  gt     lt property name  name  value  Russia    gt     lt property name  capital  value  Moscow    gt    lt  bean gt      lt bean id  demoCountryCapitals  name  demoCountryCapitals  class  com sample pojo Countries  gt     lt property name  favoriteCountries  gt      lt list gt       lt ref bean  india    gt       lt ref bean  russia    gt      lt  list gt     lt  property gt    lt  bean gt    Reference Link

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Another option is to use JavaConfig  Assuming that all stages are already registered as spring beans you just have to    Autowired private List lt Stage gt  stages    and spring will automatically inject them into this list  If you need to preserve order  upper solution doesn t do that  you can do it in that way    Configuration public class MyConfiguration      Autowired   private Stage1 stage1      Autowired   private Stage2 stage2      Bean   public List lt Stage gt  stages         return Lists newArrayList stage1  stage2           The other solution to preserve order is use a  Order annotation on beans  Then list will contain beans ordered by ascending annotation value    Bean  Order 1  public Stage stage1         return new Stage1        Bean  Order 2  public Stage stage2         return new Stage2

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Use the util namespace  you will be able to register the list as a bean in your application context  You can then reuse the list to inject it in other bean definitions

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Here is one method    lt bean id  stage1  class  Stageclass   gt   lt bean id  stage2  class  Stageclass   gt    lt bean id  stages  class  java util ArrayList  gt       lt constructor-arg gt           lt list gt               lt ref bean  stage1    gt               lt ref bean  stage2    gt                           lt  list gt       lt  constructor-arg gt   lt  bean gt

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Stacker posed a great answer  I would go one step farther to make it more dynamic and use Spring 3 EL Expression     lt bean id  listBean  class  java util ArrayList  gt           lt constructor-arg gt               lt value gt   springDAOBean getGenericListFoo    lt  value gt           lt  constructor-arg gt   lt  bean gt    I was trying to figure out how I could do this with the util list but couldn t get it work due to conversion errors

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You just remove id out of beans inside  lt list gt  tag  Like this    lt property name  listStaff  gt     lt list gt       lt bean class  com test entity Staff  gt           lt constructor-arg name  name  value    Jonh   gt           lt constructor-arg name  age  value    30   gt       lt  bean gt       lt bean class  com test entity Staff  gt           lt constructor-arg name  name  value    Jam   gt           lt constructor-arg name  age  value    21   gt       lt  bean gt     lt  list gt   lt  property gt

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lt bean id  someBean        class  com somePackage SomeClass  gt       lt property name  myList  gt           lt list value-type  com somePackage TypeForList  gt               lt ref bean  someBeanInTheList   gt               lt ref bean  someOtherBeanInTheList   gt               lt ref bean  someThirdBeanInTheList   gt           lt  list gt       lt  property gt   lt  bean gt    And in SomeClass   class SomeClass        List lt TypeForList gt  myList        Required     public void setMyList List lt TypeForList gt  myList            this myList   myList

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As an addition to Jakub s answer  if you plan to use JavaConfig  you can also autowire that way   import com google common collect Lists   import java util List   import org springframework context annotation Configuration  import org springframework context annotation Bean    lt     gt    Configuration public class MyConfiguration         Bean     public List lt Stage gt  stages final Stage1 stage1  final Stage2 stage2            return Lists newArrayList stage1  stage2

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And this is how to inject set in some property in Spring    lt bean id  process        class  biz bsoft processing  gt       lt property name  stages  gt           lt set value-type  biz bsoft AbstractStage  gt               lt ref bean  stageReady   gt               lt ref bean  stageSteady   gt               lt ref bean  stageGo   gt           lt  set gt       lt  property gt   lt  bean gt

[java] How to define a List bean in Spring?

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