How to make spring inject value into a static field

Question

I know this may looks like a previously asked question but I m facing a different problem here   I have a utility class that has only static methods  I don t and I won t take an instance from it   public class Utils      private static Properties dataBaseAttr      public static void methodA                public static void methodB               Now I need Spring to fill dataBaseAttr with database attributes Properties Spring config is    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-3 0 xsd  gt    lt util properties id  dataBaseAttr          location  file   classPathVariable path  dataBaseAttr properties    gt   lt  beans gt    I already done it in other beans but the problem here in this class  Utils  isn t a bean  And if I make it a bean nothing changes I still can t use the variable since the class will not be instantiated and variable always equals null

User · Accepted Answer

You have two possibilities    non-static setter for static property field  using org springframework beans factory config MethodInvokingFactoryBean to invoke a static setter    In the first option you have a bean with a regular setter but instead setting an instance property you set the static property field   public void setTheProperty Object value        foo bar Class STATIC VALUE   value      but in order to do this you need to have an instance of a bean that will expose this setter  its more like an workaround    In the second case it would be done as follows     lt bean class  org springframework beans factory config MethodInvokingFactoryBean  gt       lt property name  staticMethod  value  foo bar Class setTheProperty   gt       lt property name  arguments  gt           lt list gt               lt ref bean  theProperty   gt           lt  list gt      lt  property gt   lt  bean gt     On you case you will add a new setter on the Utils class   public static setDataBaseAttr Properties p    and in your context you will configure it with the approach exemplified above  more or less like     lt bean class  org springframework beans factory config MethodInvokingFactoryBean  gt       lt property name  staticMethod  value  foo bar Utils setDataBaseAttr   gt       lt property name  arguments  gt           lt list gt               lt ref bean  dataBaseAttr   gt           lt  list gt      lt  property gt   lt  bean gt

User · Answer

As these answers are old  I found this alternative  It is very clean and  works with just java annotations      To fix it  create a    none static setter    to assign the injected value for the static variable  For example     import org springframework beans factory annotation Value  import org springframework stereotype Component    Component public class GlobalValue    public static String DATABASE    Value    mongodb db    public void setDatabase String db        DATABASE   db        https   www mkyong com spring spring-inject-a-value-into-static-variables

User · Answer

I ve had a similar requirement  I needed to inject a Spring-managed repository bean into my Person entity class   entity  as in  something with an identity   for example an JPA entity   A Person instance has friends  and for this Person instance to return its friends  it shall delegate to its repository and query for friends there    Entity public class Person       private static PersonRepository personRepository        Id      GeneratedValue     private long id       public static void setPersonRepository PersonRepository personRepository           this personRepository   personRepository             public Set lt Person gt  getFriends            return personRepository getFriends id                          Repository public class PersonRepository        public Person get Person long id               do database-related stuff            public Set lt Person gt  getFriends long id               do database-related stuff                    So how did I inject that PersonRepository singleton into the static field of the Person class     I created a  Configuration  which gets picked up at Spring ApplicationContext construction time  This  Configuration gets injected with all those beans that I need to inject as static fields into other classes  Then with a  PostConstruct annotation  I catch a hook to do all static field injection logic    Configuration public class StaticFieldInjectionConfiguration         Inject     private PersonRepository personRepository        PostConstruct     private void init             Person setPersonRepository personRepository

[java] How to make spring inject value into a static field

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