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:
<?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: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">
<util:properties id="dataBaseAttr"
location="file:#{classPathVariable.path}/dataBaseAttr.properties" />
</beans>
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.
This question is related to
java
spring
configuration
app-config
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<Person> getFriends(){
return personRepository.getFriends(id);
}
...
}
.
@Repository
public class PersonRepository {
public Person get Person(long id) {
// do database-related stuff
}
public Set<Person> 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);
}
}
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/
Source: Stackoverflow.com