Say I have this dependency in a Spring @Configuration
:
@Bean
public SomeClass someClass(SomeClass1 someClass1, SomeClass2 someClass2, ...) {
return new SomeClass(someClass1, someClass2, ...);
}
Say I want do do something in @PostConstruct
that includes someClass
dependency:
@PostConstruct
public void init() {
someClass.doSomething();
}
This cannot be injected:
@PostConstruct
public void init(SomeClass someClass) {
someClass.doSomething();
}
causes:
Caused by: java.lang.IllegalStateException: Lifecycle method annotation requires a no-arg method: ...
This cannot be autowired in the same config like this:
@Autowire
private SomeClass someClass;
@Bean
public SomeClass someClass(SomeClass1 someClass1, SomeClass2 someClass2, ...) {
return new SomeClass(someClass1, someClass2, ...);
}
as that leads to:
Caused by: org.springframework.beans.factory.BeanCurrentlyInCreationException: Error creating bean with name 'globalBus': Requested bean is currently in creation: Is there an unresolvable circular reference?
A config can be split (so @Bean
goes to the other config) and @Import
-ed by this one and it works OK. Probably other solutoins exist - e.g. creating a separate initialization bean or so.
Is there a way to do this within one @Configuration
?
Edit
As requested by @SotiriosDelimanolis, a sscce for the exception when using @Autowired
:
public class ConfigPostConstructDependenciesPrb {
public static void main(String[] args) {
AnnotationConfigApplicationContext ctx = new AnnotationConfigApplicationContext(Config.class);
ctx.getBean(Service.class);
ctx.close();
}
public static class Service {
private final Dependency dependency;
public Service(Dependency dependency) {
this.dependency = dependency;
}
public void work() {
System.out.println(dependency.getNum());
}
@Override
public String toString() {
StringBuilder sb = new StringBuilder();
sb.append("Service [dependency=");
sb.append(dependency);
sb.append("]");
return sb.toString();
}
}
public static class Dependency {
private final int num;
public Dependency(int num) {
this.num = num;
}
public int getNum() {
return this.num;
}
@Override
public String toString() {
StringBuilder sb = new StringBuilder();
sb.append("SomeClass1 [num=");
sb.append(num);
sb.append("]");
return sb.toString();
}
}
@Configuration
public static class BaseConfig {
@Autowired
private Service service;
@Bean
public Dependency dependency() {
return new Dependency(42);
}
@Bean
public Service service(Dependency dependency) {
return new Service(dependency);
}
@PostConstruct
public void init() {
service.work();
}
}
@Configuration
@Import(BaseConfig.class)
public static class Config {
@Autowired
private Service service;
}
}
When we annotate a method in Spring Bean with @PostConstruct annotation, it gets executed after the spring bean is initialized. We can have only one method annotated with @PostConstruct annotation. This annotation is part of Common Annotations API and it's part of JDK module javax.
In jdk9 @PostConstruct and @PreDestroy are in java. xml. ws. annotation which is deprecated and scheduled for removal.
The PreDestroy annotation is used on methods as a callback notification to signal that the instance is in the process of being removed by the container. The method annotated with PreDestroy is typically used to release resources that it has been holding.
In a single class, it allows to have more than one @PostConstruct annotated method, and also the order of execution is random.
(Tested in Spring 4.3.6)
Create a nested class inside your @Configuration and put there declarations of @Autowired service
and @PostConstruct init()
:
@Configuration
public static class BaseConfig {
//...
@Bean
public Service service(Dependency dependency) {
return new Service(dependency);
}
@Configuration
public static class Setup {
@Autowired
private Service service;
@PostConstruct
public void init() {
service.work();
}
}
}
Below is your full example updated accordingly.
Notice that you don't have to add explicit reference to BaseConfig.Setup
(look at the @Import
annotation before Config
class - it only refers to BaseConfig
itself).
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.annotation.*;
import javax.annotation.PostConstruct;
public class ConfigPostConstructDependenciesPrb {
public static void main(String[] args) {
AnnotationConfigApplicationContext ctx = new AnnotationConfigApplicationContext(Config.class);
ctx.getBean(Service.class);
ctx.close();
}
public static class Service {
private final Dependency dependency;
public Service(Dependency dependency) {
this.dependency = dependency;
}
public void work() {
System.out.println(dependency.getNum());
}
@Override
public String toString() {
StringBuilder sb = new StringBuilder();
sb.append("Service [dependency=");
sb.append(dependency);
sb.append("]");
return sb.toString();
}
}
public static class Dependency {
private final int num;
public Dependency(int num) {
this.num = num;
}
public int getNum() {
return this.num;
}
@Override
public String toString() {
StringBuilder sb = new StringBuilder();
sb.append("SomeClass1 [num=");
sb.append(num);
sb.append("]");
return sb.toString();
}
}
@Configuration
public static class BaseConfig {
@Bean
public Dependency dependency() {
return new Dependency(42);
}
@Bean
public Service service(Dependency dependency) {
return new Service(dependency);
}
@Configuration
public static class Setup {
@Autowired
private Service service;
@PostConstruct
public void init() {
service.work();
}
}
}
@Configuration
@Import(BaseConfig.class)
public static class Config {
@Autowired
private Service service;
}
}
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