I was just going through spring documentation for Lifecycle callbacks for a bean. For initialization callback the documentation recommends using #PostConstruct annotation instead of using the InitializingBean interface implementation as it couples code with Spring. Could someone please explain what they mean when they say coupling code with spring. I will share the link to the section i was going through here.
The #PostContruct annotation is not Spring-specific, but from Jakarta Annotations. This way, the core part of your code is not tied to Spring specifically, but could also work in a non-Spring environment, including any Jakarta EE implementation (see "Certified referencing runtimes" in the article), for example, GlassFish or WildFly.
Here is the relevant Javadoc from the Jakarta documentation: PostConstruct.
InitializingBean is pure Spring and will only work in Spring. #PostConstruct is ordinary Java 1.8. Sadly, from 9 it's dependent on javax.annotation:javax.annotation-api:1.3.2
Related
I'm using spring applications which sometimes uses #PostConstruct for setup in code and tests
It seems that annotation will be excluded from Java 11:
Note that both #PostConstruct and #PreDestroy annotations are part of Java EE. And since Java EE has been deprecated in Java 9 and removed in Java 11 we have to add an additional dependency to use these annotations
Article suggest replacing all #PostConstruct with afterPropertiesSet method
I recommend you to change implementation from #PostConstruct annotation to implement org.springframework.beans.factory.InitializingBean interface.
Can I blindly replace it in all cases? or are there other considerations?
EDIT
As #JBNizet suggested, this maybe not a must or needed, as Spring doc suggest the opposite
We recommend that you do not use the InitializingBean interface, because it unnecessarily couples the code to Spring. Alternatively, we suggest using the #PostConstruct annotation or specifying a POJO initialization method.
EDIT 2
Another option is using initMethod:
With Java configuration, you can use the initMethod attribute of #Bean
#Bean(initMethod = "init")
public BeanOne beanOne() {
return new BeanOne();
}
Spring uses jakarta.annotation.PostConstruct. As a contributor in spring-cloud-kubernetes, I have used it and included it in that project numerous times. As a matter of fact we favor dropping InitializingBean.
Ref https://docs.spring.io/spring-framework/docs/current/reference/html/core.html#beans-postconstruct-and-predestroy-annotations
Like #Resource, the #PostConstruct and #PreDestroy annotation types were a part of the standard Java libraries from JDK 6 to 8. However, the entire javax.annotation package got separated from the core Java modules in JDK 9 and eventually removed in JDK 11. If needed, the javax.annotation-api artifact needs to be obtained via Maven Central now, simply to be added to the application’s classpath like any other library.
I have a basic know-how understanding about EJB3 and CDI but i want to dig deeper and understand how this 2 DI implementations actual work.
stackoverflow.com/questions/4684112/how-do-cdi-and-ejb-compare-interact
I have studied them but i fail to find what entity deals with the actual injection of the objects in the annotated variables and and by who is called.
Any help in this is welcomed. Thank you!
The "entity" that handles the injection is any injection framework, such as the reference implementation Weld for CDI or any particular EJB framework included in an application server.
The calling is done by the client code, which will reference the framework's proxies and enable the framework to perform actions.
I want to add a listener on java method and I saw the annotation #Interceptors and #AroundInvoke.
I want to use it in a classic java project but all tutorials show me Java EE projects.
Is it possible ?
Interceptor is a DI (Dependency injection) concept based on AOP (aspects oriented programming).
Since Java-ee 6 you have a lightweight DI container named CDI.
You can use CDI in a java-se context if you provide an implementation allowing a standalone deployment like jboss weld :
See Is it possible to use javax.interceptor in a Java SE environment?
Otherwise, you can use spring, which also provides a lightweight DI container with the same kind of features and may be better suited for a java-se context usage.
I don't think so, those are managed by the Java EE container.
An easy way is to create a proxy/wrapper over all instances of your class.
Or use Spring AOP (but you will have to configure Spring) or AspectJ.
Check this out: http://www.javacodegeeks.com/2012/06/simple-introduction-to-aop.html
Reading the doc here: https://docs.oracle.com/javaee/6/tutorial/doc/gkigq.html
Interceptors are used in conjunction with Java EE managed classes to allow developers to invoke interceptor methods on an associated target class, in conjunction with method invocations or lifecycle events.
So I guess the answer to your question is no.
I'm reading the Arquillian Reference Guide which is very well written, however in the chapter that talks about setting up dependency injection I can't find where you actually specify the beans/bindings.
Most of the Arquillian CDI code examples show the use of Java's #Inject annotation. So I'm just wondering, where I define these beans/DI mappings/bindings, and how do I configure Arquillian to use them?
In Spring DI, you specify a bean descriptor, like spring-config.xml. In Guice you implement a Module and define its configure(Binder) method. What does this look like in Arquillian-land when using javax.inject.Inject? Thanks in advance.
The short answer - there is no need to define bean mappings in CDI, because CDI works with annotations exclusively. You can add extra information in config-files, but this is usually not required.
The long answer is best taken from this excellent introduction into CDI.
I think you need to use "Alternatives" CDI mechanism
Alternatives are beans whose implementation is specific to a particular client module or deployment scenario.
Does anybody know what Spring JAR (and where to find it!) contains the functionality for Spring's so-called "meta-annotations". As this article shows, these cool "new" (well, sorta) constructs allow code like this:
#Service
#Scope("request")
#Transactional(rollbackFor=Exception.class)
#Retention(RetentionPolicy.RUNTIME)
public #interface MyService {
}
#MyService
public class RewardsService {
…
}
Basically, I have a Swing app that does not currently use Spring. I have a sudden requirement change that would be made supremely-easier if I could use these annotations.
So I'm just looking for the smallest, minimally-invasive Spring JAR where this functionality can be found. If absolute-need-be, I can use the entire Spring JAR, but it would be a very heavy-handed solution. It would be nice if Spring released a smaller JAR with smaller-scope functionality.
I'm browswing Maven Repo and see spring-core which contains a package called:
org.springframework.core.annotation
But upon inspection of the API docs it doesn't seem to be what I need...
Ancillary question: is it even possible to use these meta-annotations as standalone constructs, or do I have to use them along with, say, Spring DI or AOP or other major parts of the Spring framework?
Thanks in advance!
The annotations you want will be with the jar it is related to. For instance, the annotation org.springframework.transaction.annotation.Transactional will be in the spring-transactions artifact.
Meta-annotations are not really different from regular annotations other than the fact that Spring now detects Annotations on annotations whereas it didn't before. Whether annotations "work" or not depends on what is looking for them (in this case something in the Spring context).
For further reading see Annotation-based container configuration in the Spring framework reference.
There is project on github which is trying to provide meta-annotation functionality.
https://github.com/dblevins/metatypes/