In a latest video about Kotlin and Spring Boot: Spring Tips: Bootiful Kotlin Redux. The Application class of Spring Boot looks like:
class SpringBootKotlinApplication
fun main(args: Array<String>) {
}
I remember a Kotlin has to be annotated as open in Spring Boot.
open class SpringBootKotlinApplication
See this video.
So why it is not necessary to be annotated open now? Spring Boot does need to extend the Application class now?
When you have a look at one of the speaker’s sample projects like this, you will notice a compiler plugin, in this case kotlin-maven-allopen. It’s described in the official docs:
For instance, when you use Spring, you don't need all the classes to be open, but only classes annotated with specific annotations like #Configuration or #Service. All-open allows to specify such annotations.
As SpringBootAnnotation, as a meta annotation, is fulfilling that condition, there’s no need to make the class open in the source code since the compiler does it behind the scenes.
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I am trying to implement a Spring Boot REST API but I was asked to use a interface as dependency but no impl, and I don't know how to achieve this. The way I implemented was to have service classes for my entities and there I would just call the repository in my methods. I would like an example of implementation like this.
I watched some youtube tutorials but they all used impl classes
Your controller should have a field of your interface type, with the injecting annotation (in spring it's #Autowired). The DI framework will do the heavy-lifting on startup and inject the correct implementation at runtime
#Controller
public class MyController {
#Autowired
private MyInterface myInterface;
....
}
For this to work, your framework needs to recognize the concrete class. In spring you can achieve this in multiple ways - scanning package paths, xml configuration files and more.
Check the spring documentation to see which way suits you best
Upgrading an existing system to Spring Boot with Auto config. Currently the system is all Java config. I'm confused over whether to continue the use of #Profile. Is this annotation no longer needed? I searched extensively about upgrading and found only references to non-Spring Java migration and creating new projects.
Typical #Profile usage in our configuration classes looks something like:
#Bean
#Profile("is-standalone")
public Service unsecuredService(SomeApi someApi) {
return new ...
}
I inferred from the Spring Boot examples that using one of the #Conditional annotations is recommended like this:
#Bean
#ConditionalOnProperty("unsecured.enabled")
public Service unsecuredService(SomeApi someApi) {
return new ...
}
Then in a YAML file the is-standalone Profile enables or disables all the various properties for that Profile. Is this the proper way to upgrade? To repeat a question from above differently, can the #Profile usage be left as is? This is for a fairly large project, the upgrade is non-trivial, so I would like to do this only once!
Depends where your previous #Profile annotation is coming from. If you're using Spring's #Profile, the functionality is as follows:
Annotating a class with #Profile("dev") will load the class and register it in the Spring context only when the dev profile is active
Annotating a class with #Profile("!dev") will load the class and register it in the Spring context only when the dev profile is inactive
If this sounds like what you have already, no change is needed.
I have a spring boot rest service that included an external project in pom as it's dependency. That external project is basically a jar that has spring AOP code.
The base package in my main application that includes this external jar with spring AOP code is x.y.z
The class in external jar where the #before advice is, is under the package a.b.c
With this class under a.b.c package, it doesn't get recognized by the main application where I want to use the spring aop implementation and apply the aspect. However, when I change it's package from a.b.c to x.y.z (which I really can't do in real life) it works fine.
I know that in spring boot service which happens to be the including service, it scans everything under root package given in the application class, x.y.z in this case and that is why aspect works fine if it's class is under x.y.z.
however, the problem is that this spring app jar will be used across multiple applications. So changing package name like this is not an option.
Is there a way to accomplish this without changing the package name of the class where spring app code is ?
Probably component scan is only activated for your application class packages by default. You can extend it to multiple packages, including the aspect package:
XML style configuration:
<context:component-scan base-package="x.y.z, a.b.c" />
Annotation style configuration:
#ComponentScan(basePackages = {"x.y.z", "a.b.c"})
Disclaimer: I am not a Spring user, only an AspectJ expert. I just knew that you can configure component scan, googled the syntax for you and hope it is correct.
Please define the bean (of jar project )inside main application. Give the #ComponentScan(basePackages = {"x.y.z", "a.b.c"}) as well as #EnableAspectJAutoProxy. Also include below piece of code.
ex:
` #Bean
public LoggingHandler loggingHandler()
{
return new LoggingHandler();
}`
Also annotate external jar code with:
`#Aspect
#Component
public class LoggingHandler {`
What #kriegaex suggests is correct. In addition to that, please make sure you are using #Component along with #Aspect. Since #Aspect is not a Spring annotation, Spring won't recognize it and hence your aspect won't be registered. So, using #Component is mandatory to getting aspects to work in Spring environment.
Spring boot provides #ComponentScan to find packages to be scanned.
I am building a library which has #RestControllers inside with package com.mylib.controller. There are other classes as well with stereotype annotations in different packages.
So, if some one is developing SpringBoot Application with com.myapp base package.
He uses my library in his application. He need to mention #ComponentScan("com.mylib") to discover stereotype components of library.
Is there any way to scan components without including library package in #ComponentScan?
As spring-boot-starter-actuator expose its endpoints just with dependency, without defining #ComponentScan. OR any default package which is scanned regardless of application base package.
You could create a Spring Boot Starter in the same style as the Spring Provided Starters. They are essentially a jar'd library with a a spring.factories file pointing to the #Configuration class to load with some other annotations on there to provide overriding/bean back off (#ConditionalOnMissingBean) and generally provide their own #ConfigurationProperties.
Stéphane Nicoll provided an excellent demo of how to build one.
https://github.com/snicoll-demos/hello-service-auto-configuration
It is also documented in the Spring Boot documentation. https://docs.spring.io/spring-boot/docs/current/reference/html/boot-features-developing-auto-configuration.html
The library approach would also work but I see no benefit in not making it a starter. Additionally for any library/starter I'd recommend dropping the #ComponentScan and just defining the beans in a #Configuration. This will work for sterotypes like #RestController etc. will function as normal if you create an #Bean out of it in a configuration.
Spring boot starter are special artifacts designed by Spring and used by Spring.
You can check that in the source code that contains mainly a
spring.provides file :
provides: spring-boot-actuator,micrometer-core
I don't know the exact way to process in the same way as Spring Boot Starter but as probably acceptable workaround, you could define in your jar a #Configuration class that specifies #ComponentScan("com.mylib").
#Configuration
#ComponentScan("com.mylib")
public class MyLibConfig {
//...
}
In this way, clients of the jar need "only" to import the #Configuration class :
#Import(MyLibConfig.class)
#Configuration
public class ClientConfig{
//...
}
I am writing a library to provide some functionality that is shared between multiple different Spring Boot applications that I work with.
I would like to do something similar to the auto-configuration that is provided by the many Spring Boot starter libraries exist. That, or some other simple declarative way to integrate my library with the ApplicationContext of the apps using it.
I have found some resources explaining how auto configuration works. I can figure out the above problem.
However, I have not been able to find any good examples of how I can test as part of my library's test suite that it suitably integrates with a Spring Boot application. Ideally, I would start up a simple Spring Boot app written in the library's test directly just for the sake of testing, add the right annotation to it, and be able to assert that the correct beans are then configured.
I have tried creating a TestApplication class that does that and writing integration tests using the SpringBootTest annotation but the TestApplication was never started before my test started.
What can I do to start up a simple app like that solely for the purpose of testing my library? My tests are written with Spock and Spock-Spring in case that changes things versus other test frameworks.
I was able to make it work with the following test class:
#SpringBootTest
#ContextConfiguration(classes = TestApplication)
class DummyIntegrationSpec extends Specification {
#Autowired
DummyService dummyService
void 'dummy service should exist'() {
expect:
dummyService.getMessage() == DummyConfiguration.MESSAGE
}
}
and this TestApplication class at src/test/groovy/com/example/project/TestApplication.groovy
#SpringBootApplication(scanBasePackages = 'com.example.project.config')
#EnableAutoConfiguration
class TestApplication extends SpringBootServletInitializer {
#Override
protected SpringApplicationBuilder configure(SpringApplicationBuilder application) {
return application.sources(TestApplication)
}
static void main(String[] args) {
SpringApplication.run(TestApplication, args)
}
}
The two key changes I had to make in order for the TestApplication to start and load the correct context when I moved my TestApplication class from src/main to src/test were:
the TestApplication class needed to be added to the ContextConfiguration annotation
the package that my library's Java config files live in needed to be added to the SpringBootApplication scanBasePackages field
The library auto-configuration does follow a similar structure to the one mentioned in the link tom provided.
Your auto-configuration should be automatically picked while your main spring application/test is starting and all beans will be registered in your context. They will be available for auto-wiring and follow your conditions and init order.
As a summary, make sure you have an auto-configuration annotated by #Configuration class with an #Import that imports your #Configuration annotated configuration classes (inside of them you define beans with methods annotated with #Bean). Also make sure you created a spring.factories file that include your auto-configuration class and that you removed the spring boot maven plugin (for the packaging to be right).
Also, make sure your auto-configuration project is NOT annotated by things like #SpringBootApplication, #EnableAutoConfiguration, #ComponentScan or other spring boot annotations that need to be only in the main spring boot projects (There should be one of them in each stack).
Please also see the article below:
Spring boot is based on a lot of pre-made auto-configuration parent projects. You should already be familiar with spring boot starter projects.
You can easily create your own starter project by doing the following easy steps:
Create some #Configuration classes to define default beans. You should use external properties as much as possible to allow customization and try to use auto-configuration helper annotations like #AutoConfigureBefore, #AutoConfigureAfter, #ConditionalOnBean, #ConditionalOnMissingBean etc. You can find more detailed information on each annotation in the official documentation Condition annotations
Place an auto-configuration file/files that aggregates all of the #Configuration classes.
Create a file named spring.factories and place it in src/main/resources/META-INF.
In spring.factories, set org.springframework.boot.autoconfigure.EnableAutoConfiguration property with comma separated values of your #Configuration classes:
org.springframework.boot.autoconfigure.EnableAutoConfiguration=
com.mycorp.libx.autoconfigure.LibXAutoConfiguration,
com.mycorp.libx.autoconfigure.LibXWebAutoConfiguration
Using this method you can create your own auto-configuration classes that will be picked by spring-boot. Spring-boot automatically scan all maven/gradle dependencies for a spring.factories file, if it finds one, it adds all #Configuration classes specified in it to its auto-configuration process.
Make sure your auto-configuration starter project does not contain spring boot maven plugin because it will package the project as an executable JAR and won't be loaded by the classpath as intended - spring boot will not be able to find your spring.factories and won't load your configuration