I need to publish a Spring boot based jar which should be consumed in other Spring/Spring boot based applications.
In my reuse jar I have a class(BusinessConfig) annotated with #Configuration and it gives out two beans. This class is in the base package of the reuse jar.
#Configuration
public class BusinessConfig {
#Bean(name = "BusinessRepoManager")
public BusinessRepoManager businessRepoManager(){
return BusinessRepoManager.getInstance();
}
#Autowired
#Bean(name = "CustomerManager")
#Scope("request")
public CustomerManager customerManager(BusinessRepoManager busrepoManager){
return CustomerManager.getInstance();
}
}
In the second application, I have added the dependency and in the application class I have the statement
#ComponentScan(basePackageClasses = {BusinessConfig.class})
to inform Spring context to look for beans provided in BusinessConfig class as well.
This works well, as I could see the beans getting created.
Is there any possibility to simplify this, should all consuming applications know the class name in which my configuration exists/package name.
I tried creating a custom annotation in the jar project and used that in the consuming application.
#ComponentScan(basePackageClasses = {BusinessConfig.class})
#Retention(RetentionPolicy.RUNTIME)
#Target(ElementType.TYPE)
#Component
public #interface EnableDemoBusiness {
}
Then in my consuming application I just added
#EnableDemoBusiness
#SpringBootApplication
public class DemoApplication {
public static void main(String[] args) {
SpringApplication.run(DemoApplication.class, args);
}
}
Is there any way to get this work ?
Thanks in advance !
You have a couple of options:
Option 1
You can turn your class into "auto-configuration", by creating a META-INF/spring.factories file in your jar with the following content:
org.springframework.boot.autoconfigure.EnableAutoConfiguration=\
com.your.package.BusinessConfig
Now in applications using your jar if #EnableAutoConfiguration or #SpringBootApplication annotations are used, your configuration will be processed and the beans created.
You might want to annotate your configuration with some #ConditionalXXX annotations if required to give applications that use your jar more control.
Refer to the documentation for more information.
Options 2
You can create a custom #EnableXXX annotation like you attempted.
#Retention(RetentionPolicy.RUNTIME)
#Target(ElementType.TYPE)
#Import(com.your.package.BusinessConfig.class)
public #interface EnableDemoBusiness {
}
Related
I read inside many articles that #ComponentScan should be placed with #Configuration on top of a class. Here some references:
we use the #ComponentScan annotation along with #Configuration
annotation to specify the packages that we want to be scanned
(https://www.baeldung.com/spring-component-scanning)
#ComponentScan(basePackages = "com.zetcode") #Configuration public
class Application { ... } (http://zetcode.com/spring/componentscan)
The #ComponentScan annotation is used with the #Configuration
annotation to tell Spring the packages to scan for annotated
components. (https://dzone.com/articles/spring-component-scan)
I was curious to try if without #Configuration an exception would have been thrown. Surprisingly everything works fine even without #Configuration. Here the code:
#ComponentScan
public class AppConfig {
public static void main(String[] args) {
ApplicationContext context = new AnnotationConfigApplicationContext(AppConfig.class);
for (String beanDefinitionName : context.getBeanDefinitionNames()) {
System.out.println(beanDefinitionName);
}
}
}
I had just one sample bean which got printed.
#Component
public class Car {
}
This was the output of the main method:
org.springframework.context.annotation.internalConfigurationAnnotationProcessor
org.springframework.context.annotation.internalAutowiredAnnotationProcessor
org.springframework.context.annotation.internalCommonAnnotationProcessor
org.springframework.context.event.internalEventListenerProcessor
org.springframework.context.event.internalEventListenerFactory
appConfig
car
Why does it work? and why do they tell to use it with configuration? was it an old requirement?
And even more surprisingly appConfig becomes a bean, even if it does not have any particular annotation such as #Configuration or #Component. So does that mean that anything that gets put as argument of new AnnotationConfigApplicationContext() gets turned into a bean no matter what annotation does it has or has not?
I probably miss some core spring behavior which would justify this. Any idea?
You are still using #Configuration together with #ComponentScan implicitly. By pasing the AppConfig.class as param to the context, it considers it configuration. That would explain the bean created for it as well
I know that #ComponentScan with #Configuration tell Spring where to look for beans.
#ComponentScan
#Configuration
public class MyApp{
...
}
What I do not understand is on which class I have to put these two annotations. Should they stay on the class containing the main method?
Like this
#ComponentScan
#Configuration
public class MyApp{
public static void main(String[] args) {
...
}
}
Or they can stay on whatever class of the application?
The question comes from the fact that Spring has to know the location of #ComponentScan... or is there an automatic way of detection of the #ComponentScan annotation which Spring is performing under the hood?
Hope to have explained myself!
You can put it wherever you want (I usually put mine in com.domain.project-name.config) and just specify the directories it should scan, for example if you want it to scan everything in project use
#ComponentScan("com.domain.project-name")
#Configuration
public class Config {
...
By default, ComponentScan scans all the annotated classes at the current directory level and below.
#Configuration annotation tells the Spring container that the class contains Spring bean configuration.
#ComponentScan annotation tells the Spring container that the annotated class to scan/searches for other annotations and components. You can also define package name to scan with the annotation like #ComponentScan("your.package.name") or you can give package/class names that need not be scanned.
Hence, you can put these annotations on any class that defines your bean configuration and could be required by spring container to parse and create objects for your entities/POJOs, services and DAOs.
To conclude, I would like to add #ComponentScan and other annotations are there for automatic detection. Else, you would need to define XMLs (that's what happens under the hood with annotations) for spring to read and perform these actions.
Using simple example. You can place #ComponentScan with #Configuration in any class which main method can scan.
Main class scans MyScan class which then scan for bean class.
package com.boot.spring;
#SpringBootApplication
#ComponentScan(basePackages = "com.boot.scan")
public class BootApplication {
public static void main(String[] args) {
ConfigurableApplicationContext ctx = SpringApplication.run(BootApplication.class, args);
System.out.println(ctx.getBean("demoBean"));
}
}
Bean class is in different package
package com.boot.bean;
#Service
public class DemoBean {
}
Now, bean class is discovered through DemoScan class
package com.boot.scan;
#ComponentScan(basePackages = "com.boot.bean")
#Configuration
public class DemoScan {
}
I have a bunch of #Value annotated fields in a SpringBoot configuration file, with the matching values in the standard application.properties . If I don't annotate the configuration file with #PropertySource("classpath:application.properties") it will just copy the "${prop1}" string into the actual variable.
I tried adding #EnableAutoConfiguration to the #Configuration class (instead of the PropertySource annotation), but all it does is to break when a requested property is not found.
SpringBoot is supposed to resolve the properties automatically from the standard application.properties file, why this behaviour? Using version 2.2.2.RELEASE
Update:
The answers are correct, the reason it was not working was that I was calling these properties in a test. Annotating the test with #SpringBootTest fixes the issue. In fact when the application is running it is #SpringBootApplication that does the magic
As you can read in this article (chapter 5), SpringBoot manage automatically the application.properties file.
I don't know if this is your problem because I've not seen the code, but in Spring Boot the Application class should be annotated with #SpringBootApplication.
#SpringBootApplication
public class App {
public static void main(String[] args) {
SpringApplication.run(App.class, args);
}
}
Take a look at this starting example.
You can then inject the value for example in a controller class in this way:
#RestController
public class HelloController {
#Value("${test}")
private String test;
#RequestMapping("/test")
String hello() {
return test;
}
}
I try to create a simple custom spring boot starter that read property in application.properties :
#EnableConfigurationProperties({ CustomStarterProperties.class })
#Configuration
public class CustomStarterAutoConfiguration {
#Autowired
private CustomStarterProperties properties;
#Bean
public String customStarterMessage() {
return properties.getMessage();
}
}
with its ConfigurationProperties :
#ConfigurationProperties(prefix = "custom.starter")
public class CustomStarterProperties {
private String message;
/* getter and setter */
...
}
There is also the corresponding application.properties and META-INF/spring.factories to enable the autoconfiguration.
I have another project that declares this starter as a dependency and in which I write a test to see if the customStarterMessage Bean is created :
#RunWith(SpringRunner.class)
#EnableAutoConfiguration
public class TotoTest {
#Autowired
String customStarterMessage;
#Test
public void loadContext() {
assertThat(customStarterMessage).isNotNull();
}
}
This test fails (even with the appropriate application.properties file in the project) because the application.properties seems to not be read.
It works well with a #SpringBootTest annotation instead of the #EnableAutoConfiguration but I would like to understand why EnableAutoConfiguration is not using my application.properties file whereas from my understanding all the Spring AutoConfiguration are based on properties.
Thanks
#EnableAutoConfiguration on test classes don't prepare required test context for you.
Whereas #SpringBootTest does default test context setup for you based on default specification like scanning from root package, loading from default resources. To load from custom packages which are not part of root package hierarchy, loading from custom resource directories you have define that even in test context configuration. All your configurations will be automatically done in your actual starter project based on #EnableAutoConfiguration you defined.
I have a configuration class which registers beans based on a very simple condition (checking a property value in application.properties). The configuration class and the condition are the following:
#Configuration
#Conditional(DatabaseConfigurationCondition.class)
#ComponentScan(basePackageClasses = DBConfigComponents.class)
public class DatabaseConfigurationLoader {
#Bean
public DatabaseConfigurationRepository databaseConfigurationRepository() {
return new DatabaseConfigurationRepository();
}
}
and
public class DatabaseConfigurationCondition implements Condition {
#Override
public boolean matches(ConditionContext conditionContext, AnnotatedTypeMetadata annotatedTypeMetadata) {
return conditionContext.getEnvironment().getProperty("configuration.type").contains("db");
}
}
In addition of the beans registered in this configuration class I have component scan which scans for other components. When the condition is not met, I expect the beans which are defined in the configuration class not to be registered (which happens to be a case), but also I expect other classes which are annotated with #Component (or #Repository, #Service, etc.. ) and are in same folder as DBConfigComponents.class marker interface not to be registered, which does not happen. Beans which are scanned are always registered, no matter if the condition is fulfilled or not.
When I put the #Conditional(DatabaseConfigurationCondition.class) on each #Component annotated class, than it's working correctly, but I don't want to put it on each class separately.
Any suggestion?
Fortunately, I managed to fix this. The problem in my case was that I had another #ComponentScan annotation placed in other configuration class in other Maven module - not conditional on any property. The components which are in same package as DBConfigComponents marker interface were actually scanned by the other configuration class.
The way #ComponentScan works is on package level. Although, in different Maven modules, both configuration classes were in same package. #ComponentScan works perfectly fine with #Conditional. No need #Conditional to be placed on each component separately.
The best way to achieve this is not to annotate these beans using #Component / #Service and #Repository annotations. Instead you should return these as part of the configuration you have setup which would be DatabaseConfigurationLoader. See sample below.
#Configuration
#Conditional(DatabaseConfigurationCondition.class)
public class DatabaseConfigurationLoader {
#Bean
public DatabaseConfigurationRepository databaseConfigurationRepository() {
return new DatabaseConfigurationRepository();
}
#Bean
public SomeService someService() {
return new SomeService();
}
#Bean
public SomeComponent someComponent() {
return new SomeComponent();
}
}
Note: Typically #Configuration with #Conditional are used in libraries that you want to include in your spring boot application. Such libraries should not share the same package as your spring boot application. Thus they should not be picked up by #ComponentScan annotation. Beans from libraries should not be annotated with #Component / #Service / #Repository annotations. Spring suggests using AutoConfiguration for that. See https://docs.spring.io/spring-boot/docs/current/reference/html/using-boot-auto-configuration.html & https://docs.spring.io/spring-boot/docs/current/reference/html/boot-features-developing-auto-configuration.html
No need to implement Condition interface, you need to use '#ConditionalOnProperty' annotation:
#Configuration
#ComponentScan(basePackageClasses = DBConfigComponents.class)
#ConditionalOnProperty(name = "configuration.type", havingValue = "db")
public class DatabaseConfigurationLoader {
#Bean
public DatabaseConfigurationRepository databaseConfigurationRepository() {
return new DatabaseConfigurationRepository();
}
}
you can use 'prefix' instead of 'havingValue' depending on your needs.