We Keep Coding

Rest Controller works just for Application class

I'm trying to do a getmapping method using rest-api which will return as a JSON on localhost: 8080. When I do this from the default Application class it works great but when I move this functionality to another class nothing happens. Could someone help me with this, please?

The issue is that your package structure prevents BookController from being component scanned.
When you have your #SpringBootApplication defined in package com.xenon.myspringbootapp, anything in that package and in nested packages is eligible for component scanning, which will register a bean out of #(Rest)Controller and other stereotypes.
Because BookController is defined in book, it is outside of the component scanned packages and will therefore not be component scanned by your #SpringBootApplication annotation.
See the reference docs for more best practices on package structure with Spring Boot applications.
To resolve this, there are two choices to get your class component scanned.
The first (and the way I would recommend) is just to restructure your packages so that the #SpringBootApplication class is at the "base" of your application packages. For example, you could move book.BookController to be at com.xenon.myspringbootapp.book.BookController.
The second is to change the component scanning configuration to include your book package. You can do this either on the #SpringBootApplication annotation itself:
#SpringBootApplication(scanBasePackages = {
"com.xenon.myspringbootapp",
"book"
})
Or, define a different #ComponentScan. Note that the configuration class annotated with #ComponentScan must still be component scanned itself.
#SpringBootApplication
public class MySpringBootAppApplication {
#Configuration
#ComponentScan("book")
public static class MyBookComponentScanConfiguration {}
public static void main(String[] args) {
SpringApplication.run(MySpringBootAppApplication.class);
}
}

Reason 1: Default Spring's component scanning can't fount your #RestController component, so you can try to do #ComponentScan directly.
Reason 2: You need to specify an endpoint for your #GetMapping by using #RequestMapping/#GetMapping("url") or both of them.

Failing to import external jar containing bean

I'm a little new t working with Spring so any help provided would be great.
I have a SpringApplication class (annotated with #SpringBootApplication. In another class (within the same project), it contains a ServiceClass class. When the class is in the same project, it runs as expected.
When the ServiceClass is moved to an external jar, I get the following error.
Description:
Field service in
package-to-class.Comp required a
bean of type 'package-to-class.ServiceClass'
that could not be found.
The injection point has the following annotations:
#org.springframework.beans.factory.annotation.Autowired(required=true)
Action:
Consider defining a bean of type
'package-to-class.ServiceClass' in your
configuration.
I am trying to find what I need to do to inject (#AutoWired) into my project with the above error.

By default, Spring Boot's component scanning only looks in the same package as the #SpringBootApplication and its descendants.
The approach I would suggest is using #Import to import specific beans from outside the project, or use #ComponentScan to import all beans from a package in another project.
#SpringBootApplication
#Import(ServiceClass.class)
public class SpringApplication {
// ...
}
or
#SpringBootApplication
#ComponentScan(basePackages = "com.example.mylibrary")
public class SpringApplication {
// ...
}

Okey some basic things, you have mixed up your packages a bit.
#SpringBootApplication will scan all classes in packages below the class this is annotated on. This annotation is an alias for #EnableAutoConfiguration, #Configuration and #ComponentScan means that #ComponentScan(basePackages = {"com.springdi.example"}, basePackageClasses = DependencyBasePackageClass.class) is not needed.
com.springdi.example // class with #SpringBootApplication annotation
|
|
|
com.springdi.example.* // Will find all #Service, #Component, #Configuration
// in subpackages below the #SpringBootApplication
// annotation
You can read more about the annotation here SpringBootApplication
Since your other annotated classes are NOT in the same package structure as the #SpringBootApplication you need to define all the places you want to scan for annotations.
#SpringBootApplication(scanBasePackages = {"com.springdi.example", "com.dependency.example"})
will probably include all the packages that you want to scan through.

How to #Autowire services in SpringBoot

Good day, guys. I have a question about autowiring services into my classes when using Springboot. All of the examples I have seen on the Internet as well as in the Springboot specification do something of the like (taking an excerpt from the Springboot version 1.5.7 specification):
package com.example.service;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
#Service
public class DatabaseAccountService implements AccountService {
private final RiskAssessor riskAssessor;
#Autowired
public DatabaseAccountService(RiskAssessor riskAssessor) {
this.riskAssessor = riskAssessor;
}
// ...
}
This is a class that injects a property through its constructor, by means of #Autowiring the constructor. Another form is to #Autowire the property like this:
#Autowired
private final RiskAssessor riskAssessor
But, where I work, for these two methods to work, I have been told that I need to use this method:
applicationContext.getAutowireCapableBeanFactory().autowireBean(Object.class)
They have told me that I need this in order for the #Autowired annotation to work.
Now my question to you is: why is there no simple annotation that allows the #Autowire to function correctly? (Something like #AutowiredClass). The above method is too verbose and hard to remember, so surely there must be a better way to make #Autowired work on classes in order to inject services, just like we do in Grails where we just say def someService and it is automatically injected.

If you want properly use #Autowired in your spring-boot application, you must do next steps:
Add #SpringBootApplicationto your main class
Add #Service or #Component annotation to class you want inject
Use one of two ways that you describe in question, to autowire

If you don't have any wiered package structure and the main class package includes all other classes you want spring to instantiate (directly or in the subpackages) a simple annotation #ComponentScan on your main class will help you save all those boiler plate code. Then spring will do the magic, it will go and scan the package(and subpackages) and look for classes annotated with #Service, #Component etc and instantiate it.
Even better, use #SpringBootApplication in your main class, this will cover #Configuration as well. If it is a green field project , I would encourage to start from start.spring.io - a template generation/scaffolding tool for spring

Now my question to you is: why is there no simple annotation that allows the #Autowire to function correctly?
There is: #SpringBootApplication
If you put this at the root of your application (file that contains the main class) and as long as your services are at the same package or a sub-package, Spring will auto-discover, instantiate, and inject the proper classes.
There's an example in this walk-through: REST Service with Spring Boot
As described in that page:
#SpringBootApplication is a convenience annotation that adds all of the following:
#Configuration tags the class as a source of bean definitions for the application context.
#EnableAutoConfiguration tells Spring Boot to start adding beans based on classpath settings, other beans, and various property settings.
#ComponentScan tells Spring to look for other components, configurations, and services in the hello package, allowing it to find the controllers.

You need to annotate the implementation of RestService as a #Service or #Component so Spring would pick it up.
#Service
public class MyRiskAssessorImpl implements RiskAssessor {
///
}

#Autowired almost works out of the box. Just do your component scanning of the class you want to autowire and you are done. Just make sure your main class (or main configuration class) uses #ComponentScan("{com.example.app}") or #SpringBootApplication (main class). The docs explain this stuff pretty good

Spring - excluding a bean being scanned by a parent class' configuration

In Spring, is there a way to exclude a bean that is being scanned by some configuration in a parent class?
I have the following scenario:
#Configuration
#ComponentScan("com.foo")
public class Config {}
#ContextConfiguration(classes = Config.class)
public abstract class A {}
public class B extends A {}
The Config class is causing some bean com.foo.X to be scanned, but I want to exclude it in the context of class B.
In my specific scenario, A and B are test classes. I want my test class B to be able to extend A, and thus inherit the Config spring configuration, but I want to be able to exclude some specific classes from being scanned. Is this possible using Spring, or will I have to remove the #Component annotation from the classes I want to exclude?
I have tried attempting to override the configuration and using #ComponentScan(excludeFilters=...) but that did not work.

Spring #ComponentScan for #Service

I have a package named com.example.service, and in my Spring Configuration class I have the annotation #ComponentScan({"com.example.service"},{"com.example.controller"}).
When I try to #Autowire a service, code compilation fails with a NoSuchBeanDefinitionException. The MyService interface is annotated with #Service.
Currently I use a quite ugly workaround and declare every single service bean in my ExampleConfig.java like
#Bean
public MyService myService() {
return new MyServiceImpl();
}
Generally the #ComponentScan seems to work, if I remove the controller package, the controllers are not found. What did I understand wrong? Please let me know, if I missed out any relevant information.

The MyService interface is annotated with #Service
You must annotate the implementation of your interface. Not the interface itself.

Try using below code for ComponentScan annotation for scanning multiple packages:
#ComponentScan({"com.example.service","com.example.controller"})
instead of
#ComponentScan({"com.example.service"},{"com.example.controller"})
#ComponentScan uses string array for scanning multiple base packages.