Spring: Inject list of beans of specific type

Using Spring @Autowired annotation, we can inject all java beans of specific type to a collection like List.

For example, In the below snippet, resources collection contains all the Resource beans created by spring.

@Component
public class ResourceManager {

 @Autowired
 private List<Resource> resources;

 ......
 ......
}

Find the below working application.

Resource.java

package com.sample.app.model;

public class Resource {
 public int id;
 public String name;

 public Resource(int id, String name) {
  this.id = id;
  this.name = name;
 }

 public int getId() {
  return id;
 }

 public void setId(int id) {
  this.id = id;
 }

 public String getName() {
  return name;
 }

 public void setName(String name) {
  this.name = name;
 }

 public void closeMe() {
  System.out.println("Closing the resource : [" + id + " , " + name + "]");
 }

}

BeanConfiguration.java

package com.sample.app.config;

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

import com.sample.app.model.Resource;

@Configuration
public class BeanConfiguration {

 @Bean
 public Resource fileResource() {
  return new Resource(1, "File Resource");
 }
 
 @Bean
 public Resource dbResource() {
  return new Resource(2, "Database Resource");
 }
 
 @Bean
 public Resource printerResource() {
  return new Resource(3, "Printer Resource");
 }
}

ResourceManager.java

package com.sample.app.cleanup;

import java.util.List;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Component;

import com.sample.app.model.Resource;

@Component
public class ResourceManager {

 @Autowired
 private List<Resource> resources;
 
 public void closeResources() {
  for(Resource resource: resources) {
   resource.closeMe();
  }
 }
}

App.java

package com.sample.app;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.CommandLineRunner;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.ConfigurableApplicationContext;

import com.sample.app.cleanup.ResourceManager;

@SpringBootApplication
public class App implements CommandLineRunner {

 @Autowired
 private ResourceManager resourceManager;

 public static void main(String args[]) {
  ConfigurableApplicationContext context = SpringApplication.run(App.class, args);
  
  //System.out.println("Closing all the beans managed by spring boot");
  context.close();

 }

 @Override
 public void run(String... args) throws Exception {
  resourceManager.closeResources();
 }
}

pom.xml

<project xmlns="http://maven.apache.org/POM/4.0.0"
 xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
 xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
 <modelVersion>4.0.0</modelVersion>
 <groupId>springbootCore</groupId>
 <artifactId>springbootCore</artifactId>
 <version>1</version>


 <parent>
  <groupId>org.springframework.boot</groupId>
  <artifactId>spring-boot-starter-parent</artifactId>
  <version>2.1.6.RELEASE</version>
 </parent>

 <dependencies>

  <dependency>
   <groupId>org.springframework.boot</groupId>
   <artifactId>spring-boot-starter</artifactId>
  </dependency>

 </dependencies>
</project>

Total project structure looks like below.

Run App.java, you can see below messages in console.

Closing the resource : [1 , File Resource]
Closing the resource : [2 , Database Resource]
Closing the resource : [3 , Printer Resource]

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