How to Get All Spring-Managed Beans

Spring Framework's powerful dependency injection mechanism allows you to manage beans within the Spring container. Sometimes, you may need to get a list of all beans managed by the Spring container for debugging, monitoring, or documentation purposes. This tutorial will guide you through different methods to retrieve all Spring-managed beans in a Spring Boot application.

Prerequisites

• JDK 17 or later
• Maven or Gradle
• IDE (IntelliJ IDEA, Eclipse, etc.)

Step 1: Set Up a Spring Boot Project

1.1 Create a New Spring Boot Project

Use Spring Initializr to create a new project with the following dependencies:

• Spring Web

Download and unzip the project, then open it in your IDE.

1.2 Configure application.properties

Set up the application properties for your project. This file is located in the src/main/resources directory.

# src/main/resources/application.properties

server.port=8080

Step 2: Retrieve All Spring-Managed Beans Programmatically

2.1 Create a Spring Component

Create a Spring component that retrieves all beans managed by the Spring container using ApplicationContext.

package com.example.demo;

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

import javax.annotation.PostConstruct;
import java.util.Arrays;

@Component
public class BeanLister {

    @Autowired
    private ApplicationContext applicationContext;

    @PostConstruct
    public void listBeans() {
        String[] beanNames = applicationContext.getBeanDefinitionNames();
        Arrays.sort(beanNames);
        for (String beanName : beanNames) {
            System.out.println(beanName);
        }
    }
}

Explanation:

• @Component: Marks this class as a Spring component.
• ApplicationContext: The Spring container that holds all the beans.
• @PostConstruct: Indicates that the listBeans method should be executed after the bean has been constructed.

2.2 Create a REST Controller

Create a REST controller to expose an endpoint that retrieves all Spring-managed beans.

package com.example.demo;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.ApplicationContext;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;

import java.util.Arrays;
import java.util.List;

@RestController
public class BeanController {

    @Autowired
    private ApplicationContext applicationContext;

    @GetMapping("/beans")
    public List<String> getAllBeans() {
        String[] beanNames = applicationContext.getBeanDefinitionNames();
        Arrays.sort(beanNames);
        return Arrays.asList(beanNames);
    }
}

Explanation:

• @RestController: Marks this class as a REST controller.
• @GetMapping("/beans"): Maps HTTP GET requests to the getAllBeans method.
• ApplicationContext: Injected to retrieve the bean names.

Step 3: Running and Testing the Application

3.1 Run the Application

Run the Spring Boot application using your IDE or the command line:

./mvnw spring-boot:run

3.2 Access the Endpoint

Open your browser and navigate to http://localhost:8080/beans. You should see a list of all Spring-managed beans in JSON format.

Step 4: Using Spring Boot Actuator to List All Beans

Spring Boot Actuator provides an easy way to list all Spring-managed beans without writing custom code.

4.1 Add Actuator Dependency

Ensure that you have included the Spring Boot Actuator dependency in your pom.xml (for Maven) or build.gradle (for Gradle).

For Maven:

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

For Gradle:

implementation 'org.springframework.boot:spring-boot-starter-actuator'

4.2 Configure Actuator Endpoints

Expose the Actuator endpoints in the application.properties file.

management.endpoints.web.exposure.include=*

4.3 Access the Beans Endpoint

Run your application and navigate to http://localhost:8080/actuator/beans. This endpoint provides a comprehensive list of all Spring-managed beans along with their dependencies and configurations.

Conclusion

In this tutorial, you have learned how to retrieve all Spring-managed beans in a Spring Boot application. We covered:

• Retrieving beans programmatically using ApplicationContext.
• Creating a REST endpoint to expose the list of beans.
• Using Spring Boot Actuator to easily list all beans with detailed information.

By leveraging these methods, you can effectively monitor and debug your Spring application, ensuring that all necessary beans are properly managed and configured.