To get a list of all endpoints after startup in a Spring Boot application, developers often look for ways to programmatically extract or log these endpoints for documentation, troubleshooting, or monitoring purposes. This article delves into various methods of retrieving active endpoints post-startup in Spring Boot applications.

Accessing Endpoint List

Spring Boot provides a few built-in mechanisms to access endpoint information. You can leverage the Actuator library and other programmatic approaches to accomplish this. Here are some detailed methods and technical explanations to achieve this functionality.

Using Spring Boot Actuator

Spring Boot Actuator is a sub-project of Spring Boot focusing on monitoring and controlling applications. It provides production-ready features like health checks and metrics, and also gives access to endpoints at runtime.

Step-by-step Guide

1. Add Dependency:
   Ensure that you have Spring Boot Actuator included in your pom.xml for Maven:

1   <dependency>
2       <groupId>org.springframework.boot</groupId>
3       <artifactId>spring-boot-starter-actuator</artifactId>
4   </dependency>

Or in build.gradle for Gradle:

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

1. Configure Endpoints:
   Enable the endpoint exposure in your application.properties file:

   management.endpoints.web.exposure.include=*

This configuration allows you to expose all available actuator endpoints. Alternatively, you can expose specific endpoints as needed.

1. Accessing the Endpoints:
   Once the application is running, access the actuator endpoint to view all available endpoints. The default URL for the list of endpoints is:

   http://localhost:8080/actuator

Here, you will see a JSON object listing all exposed endpoints.

Programmatic Approach

If you need a programmatic way to list all endpoints within a Spring Boot application, using the RequestMappingHandlerMapping bean is an effective strategy.

Implementation Example

1. Autowire RequestMappingHandlerMapping:
   You can tap into Spring's request mapping infrastructure to extract endpoint information:

1   import org.springframework.beans.factory.annotation.Autowired;
2   import org.springframework.context.event.ContextRefreshedEvent;
3   import org.springframework.context.event.EventListener;
4   import org.springframework.stereotype.Component;
5   import org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerMapping;
6
7   @Component
8   public class EndpointLister {
9
10       @Autowired
11       private RequestMappingHandlerMapping requestMappingHandlerMapping;
12
13       @EventListener
14       public void handleContextRefresh(ContextRefreshedEvent event) {
15           requestMappingHandlerMapping.getHandlerMethods().forEach((requestMappingInfo, handlerMethod) -> {
16               System.out.println("Endpoint: " + requestMappingInfo + ", Method: " + handlerMethod);
17           });
18       }
19   }

Here, we listen to application context refresh events and then retrieve handler methods associated with URL patterns.

Additional Considerations

• Security: Be cautious about exposing sensitive endpoints in a production environment. Make sure that access to actuator endpoints is secured using Spring Security or IP whitelisting.
• Customization: Spring Boot Actuator allows you to customize endpoints and create custom endpoints to suit your specific needs.
• Environment Configuration: Ensure the appropriate environment configuration is set when deploying your application (e.g., application profiles).

Summary Table

Through this comprehensive exploration, you can choose the method that best fits your development and operational strategies. Whether using Spring Boot Actuator or a custom programmatic approach, it's crucial to balance ease of access with application security needs.