35 Essential Spring Boot Annotations for Faster Development

You might have spent hours configuring your Spring application in the past, dealing with countless XML lines just to set up a few beans. That's where Spring Boot annotations come in. Instead of complicated XML files, you now have annotations that handle all the heavy lifting for you. Attaching specific annotations tells Spring Boot exactly how to handle components and configurations behind the scenes.  

Boost your career by mastering cutting-edge technology! Enroll in Artificial Intelligence & Machine Learning Courses and stay ahead in the evolving tech industry.

Here are a few reasons Spring Boot annotations matter:

• They define bean declarations in a direct, organized way.
• They cut down on the learning curve for anyone new to the project.
• They bring structure to your layers with stereotype-based markers.
• They support a convention-over-configuration principle that saves time.

This blog will teach you about stereotypes that mark classes for specific roles, property-based annotations that manage external settings, and advanced conditional annotations.

Spring Boot Annotations List 

Spring Boot offers a collection of annotations that guide how an application’s components behave and interact with one another. You can handle core configurations, manage bean lifecycles, define request handling endpoints, and more. 

Take your skills to the next level with industry-leading AI and Machine Learning programs:

• PG Diploma in Machine Learning & AI - IIIT Bangalore
• PG Certification in Machine Learning & Deep Learning - IIIT Bangalore
• Master of Science in AI & Data Science - Jindal Global University

Take a look at the table below to see the major categories and where each annotation in Java Spring Boot fits. 

Take the leap into Spring Boot and DevOps with upGrad’s comprehensive software engineering courses today!

Also Read: Top Spring Boot Features for Java Developers

5 Core Configuration Spring Boot Annotations

When you begin a Spring Boot project, core configuration Spring Boot annotations help you organize essential details so your application can run without extra effort.They handle tasks like automatic bean creation, scanning the correct packages, and keeping your main class as streamlined as possible.

Take a look at how these configurations come together:

• Automatic Setup: These annotations handle typical setup tasks behind the scenes.
• Centralized Definitions: You place core details in predictable spots for simpler maintenance.
• Reduced Clutter: You can skip large amounts of XML in favor of clear, direct annotations.
• Adaptable Structure: You can drop in new functionality and stay consistent in your approach.

Now, let’s explore the annotations in detail.

1. @SpringBootApplication  

You rely on @SpringBootApplication to unify three vital Spring Boot features under one annotation. It brings together the following:

1. @Configuration for defining beans
2. @EnableAutoConfiguration for setting up common dependencies
3. @ComponentScan for discovering components. 

Placing this annotation in Java Spring Boot on your main class streamlines the entire configuration process. It also makes your application's entry point obvious, simplifying maintenance and onboarding as your project grows.

Here’s how it distinguishes itself:

• Combines Multiple Annotations: Merges @Configuration, @ComponentScan, and @EnableAutoConfiguration
• Minimizes Redundancy: Lets you replace three separate annotations with a single line
• Targets Main Class: Makes it easy to locate application startup logic in one place
• Promotes Convention: Sticks to Spring Boot’s principle of providing sensible defaults

Sample Example of @SpringBootApplication in Action

Below is a brief example to demonstrate how this single annotation simplifies a core setup. Notice how everything from bean configuration to component scanning is activated under the hood:

@SpringBootApplication
public class SarikaApplication {
    public static void main(String[] args) {
        SpringApplication.run(SarikaApplication.class, args);
    }
}

In this snippet, @SpringBootApplication ensures that configuration, auto-configuration, and component scanning run automatically. You no longer have to specify each annotation individually or rely on extensive XML files.

2. @EnableAutoConfiguration

@EnableAutoConfiguration automates much of the setup required for Spring Boot applications. This annotation inspects your classpath and brings in the configurations that align with the dependencies you’ve added. It spares you from manually defining each piece of the puzzle — so your project benefits from what’s already present. 

You then spend less time on infrastructure and more time refining the unique features of your application.

Here’s why it makes a difference:

• Scans Classpath: Identifies which modules (like web, JPA) need to be turned on
• Saves Configuration Time: Provides defaults, freeing you from extra code
• Works Seamlessly with Spring Boot: Integrates with other annotations for fewer manual steps
• Can Exclude Unnecessary Parts: Lets you skip certain configurations if you don’t need them

Sample Example of @EnableAutoConfiguration in Action

Below is a short code example. Notice that @EnableAutoConfiguration takes care of enabling any features you have placed on your classpath:

@Configuration
@EnableAutoConfiguration
public class RohanAutoConfig {
    // Beans and additional settings can go here
}

This snippet shows how the annotation checks what your project includes. If you have a MySQL driver, it configures a data source. If you add web dependencies, it sets up MVC components. Thanks to auto-configuration, you don't write those lines yourself.

3. @SpringBootConfiguration

You can use @SpringBootConfiguration in scenarios that call for a class dedicated to Spring Boot–specific settings. It still indicates a source of bean definitions (like @Configuration does) but also flags that this configuration ties directly into Spring Boot’s internal processes. You might not see it as commonly because @SpringBootApplication often covers its functionality, but it remains an option.

Here’s what stands out:

• Aligns with Boot: Expresses you’re dealing with a Spring Boot project rather than plain Spring
• Class-Level Marker: Makes it clear your class provides core setup details
• Overlaps with @Configuration: Performs a similar role but focuses on Boot’s environment
• Sometimes Used for Testing: You can isolate certain Boot config for integration tests

Sample Example of @SpringBootConfiguration in Action

Below is a code example. Notice how you can still define beans exactly like you do with regular configuration classes:

@SpringBootConfiguration
public class MeenaBootConfig {
    
    @Bean
    public String greeting() {
        return "Hello from a Boot-specific config class!";
    }
}

Here, you see how this annotation makes your class recognizable as a source of Spring Boot configuration. The methods you mark as beans are picked up automatically when your application starts.

4. @ComponentScan

You rely on @ComponentScan to tell Spring which packages contain the components you want to manage. It spares you from individually declaring each class that should be a bean, bringing them all into your application context. If you’re organizing multiple packages, you can list them here so nothing is overlooked.

Here are the key points you must know about this annotation in Java Spring Boot:

• Discovers Components: Searches designated packages for classes annotated with @Component, @Service, @Repository, @Controller, etc.
• Supports Multiple Packages: Lets you specify more than one base package if your codebase is spread out.
• Pairs with Configuration: Often used within a class marked @Configuration or under @SpringBootApplication.
• Prevents Missing Beans: Ensures you never skip important components that belong in your app context.

Sample Example of @ComponentScan in Action

See the example below. Notice how you can point to a specific package or multiple packages:

@Configuration
@ComponentScan(basePackages = {"com.example.raviapp", "com.example.helpdesk"})
public class RaviAppConfig {
    // Additional setup logic
}

In this snippet, classes marked with stereotype annotations in the com.example.raviapp and com.example.helpdesk packages become beans automatically. You don’t write extra lines to register them.

5. @Configuration

You rely on @Configuration to create a class that declares one or more beans. This straightforward, code-based approach replaces the verbose XML files of older Spring versions. By grouping related beans in the same configuration class, you keep them easy to find and maintain.

Consider the following benefits:

• Direct Code Approach: You define beans in methods, reducing or removing XML entries
• Encapsulation: Each configuration class can group beans around a single theme
• Clear Lifecycle: Every bean you define is handled by the Spring container at runtime
• Pairs with @Bean: Methods that return beans carry this annotation for direct instantiation

Sample Example of @Configuration in Action

The example below shows how you might declare a bean in a simple config file. You’ll see how @Configuration becomes the root that allows @Bean to work:

@Configuration
public class TinaConfiguration {
    
    @Bean
    public MessageService messageService() {
        return new WhatsAppService();
    }
}

This snippet illustrates how any method tagged with @Bean is recognized as a Spring bean. The Spring container manages its lifecycle without further intervention from you.

Also Read: Spring vs Spring Boot: Understanding the Difference Between Spring and Spring Boot in 2025

4 Bean Creation and Management Spring Boot Annotations

Bean creation and management ensure that your objects are well-organized, automatically instantiated, and supervised by the Spring container. The four annotations in this section have a unique job, whether it’s marking classes for discovery, defining service logic, or handling persistence. In short, these annotations highlight the distinct roles of each class while saving you from configuring everything by hand.

Here’s a glimpse of what these annotations offer:

• Differentiated Roles: Each annotation reflects a specific responsibility, such as core logic, database operations, or general-purpose utilities
• Unified Lifecycle: All beans, regardless of annotation type, are automatically tracked and managed by the Spring container
• Reduced Setup: You avoid manual definitions of objects, so you stay focused on core features and spend less time writing repetitive code
• Simple Maintenance: With clear markings for each component, future updates and debugging remain less complicated

Next, you will see these annotations broken down individually so you can decide exactly how each one might strengthen your application’s structure.

6. @Bean

You use @Bean to declare a method whose return value will be managed as a bean in the Spring container. It allows you to replace large XML chunks with straightforward Java code. When Spring discovers this annotation on a method, it automatically invokes that method to retrieve the resulting bean instance. This setup eliminates unnecessary verbosity and keeps the essence of each bean front and center.

Here’s why it works well:

• Method-Based Declaration: Each annotated method returns a specific bean
• Built-In Lifecycle: Spring fully handles creation and destruction without extra configs
• Improved Readability: Java code replaces XML definitions for a cleaner approach
• Centralized Configuration: You can group related beans in a single class

Sample Example of @Bean in Action

The snippet below demonstrates a typical usage. Notice how @Bean is placed on a method that returns a specific object:

@Configuration
public class PriyaConfiguration {

    @Bean
    public PaymentProcessor paymentProcessor() {
        return new UpiPaymentProcessor(); 
    }
}

In this example, paymentProcessor() becomes a bean named paymentProcessor. Spring will control its lifecycle, inject it wherever needed, and free you from writing additional boilerplate code.

7. @Component

You rely on @Component to mark a class that should be picked up by Spring’s component scanning mechanism. It is the foundation for more specialized annotations like @Service and @Repository. By annotating a class with @Component, you declare that it is a candidate for auto-detection and automatic instantiation.

Here’s what makes it helpful:

• Generic Stereotype: A class doesn’t need a specialized annotation if it doesn’t fit the service or repository category
• Auto-Detection: Once @Component is present, Spring scans for this class and creates a bean automatically
• Versatile Usage: You can apply it to utilities, helpers, or any general-purpose class
• Customizable Bean Name: You can provide a specific bean name if needed

Sample Example of @Component in Action

Check out the following snippet. Notice how @Component alone is enough to let Spring pick up the class:

@Component
public class VinayLogger {

    public void logMessage(String message) {
        System.out.println("[VinayLogger] " + message);
    }
}

In this case, VinayLogger is discovered during component scanning and turned into a bean without any additional configuration. You simply call it wherever you want a logging helper.

8. @Service

You typically apply @Service when a class holds your business logic or application functionality. It’s a more specialized version of @Component, indicating that the core purpose of this class lies in performing operations or calculations, often in coordination with repositories or external APIs. 

Marking a class with @Service keeps your application organized in a layered format, where controllers handle requests, services perform logic, and repositories manage data.

Here are the key reasons to use it:

• Semantic Clarity: Makes it obvious that the class is for business operations
• Cleaner Application Layers: Splits your application into well-defined parts
• Reduced Boilerplate: Auto-discovered by Spring, so you don’t create extra wiring code
• Works Smoothly with @Repository: Services call repositories to store or fetch data

Sample Example of @Service in Action

In the snippet below, you’ll see how @Service fits right into the flow between controllers and repositories:

@Service
public class AnkitaOrderService {

    public String placeOrder(String productName) {
        // Some business logic, e.g., check inventory, apply discount
        return "Order placed for " + productName;
    }
}

This code clarifies that AnkitaOrderService is part of the service layer, making it simpler to see where business logic resides when you read through the application.

9. @Repository

You rely on @Repository to define a class responsible for data-related operations, whether you’re using JPA, JDBC, or another data access tool. This annotation signals to Spring that you want consistent handling of exceptions and auto-detection of your persistence classes. 

It’s a specialization of @Component with added database-oriented features, so it fits neatly into applications that need clear separation between business logic and data management.

Here are some of its notable points:

• Data-Focused: Indicates that the class interacts with the database layer
• Exception Translation: Errors become Spring’s DataAccessException hierarchy for uniform handling
• Stereotype for Persistence: Reinforces the concept of layered architecture
• Auto-Discovery: Appears in the same component-scan as services and controllers

Sample Example of @Repository in Action

Below is an example of how you might apply @Repository. Notice that Spring recognizes it as a class that deals specifically with data storage:

@Repository
public interface TicketRepository extends JpaRepository<Ticket, Long> {

    List<Ticket> findBySeatCategory(String category);
}

Here, TicketRepository inherits database operations from JpaRepository, and Spring sees it as part of the data layer. This separates it from your service logic and avoids confusion over the class’s purpose.

Want to learn more about Spring Boot and development? Then join upGrad’s Full Stack Bootcamp today!

7 Request Handling and Controller Annotations in Spring Boot

When you build a web application, your code needs to listen for incoming calls, process the details, and send back a suitable response. Request handling annotations in Spring Boot define which class or method is responsible for specific URLs, allowing you to map each path or action with precision. 

In many cases, you can automatically parse query parameters, path segments, and even entire request bodies into Java objects. This approach transforms what could be complex routing logic into well-organized methods that are easy to read and maintain.

Let’s examine how these request mapping and controller annotations guide your application logic:

• Definitive Routing: You can assign individual URLs to specific methods
• Built-In HTTP Verb Support: Each method can be tied to GET, POST, PUT, DELETE, or PATCH requests
• Parameter Parsing: Request parameters and path variables map directly to method arguments
• Structured Responses: You can return JSON objects or HTML views depending on the annotation setup

Up next, you’ll get an in-depth look at these annotations so you can adapt them to your own needs.

10. @Controller

You rely on @Controller when you develop a web application that returns views rather than JSON responses. This annotation informs Spring that the class handles incoming requests, often linking them to a template engine such as Thymeleaf or JSP. Organizing your code around these controllers keeps related actions and routes in one place.

Here are the key benefits of this annotation in Java Spring Boot:

• Handles Web Requests: Maps URLs to specific methods that generate views
• Interacts with Model: You pass data into templates through model attributes
• Part of MVC Flow: Separates logic from view rendering for neater code
• Clear Structure: Each controller manages a logical set of page requests

Sample Example of @Controller in Action

Below is a small example. Notice how the method returns a view name, and Spring decides which template to use:

@Controller
public class AdityaController {

    @RequestMapping("/greeting")
    public String showGreetingPage(Model model) {
        model.addAttribute("msg", "Hello from AdityaController!");
        return "greeting";  // Points to a template named greeting
    }
}

In this snippet, showGreetingPage receives a request for /greeting, sets a message for the view, and returns the name of a template to render.

11. @RestController

Use @RestController when you want to produce data — commonly JSON — directly from your endpoints. It fuses @Controller with @ResponseBody, which means you no longer return a view name. Instead, you provide an object or string that Spring automatically writes to the HTTP response body. This approach suits applications that operate as APIs.

Here are some of the most important highlights of this annotation in Java Spring Boot:

• No View Names: Returns data directly instead of rendering an HTML template
• Simplifies REST Calls: Applies to RESTful services or endpoints used by front-end JavaScript or other clients
• Encapsulates @ResponseBody: Saves you from writing @ResponseBody on every method
• Integrates with JSON Conversion: Often pairs with libraries that convert objects to JSON

Sample Example of @RestController in Action

The example below shows how returning data in JSON becomes natural. Notice you skip any template-based rendering:

@RestController
@RequestMapping("/api")
public class RaviRestController {

    @GetMapping("/products")
    public List<String> getProducts() {
        return List.of("Laptop", "Smartphone", "Camera");
    }
}

Here, RaviRestController serves a JSON list of products to requests on /api/products. You don’t attach view names or manage a model object for HTML content.

12. @RequestMapping

You use @RequestMapping to connect a specific HTTP path with a handler method or class. It tells Spring, “When a request arrives for this path, please call this method.” You can apply it at both the class level (for a base URL) and method level (for more detailed paths).

Here are the key reasons to use it:

• Flexible URL Matching: Supports placeholders, path variables, and optional parameters
• Method-Scoped: Assign different HTTP methods for each request route
• Combines with Parameters: Works with query params and headers when needed
• Organized Code: Groups endpoints in a logical manner when used at the class level

Sample Example of @RequestMapping in Action

Below is a short code snippet. Notice how one path method can differ from another in the same controller:

@Controller
@RequestMapping("/catalog")
public class ShrutiCatalogController {

    @RequestMapping("/electronics")
    public String showElectronics(Model model) {
        model.addAttribute("items", List.of("TV", "Headphones"));
        return "electronicsPage";
    }

    @RequestMapping("/books")
    public String showBooks(Model model) {
        model.addAttribute("items", List.of("Novel", "Comic"));
        return "booksPage";
    }
}

In this snippet, any request that starts with /catalog routes to ShrutiCatalogController. Each method then responds to a more specific path, such as /catalog/electronics.

13. @GetMapping / @PostMapping / @PutMapping / @DeleteMapping

You choose these Spring Boot annotations for more explicit matching of HTTP methods. Each one tells Spring exactly which verb a handler method should respond to, which cuts down on repetition in your code. Instead of writing @RequestMapping(value = "/items", method = RequestMethod.GET), you say @GetMapping("/items").

Key uses:

• Clear Intent: Each mapping states the verb (GET, POST, PUT, DELETE) plainly
• Reduces Boilerplate: You skip the method parameter in @RequestMapping
• Aligns with REST: Ties easily to RESTful resource operations
• Consistent Style: Standardizes your codebase for others to follow

Sample Example

Below is an example. Notice how each request uses an annotation matching its HTTP action:

@RestController
@RequestMapping("/users")
public class DeveshUserController {

    @GetMapping
    public List<String> getAllUsers() {
        return List.of("Rahul", "Meera");
    }

    @PostMapping
    public String createUser(@RequestBody String userName) {
        return userName + " created successfully!";
    }
}

Here, getAllUsers() listens for GET requests on /users, while createUser() listens for POST requests on the same path.

Also Read: HTTP Get Method and Post Method

14. @PathVariable

Apply @PathVariable when the identifier appears right in the URL path, such as /product/123. Instead of a query parameter, you rely on the path segment to carry the necessary information. Spring automatically parses that portion of the URL and passes it to your method.

Here are some significant points about this annotation in Java Spring Boot:

• Extracts URL Segments: Picks out the data in a placeholder like /{id}
• Strong Type Checking: Matches the type of your method parameter (e.g., integer)
• Keeps URLs Clean: Embeds identifiers in the route without query strings
• Useful for REST: Common for showing or editing resources by ID

Sample Example of @PathVariable in Action

See the snippet below. Notice how @PathVariable("orderId") picks up the numeric segment and stores it in the orderId parameter:

@RestController
@RequestMapping("/orders")
public class AnuOrderController {

    @GetMapping("/{orderId}")
    public String getOrderDetails(@PathVariable("orderId") Long orderId) {
        return "Details for order " + orderId;
    }
}

In this example, a request to /orders/20 calls getOrderDetails() with orderId equal to 20.

15. @RequestParam

You call on @RequestParam to retrieve query parameters from the request URL, such as /search?keyword=laptop. This annotation identifies a query parameter by name and then maps it to a method parameter. You can make it required or assign a default value for scenarios when it’s not specified in the request.

Reasons to choose it:

• Grabs Query Parameters: Extracts data from ?key=value in the URL
• Optional or Required: You can set parameters to optional (with a default) or mandatory
• Cleaner Code: Saves you from manually parsing the request object
• Easy Conversion: Automatically converts string parameters into integers or other types

Sample Example of @RequestParam in Action

Here’s an example. Notice how @RequestParam aligns the URL parameter with the method argument:

@RestController
@RequestMapping("/search")
public class PoojaSearchController {

    @GetMapping
    public String findResults(@RequestParam(name="keyword", defaultValue="mobile") String keyword) {
        return "You searched for: " + keyword;
    }
}

In this snippet, if the keyword doesn’t appear in the query string, Spring will treat it as "mobile" by default.

16. @RequestBody / @ResponseBody

You rely on @RequestBody to bind the body of an incoming HTTP request to a method parameter. Spring translates the JSON or XML into a Java object. 

Meanwhile, @ResponseBody applies to a method that directly returns a Java object, which Spring then converts into JSON or XML in the response body. @RestController implicitly uses @ResponseBody on every method, so it’s common when building APIs.

Here are the core points to remember:

• JSON <-> Java Conversion: Applies to data in the request or response
• No View Rendering: Bypasses templates entirely for direct data exchange
• Simplifies REST: Provides out-of-the-box object mapping for JSON or XML
• Works Well with DTOs: Lets you parse complex request bodies into specific data transfer objects

Sample Example of @RequestBody / @ResponseBody in Action

Check out the following snippet. Notice that @RequestBody converts incoming JSON into a User object, and returning User with @ResponseBody sends JSON back:

@RestController
@RequestMapping("/accounts")
public class SameerAccountController {

    @PostMapping
    public @ResponseBody User createAccount(@RequestBody User newUser) {
        // Simulate saving
        newUser.setId(100L);
        return newUser;
    }
}

In this code, the user data arrives as JSON, Spring maps it to a User object, and you return that object, which goes back to JSON for the client.

3 Dependency Injection and Property Management Spring Boot Annotations

You might want certain classes to be automatically available in your code without writing manual new statements, or you might prefer reading important details — like port numbers or API keys — from property files instead of hardcoding them. Dependency injection and property-based Spring Boot annotations handle these needs for you. 

They simplify your classes and let you adjust values outside your code when requirements change later. It all comes down to managing resources, application settings, and object lifecycles in a seamless way.

Consider the following main benefits:

• Seamless Bean Injection: You skip manually instantiating objects, and Spring takes care of creation and wiring.
• Property-Based Setup: You can store critical details in external files so you can easily swap them out per environment.
• Reduced Repetitive Code: You stay focused on core features instead of building repetitive setters or constructors.
• Type-Safe Config: Annotations can map external values directly to fields, preventing errors in your configuration.

Up next, you’ll see how each annotation addresses a different aspect of dependency injection and property management.

17. @Autowired in Spring Boot

You can let Spring handle object creation and linking for you by marking fields or constructors with @Autowired. 

Autowired in Spring Boot looks for an available bean of a matching type and automatically assigns it. This spares you the trouble of manually instantiating dependencies in your classes and helps keep each class focused on its core responsibilities instead of a boilerplate setup.

Here are its main strengths:

• Reduced Manual Work: You don’t have to write multiple constructor calls yourself
• Cleaner Code: A single annotation can replace extensive wiring logic
• Flexible Injection Points: You can apply it to constructors, setters, or even fields
• Decoupled Classes: Each class focuses on its task while Spring coordinates the connections

Sample Example of @Autowired in Action

Below is a brief code example. Note how the constructor injection style offers clarity:

@Service
public class PriyaNotificationService {

    private final UserRepository userRepository;

    @Autowired
    public PriyaNotificationService(UserRepository userRepository) {
        this.userRepository = userRepository;
    }
}

Here, PriyaNotificationService gets an instance of UserRepository without you calling new UserRepository(). Spring identifies the right bean and wires it in at startup so you stay focused on the service’s main logic.

18. @Qualifier

You may prefer @Qualifier when you have more than one bean of the same type and want to pick a specific one. Perhaps you define multiple payment gateways or loggers, and each serves a unique purpose. Marking your bean with @Qualifier("identifier") helps Spring know exactly which bean to inject in your class.

Here are some key points about this annotation in Java Spring Boot:

• Distinguishes Beans: Finds the correct bean by matching the name you declare
• Works with @Autowired: You still rely on automatic dependency injection, just more selectively
• Prevents Ambiguity: Avoids errors if two beans share the same interface or parent class
• Names Aligned with Usage: You can label each bean to describe its actual role

Sample Example of @Qualifier in Action

Here is a simple code example. Notice how you pick the right bean for your class:

@Service("smsService")
public class SmsAlertService {
    // ...
}

@Service("emailService")
public class EmailAlertService {
    // ...
}

@Service
public class AlertManager {

    private final AlertService service;

    @Autowired
    public AlertManager(@Qualifier("smsService") AlertService service) {
        this.service = service;
    }
}

In this snippet, two beans share an AlertService interface, but AlertManager depends on the one labeled "smsService". By attaching @Qualifier("smsService"), you confirm which bean to use.

19. @Value

You can keep your configuration flexible by reading values from .properties or .yml files using @Value. Rather than hard coding things like URLs, passwords, or feature toggles, you store them externally and bind them at runtime. This setup adapts easily to different environments, so you don’t have to rebuild whenever you change a setting.

Here are some crucial benefits of this annotation:

• Externalized Settings: Adjust your properties without touching code
• Type Conversion: Automatically maps strings to integers or booleans when needed
• Default Fallback: Provides a backup if a certain property is not set
• Environment Switching: Lets you run dev and prod with minimal hassle

Sample Example of @Value in Action

Below is a code sample. Observe how a single field references a property key:

@RestController
public class FeedbackController {

    @Value("${feedback.email:help@myapp.com}")
    private String feedbackEmail;

    @GetMapping("/feedbackContact")
    public String getFeedbackEmail() {
        return "Please send feedback to: " + feedbackEmail;
    }
}

In this snippet, if you don’t define feedback.email in your property files, Spring will use "help@myapp.com" as a fallback. This approach keeps your configuration flexible and helps you alter environment details quickly.

Learn more about Spring Boot and its use in Java with upGrad’s free Core Java Basics course today!

11 Auto Conditional Spring Boot Annotations 

Sometimes, you want a piece of logic to activate only if certain conditions are met, like the presence of a specific dependency or a property set to a particular value. Conditional annotations keep your application from loading anything you don’t actually need, which can streamline performance and reduce clutter. 

Each annotation checks for a unique factor — be it a class in the classpath or a property’s value — before deciding whether to bring certain beans or configurations to life. This results in an application that adapts to different environments, libraries, and preferences with very little manual effort.

Here are a few core strengths conditional annotations provide:

• Selective Loading: They make decisions at runtime so only relevant beans or configs appear.
• Environment Awareness: They pick up cues from properties, classes, or resources to guide setup.
• Modular Setup: You avoid bloated configurations by using conditions to include or skip certain features.
• Less Manual Checking: There’s no need for if-else code blocks in your configuration classes.

Next, you will find each of these annotations broken down, revealing how they determine the right time to enable or bypass particular configurations.

20. @ConditionalOnClass

You can use @ConditionalOnClass when a certain Java class or library must be present on the classpath before activating a bean or configuration. This annotation in Java Spring Boot checks for that presence during startup and only proceeds if the class is detected. It’s especially helpful when your code depends on optional libraries that might not always be installed.

Here are some key points you must know about this annotation:

• Classpath Check: Looks for a named class at startup
• Optional Dependencies: Enables features only if a library is already in use
• Lower Risk of Errors: Skips configurations that would fail without the required classes
• Flexible Add-Ons: Lets you layer additional modules without forcing them on all setups

Sample Example of @ConditionalOnClass in Action

Below is an example. Notice how the configuration appears only if org.postgresql.Driver exists:

@Configuration
@ConditionalOnClass(name = "org.postgresql.Driver")
public class PostgresAutoConfig {

    @Bean
    public DataSource postgresDataSource() {
        // Return configured DataSource for PostgreSQL
        return new HikariDataSource();
    }
}

In this snippet, PostgresAutoConfig becomes active only if the PostgreSQL driver is on the classpath. If you leave that library out, Spring ignores this configuration.

21. @ConditionalOnMissingClass

You can turn to @ConditionalOnMissingClass when you want a bean or configuration to load, but only if a particular class is not found on the classpath. This annotation fits a scenario where you plan to supply a fallback option if a primary dependency is absent.

Consider these benefits:

• Fallback Logic: Provides an alternative when the main class is unavailable
• Clear Conditions: Avoids confusion by making sure you have only one active configuration at a time
• Selective Loading: Keeps your application smaller if unneeded dependencies stay out
• Error Prevention: Skips code that would break if the required library is missing

Sample Example of @ConditionalOnMissingClass in Action

Here’s a small code snippet. Notice how it checks for a class name and loads the fallback configuration if that class is absent:

@Configuration
@ConditionalOnMissingClass(value = "com.legacy.LegacyDriver")
public class ModernDbConfig {

    @Bean
    public DataSource modernDataSource() {
        // Return an alternative data source
        return new HikariDataSource();
    }
}

With this setup, ModernDbConfig only activates when com.legacy.LegacyDriver isn’t around, ensuring you don’t overlap conflicting drivers.

22. @ConditionalOnBean

You might use @ConditionalOnBean if your new configuration or bean should load only when another specific bean already exists. It’s common in layered setups where one bean relies on another’s presence for correct operation.

Here are some of its key purposes:

• Bean Presence: Responds to whether a named or typed bean is available
• Safety Net: Avoids creating beans that would fail without the required dependency
• Layered Setup: Activates features in an orderly manner when building multiple modules
• Lean Startup: Doesn’t bother loading sections of logic that won’t function properly anyway

Sample Example of @ConditionalOnBean in Action

Below is an example. Notice how @ConditionalOnBean references a bean type:

@Configuration
public class AnalyticsConfig {

    @Bean
    @ConditionalOnBean(UserService.class)
    public AnalyticsService analyticsService() {
        return new AnalyticsService();
    }
}

In this snippet, if UserService isn’t found, analyticsService() won’t load. This helps avoid partial setups that can cause runtime errors.

23. @ConditionalOnMissingBean

Use @ConditionalOnMissingBean when you want Spring to load a bean only if a certain bean isn’t already present. It’s especially useful for setting defaults that anyone can override. If someone else defines a bean of the same type or name, your fallback bean stays out of the way.

Check out these key highlights about this annotation in Java Spring Boot:

• Default Options: Provides a bean that steps in only when no other candidate is found
• Extensible Design: Encourages overrides without rewriting core code
• Prevent Bean Collisions: Automatically checks if something similar already exists
• Streamlined Upgrades: Lets developers inject custom versions of beans easily

Sample Example of @ConditionalOnMissingBean in Action

Below is a code snippet. Notice that a default user service bean will load only if none other exists:

@Configuration
public class DefaultUserConfig {

    @Bean
    @ConditionalOnMissingBean(UserService.class)
    public UserService defaultUserService() {
        return new BasicUserService();
    }
}

If a different UserService bean is present, Spring ignores defaultUserService(). That way, you can still rely on it if no custom version exists.

upGrad’s Exclusive Software and Tech Webinar for you –

SAAS Business – What is So Different?

24. @ConditionalOnProperty

Rely on @ConditionalOnProperty if a particular property key or a specific value in your configuration determines whether a bean should load. This annotation in Java Spring Boot reads application properties and decides if the logic stays active based on a match.

Points of interest:

• Property Driven: Checks a named property, such as “feature.enabled”
• Granular Control: Lets you differentiate between various environment or feature states
• Straightforward Setup: No need for manual code checks in your configuration class
• Easy Toggle: Switching a property toggles the configuration on or off

Sample Example of @ConditionalOnProperty in Action

Below is a sample code block. Notice how it checks a property’s name and value:

@Configuration
public class FeatureToggles {

    @Bean
    @ConditionalOnProperty(name = "feature.advancedMode", havingValue = "true")
    public AdvancedService advancedService() {
        return new AdvancedService();
    }
}

Here, if feature.advancedMode=true, you enable AdvancedService. If someone sets it to false in application.properties, Spring skips that bean.

25. @ConditionalOnResource

You choose @ConditionalOnResource when the existence of a resource file (like a configuration file or image) decides if a certain config should load. It ties the presence of that file on the classpath to your bean creation.

Here are the key aspects of this annotation in Java Spring Boot that you must know:

• Resource Check: Looks for a file in the classpath, such as classpath:data.properties
• Customizable: Could refer to images, properties, or any other resource
• Guard Rails: Ensures you don’t start logic depending on files that aren’t there
• Lightweight Control: Doesn’t require advanced code for verifying files

Sample Example of @ConditionalOnResource in Action

Below is an example. Notice how it checks the presence of a file before setting up the bean:

@Configuration
public class ResourceDrivenConfig {

    @Bean
    @ConditionalOnResource(resources = "classpath:reports.yaml")
    public ReportService reportService() {
        return new ReportService();
    }
}

With this condition, if reports.yaml isn’t in the classpath, Spring will ignore reportService(). That helps avoid file-not-found errors.

26. @ConditionalOnWebApplication

Turn to @ConditionalOnWebApplication when you want a bean or configuration to load only in a web setting. This annotation checks if your application runs in a web environment, meaning it can handle HTTP requests and responses. It’s perfect for beans that rely on HTTP details.

Here’s why it helps:

• Web-Exclusive Beans: Summaries or error-page handlers load only if you have a web context
• Avoids Unused Logic: Skips overhead in a non-web environment
• Safer Setup: Doesn’t risk referencing web classes if no web container is running
• Clear Separation: You split web features from other modules

Sample Example of @ConditionalOnWebApplication in Action

Below is an example. Notice how it ensures a web-based configuration:

@Configuration
public class WebSecurityConfig {

    @Bean
    @ConditionalOnWebApplication
    public SecurityFilter webSecurityFilter() {
        return new SecurityFilter();
    }
}

If you’re not running a web context, webSecurityFilter() does not appear in the application context.

27. @ConditionalOnNotWebApplication

Use @ConditionalOnNotWebApplication for the reverse scenario: You need certain beans only if the application does not run as a web service. This approach helps you avoid configuring servlets, web filters, or other HTTP-related items in a standalone or batch application.

Consider its value:

• Non-Web Beans: Targets CLI tools, batch processors, or background jobs
• Prevents Extra Overhead: Skips all web-based libraries or setups
• Focus on Backend: Keeps logic streamlined for tasks with no front-end requests
• Minimal Complexity: Reduces confusion by not mixing web logic in a non-web environment

Sample Example of @ConditionalOnNotWebApplication in Action

Below is a snippet. Notice how the bean is only relevant if there’s no web context:

@Configuration
public class ConsoleConfig {

    @Bean
    @ConditionalOnNotWebApplication
    public ConsoleLogger consoleLogger() {
        return new ConsoleLogger();
    }
}

If the application starts as a web server, consoleLogger() is skipped. That avoids injecting console-related beans where they aren’t required.

28. @ConditionalOnExpression

You can harness @ConditionalOnExpression to evaluate a SpEL (Spring Expression Language) string and decide if a bean or config should load. This is handy when you want more complex checks that go beyond just detecting a property or file — maybe arithmetic or combining multiple conditions.

Here’s what you can do:

• Rich Expressions: Compare multiple properties or perform logical operations
• Custom Logic: Evaluate booleans, strings, or numeric conditions
• Dynamic Decisions: Adjust your setup based on more than one factor
• Fine-Grained Control: Offers detailed rules that go beyond simple checks

Sample Example of @ConditionalOnExpression in Action

Below is a simple code example. Notice the annotation runs a quick SpEL check before loading the bean:

@Configuration
public class ExpressionConfig {

    @Bean
    @ConditionalOnExpression("${feature.x} == true and ${system.mode} == 'advanced'")
    public XAdvancedBean xAdvancedBean() {
        return new XAdvancedBean();
    }
}

If both conditions match — feature.x is true, and system.mode is 'advanced' — then xAdvancedBean() is activated. Otherwise, Spring ignores it.

29. @ConditionalOnCloudPlatform

Use @ConditionalOnCloudPlatform when you want a configuration to load only if your application runs on a specified cloud platform, such as Cloud Foundry. It checks the environment and ensures you bring in the right settings for that hosting service.

Here are a few key points about this annotation in Java Spring Boot:

• Cloud-Specific: Focuses on recognized platforms like Cloud Foundry or Heroku
• Targeted Config: Loads beans or features that only work on that platform
• Easy Maintenance: Skips unneeded classes in non-cloud setups
• Less Manual Checking: No manual if-else code for verifying the hosting environment

Sample Example of @ConditionalOnCloudPlatform in Action

Below is an example snippet. Notice it ties the logic to a named platform:

@Configuration
@ConditionalOnCloudPlatform(CloudPlatform.CLOUD_FOUNDRY)
public class CloudFoundryConfig {

    @Bean
    public LoggingService cfLoggingService() {
        return new LoggingService();
    }
}

This code only takes effect if your application is running in a Cloud Foundry environment. If you deploy elsewhere, the configuration stays dormant.

30. @Conditional

@Conditional is the most generic form of conditional annotation in Java Spring Boot. You provide a custom Condition class that implements logic in the matches method, which either allows or blocks the configuration. This is your fallback if none of the other condition annotations meet a specific scenario.

Here are a few important details:

• Custom Logic: Write any conditions you can’t express with property or class checks
• Powerful: Evaluate environment variables, system details, or any other factor
• Extensible: Combine with your own code to meet business or system rules
• Method or Class: Mark a class or a bean method to apply this condition

Sample Example of @Conditional in Action

Below is an example. Notice how your condition class can hold advanced checks:

@Configuration
@Conditional(WindowsCheck.class)
public class WindowsOnlyConfig {

    @Bean
    public WindowsHelper windowsHelper() {
        return new WindowsHelper();
    }
}

// Condition class:
public class WindowsCheck implements Condition {
    @Override
    public boolean matches(ConditionContext context, AnnotatedTypeMetadata metadata) {
        return System.getProperty("os.name").toLowerCase().contains("win");
    }
}

Here, WindowsOnlyConfig activates if your custom WindowsCheck class returns true. It grants total flexibility for deciding how to run your application under special circumstances.

Profile-Based Annotation in Java Spring Boot

You might want some features to work differently depending on whether you’re using a local setup or deploying to a hosting service. That’s where the concept of profiles becomes useful: you organize beans or configurations so that they only activate under a specific label, such as “dev” or “prod.” 

By grouping settings like database credentials or debugging switches in this way, you can keep a single codebase that neatly adapts to each environment.

Now, take a quick look at how profiles boost flexibility:

• Selective Activation: You load or skip certain beans based on the chosen profile.
• Single Codebase: You avoid separating environment variations into multiple branches.
• Consistent Workflow: Your application remains the same at its core — only the environment-based parts change.
• Ease of Maintenance: You edit one place for each environment rather than sifting through countless conditionals.

Next, you’ll see how the @Profile annotation fulfills these ideas by cleanly dividing your application into tailored configurations.

31. @Profile

When your application needs different behavior in development, staging, or production, you can mark entire classes or bean definitions with @Profile. Attaching this label ensures those configurations only load if that profile is activated.

This mechanism works well for environment-specific database connections, logging levels, or third-party integrations. Rather than duplicating your entire codebase, you keep it all in one place and let Spring pick which beans to load based on the selected profile.

Let’s break down how this annotation makes multiple environments easier:

• Environment Isolation: You run only the beans and settings meant for each environment.
• Flexible Deployment: A single codebase, like dev or prod, can smoothly swap between profiles.
• Clear Labeling: Each profile block is neatly indicated, so it’s obvious which parts apply where.
• Easy Switching: You modify one property to flip between different profiles rather than changing many files.

Sample Example of @Profile in Action

Below is a quick code snippet. Notice how the annotation on each configuration class or bean ensures they appear only under the specified label:

@Configuration
@Profile("dev")
public class DevDatabaseConfig {

    @Bean
    public DataSource devDataSource() {
        // Return a DataSource pointing to your dev environment
        return new HikariDataSource();
    }
}

@Configuration
@Profile("prod")
public class ProdDatabaseConfig {

    @Bean
    public DataSource prodDataSource() {
        // Return a DataSource pointing to your prod environment
        return new HikariDataSource();
    }
}

Here, when you launch the application with spring.profiles.active=dev, Spring picks the DevDatabaseConfig. If you change it to prod, Spring loads the ProdDatabaseConfig. This approach keeps environment-specific logic in distinct files, simplifying updates and troubleshooting later.

2 Annotations in Java Spring Boot for Handling Configuration Properties

When your application starts growing, you might prefer keeping settings such as URLs, ports, or custom toggles in external property files instead of embedding them in your code. This practice makes it simpler to modify or replace configurations without affecting the logic of your classes. 

You also maintain a clear separation between business code and environment-based variables, which helps when you switch from one runtime setting to another.

Here are a few reasons these property-based annotations prove valuable:

• Centralized Config: All environment or feature-related options can live in dedicated files.
• Flexible Adjustments: You can change parameters by editing properties rather than touching any code.
• Easy Debugging: You quickly spot which settings differ across development or testing.
• Tidy Codebase: Instead of scattering your configuration throughout the code, you keep it focused in one place.

Let’s get started with the annotation now.

32. @ConfigurationProperties

You can attach @ConfigurationProperties to a class that holds external values such as URLs, user credentials, or timeouts. This approach provides type safety because each field in your class matches up with a specific property key. In addition, you keep these fields organized under a prefix, which makes it clear which part of your application the properties belong to.

Here’s how this annotation in Java Spring Boot promotes clarity in your project:

• Grouped Settings: Each class can hold configuration details for a specific function, like security or messaging.
• Simple Updates: You change the value in .properties or .yml, and the code picks it up at runtime.
• Reduced Boilerplate: You don’t need separate lines of @Value for each property.
• Type-Safe Binding: If a property should be an integer but you mistakenly provide a string, you’ll catch it early.

Sample Example of @ConfigurationProperties in Action

Below is a typical code snippet for @ConfigurationProperties. Notice how the prefix corresponds to keys in your property files:

@ConfigurationProperties(prefix = "mail")
public class MailConfigProps {
    
    private String host;
    private int port;
    private String username;
    private String password;

    // Getters and setters omitted for brevity
}

When you define mail.host, mail.port, and so on in your .properties or .yml, Spring populates these fields automatically, saving you from writing multiple @Value statements.

33. @EnableConfigurationProperties

Use @EnableConfigurationProperties to activate classes annotated with @ConfigurationProperties. Without it, your property-binding class might remain undiscovered. By telling Spring to look for one or more @ConfigurationProperties classes, you ensure these fields are recognized and properly bound during startup.

Take a quick look at what this annotation contributes:

• Auto-Registration: Makes Spring aware that it should load and manage @ConfigurationProperties beans
• Multiple Properties: You can enable several classes at once if they hold different sets of configurations
• Seamless Integration: Avoids the need to manually wire each property-based class into your context
• Organization: Keeps configuration logic consolidated in one place

Sample Example of @EnableConfigurationProperties in Action

See the snippet below. Notice how it references the class containing your properties:

@Configuration
@EnableConfigurationProperties(MailConfigProps.class)
public class MailAutoConfig {
    
    @Bean
    public MailService mailService(MailConfigProps props) {
        // Use props.getHost(), props.getPort() to set up your service
        return new MailService(props.getHost(), props.getPort());
    }
}

Here, @EnableConfigurationProperties(MailConfigProps.class) ensures MailConfigProps becomes a bean whose values are injected from your external files. You then take those values and pass them to a MailService, keeping your code free from hardcoded settings.

2 Error Handling Spring Boot Annotations

Whether you work on a small web app or a large enterprise platform, dealing with unexpected issues is unavoidable. Spring Boot provides built-in annotations that let you define a central spot for exception handling while allowing you to manage individual errors at a more fine-grained level. 

This setup prevents scattered try-catch blocks and promotes cleaner, more predictable responses when something goes wrong.

Before diving into the specific Spring Boot annotations list, let’s see why this centralized approach pays off:

• Unified Handling: You avoid handling similar exceptions in multiple controllers by using a common handler.
• Consistent Feedback: Each client call gets structured, coherent responses when an error happens.
• Reduced Code Duplication: You no longer write repetitive try-catch logic for every endpoint.
• Focus on Logic: Controllers remain dedicated to request processing, while specialized methods take care of error messages.

Let’s check out the annotations now.

34. @ControllerAdvice

You can mark a class with @ControllerAdvice to handle errors and specific outcomes across multiple controllers in one place. This annotation in Java Spring Boot frees each controller from having its own exception-handling methods and gives you a single spot to set up responses for different error types. 

You keep your controllers cleaner and maintain a clear view of how your application manages unexpected events.

Let’s look at how this annotation helps you keep your error handling organized:

• Global Scope: It manages exceptions for every controller unless you say otherwise.
• Separation of Concerns: Controllers focus on request logic, while the advice class focuses on handling edge cases.
• Exception Logging: You record errors in one spot, which makes debugging less confusing.
• Consistent Output: Clients receive uniform messages and statuses when things go wrong.

Sample Example of @ControllerAdvice in Action

Below is a short example. Notice how this advice class offers a method for catching a specific exception:

@ControllerAdvice
public class GlobalErrorAdvisor {

    @ExceptionHandler(NullPointerException.class)
    public ResponseEntity<String> handleNullPointer(NullPointerException ex) {
        return new ResponseEntity<>("An unexpected issue occurred.", HttpStatus.BAD_REQUEST);
    }
}

Here, GlobalErrorAdvisor catches any NullPointerException that happens in any controller. You can add more methods to handle additional exceptions as you see fit.

35. @ExceptionHandler

You place @ExceptionHandler on methods that react to specific exceptions. This annotation can live inside a regular controller or in a class annotated with @ControllerAdvice for centralized error handling. 

It helps you define one method per exception type, leading to simpler code than try-catch blocks sprinkled around your entire project.

Check out how this annotation in Java Spring Boot streamlines error handling:

• Targeted Approach: You pair each method with a particular exception type
• Exact Response Control: You decide what message and status code to send back
• Unified Flow: You maintain a tidy approach to dealing with errors instead of mixing logic into each endpoint
• Flexible Placement: You can keep it local to a single controller or place it in a global advice class

Sample Example of @ExceptionHandler in Action

Here’s an example. Notice how @ExceptionHandler specifies the exception it catches:

@RestController
public class PaymentController {

    @PostMapping("/pay")
    public String processPayment(@RequestBody PaymentRequest request) {
        // Possibly throws a custom exception
        return "Payment processed!";
    }

    @ExceptionHandler(InvalidPaymentException.class)
    public ResponseEntity<String> handleInvalidPayment(InvalidPaymentException ex) {
        return new ResponseEntity<>("Payment failed: " + ex.getMessage(), HttpStatus.UNPROCESSABLE_ENTITY);
    }
}

In this snippet, handleInvalidPayment only responds if InvalidPaymentException surfaces in PaymentController. You gain precision by specifying distinct methods for each possible exception, rather than mixing different error types into a single handler.

What are the Best Practices for Using Spring Boot Annotations?

Many Spring Boot annotations appear to do similar things, but each one carries a specific responsibility. You avoid confusion by applying the right annotation in the right context. That means you skip overlapping markers on the same class and aim to keep your codebase understandable over time. 

It also keeps your configuration consistent so any team member can make adjustments without breaking your setup.

Here are a few strategies to keep your annotations organized and purposeful:

• Use Stereotype Annotations Wisely: Stick to @Service, @Repository, and @Controller to highlight each class’s role.
• Lean on @SpringBootApplication: Let the built-in auto-configuration and component scanning do their work unless you have unusual requirements.
• Cut Out Redundancies: Skip over-decorating your code; make sure each annotation has a clear reason for being there.
• Adopt Constructor Injection: Prefer constructor-based @Autowired in Spring Boot for simpler testing and better clarity in your dependencies.
• Rely on Profiles for Environments: Mark environment-specific settings with @Profile so your app can adapt to various scenarios.
• Adopt Type-Safe Configuration: Apply @ConfigurationProperties to tie external properties to well-defined fields in your classes.
• Apply Conditional Annotations: Only load configurations you actually need by evaluating classpath checks, property flags, or other conditions.

How Can upGrad Enhance Your Understanding of Spring Boot Annotations?

upGrad offers top-notch programs to help you master Spring Boot Annotations and advance your development skills.

Here are some of the most popular courses:

• Cloud Computing and DevOps Program by IIITB - (Executive)
• Professional Certificate Program in Cloud Computing and DevOps
• Master the Cloud and Lead as an Expert Cloud Engineer

Boost your skills — enroll in upGrad’s programs today and excel in Spring Boot development! Get personalized career counseling from upGrad’s experts to help you choose the right program for your goals. You can also visit your nearest upGrad offline Career Center to kickstart your future!

Boost your career with our popular Software Engineering courses, offering hands-on training and expert guidance to turn you into a skilled software developer.

Explore our Popular Software Engineering Courses

Master in-demand Software Development skills like coding, system design, DevOps, and agile methodologies to excel in today’s competitive tech industry.

In-Demand Software Development Skills

Stay informed with our widely-read Software Development articles, covering everything from coding techniques to the latest advancements in software engineering.

Read our Popular Articles related to Software