Top 10 Spring Boot Libraries Every Developer Should Know
Table of Contents
- Spring Boot Starter Web
- Spring Boot Starter Data JPA
- Spring Boot Starter Security
- Spring Boot Starter Actuator
- Spring Boot Starter Cache
- Spring Boot Starter AOP
- Spring Boot Starter Test
- Spring Boot Starter Validation
- Spring Boot Starter Thymeleaf
- Spring Boot Starter Cloud Netflix Eureka
1. Spring Boot Starter Web
Core Principles
The Spring Boot Starter Web library is designed to simplify the development of web applications in Spring Boot. It includes embedded servers like Tomcat, Jetty, or Undertow, and also provides a foundation for building RESTful web services.
Design Philosophies
It follows the convention - over - configuration principle, meaning that it provides sensible default configurations, so developers don’t have to write a lot of boilerplate code.
Performance Considerations
Using an embedded server reduces the overhead of deploying to a separate server. However, for high - traffic applications, you may need to fine - tune the server configuration.
Code Example
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;
// This annotation marks the class as a Spring Boot application
@SpringBootApplication
// This annotation marks the class as a REST controller
@RestController
public class WebAppExample {
public static void main(String[] args) {
// Start the Spring Boot application
SpringApplication.run(WebAppExample.class, args);
}
// This method maps to the root URL ("/") and returns a simple message
@GetMapping("/")
public String hello() {
return "Hello, Spring Boot Web!";
}
}
Common Trade - offs and Pitfalls
One trade - off is that the default configurations may not be suitable for all scenarios. For example, the default embedded server may not be optimized for specific workloads. A common pitfall is not handling exceptions properly, which can lead to unexpected behavior.
Best Practices
Use proper exception handling and validation in your controllers. Also, separate the business logic from the controller code for better maintainability.
2. Spring Boot Starter Data JPA
Core Principles
Spring Boot Starter Data JPA simplifies database access in Spring Boot applications. It provides a high - level abstraction over JDBC and allows you to interact with databases using Java Persistence API (JPA).
Design Philosophies
It promotes the use of object - relational mapping (ORM) to map Java objects to database tables. This reduces the amount of SQL code you need to write.
Performance Considerations
Proper indexing and query optimization are crucial for good performance. Also, be aware of the N + 1 query problem, which can occur when fetching related entities.
Code Example
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.data.jpa.repository.JpaRepository;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;
import java.util.List;
// This annotation marks the class as a Spring Boot application
@SpringBootApplication
// This annotation marks the class as a REST controller
@RestController
public class DataJpaExample {
public static void main(String[] args) {
// Start the Spring Boot application
SpringApplication.run(DataJpaExample.class, args);
}
// Define an entity class
public static class User {
private Long id;
private String name;
// Getters and setters
public Long getId() {
return id;
}
public void setId(Long id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
}
// Define a repository interface
public interface UserRepository extends JpaRepository<User, Long> {
}
private final UserRepository userRepository;
public DataJpaExample(UserRepository userRepository) {
this.userRepository = userRepository;
}
// This method maps to the "/users" URL and returns all users
@GetMapping("/users")
public List<User> getUsers() {
return userRepository.findAll();
}
}
Common Trade - offs and Pitfalls
One trade - off is the performance overhead introduced by ORM. A common pitfall is not understanding the lazy and eager loading strategies, which can lead to unexpected database queries.
Best Practices
Use named queries and projections to optimize database access. Also, understand the different fetching strategies and use them appropriately.
3. Spring Boot Starter Security
Core Principles
Spring Boot Starter Security provides authentication and authorization features for Spring Boot applications. It helps you secure your web services and REST endpoints.
Design Philosophies
It follows the principle of securing your application at different levels, such as URL - based security and method - level security.
Performance Considerations
The security filters can add some overhead to the application. However, proper configuration can minimize this impact.
Code Example
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.annotation.Bean;
import org.springframework.security.config.annotation.web.builders.HttpSecurity;
import org.springframework.security.config.annotation.web.configuration.EnableWebSecurity;
import org.springframework.security.config.annotation.web.configuration.WebSecurityConfigurerAdapter;
import org.springframework.security.core.userdetails.User;
import org.springframework.security.core.userdetails.UserDetails;
import org.springframework.security.core.userdetails.UserDetailsService;
import org.springframework.security.provisioning.InMemoryUserDetailsManager;
// This annotation marks the class as a Spring Boot application
@SpringBootApplication
// This annotation enables web security
@EnableWebSecurity
public class SecurityExample extends WebSecurityConfigurerAdapter {
public static void main(String[] args) {
// Start the Spring Boot application
SpringApplication.run(SecurityExample.class, args);
}
@Override
protected void configure(HttpSecurity http) throws Exception {
http
.authorizeRequests()
.antMatchers("/public").permitAll()
.anyRequest().authenticated()
.and()
.formLogin()
.and()
.httpBasic();
}
@Bean
@Override
public UserDetailsService userDetailsService() {
UserDetails user =
User.withDefaultPasswordEncoder()
.username("user")
.password("password")
.roles("USER")
.build();
return new InMemoryUserDetailsManager(user);
}
}
Common Trade - offs and Pitfalls
One trade - off is the complexity of configuring security. A common pitfall is not properly protecting sensitive endpoints, which can lead to security vulnerabilities.
Best Practices
Use role - based access control and keep your security configuration up - to - date. Also, use HTTPS in production environments.
4. Spring Boot Starter Actuator
Core Principles
Spring Boot Starter Actuator provides production - ready features to help you monitor and manage your Spring Boot application. It exposes various endpoints that provide information about the application’s health, metrics, and configuration.
Design Philosophies
It follows the principle of providing useful information about the application’s internal state without requiring a lot of additional configuration.
Performance Considerations
Exposing too many actuator endpoints can have a performance impact, especially in high - traffic applications.
Code Example
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
// This annotation marks the class as a Spring Boot application
@SpringBootApplication
public class ActuatorExample {
public static void main(String[] args) {
// Start the Spring Boot application
SpringApplication.run(ActuatorExample.class, args);
}
}
To access the actuator endpoints, you can simply make HTTP requests to URLs like /actuator/health and /actuator/metrics.
Common Trade - offs and Pitfalls
One trade - off is the security risk associated with exposing actuator endpoints. A common pitfall is not securing these endpoints properly, which can lead to information leakage.
Best Practices
Secure the actuator endpoints using Spring Security and only expose the necessary endpoints in production.
5. Spring Boot Starter Cache
Core Principles
Spring Boot Starter Cache simplifies caching in Spring Boot applications. It provides a unified way to integrate different caching providers like Ehcache, Caffeine, or Redis.
Design Philosophies
It follows the principle of reducing the number of database queries by caching frequently accessed data.
Performance Considerations
Proper cache configuration is crucial for performance. You need to set the right cache size, eviction policy, and expiration time.
Code Example
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cache.annotation.Cacheable;
import org.springframework.cache.annotation.EnableCaching;
import org.springframework.stereotype.Service;
// This annotation marks the class as a Spring Boot application
@SpringBootApplication
// This annotation enables caching
@EnableCaching
public class CacheExample {
public static void main(String[] args) {
// Start the Spring Boot application
SpringApplication.run(CacheExample.class, args);
}
@Service
public static class MyService {
// This method is cacheable with the cache name "myCache"
@Cacheable("myCache")
public String getData() {
// Simulate a slow operation
try {
Thread.sleep(2000);
} catch (InterruptedException e) {
e.printStackTrace();
}
return "Data from slow operation";
}
}
}
Common Trade - offs and Pitfalls
One trade - off is the memory overhead associated with caching. A common pitfall is not invalidating the cache when the underlying data changes, which can lead to stale data.
Best Practices
Use cache eviction and invalidation mechanisms properly. Also, monitor the cache usage to ensure optimal performance.
6. Spring Boot Starter AOP
Core Principles
Spring Boot Starter AOP allows you to implement aspect - oriented programming (AOP) in Spring Boot applications. AOP helps you separate cross - cutting concerns like logging, security, and transaction management from the core business logic.
Design Philosophies
It follows the principle of modularizing cross - cutting concerns and applying them to multiple parts of the application without modifying the core code.
Performance Considerations
AOP can add some overhead to the application, especially if there are many aspects. However, proper configuration can minimize this impact.
Code Example
import org.aspectj.lang.JoinPoint;
import org.aspectj.lang.annotation.After;
import org.aspectj.lang.annotation.Aspect;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.EnableAspectJAutoProxy;
// This annotation marks the class as a Spring Boot application
@SpringBootApplication
// This annotation enables AspectJ auto - proxying
@EnableAspectJAutoProxy
public class AopExample {
public static void main(String[] args) {
// Start the Spring Boot application
SpringApplication.run(AopExample.class, args);
}
@Aspect
@Configuration
public static class LoggingAspect {
// This advice is executed after any method in the com.example.service package
@After("execution(* com.example.service.*.*(..))")
public void logAfter(JoinPoint joinPoint) {
System.out.println("Method executed: " + joinPoint.getSignature().getName());
}
}
}
Common Trade - offs and Pitfalls
One trade - off is the complexity of understanding and configuring AOP. A common pitfall is overusing aspects, which can make the code hard to understand and maintain.
Best Practices
Use AOP for cross - cutting concerns only and keep the aspects simple and focused.
7. Spring Boot Starter Test
Core Principles
Spring Boot Starter Test provides a set of tools and libraries for testing Spring Boot applications. It includes JUnit, Mockito, and Spring Test framework.
Design Philosophies
It follows the principle of making it easy to write unit, integration, and end - to - end tests for Spring Boot applications.
Performance Considerations
Running a large number of tests can be time - consuming. You need to optimize your test suite by using techniques like parallel test execution.
Code Example
import org.junit.jupiter.api.Test;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.autoconfigure.web.servlet.WebMvcTest;
import org.springframework.test.web.servlet.MockMvc;
import static org.springframework.test.web.servlet.request.MockMvcRequestBuilders.get;
import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.content;
import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.status;
// This annotation is used to test the web layer of the application
@WebMvcTest
public class WebAppTest {
@Autowired
private MockMvc mockMvc;
@Test
public void testHello() throws Exception {
mockMvc.perform(get("/"))
.andExpect(status().isOk())
.andExpect(content().string("Hello, Spring Boot Web!"));
}
}
Common Trade - offs and Pitfalls
One trade - off is the time and effort required to write and maintain tests. A common pitfall is not writing comprehensive tests, which can lead to undetected bugs.
Best Practices
Write unit tests for individual components, integration tests for the interaction between components, and end - to - end tests for the overall application flow.
8. Spring Boot Starter Validation
Core Principles
Spring Boot Starter Validation simplifies input validation in Spring Boot applications. It provides a set of annotations to validate the input data in your controllers.
Design Philosophies
It follows the principle of validating data as early as possible to prevent invalid data from entering the application.
Performance Considerations
Validation can add some overhead, but it is necessary to ensure data integrity.
Code Example
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RequestBody;
import org.springframework.web.bind.annotation.RestController;
import javax.validation.Valid;
// This annotation marks the class as a Spring Boot application
@SpringBootApplication
// This annotation marks the class as a REST controller
@RestController
public class ValidationExample {
public static void main(String[] args) {
// Start the Spring Boot application
SpringApplication.run(ValidationExample.class, args);
}
public static class User {
private String name;
// Getters and setters
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
}
// This method maps to the "/users" URL and validates the input user object
@PostMapping("/users")
public String createUser(@Valid @RequestBody User user) {
return "User created: " + user.getName();
}
}
Common Trade - offs and Pitfalls
One trade - off is the additional code required for validation. A common pitfall is not handling validation errors properly, which can lead to unexpected behavior.
Best Practices
Use proper validation annotations and handle validation errors gracefully in your controllers.
9. Spring Boot Starter Thymeleaf
Core Principles
Spring Boot Starter Thymeleaf is a template engine for Spring Boot applications. It allows you to create dynamic web pages by combining HTML templates with Java objects.
Design Philosophies
It follows the principle of separating the presentation layer from the business logic.
Performance Considerations
Template compilation and rendering can have a performance impact. You need to optimize the templates and use caching.
Code Example
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.stereotype.Controller;
import org.springframework.ui.Model;
import org.springframework.web.bind.annotation.GetMapping;
// This annotation marks the class as a Spring Boot application
@SpringBootApplication
// This annotation marks the class as a controller
@Controller
public class ThymeleafExample {
public static void main(String[] args) {
// Start the Spring Boot application
SpringApplication.run(ThymeleafExample.class, args);
}
// This method maps to the "/hello" URL and adds a message to the model
@GetMapping("/hello")
public String hello(Model model) {
model.addAttribute("message", "Hello, Thymeleaf!");
return "hello";
}
}
Create a hello.html file in the src/main/resources/templates directory:
<!DOCTYPE html>
<html xmlns:th="http://www.thymeleaf.org">
<head>
<title>Thymeleaf Example</title>
</head>
<body>
<h1 th:text="${message}">Default message</h1>
</body>
</html>
Common Trade - offs and Pitfalls
One trade - off is the learning curve associated with Thymeleaf syntax. A common pitfall is not properly handling template inheritance and layout, which can lead to code duplication.
Best Practices
Use template inheritance and layout to reduce code duplication. Also, optimize the templates for performance.
10. Spring Boot Starter Cloud Netflix Eureka
Core Principles
Spring Boot Starter Cloud Netflix Eureka is a service discovery server and client. It allows micros