These are some of the best practices we collected in our Spring projects. You can find a checklist at the end of the post.

These notes originate from real-world experience in business-critical projects. They are primarily addressed to backend teams and can be used as a production readiness checklist.

Architecture and transaction boundaries

Disable Open Session in View: spring.jpa.open-in-view=false

By default, Spring Boot registers an OpenEntityManagerInViewInterceptor (spring.jpa.open-in-view=true).

With this option, Spring Boot binds a JPA EntityManager to the thread for the entire processing of the request.

This practice was useful in the past (using JSP and other view renderers) to avoid the LazyInitializationException when some entities were retrieved in a transaction and, in subsequent code, the application tried to access some lazy loaded entities linked to the result.

At this point the transaction was already closed and the entities detached.

For most applications this feature is not necessary anymore, some developers wanted to disable it by default in Spring Boot 2 already.

This triggered a debate between 'java gurus' regarding the utility and the performance impact of this binding.

I recommend starting a project setting

# Disable OSIV to prevent connection holding and N+1 issues
spring.jpa.open-in-view=false

and activate it only if really necessary. For REST applications with a transaction managed at service level, this interceptor should not be necessary.

De-activating open-in-view will avoid to bind an entity manager to the thread at every request and unbind it at the end of the request. The code concerned is in the org.springframework.orm.jpa.support.OpenEntityManagerInViewInterceptorclass.

Risks of keeping open-in-view enabled:

• Cause accidental N+1 queries in controllers
• Hide missing transactional boundaries
• Make performance debugging harder

Understand proxies and transactional behavior

Spring uses proxies for features like @Transactional.

Important implications:

• Self-invocation does not trigger transactional behavior
• final methods cannot be proxied (with CGLIB that creates subclasses)
• Multiple internal calls to @Transactional methods won’t start new transactions

Understanding how proxies work prevents subtle production bugs.

Use Interfaces when is appropriate to avoid CGLIB

Interfaces allow clean code debugging and a faster and smaller deployment. Here you can find more details: https://marmo.dev/spring-interfaces-cglib

Benefits:

• Simpler debugging
• Fewer proxy limitations
• Cleaner separation of responsibilities

It’s not mandatory — but in layered architectures, it improves clarity. In many projects we had big debates about interfaces, the team should decide the best approach for the project.

Configuration & Dependency Injection

Use Constructor Injection

Good

• the beans cannot be null;
• the object is immutable;
• the object can be defined final;
• in case the bean has only one constructor you can omit @Autowired;
• forces better design decisions and discourages oversized service classes.

If you are using lombok you can use @AllArgsConstructor or @RequiredArgsConstructor and simply declare your components as final fields (this is my favorite approach).

Lombok will create the constructor that will be used by Spring to inject the components.

Avoid Field Injection

Field injection (@Autowired):

• Hides dependencies
• Complicates testing
• Breaks immutability
• Encourages oversized classes

In unit tests field injection can be practical and justified.

Constructor injection forces better design decisions.

Prefer @ConfigurationProperties Over @Value

Spring Boot introduced the `@ConfigurationProperties annotation that is 'far more superior than the basic @Value approach' according to Stéphane Nicoll (Pivotal).

The advantages:

• You inject only an object a POJO and not a list of fields
• There is less risk to do typos in the declaration of the property
• The POJO is TypeSafe and can contain complex structures (e.g. 'database.configuration.mysql.connection')
• Adding Bean Validation (spring-boot-starter-validation) you can use @Validated on your config properties.

Here you can find the documentation:

• Spring Boot: Type-safe Configuration Properties

Instead of @Value("${app.timeout}") use @ConfigurationProperties(prefix = "app")

Always Explicitly Name Parameters for @RequestParam, @PathVariable and @Param

When working with Spring MVC and Spring Data JPA, it's a best practice to explicitly declare the names of your parameters in annotations like @RequestParam, @PathVariable, and @Param.

Spring MVC Example

@GetMapping("/users")
public String getUserById(@RequestParam("id") String userId) {
    return "User ID: " + userId;
}

By specifying the parameter name ("id"), you're making the binding explicit. This ensures Spring correctly maps the request parameter to your method argument—regardless of how the code is compiled or whether the -parameters flag is used.

If you omit the name, Spring will attempt to infer it from the method signature, which only works if your code is compiled with -parameters.

While enabling -parameters allows Spring to infer names via reflection, it’s still safer and clearer to be explicit—especially in larger or collaborative codebases.

To enable '-parameters' in Maven:

<compilerArgs>
    <arg>-parameters</arg>
</compilerArgs>

Spring Data JPA Example

Not good (positional binding):

@Query("SELECT u FROM User u WHERE u.username = ?1 AND u.code = ?2")
List<User> findByUsernameAndCode(String username, String code);

Better (explicit named binding):

@Query("SELECT u FROM User u WHERE u.username = :username AND u.code = :code")
List<User> findByUsernameAndCode(@Param("username") String username, @Param("code") String code);

Using @Param with named placeholders makes it obvious which method argument maps to which part.

What is -parameters?

Java, by default, strips method parameter names during compilation unless you explicitly tell it not to.

public void greet(String name) { ... }

Without -parameters, reflection sees:

greet(java.lang.String arg0)

With -parameters, it sees:

greet(java.lang.String name)

This matters because Spring MVC and Spring Data JPA use reflection to map method parameters to inputs from HTTP requests or database queries.

---

Performance and scalability

Virtual Threads

If you are using Java 21 or later and Spring 3.2 you can activate Virtual Threads in Spring using: spring.threads.virtual.enabled=true

Spring will:

• configure Tomcat/Jetty to use virtual threads
• configure `@Async to use a virtual thread executor

If your application has a lot of web requests or is using @Async methods you could see an improvement in the performances.

Traditionally, each web request opens a new thread at OS level; this operation is expensive. With virtual threads the Java Runtime will create a light thread with improved utilization of the resources.

Virtual threads reduce the need to switch to a reactive stack (and co-routines in Kotlin) for many I/O-bound applications.

Server compression

This feature can be useful if your deployment doesn't use a proxy (e.g. nginx), we can ask Spring to compress the static assets and reduce the size of the files sent to the client. Compression improves bandwidth usage but increases CPU usage — always measure under load.

# Enable response compression
server.compression.enabled=true
# Mime types that should be compressed
server.compression.mime-types=text/html,text/xml,text/plain,text/css,text/javascript,application/javascript,application/json
# Only compress responses larger than 8KB
server.compression.min-response-size=8192
# Caching for static resources
spring.web.resources.cache.cachecontrol.max-age=15768000

This works with embedded Tomcat, Jetty, or Undertow.

The best solution is still to use a dedicated proxy server (nginx, apache) or cloud providers (CloudFront, Cloudflare) with caching features. You can find an example in my post: Docker with Angular and Nginx

Cache

Check if your view template engine supports caching in Spring and use it in case of benefits. Example, this blog mustache and the caching has to be activated: spring.mustache.servlet.cache=true

Monitor slow queries

You can easily log slow queries with Spring adding a threshold in the configuration:

``` properties

define the millisecons that will triggert the log

spring.jpa.properties.hibernate.session.events.log.LOGQUERIESSLOWERTHANMS=300 logging.level.org.hibernate.SQL_SLOW=INFO