Spring Boot 3 feature updates & best practices

[dhiraj_jaiswal]

Introduction: Spring Boot 3.0 will require Java 17 and spring framework 6 hence it becomes important for developers to get familiar with the changes and enhancements done in spring libraries as well as third-party library to adopt the new technology as part of best practices. In this blog I have tried to cover recent enhancements that are done in spring project using which code base can be simplified and developer experience can be improved.

Spring Framework 6 changes

Validator factory: A functional approach to using validator.

Introduction of method in Validator to provide a way to create a validator for the specific type <T> and define the validator in a functional way. reference

package com.example.validatingforminput;



import am.ik.yavi.builder.ValidatorBuilder;

import am.ik.yavi.core.Validator;



public class PersonForm {



    public static Validator<PersonForm> validator = ValidatorBuilder.<PersonForm>of()

            .constraint(PersonForm::getName, "name", c -> c.notNull().greaterThanOrEqual(2).lessThanOrEqual(30))

            .constraint(PersonForm::getAge, "age", c -> c.notNull().greaterThanOrEqual(18))

            .build();



    // ...

}

package com.example.validatingforminput;



import org.springframework.stereotype.Controller;

import org.springframework.validation.BindingResult;

import org.springframework.validation.Errors;

import org.springframework.validation.Validator;

import org.springframework.validation.annotation.Validated;

import org.springframework.web.bind.WebDataBinder;

import org.springframework.web.bind.annotation.GetMapping;

import org.springframework.web.bind.annotation.InitBinder;

import org.springframework.web.bind.annotation.PostMapping;





@Controller

public class WebController {



    @InitBinder

    void initBinder(WebDataBinder binder) {

        Validator personValidator = Validator.forInstanceOf(PersonForm.class, PersonForm.validator.toBiConsumer(Errors::rejectValue));

        binder.addValidators(personValidator);

    }



    @GetMapping("/")

    public String showForm(PersonForm personForm) {

        return "form";

    }



    @PostMapping("/")

    public String checkPersonInfo(@Validated PersonForm personForm, BindingResult bindingResult) {



        if (bindingResult.hasErrors()) {

            return "form";

        }



        return "redirect:/results";

    }

}

New methods in DataAccessUtils

DataAccessUtils provides an optionalResult method for Collection as well as Stream arguments.

protected final <T> T findSingle(String query) {

    return (T) DataAccessUtils.optionalResult(em.createNamedQuery(query).getResultList());

}​

Multiple TaskSchedulers to be supported with @Scheduled

Now we can have multiple scheduled tasks in our application, with multiple their pool size, thread name and some as daemon. Previously a single application could have only 1 task scheduler. Now we could define multiple schedulers and refer them in the @Scheduled annotation. reference

    @Scheduled(scheduler="${name}",cron = "${scheduler.pay.partner.transaction.cron.expression}", zone = "UTC")

Spring Language Expression(SpEL) enchancement

We can extend SpEL by registering user-defined functions that can be called within the expression string.The function is registered through the EvaluationContext. The following example shows how to register a user-defined function to be invoked via reflection (i.e. a Method).Reference

[Reference](https://docs.spring.io/spring-framework/reference/6.1-SNAPSHOT/core/expressions/language-ref/functio...)

public abstract class StringUtils {



	public static String reverseString(String input) {

		StringBuilder backwards = new StringBuilder(input.length());

		for (int i = 0; i < input.length(); i++) {

			backwards.append(input.charAt(input.length() - 1 - i));

		}

		return backwards.toString();

	}

}

ExpressionParser parser = new SpelExpressionParser();



EvaluationContext context = SimpleEvaluationContext.forReadOnlyDataBinding().build();

context.setVariable("reverseString",

		StringUtils.class.getDeclaredMethod("reverseString", String.class));



String helloWorldReversed = parser.parseExpression(

		"#reverseString('hello')").getValue(context, String.class);

Notable enhancements

• Virtual Threads in JDK 19. https://openjdk.org/jeps/444


• New PartEvent API to stream multipart form uploads


• In ThreadPoolTaskExecuter we can pause/resume.


• For reactive java, support of cache/scheduled etc.


• The new RestClient is a synchronous HTTP client that offers an API similar to WebClient, using the same infrastructure as RestTemplate.


• Support for recording asynchronous events with @RecordApplicationEvents in testing


• JdbcClient for JdbcTemplate with fluent api https://github.com/spring-projects/spring-framework/wiki/What's-New-in-Spring-Framework-6.x

Spring Data changes

New CRUD repository interfaces that return List instead of Iterable

Spring Data offers new variants of the CRUD repositories. These return a List for methods that return multiple entities:

- ListCrudRepository

- ListQuerydslPredicateExecutor

- ListQueryByExampleExecutor

They can be used as a drop-in replacement for the interfaces of same name but without the List prefix.

SpEL support in Spring Data JPA @Query definitions

Spring Data JDBC now does support SpEL expressions in @Query annotations and named queries. It works just as for Spring Data JPA .

@InsertOnlyProperty.

You may now annotate properties of the aggregate root with @InsertOnlyProperty. Properties annotated in such way will be written to the database only during insert operations, but they will not be updated afterwards.

reference

@SpringBootTest with Main Methods

The @SpringBootTest annotation can now use the main of any discovered @SpringBootConfiguration class if it’s available. This means that any custom SpringApplication configuration performed by your main method can now be picked up by tests.

To use the main method for a test set the useMainMethod attribute of @SpringBootTest to UseMainMethod.ALWAYS or UseMainMethod.WHEN_AVAILABLE.

Reference

Observability with Spring Boot 3

Spring boot 3 contain numerous autoconfigurations for improved metrics with Micrometer and new distributed tracing support with Micrometer Tracing. A very detailed explanation is provided here

Log4j2 Enhacements

Spring Boot 3 has introduced new Log4j2 extensions that includes the following additional features:

- Profile-specific Configuration

- Environment Properties Lookup

- Log4j2 System Properties

<SpringProfile name=”dev | test”>

<! — configuration to be enabled when the “dev” or “test” profiles are active →

</SpringProfile>



<SpringProfile name=”staging”>

<! — configuration to be enabled when the “staging” profile is active →

</SpringProfile>



<SpringProfile name=”!production”>

<! — configuration to be enabled when the “production” profile is not active →

</SpringProfile>



<Properties> <Property name=”applicationName”>${spring:spring.application.name}</property> </Properties>

​

Notable enhancements

- Native Images with Spring Boot and GraalVM. [Reference](https://www.baeldung.com/spring-native-intro)

Reference

• https://docs.spring.io/spring-boot/docs/3.0.0/reference/htmlsingle/#features.spring-application


• https://github.com/spring-projects/spring-boot/wiki/Spring-Boot-3.0-Release-Notes

If you want to know about JDK 17 feature please have a loot at my previous blog Java 17 – Best Practices and features.
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