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dhiraj_jaiswal
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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



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




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)

If you want to know about JDK 17 feature please have a loot at my previous blog Java 17 – Best Practices and features.
Please share your thoughts about this blog in the comment section.

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