Spring Boot 2.4.0 M2 Release Notes

For changes in earlier milestones, please refer to:

v2.4.0 M1

Upgrading from Spring Boot 2.3

Config File Processing (application properties and YAML files)

Spring Boot 2.4 has changed the way that application.properties and application.yml files are processed. If you only have a simple application.properties or application.yml file, your upgrade should be seamless. If, however, you’ve have a more complex setup (with profile specific properties, or profile activation properties) you may need to make some changes if you want to use the new features.

If you just want Spring Boot 2.3 compatible logic, you can set a spring.config.use-legacy-processing property to true in your application.properties or application.yml file.

Neo4j

This release brings a significant overhaul of the Neo4j support. A number of properties in spring.data.neo4j.* have been removed and the support of Neo4j OGM has been removed as well.

Configuration of the Neo4j driver is done via the spring.neo4j.* namespace although URI and basic authentication from the data namespace are still supported in a deprecated fashion.

For more details about this change and what Spring Data Neo4j 6 brings, check the documentation.

R2DBC

The core infrastructure of R2DBC has moved to Spring Framework with a new spring-r2dbc module. If you are using this infrastructure, make sure to migrate deprecated access to the new core support.

Cookie request headers and Set-Cookie response headers are no longer included in HTTP traces by default. To restore Spring Boot 2.3’s behaviour, set management.trace.http.include to cookies, errors, request-headers, response-headers.

Metrics export in integration tests

@SpringBootTest no longer configures available monitoring systems and only provide the in-memory MeterRegistry. If you were exporting metrics as part of an integration test, you can add @AutoConfigureMetrics to your test to restore the previous behaviour.

Version management for `exec-maven-plugin`

The version management for the exec-maven-plugin has been removed. If you are using this plugin, make sure to specify a version in your own pluginManagement.

Deprecations from Spring Boot 2.3

Reflecting Spring Boot 2.4’s move to a 6-month release cadence, code deprecated in Spring Boot 2.3 will not be removed until Spring Boot 2.5.

Minimum requirements changes

None.

New and Noteworthy

Tip	Check the configuration changelog for a complete overview of the changes in configuration.

Spring Framework 5.3-M2

Spring Boot 2.4 will include Spring Framework 5.3, and this milestone upgrades to Spring Framework 5.3.0-M2. Please refer to this blog post to learn more.

Spring Data 2020.0-M2

Spring Boot 2.4 will include version 2020.0 (code-named Ockham) of the Spring Data release train, and this milestone includes M2.

Neo4j

This release brings support of reactive repositories and rely on a separate auto-configuration for the Neo4j driver. As a result, it is now possible to use Neo4j with or without Spring Data.

Health checks for Neo4j use the Driver and are available as long as the Neo4j driver is configured.

If you want to use @Transactional with reactive access, you’d need to configure the Neo4jReactiveTransactionManager bean yourself for now.

@Bean(ReactiveNeo4jRepositoryConfigurationExtension.DEFAULT_TRANSACTION_MANAGER_BEAN_NAME)
public ReactiveTransactionManager reactiveTransactionManager(Driver driver,
      ReactiveDatabaseSelectionProvider databaseNameProvider) {
    return new ReactiveNeo4jTransactionManager(driver, databaseNameProvider);
}

We expect to alleviate this limitation in a future milestone

R2DBC

A R2dbcEntityTemplate is available to simplify the use of Reactive R2DBC usage through entities

Importing Additional Application Config

As long as you haven’t set spring.config.use-legacy-processing to true, you can now import additional properties and yaml files directly from your main application.properties or application.yml.

You can use the spring.config.import property to specify one or more additional config files that should be imported into the Spring Environment. See this section of the reference guide for more details.

We’ve also published a short blog explaining why we’ve made these changes.

Volume Mounted Config Directory Trees

The spring.config.import property can also be used to import configuration trees that are commonly used with Kubernetes. A configuration tree is an alternative way of providing key/value pairs. Each pair is declared in its own file, with the filename forming the property key, and the file contents providing the value.

For a complete example, see the updated reference documentation.

Custom property name support

When using constructor binding the name of the property is derived from the parameter name. This can be a problem if you want to use a java reserved keyword. For such situations, you can now use the @Name annotation, something like:

@ConfigurationProperties(prefix = "sample")
public class SampleConfigurationProperties {

  private final String importValue;

  public SampleConfigurationProperties(@Named("import") String importValue) {
    this.importValue = importValue;
  }

}

The sample above exposes a sample.import property.

Layered jar enabled by default

This release enables layered jars and include the layertools by default. This should improve the efficiency of generated image using the build pack out-of-the-box and lets you benefit of that feature when crafting custom Dockerfile.

Slice test for Cassandra

An additional test slice can be used to test components that rely on Cassandra using @DataCassandraTest. As usual, only Cassandra Repositories and the required infrastructure is configured by default.

Here is an example using Testcontainers and @DynamicPropertSource:

@DataCassandraTest(properties = "spring.data.cassandra.local-datacenter=datacenter1")
@Testcontainers(disabledWithoutDocker = true)
class SampleDataCassandraTestIntegrationTests {

	@Container
	static final CassandraContainer<?> cassandra = new CassandraContainer<>().withStartupAttempts(5)
			.withStartupTimeout(Duration.ofMinutes(2));

	@DynamicPropertySource
	static void cassandraProperties(DynamicPropertyRegistry registry) {
		registry.add("spring.data.cassandra.contact-points",
				() -> cassandra.getHost() + ":" + cassandra.getFirstMappedPort());
	}

	...

}

Dependency Upgrades

Spring Boot 2.4 M2 moves to new versions of several Spring projects:

Reactor 2020.0.0-M2
Spring AMQP 2.3.0-M2
Spring Batch 4.3.0-M2
Spring Data 2020.0.0-M2
Spring Framework 5.3.0-M2
Spring Integration 5.4.0-M2
Spring Kafka 2.6.0-M1
Spring Security 5.4.0-RC1

Numerous third-party dependencies have also been updated, some of the more noteworthy of which are the following:

Elasticsearch 7.8
Mockito 3.4
MongoDB 4.1

Miscellaneous

Apart from the changes listed above, there have also been lots of minor tweaks and improvements including:

R2DBC pool support exposes additional configuration properties.
Exception handling in LdapTemplate can be configured to ignore certain exceptions.
ISO offset date time format is support for MVC and Webflux.
Add a configuration property to opt-in for the new PathPatternParser in lieu of AntPathMatcher to parse and match request mapping path patterns.
@DurationUnit, @DataSizeUnit, and @PeriodUnit can annotate a constructor parameter using @ConstructorBinding.
The auto-configured RabbitConnectionFactory checks for the presence of CredentialsProvider and CredentialsRefreshService.
A health group can be defined with only exclusions.
AbstractRoutingDataSource can be ignored in health checks using management.health.db.ignore-routing-data-sources.
The localEntityIdTemplate of A SAML Relying party can be configured.
HTTP traces are measures with nanosecond precision.
A dedicated FailureAnalyzer provides a meaningful message when a Liquibase changelog is missing.
Netty’s request decoder can be customized using server.netty.* properties.
Plugin management for the Liquibase Maven Plugin that is consistent with the Liquibase version a Spring Boot version manages.
Basic authentication support for Prometheus PushGateway.
Allow selecting Jedis when both Jedis and Lettuce are available using spring.redis.client-type.
Allow disabling Redis Cluster dynamic sources refresh using spring.redis.lettuce.cluster.refresh.dynamic-sources.

Deprecations in Spring Boot 2.4.0 M2

ConfigFileApplicationListener has been deprecated in favor of ConfigDataEnvironmentPostProcessor.
SpringApplicationBuilder and SpringApplication methods relating to the contextClass have been deprecated in favor of alternatives that use a contextFactory.
Some methods of CloudFoundryVcapEnvironmentPostProcessor have been deprecated to work with EnvironmentPostProcessor updates (these should affect most users).
The BuildLog build pack support class has deprecated a few methods and replaced them with alternatives that provide more details.