This version is still in development and is not considered stable yet. For the latest stable version, please use Spring Framework 6.0.26! |
WebFlux Config
The WebFlux Java configuration declares the components that are required to process
requests with annotated controllers or functional endpoints, and it offers an API to
customize the configuration. That means you do not need to understand the underlying
beans created by the Java configuration. However, if you want to understand them,
you can see them in WebFluxConfigurationSupport
or read more about what they are
in Special Bean Types.
For more advanced customizations, not available in the configuration API, you can gain full control over the configuration through the Advanced Configuration Mode.
Enabling WebFlux Config
You can use the @EnableWebFlux
annotation in your Java config, as the following example shows:
-
Java
-
Kotlin
@Configuration
@EnableWebFlux
public class WebConfig {
}
@Configuration
@EnableWebFlux
class WebConfig
The preceding example registers a number of Spring WebFlux infrastructure beans and adapts to dependencies available on the classpath — for JSON, XML, and others.
WebFlux config API
In your Java configuration, you can implement the WebFluxConfigurer
interface,
as the following example shows:
-
Java
-
Kotlin
@Configuration
@EnableWebFlux
public class WebConfig implements WebFluxConfigurer {
// Implement configuration methods...
}
@Configuration
@EnableWebFlux
class WebConfig : WebFluxConfigurer {
// Implement configuration methods...
}
Conversion, formatting
By default, formatters for various number and date types are installed, along with support
for customization via @NumberFormat
and @DateTimeFormat
on fields.
To register custom formatters and converters in Java config, use the following:
-
Java
-
Kotlin
@Configuration
@EnableWebFlux
public class WebConfig implements WebFluxConfigurer {
@Override
public void addFormatters(FormatterRegistry registry) {
// ...
}
}
@Configuration
@EnableWebFlux
class WebConfig : WebFluxConfigurer {
override fun addFormatters(registry: FormatterRegistry) {
// ...
}
}
By default Spring WebFlux considers the request Locale when parsing and formatting date values. This works for forms where dates are represented as Strings with "input" form fields. For "date" and "time" form fields, however, browsers use a fixed format defined in the HTML spec. For such cases date and time formatting can be customized as follows:
-
Java
-
Kotlin
@Configuration
@EnableWebFlux
public class WebConfig implements WebFluxConfigurer {
@Override
public void addFormatters(FormatterRegistry registry) {
DateTimeFormatterRegistrar registrar = new DateTimeFormatterRegistrar();
registrar.setUseIsoFormat(true);
registrar.registerFormatters(registry);
}
}
@Configuration
@EnableWebFlux
class WebConfig : WebFluxConfigurer {
override fun addFormatters(registry: FormatterRegistry) {
val registrar = DateTimeFormatterRegistrar()
registrar.setUseIsoFormat(true)
registrar.registerFormatters(registry)
}
}
See FormatterRegistrar SPI
and the FormattingConversionServiceFactoryBean for more information on when to
use FormatterRegistrar implementations.
|
Validation
By default, if Bean Validation is present
on the classpath (for example, the Hibernate Validator), the LocalValidatorFactoryBean
is registered as a global validator for use with @Valid
and
@Validated
on @Controller
method arguments.
In your Java configuration, you can customize the global Validator
instance,
as the following example shows:
-
Java
-
Kotlin
@Configuration
@EnableWebFlux
public class WebConfig implements WebFluxConfigurer {
@Override
public Validator getValidator() {
// ...
}
}
@Configuration
@EnableWebFlux
class WebConfig : WebFluxConfigurer {
override fun getValidator(): Validator {
// ...
}
}
Note that you can also register Validator
implementations locally,
as the following example shows:
-
Java
-
Kotlin
@Controller
public class MyController {
@InitBinder
protected void initBinder(WebDataBinder binder) {
binder.addValidators(new FooValidator());
}
}
@Controller
class MyController {
@InitBinder
protected fun initBinder(binder: WebDataBinder) {
binder.addValidators(FooValidator())
}
}
If you need to have a LocalValidatorFactoryBean injected somewhere, create a bean and
mark it with @Primary in order to avoid conflict with the one declared in the MVC config.
|
Content Type Resolvers
You can configure how Spring WebFlux determines the requested media types for
@Controller
instances from the request. By default, only the Accept
header is checked,
but you can also enable a query parameter-based strategy.
The following example shows how to customize the requested content type resolution:
-
Java
-
Kotlin
@Configuration
@EnableWebFlux
public class WebConfig implements WebFluxConfigurer {
@Override
public void configureContentTypeResolver(RequestedContentTypeResolverBuilder builder) {
// ...
}
}
@Configuration
@EnableWebFlux
class WebConfig : WebFluxConfigurer {
override fun configureContentTypeResolver(builder: RequestedContentTypeResolverBuilder) {
// ...
}
}
HTTP message codecs
The following example shows how to customize how the request and response body are read and written:
-
Java
-
Kotlin
@Configuration
@EnableWebFlux
public class WebConfig implements WebFluxConfigurer {
@Override
public void configureHttpMessageCodecs(ServerCodecConfigurer configurer) {
configurer.defaultCodecs().maxInMemorySize(512 * 1024);
}
}
@Configuration
@EnableWebFlux
class WebConfig : WebFluxConfigurer {
override fun configureHttpMessageCodecs(configurer: ServerCodecConfigurer) {
// ...
}
}
ServerCodecConfigurer
provides a set of default readers and writers. You can use it to add
more readers and writers, customize the default ones, or replace the default ones completely.
For Jackson JSON and XML, consider using
Jackson2ObjectMapperBuilder
,
which customizes Jackson’s default properties with the following ones:
-
DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES
is disabled. -
MapperFeature.DEFAULT_VIEW_INCLUSION
is disabled.
It also automatically registers the following well-known modules if they are detected on the classpath:
-
jackson-datatype-joda
: Support for Joda-Time types. -
jackson-datatype-jsr310
: Support for Java 8 Date and Time API types. -
jackson-datatype-jdk8
: Support for other Java 8 types, such asOptional
. -
jackson-module-kotlin
: Support for Kotlin classes and data classes.
View Resolvers
The following example shows how to configure view resolution:
-
Java
-
Kotlin
@Configuration
@EnableWebFlux
public class WebConfig implements WebFluxConfigurer {
@Override
public void configureViewResolvers(ViewResolverRegistry registry) {
// ...
}
}
@Configuration
@EnableWebFlux
class WebConfig : WebFluxConfigurer {
override fun configureViewResolvers(registry: ViewResolverRegistry) {
// ...
}
}
The ViewResolverRegistry
has shortcuts for view technologies with which the Spring Framework
integrates. The following example uses FreeMarker (which also requires configuring the
underlying FreeMarker view technology):
-
Java
-
Kotlin
@Configuration
@EnableWebFlux
public class WebConfig implements WebFluxConfigurer {
@Override
public void configureViewResolvers(ViewResolverRegistry registry) {
registry.freeMarker();
}
// Configure Freemarker...
@Bean
public FreeMarkerConfigurer freeMarkerConfigurer() {
FreeMarkerConfigurer configurer = new FreeMarkerConfigurer();
configurer.setTemplateLoaderPath("classpath:/templates");
return configurer;
}
}
@Configuration
@EnableWebFlux
class WebConfig : WebFluxConfigurer {
override fun configureViewResolvers(registry: ViewResolverRegistry) {
registry.freeMarker()
}
// Configure Freemarker...
@Bean
fun freeMarkerConfigurer() = FreeMarkerConfigurer().apply {
setTemplateLoaderPath("classpath:/templates")
}
}
You can also plug in any ViewResolver
implementation, as the following example shows:
-
Java
-
Kotlin
@Configuration
@EnableWebFlux
public class WebConfig implements WebFluxConfigurer {
@Override
public void configureViewResolvers(ViewResolverRegistry registry) {
ViewResolver resolver = ... ;
registry.viewResolver(resolver);
}
}
@Configuration
@EnableWebFlux
class WebConfig : WebFluxConfigurer {
override fun configureViewResolvers(registry: ViewResolverRegistry) {
val resolver: ViewResolver = ...
registry.viewResolver(resolver
}
}
To support Content Negotiation and rendering other formats
through view resolution (besides HTML), you can configure one or more default views based
on the HttpMessageWriterView
implementation, which accepts any of the available
Codecs from spring-web
. The following example shows how to do so:
-
Java
-
Kotlin
@Configuration
@EnableWebFlux
public class WebConfig implements WebFluxConfigurer {
@Override
public void configureViewResolvers(ViewResolverRegistry registry) {
registry.freeMarker();
Jackson2JsonEncoder encoder = new Jackson2JsonEncoder();
registry.defaultViews(new HttpMessageWriterView(encoder));
}
// ...
}
@Configuration
@EnableWebFlux
class WebConfig : WebFluxConfigurer {
override fun configureViewResolvers(registry: ViewResolverRegistry) {
registry.freeMarker()
val encoder = Jackson2JsonEncoder()
registry.defaultViews(HttpMessageWriterView(encoder))
}
// ...
}
See View Technologies for more on the view technologies that are integrated with Spring WebFlux.
Static Resources
This option provides a convenient way to serve static resources from a list of
Resource
-based locations.
In the next example, given a request that starts with /resources
, the relative path is
used to find and serve static resources relative to /static
on the classpath. Resources
are served with a one-year future expiration to ensure maximum use of the browser cache
and a reduction in HTTP requests made by the browser. The Last-Modified
header is also
evaluated and, if present, a 304
status code is returned. The following listing shows
the example:
-
Java
-
Kotlin
@Configuration
@EnableWebFlux
public class WebConfig implements WebFluxConfigurer {
@Override
public void addResourceHandlers(ResourceHandlerRegistry registry) {
registry.addResourceHandler("/resources/**")
.addResourceLocations("/public", "classpath:/static/")
.setCacheControl(CacheControl.maxAge(365, TimeUnit.DAYS));
}
}
@Configuration
@EnableWebFlux
class WebConfig : WebFluxConfigurer {
override fun addResourceHandlers(registry: ResourceHandlerRegistry) {
registry.addResourceHandler("/resources/**")
.addResourceLocations("/public", "classpath:/static/")
.setCacheControl(CacheControl.maxAge(365, TimeUnit.DAYS))
}
}
The resource handler also supports a chain of
ResourceResolver
implementations and
ResourceTransformer
implementations,
which can be used to create a toolchain for working with optimized resources.
You can use the VersionResourceResolver
for versioned resource URLs based on an MD5 hash
computed from the content, a fixed application version, or other information. A
ContentVersionStrategy
(MD5 hash) is a good choice with some notable exceptions (such as
JavaScript resources used with a module loader).
The following example shows how to use VersionResourceResolver
in your Java configuration:
-
Java
-
Kotlin
@Configuration
@EnableWebFlux
public class WebConfig implements WebFluxConfigurer {
@Override
public void addResourceHandlers(ResourceHandlerRegistry registry) {
registry.addResourceHandler("/resources/**")
.addResourceLocations("/public/")
.resourceChain(true)
.addResolver(new VersionResourceResolver().addContentVersionStrategy("/**"));
}
}
@Configuration
@EnableWebFlux
class WebConfig : WebFluxConfigurer {
override fun addResourceHandlers(registry: ResourceHandlerRegistry) {
registry.addResourceHandler("/resources/**")
.addResourceLocations("/public/")
.resourceChain(true)
.addResolver(VersionResourceResolver().addContentVersionStrategy("/**"))
}
}
You can use ResourceUrlProvider
to rewrite URLs and apply the full chain of resolvers and
transformers (for example, to insert versions). The WebFlux configuration provides a ResourceUrlProvider
so that it can be injected into others.
Unlike Spring MVC, at present, in WebFlux, there is no way to transparently rewrite static
resource URLs, since there are no view technologies that can make use of a non-blocking chain
of resolvers and transformers. When serving only local resources, the workaround is to use
ResourceUrlProvider
directly (for example, through a custom element) and block.
Note that, when using both EncodedResourceResolver
(for example, Gzip, Brotli encoded) and
VersionedResourceResolver
, they must be registered in that order, to ensure content-based
versions are always computed reliably based on the unencoded file.
For WebJars, versioned URLs like
/webjars/jquery/1.2.0/jquery.min.js
are the recommended and most efficient way to use them.
The related resource location is configured out of the box with Spring Boot (or can be configured
manually via ResourceHandlerRegistry
) and does not require to add the
org.webjars:webjars-locator-core
dependency.
Version-less URLs like /webjars/jquery/jquery.min.js
are supported through the
WebJarsResourceResolver
which is automatically registered when the
org.webjars:webjars-locator-core
library is present on the classpath, at the cost of a
classpath scanning that could slow down application startup. The resolver can re-write URLs to
include the version of the jar and can also match against incoming URLs without versions — for example, from /webjars/jquery/jquery.min.js
to /webjars/jquery/1.2.0/jquery.min.js
.
The Java configuration based on ResourceHandlerRegistry provides further options
for fine-grained control, e.g. last-modified behavior and optimized resource resolution.
|
Path Matching
You can customize options related to path matching. For details on the individual options, see the
PathMatchConfigurer
javadoc.
The following example shows how to use PathMatchConfigurer
:
-
Java
-
Kotlin
@Configuration
@EnableWebFlux
public class WebConfig implements WebFluxConfigurer {
@Override
public void configurePathMatch(PathMatchConfigurer configurer) {
configurer
.setUseCaseSensitiveMatch(true)
.addPathPrefix("/api", HandlerTypePredicate.forAnnotation(RestController.class));
}
}
@Configuration
@EnableWebFlux
class WebConfig : WebFluxConfigurer {
@Override
fun configurePathMatch(configurer: PathMatchConfigurer) {
configurer
.setUseCaseSensitiveMatch(true)
.addPathPrefix("/api", HandlerTypePredicate.forAnnotation(RestController::class.java))
}
}
Spring WebFlux relies on a parsed representation of the request path called
Spring WebFlux also does not support suffix pattern matching, unlike in Spring MVC, where we are also recommend moving away from reliance on it. |
WebSocketService
The WebFlux Java config declares of a WebSocketHandlerAdapter
bean which provides
support for the invocation of WebSocket handlers. That means all that remains to do in
order to handle a WebSocket handshake request is to map a WebSocketHandler
to a URL
via SimpleUrlHandlerMapping
.
In some cases it may be necessary to create the WebSocketHandlerAdapter
bean with a
provided WebSocketService
service which allows configuring WebSocket server properties.
For example:
-
Java
-
Kotlin
@Configuration
@EnableWebFlux
public class WebConfig implements WebFluxConfigurer {
@Override
public WebSocketService getWebSocketService() {
TomcatRequestUpgradeStrategy strategy = new TomcatRequestUpgradeStrategy();
strategy.setMaxSessionIdleTimeout(0L);
return new HandshakeWebSocketService(strategy);
}
}
@Configuration
@EnableWebFlux
class WebConfig : WebFluxConfigurer {
@Override
fun webSocketService(): WebSocketService {
val strategy = TomcatRequestUpgradeStrategy().apply {
setMaxSessionIdleTimeout(0L)
}
return HandshakeWebSocketService(strategy)
}
}
Advanced Configuration Mode
@EnableWebFlux
imports DelegatingWebFluxConfiguration
that:
-
Provides default Spring configuration for WebFlux applications
-
detects and delegates to
WebFluxConfigurer
implementations to customize that configuration.
For advanced mode, you can remove @EnableWebFlux
and extend directly from
DelegatingWebFluxConfiguration
instead of implementing WebFluxConfigurer
,
as the following example shows:
-
Java
-
Kotlin
@Configuration
public class WebConfig extends DelegatingWebFluxConfiguration {
// ...
}
@Configuration
class WebConfig : DelegatingWebFluxConfiguration {
// ...
}
You can keep existing methods in WebConfig
, but you can now also override bean declarations
from the base class and still have any number of other WebMvcConfigurer
implementations on
the classpath.