1C.Auto Config Mechanism

trydoforOriginal6/20/22SilencerConfigAbout 3 min

1C.Auto Config Mechanism

Take advantage of SpringBoot to complete the auto config.

1C.1.Naming and Rule

There are special features of Spring naming, mainly focused on the following (the directory structure will be explained in detail later)

/wings-conf/ autoload, splitted config files
/wings-i18n/ autoload, splitted I18n files
**/spring/boot/ manual load, Boot-related config, like spring.facts
**/spring/bean/ produce bean, as specified by @ComponentScan
**/spring/conf/ Configurer or AutoConfiguration
**/spring/prop/ Property mapping
**/spring/help/ Configuration helper
*Configuration.java conditional load, with config items prefixed by wings.enabled.

When developing with idea, there will be yellow warnings or prompts, that do not affect the operation, but look like an eyesore.

Prompting "Application context not configured for this file" Just add boot/WingsAutoConfiguration manually in Project Structure/Facets/Spring.
Prompting "annotation processing", check in Settings/Annotation Processors/Enable annotation processing
Note: The inner classes in @Configuration, static class are treated as independent and not bound by the outer.

In Wings project, there will be a wings-enabled.properties to toggle the feature. Set wings.enabled.silencer.verbose=true to view the INFO of the log message.

1C.2.Property Bind and Prompt

Properties classes are unified with *Prop.java and @Data, which can be auto prompted after configuration.

manually add additional-spring-configuration-metadata.json
auto-generated spring-configuration-metadata.json

References,

1C.3.Configuring by Condition

Configuration is *Configuration.java in /spring/bean/
Property is *Prop.java in /spring/prop/
Nested configurations do not inherit from @Conditional
- merged into @ConditionalOnExpression
- or customize a @Conditional
multiple @Conditional are and logic
multiple Condition are and logic

Javadoc of Conditional

The @Conditional annotation may be used in any of the following ways:
as a type-level annotation on any class directly or indirectly annotated with @Component, including @Configuration classes
as a meta-annotation, for the purpose of composing custom stereotype annotations
as a method-level annotation on any @Bean method
If a @Configuration class is marked with @Conditional,all of the @Bean methods, @Import annotations, and @ComponentScan annotations associated with that class will be subject to the conditions.
NOTE: Inheritance of @Conditional annotations is not supported; any conditions from superclasses or from overridden methods will not be considered.

1C.4.ConditionalOnClass No Effect

The following code, ConditionalOnClass placed on the same type of bean declaration, will report a NoClassDefFoundError

@Bean
@ConditionalOnClass(SomeService.class)
public SomeService someService() {
    return new SomeService();
}

Need to change to something like the following, inner class-driven configuration,

@Configuration(proxyBeanMethods = false)
@ConditionalOnClass(SomeService.class)
public static class SomeServiceConfiguration {
    @Bean
    public SomeService someService() {
        return new SomeService();
    }
}

See Creating Your Own Auto-configuration

In the Spring @Conditional auto configuration, the On*Bean depends on the registration order of the beans, which makes it difficult to detect problems. Therefore, in Wings, we move the problem to the early startup phase to detect bean conflicts as early as possible. By setting property files, we can disable unnecessary features.

On @Configuration, @Bean and any @Component, using @ConditionalWingsEnabled and the qualified-key can disable any Component and Bean,

qualified-key = Prefix. + ClassName + .beanMethod? = true|false

Prefix - default wings.enabled
ClassName - e.g. pro.fessional.wings.silencer.spring.boot.WingsEnabledCondition
beanMethod - e.g. crc8Long

@*Configuration naming rules are as follows,

*AutoConfiguration - @AutoConfiguration @Import @Configuration
*Configuration - top @Configuration and its @Bean
*Event - inner @Configuration and its @EventListener
*Wired - inner @Configuration and its @Autowired
*Bean - inner @Configuration and wrap its single @Bean *
*Scan - inner @Configuration for @ComponentScan

@ConditionalWingsEnabled has the following enhancements

abs - absolute-key, without prefix, priority lower then qualified-key
key - relative-key, with prefix, priority lower then absolute-key
value - default value, the lowest priority, if no key found
and, not - this && and1 && and2 && !not1 && !not2

where qualified-key is equivalent to id, globally unique and the highest priority, absolute-key and relative-key are equivalent to alias, can be shared without uniqueness. and the priority of these 3 keys is from highest to lowest.

qualified-key = prefix + ClassName + methodName?
absolute-key = abs()
relative-key = prefix + key()
default = value()

In addition to the precise control of annotations, the following props can impl the ant-matcher control of qualified-key.

wings.feature.error
wings.feature.prefix
wings.feature.enable

## ... is short for the package

## @ConditionalWingsEnabled(prefix = "catty.enabled")
## disable @Bean catBean in WingsEnabledCatConfiguration
catty.enabled.pro...WingsEnabledCatConfiguration.catBean=false
## disable InnerCatConfiguration and its Bean
catty.enabled.pro...WingsEnabledCatConfiguration$InnerCatConfiguration=false

## @Conditional(WingsEnabledCondition.class) or @ConditionalWingsEnabled
## disable @Bean dogBean in WingsEnabledDogConfiguration
wings.enabled.pro...WingsEnabledDogConfiguration.dogBean=false
## disable InnerDogConfiguration and its Bean
wings.enabled.pro...WingsEnabledDogConfiguration$InnerDogConfiguration=false

1C.6. Feature Flags

The Wings FeatureFlags implementation has two levels, as follows.

Config level - @ConditionalWingsEnabled acts on the @Component and @Bean.
Thread level - FeatureFlag acts on the logical

The principle of both is the same, based on wings.feature and wings.enabled properties.

In business coding, toggling business logic can be achieved by using the following utility classes.

FeatureFlag - get the feature state using Class as key
TweakFeature - dynamically toggle feature at global or thread level

the priority of flag is as the following,

@ConditionalWingsEnabled - confClass or beanMethod
- qualified-key = prefix. + ClassName + .methodName?
- absolute-key = abs()
- relative-key = prefix. + key()
- default = value(), only if no prop
- and(), then not() - only if this enabled
wings.enabled.* - string prop, one-one
wings.feature.* - ant style prop, one-many, only if no one-one
FeatureFlag - TweakFeature, then WingsEnabledContext

1C.7.Config Bean Order

Use the wings.reorder.* attribute, where * is.

beanName - one-to-one by name, high priority
beanClass - one-to-many by type

The scope of its impact includes.

List<Bean> - injected ordered collection class
.orderedStream() -ObjectProvider ordered stream

The ordering priority is as follows, NOTE, beans are declared or scanned in different mechanisms that affect priority.

wings.reorder.* configuration, highest priority
if @Bean, @Order over Ordered
if @Component, Ordered over @Order

this disabled if any of the followings,

no property or no defined bean found
wings.enabled.silencer.bean-reorder=false

also can set Primary by wings.primary.*, but only beanName is supported.

// wings.reorder.getterClass2 = 3
@Bean
public GetterClass getterClass2()

// wings.primary.testReorderServiceImpl2=true
// wings.reorder.testReorderServiceImpl2 = 3 # or
// wings.reorder.pro.fessional.wings.silencer.app.service.impl.TestReorderServiceImpl2=3
@Service
public class TestReorderServiceImpl2