Revise configuration code for better Spring Native support

[artembilan]

See more info in Spring Native.

At the moment it is important to revise ImportSelector impls and class presence checks.

Related to: spring-projects/spring-framework#18353

[artembilan]

        at org.springframework.beans.factory.support.SimpleInstantiationStrategy.instantiate(SimpleInstantiationStrategy.java:83) ~[na:na]
        at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.instantiateBean(AbstractAutowireCapableBeanFactory.java:1308) ~[na:na]
        ... 17 common frames omitted
Caused by: java.lang.NoSuchMethodException: org.springframework.integration.config.IntegrationConfigurationBeanFactoryPostProcessor.<init>()

Looks like Spring requires explicit public default ctor for that type of beans in Native mode:

		if (NativeDetector.inNativeImage()) {
			this.instantiationStrategy = new SimpleInstantiationStrategy();
		}
		else {
			this.instantiationStrategy = new CglibSubclassingInstantiationStrategy();
		}

[artembilan]

Another more obvious reflection problem:

Caused by: org.springframework.beans.BeanInstantiationException: Failed to instantiate [org.springframework.integration.config.SourcePollingChannelAdapterFactoryBean]: No default constructor found; nested exception is java.lang.NoSuchMethodException: org.springframework.integration.config.SourcePollingChannelAd
apterFactoryBean.<init>()
        at org.springframework.beans.BeanUtils.instantiateClass(BeanUtils.java:154) ~[na:na]
        at org.springframework.integration.dsl.EndpointSpec.<init>(EndpointSpec.java:60) ~[na:na]
        at org.springframework.integration.dsl.SourcePollingChannelAdapterSpec.<init>(SourcePollingChannelAdapterSpec.java:32) ~[na:na]
        at org.springframework.integration.dsl.IntegrationFlows.from(IntegrationFlows.java:203) ~[na:na]
        at org.springframework.integration.dsl.IntegrationFlows.from(IntegrationFlows.java:195) ~[na:na]
        at org.springframework.integration.dsl.IntegrationFlows.fromSupplier(IntegrationFlows.java:166) ~[na:na]
        at org.springframework.integration.demonative.DemoNativeApplication.printSecondsFlow(DemoNativeApplication.java:20) ~[org.springframework.integration.demonative.DemoNativeApplication:na]
        at java.lang.reflect.Method.invoke(Method.java:566) ~[na:na]
        at org.springframework.beans.factory.support.SimpleInstantiationStrategy.instantiate(SimpleInstantiationStrategy.java:154) ~[na:na]
        ... 19 common frames omitted
Caused by: java.lang.NoSuchMethodException: org.springframework.integration.config.SourcePollingChannelAdapterFactoryBean.<init>()
        at java.lang.Class.getConstructor0(DynamicHub.java:3349) ~[na:na]
        at java.lang.Class.getDeclaredConstructor(DynamicHub.java:2553) ~[na:na]
        at org.springframework.beans.BeanUtils.instantiateClass(BeanUtils.java:147) ~[na:na]

where the code is like this:

protected EndpointSpec(H handler) {
	Class<?> fClass = ResolvableType.forClass(this.getClass()).as(EndpointSpec.class).resolveGenerics()[1];
	this.endpointFactoryBean = (F) BeanUtils.instantiateClass(fClass);
	this.handler = handler;
}

so, need to figure out how to avoid reflection over there or find out the way to teach it to work with Native image...

[garyrussell]

Proper doc link: https://docs.spring.io/spring-native/docs/0.9.0-SNAPSHOT/reference/htmlsingle/#how-to-contribute-design

[artembilan]

Yeah... Better to say this: https://docs.spring.io/spring-native/docs/current-SNAPSHOT/reference/htmlsingle/#how-to-contribute to align with whatever is the latest.

[artembilan]

Reopen: the work is not done yet.

[artembilan]

GroovyScriptExecutingMessageProcessor:

		GroovyObject goo = (GroovyObject) BeanUtils.instantiateClass(this.scriptClass);

MapToObjectTransformer:

Object target = (this.targetClass != null)
				? BeanUtils.instantiateClass(this.targetClass)
				: this.getBeanFactory().getBean(this.targetBeanName);

Or even JmsChannelFactoryBean:

AbstractMessageListenerContainer container = BeanUtils.instantiateClass(this.containerType);

and respective Java DSL:

protected JmsListenerContainerSpec(Class<C> aClass) {
		super(BeanUtils.instantiateClass(aClass));

Well, technically every single place where we indeed rely on the reflection at runtime.
This probably can be handled only via @NativeHint in Spring Native project.