Allow HTTP message converters to be auto-configured in a native image that is not a web app

[mhalbritter]

When running the native-image from the spring-native rsocket sample in this branch, it fails with this exception:

org.springframework.boot.context.properties.bind.BindException: Failed to bind properties under 'server.servlet.encoding' to org.springframework.boot.web.servlet.server.Encoding
	at org.springframework.boot.context.properties.bind.Binder.handleBindError(Binder.java:387) ~[rsocket:3.0.0-SNAPSHOT]
	at org.springframework.boot.context.properties.bind.Binder.bind(Binder.java:347) ~[rsocket:3.0.0-SNAPSHOT]
	at org.springframework.boot.context.properties.bind.Binder.bind(Binder.java:332) ~[rsocket:3.0.0-SNAPSHOT]
	at org.springframework.boot.context.properties.bind.Binder.bindOrCreate(Binder.java:324) ~[rsocket:3.0.0-SNAPSHOT]
	at org.springframework.boot.context.properties.bind.Binder.bindOrCreate(Binder.java:293) ~[rsocket:3.0.0-SNAPSHOT]
	at org.springframework.boot.context.properties.bind.Binder.bindOrCreate(Binder.java:278) ~[rsocket:3.0.0-SNAPSHOT]
	at org.springframework.boot.autoconfigure.http.HttpMessageConvertersAutoConfiguration$StringHttpMessageConverterConfiguration.stringHttpMessageConverter(HttpMessageConvertersAutoConfiguration.java:80) ~[rsocket:3.0.0-SNAPSHOT]
	at java.lang.reflect.Method.invoke(Method.java:568) ~[rsocket:na]
	at org.springframework.util.ReflectionUtils.invokeMethod(ReflectionUtils.java:281) ~[na:na]
	at org.springframework.beans.factory.aot.AutowiredInstantiationArgumentsResolver.instantiate(AutowiredInstantiationArgumentsResolver.java:360) ~[na:na]
	at org.springframework.beans.factory.aot.AutowiredInstantiationArgumentsResolver.instantiate(AutowiredInstantiationArgumentsResolver.java:332) ~[na:na]
	at org.springframework.beans.factory.aot.AutowiredInstantiationArgumentsResolver.resolveAndInstantiate(AutowiredInstantiationArgumentsResolver.java:195) ~[na:na]
	at org.springframework.beans.factory.aot.AutowiredInstantiationArgumentsResolver.resolveAndInstantiate(AutowiredInstantiationArgumentsResolver.java:177) ~[na:na]
	at org.springframework.boot.autoconfigure.http.HttpMessageConvertersAutoConfiguration_StringHttpMessageConverterConfiguration__BeanDefinitions.getStringHttpMessageConverterInstance(HttpMessageConvertersAutoConfiguration_StringHttpMessageConverterConfiguration__BeanDefinitions.java:52) ~[na:na]
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.obtainInstanceFromSupplier(AbstractAutowireCapableBeanFactory.java:1223) ~[rsocket:6.0.0-SNAPSHOT]
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.obtainFromSupplier(AbstractAutowireCapableBeanFactory.java:1209) ~[rsocket:6.0.0-SNAPSHOT]
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBeanInstance(AbstractAutowireCapableBeanFactory.java:1156) ~[rsocket:6.0.0-SNAPSHOT]
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:566) ~[rsocket:6.0.0-SNAPSHOT]
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:526) ~[rsocket:6.0.0-SNAPSHOT]
	at org.springframework.beans.factory.support.AbstractBeanFactory.lambda$doGetBean$0(AbstractBeanFactory.java:326) ~[rsocket:6.0.0-SNAPSHOT]
	at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:234) ~[rsocket:6.0.0-SNAPSHOT]
	at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:324) ~[rsocket:6.0.0-SNAPSHOT]
	at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:200) ~[rsocket:6.0.0-SNAPSHOT]
	at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:930) ~[rsocket:6.0.0-SNAPSHOT]
	at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:926) ~[rsocket:6.0.0-SNAPSHOT]
	at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:592) ~[rsocket:6.0.0-SNAPSHOT]
	at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:735) ~[rsocket:3.0.0-SNAPSHOT]
	at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:431) ~[rsocket:3.0.0-SNAPSHOT]
	at org.springframework.boot.SpringApplication.run(SpringApplication.java:310) ~[rsocket:3.0.0-SNAPSHOT]
	at org.springframework.boot.SpringApplication.run(SpringApplication.java:1307) ~[rsocket:3.0.0-SNAPSHOT]
	at org.springframework.boot.SpringApplication.run(SpringApplication.java:1296) ~[rsocket:3.0.0-SNAPSHOT]
	at com.example.rsocket.RSocketApplication.main(RSocketApplication.java:12) ~[rsocket:0.0.1-SNAPSHOT]
Caused by: org.springframework.beans.BeanInstantiationException: Failed to instantiate [org.springframework.boot.web.servlet.server.Encoding]: No default constructor found
	at org.springframework.beans.BeanUtils.instantiateClass(BeanUtils.java:146) ~[na:na]
	at org.springframework.boot.context.properties.bind.JavaBeanBinder.create(JavaBeanBinder.java:67) ~[na:na]
	at org.springframework.boot.context.properties.bind.Binder.create(Binder.java:369) ~[rsocket:3.0.0-SNAPSHOT]
	at org.springframework.boot.context.properties.bind.Binder.handleBindResult(Binder.java:358) ~[rsocket:3.0.0-SNAPSHOT]
	at org.springframework.boot.context.properties.bind.Binder.bind(Binder.java:344) ~[rsocket:3.0.0-SNAPSHOT]
	... 30 common frames omitted
Caused by: java.lang.NoSuchMethodException: org.springframework.boot.web.servlet.server.Encoding.<init>()
	at java.lang.Class.getConstructor0(DynamicHub.java:3585) ~[rsocket:na]
	at java.lang.Class.getDeclaredConstructor(DynamicHub.java:2754) ~[rsocket:na]
	at org.springframework.beans.BeanUtils.instantiateClass(BeanUtils.java:141) ~[na:na]
	... 34 common frames omitted

Seems there are some hints for the binding missing.

[wilkinsona]

In an app with a ServerProperties bean, I don't think this will occur as we'll already have hints for binding ServerProperties.

Two questions come to mind:

• Why are we using the binder directly rather than @EnableConfigurationProperties(ServerProperties.class)?
• Why is HttpMessageConvertersAutoConfiguration active in a pure RSocket app?

[mhalbritter]

To answer the 2nd question:

   HttpMessageConvertersAutoConfiguration matched:
      - @ConditionalOnClass found required class 'org.springframework.http.converter.HttpMessageConverter' (OnClassCondition)
      - NoneNestedConditions 0 matched 1 did not; NestedCondition on HttpMessageConvertersAutoConfiguration.NotReactiveWebApplicationCondition.ReactiveWebApplication did not find reactive web application classes (HttpMessageConvertersAutoConfiguration.NotReactiveWebApplicationCondition)

org.springframework.boot:spring-boot-starter-rsocket uses org.springframework.boot:spring-boot-starter-json, which in turn uses org.springframework:spring-web

[wilkinsona]

I'd like to discuss this with the team. I'm wondering about both tightening up the conditions and possibly switching to using ServerProperties rather than calling the binder manually.

[mbhave]

We discussed this on the team call. We don't use ServerProperties directly due to this issue. Given that, we'd need to add hints for Encoding.

[wilkinsona]

The current conditions also seemed reasonable. In such an app we suspect we will have also configured RestTemplate (which only requires spring-web) and it uses HTTP message converters.

In short, we need to configure a hint specifically for server.servlet.encoding for situations where StringHttpMessageConverterConfiguration is active without a ServerProperties bean.

[sdeleuze]

Impact Spring Cloud Config as well.