Add support for Kotlin autowired constructor with optional parameters [SPR-15847]

[spring-projects-issues]

Abhijit Sarkar opened SPR-15847 and commented

@Component
class A(val str: String = "whatever", val b: B) { 
// class A constructor(val str: String = "whatever", @Autowired val b: B) doesn't work either 
}

@Component
class B {
}

@SpringBootApplication
class DemoApplication

fun main(args: Array<String>) {
    SpringApplication.run(DemoApplication::class.java, *args)
}

org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'a' defined in file [<elided>/A.class]: Instantiation of bean failed; nested exception is org.springframework.beans.BeanInstantiationException: Failed to instantiate [com.example.demo.A]: No default constructor found; nested exception is java.lang.NoSuchMethodException: com.example.demo.A.<init>()
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.instantiateBean(AbstractAutowireCapableBeanFactory.java:1242) ~[spring-beans-5.0.0.RC3.jar:5.0.0.RC3]
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBeanInstance(AbstractAutowireCapableBeanFactory.java:1141) ~[spring-beans-5.0.0.RC3.jar:5.0.0.RC3]
Caused by: org.springframework.beans.BeanInstantiationException: Failed to instantiate [com.example.demo.A]: No default constructor found; nested exception is java.lang.NoSuchMethodException: com.example.demo.A.<init>()
	at org.springframework.beans.factory.support.SimpleInstantiationStrategy.instantiate(SimpleInstantiationStrategy.java:84) ~[spring-beans-5.0.0.RC3.jar:5.0.0.RC3]
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.instantiateBean(AbstractAutowireCapableBeanFactory.java:1234) ~[spring-beans-5.0.0.RC3.jar:5.0.0.RC3]
	... 16 common frames omitted
Caused by: java.lang.NoSuchMethodException: com.example.demo.A.<init>()
	at java.lang.Class.getConstructor0(Class.java:3082) ~[na:1.8.0_131]
	at java.lang.Class.getDeclaredConstructor(Class.java:2178) ~[na:1.8.0_131]
	at org.springframework.beans.factory.support.SimpleInstantiationStrategy.instantiate(SimpleInstantiationStrategy.java:79) ~[spring-beans-5.0.0.RC3.jar:5.0.0.RC3]
	... 17 common frames omitted

---

Affects: 5.0 RC3

Issue Links:

• Revisit handling of missing fields (without default values) for immutable data classes [SPR-15877] #20432 Revisit handling of missing fields (without default values) for immutable data classes
• Streamline and reduce Kotlin delegates [SPR-16020] #20569 Streamline and reduce Kotlin delegates

Referenced from: commits ef68ccd

[spring-projects-issues]

Sébastien Deleuze commented

Abhijit Sarkar Could you please test latest snapshots to see if this commit provides the right behavior? (I did some integration tests but for such change an extra check on your side would be useful)

[spring-projects-issues]

Abhijit Sarkar commented

Verified that the application starts with Spring 5.0.0.BUILD-SNAPSHOT.