Binder can fail when multiple overloaded setters exist

[Walliee]

If a ConfigurationProperties class has a String property but two setters for that property, one that takes a String and sets it and another that takes in a int coverts value to a String and then sets it.

@ConfigurationProperties("app")
public class ApplicationSettings {
    private String property;

    public void setProperty(int property) {
        this.property = String.valueOf(property);
    }

    public void setProperty(String property) {
        this.property = property;
    }
}

and the properties files has a String value

app.property=string

At startup, the Binder sometimes uses the setter with the int param and fails with an error as follows:

***************************
APPLICATION FAILED TO START
***************************

Description:

Failed to bind properties under 'spring.cloud.stream.kafka.binder.required-acks' to int:

    Property: spring.cloud.stream.kafka.binder.requiredacks
    Value: all
    Origin: class path resource [application.properties]:1:47
    Reason: failed to convert java.lang.String to int

Action:

Update your application's configuration

Turning on debug has the following stacktrace:

2019-03-12 02:49:07.915 DEBUG 30020 --- [           main] o.s.b.d.LoggingFailureAnalysisReporter   : Application failed to start due to an exception

org.springframework.boot.context.properties.bind.BindException: Failed to bind properties under 'app.property' to int
	at org.springframework.boot.context.properties.bind.Binder.handleBindError(Binder.java:249) ~[spring-boot-2.1.3.RELEASE.jar:2.1.3.RELEASE]
	at org.springframework.boot.context.properties.bind.Binder.bind(Binder.java:225) ~[spring-boot-2.1.3.RELEASE.jar:2.1.3.RELEASE]
	at org.springframework.boot.context.properties.bind.Binder.lambda$bindBean$3(Binder.java:336) ~[spring-boot-2.1.3.RELEASE.jar:2.1.3.RELEASE]
	at org.springframework.boot.context.properties.bind.JavaBeanBinder.bind(JavaBeanBinder.java:83) ~[spring-boot-2.1.3.RELEASE.jar:2.1.3.RELEASE]
	at org.springframework.boot.context.properties.bind.JavaBeanBinder.bind(JavaBeanBinder.java:72) ~[spring-boot-2.1.3.RELEASE.jar:2.1.3.RELEASE]
	at org.springframework.boot.context.properties.bind.JavaBeanBinder.bind(JavaBeanBinder.java:54) ~[spring-boot-2.1.3.RELEASE.jar:2.1.3.RELEASE]
	at org.springframework.boot.context.properties.bind.Binder.lambda$null$4(Binder.java:344) ~[spring-boot-2.1.3.RELEASE.jar:2.1.3.RELEASE]
	at java.util.stream.ReferencePipeline$3$1.accept(ReferencePipeline.java:193) ~[na:1.8.0_191]
	at java.util.ArrayList$ArrayListSpliterator.tryAdvance(ArrayList.java:1359) ~[na:1.8.0_191]
	at java.util.stream.ReferencePipeline.forEachWithCancel(ReferencePipeline.java:126) ~[na:1.8.0_191]
	at java.util.stream.AbstractPipeline.copyIntoWithCancel(AbstractPipeline.java:498) ~[na:1.8.0_191]
	at java.util.stream.AbstractPipeline.copyInto(AbstractPipeline.java:485) ~[na:1.8.0_191]
	at java.util.stream.AbstractPipeline.wrapAndCopyInto(AbstractPipeline.java:471) ~[na:1.8.0_191]
	at java.util.stream.FindOps$FindOp.evaluateSequential(FindOps.java:152) ~[na:1.8.0_191]
	at java.util.stream.AbstractPipeline.evaluate(AbstractPipeline.java:234) ~[na:1.8.0_191]
	at java.util.stream.ReferencePipeline.findFirst(ReferencePipeline.java:464) ~[na:1.8.0_191]
	at org.springframework.boot.context.properties.bind.Binder.lambda$bindBean$5(Binder.java:345) ~[spring-boot-2.1.3.RELEASE.jar:2.1.3.RELEASE]
	at org.springframework.boot.context.properties.bind.Binder$Context.withIncreasedDepth(Binder.java:448) ~[spring-boot-2.1.3.RELEASE.jar:2.1.3.RELEASE]
	at org.springframework.boot.context.properties.bind.Binder$Context.withBean(Binder.java:434) ~[spring-boot-2.1.3.RELEASE.jar:2.1.3.RELEASE]
	at org.springframework.boot.context.properties.bind.Binder$Context.access$400(Binder.java:388) ~[spring-boot-2.1.3.RELEASE.jar:2.1.3.RELEASE]
	at org.springframework.boot.context.properties.bind.Binder.bindBean(Binder.java:342) ~[spring-boot-2.1.3.RELEASE.jar:2.1.3.RELEASE]
	at org.springframework.boot.context.properties.bind.Binder.bindObject(Binder.java:277) ~[spring-boot-2.1.3.RELEASE.jar:2.1.3.RELEASE]
	at org.springframework.boot.context.properties.bind.Binder.bind(Binder.java:220) ~[spring-boot-2.1.3.RELEASE.jar:2.1.3.RELEASE]
	at org.springframework.boot.context.properties.bind.Binder.bind(Binder.java:208) ~[spring-boot-2.1.3.RELEASE.jar:2.1.3.RELEASE]
	at org.springframework.boot.context.properties.bind.Binder.bind(Binder.java:190) ~[spring-boot-2.1.3.RELEASE.jar:2.1.3.RELEASE]
	at org.springframework.boot.context.properties.ConfigurationPropertiesBinder.bind(ConfigurationPropertiesBinder.java:83) ~[spring-boot-2.1.3.RELEASE.jar:2.1.3.RELEASE]
	at org.springframework.boot.context.properties.ConfigurationPropertiesBindingPostProcessor.bind(ConfigurationPropertiesBindingPostProcessor.java:107) ~[spring-boot-2.1.3.RELEASE.jar:2.1.3.RELEASE]
	at org.springframework.boot.context.properties.ConfigurationPropertiesBindingPostProcessor.postProcessBeforeInitialization(ConfigurationPropertiesBindingPostProcessor.java:93) ~[spring-boot-2.1.3.RELEASE.jar:2.1.3.RELEASE]
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.applyBeanPostProcessorsBeforeInitialization(AbstractAutowireCapableBeanFactory.java:414) ~[spring-beans-5.1.5.RELEASE.jar:5.1.5.RELEASE]
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1754) ~[spring-beans-5.1.5.RELEASE.jar:5.1.5.RELEASE]
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:593) ~[spring-beans-5.1.5.RELEASE.jar:5.1.5.RELEASE]
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:515) ~[spring-beans-5.1.5.RELEASE.jar:5.1.5.RELEASE]
	at org.springframework.beans.factory.support.AbstractBeanFactory.lambda$doGetBean$0(AbstractBeanFactory.java:320) ~[spring-beans-5.1.5.RELEASE.jar:5.1.5.RELEASE]
	at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:222) ~[spring-beans-5.1.5.RELEASE.jar:5.1.5.RELEASE]
	at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:318) ~[spring-beans-5.1.5.RELEASE.jar:5.1.5.RELEASE]
	at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:199) ~[spring-beans-5.1.5.RELEASE.jar:5.1.5.RELEASE]
	at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:849) ~[spring-beans-5.1.5.RELEASE.jar:5.1.5.RELEASE]
	at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:877) ~[spring-context-5.1.5.RELEASE.jar:5.1.5.RELEASE]
	at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:549) ~[spring-context-5.1.5.RELEASE.jar:5.1.5.RELEASE]
	at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:775) [spring-boot-2.1.3.RELEASE.jar:2.1.3.RELEASE]
	at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:397) [spring-boot-2.1.3.RELEASE.jar:2.1.3.RELEASE]
	at org.springframework.boot.SpringApplication.run(SpringApplication.java:316) [spring-boot-2.1.3.RELEASE.jar:2.1.3.RELEASE]
	at org.springframework.boot.SpringApplication.run(SpringApplication.java:1260) [spring-boot-2.1.3.RELEASE.jar:2.1.3.RELEASE]
	at org.springframework.boot.SpringApplication.run(SpringApplication.java:1248) [spring-boot-2.1.3.RELEASE.jar:2.1.3.RELEASE]
	at com.walliee.springcorebindstringtointissue.SpringCoreBindStringToIntIssueApplication.main(SpringCoreBindStringToIntIssueApplication.java:12) [classes/:na]
Caused by: org.springframework.core.convert.ConversionFailedException: Failed to convert from type [java.lang.String] to type [int] for value 'string'; nested exception is java.lang.NumberFormatException: For input string: "string"
	at org.springframework.core.convert.support.ConversionUtils.invokeConverter(ConversionUtils.java:46) ~[spring-core-5.1.5.RELEASE.jar:5.1.5.RELEASE]
	at org.springframework.core.convert.support.GenericConversionService.convert(GenericConversionService.java:191) ~[spring-core-5.1.5.RELEASE.jar:5.1.5.RELEASE]
	at org.springframework.boot.context.properties.bind.BindConverter$CompositeConversionService.convert(BindConverter.java:177) ~[spring-boot-2.1.3.RELEASE.jar:2.1.3.RELEASE]
	at org.springframework.boot.context.properties.bind.BindConverter.convert(BindConverter.java:98) ~[spring-boot-2.1.3.RELEASE.jar:2.1.3.RELEASE]
	at org.springframework.boot.context.properties.bind.BindConverter.convert(BindConverter.java:90) ~[spring-boot-2.1.3.RELEASE.jar:2.1.3.RELEASE]
	at org.springframework.boot.context.properties.bind.Binder.bindProperty(Binder.java:326) ~[spring-boot-2.1.3.RELEASE.jar:2.1.3.RELEASE]
	at org.springframework.boot.context.properties.bind.Binder.bindObject(Binder.java:265) ~[spring-boot-2.1.3.RELEASE.jar:2.1.3.RELEASE]
	at org.springframework.boot.context.properties.bind.Binder.bind(Binder.java:220) ~[spring-boot-2.1.3.RELEASE.jar:2.1.3.RELEASE]
	... 43 common frames omitted
Caused by: java.lang.NumberFormatException: For input string: "string"
	at java.lang.NumberFormatException.forInputString(NumberFormatException.java:65) ~[na:1.8.0_191]
	at java.lang.Integer.parseInt(Integer.java:580) ~[na:1.8.0_191]
	at java.lang.Integer.valueOf(Integer.java:766) ~[na:1.8.0_191]
	at org.springframework.util.NumberUtils.parseNumber(NumberUtils.java:211) ~[spring-core-5.1.5.RELEASE.jar:5.1.5.RELEASE]
	at org.springframework.core.convert.support.StringToNumberConverterFactory$StringToNumber.convert(StringToNumberConverterFactory.java:62) ~[spring-core-5.1.5.RELEASE.jar:5.1.5.RELEASE]
	at org.springframework.core.convert.support.StringToNumberConverterFactory$StringToNumber.convert(StringToNumberConverterFactory.java:49) ~[spring-core-5.1.5.RELEASE.jar:5.1.5.RELEASE]
	at org.springframework.core.convert.support.GenericConversionService$ConverterFactoryAdapter.convert(GenericConversionService.java:436) ~[spring-core-5.1.5.RELEASE.jar:5.1.5.RELEASE]
	at org.springframework.core.convert.support.ConversionUtils.invokeConverter(ConversionUtils.java:40) ~[spring-core-5.1.5.RELEASE.jar:5.1.5.RELEASE]
	... 50 common frames omitted

I created a sample that can help reproduce this issue.
The issue happens intermittently, but re-running the application a few times should produce the error.

Spring Boot Version: 2.1.3.RELEASE

[wilkinsona]

@Walliee Thanks for the sample. Unfortunately, I can't reproduce the exact behaviour that you have described. The binder consistently selects the setProperty(int) method for me and fails consistently as a result. I've tried both running the app repeatedly and recompiling and running the app repeatedly. What JVM are you using and exactly how are you running the example?

[wilkinsona]

Regardless of not being able to reproduce the exact behaviour, I still think there's room for some improvement in the binder here. Looking in the debugger there's a JavaBeanBinder$BeanProperty instance with a String field but a setter that takes an int. Given that there's a setter that matches the field's type, it feels reasonable for it to be preferred.

[Walliee]

So OpenJDK jdk8u172-b11 is one of the JVMs I have seen this on. Also, it happens for me while running the app in IDE (Intellij 2018.2) and also while running the Spring Boot executable jar.

It's interesting that it consistently fails for you. The behavior I saw was that it would pick the String overloaded setter most of the time and int overloaded only one once in a while.

[wilkinsona]

I have a possible fix here. The implementation relies on the getters and setters being considered before the fields, so, rather than trying to invert that ordering, matching against the field is done lazily.

@mbhave or @philwebb could you please take a look and see if I've missed a more straightforward solution?

[mbhave]

This is the only way I can think of other than inverting the evaluation of fields and methods. If we did that, we might be able to create a BeanProperty with the field and methods and save having to call determineSetter and determineGetter in multiple places.