Binder @DefaultValue does not work with PropertyEditor converters

[jannis-baratheon]

Version information

Spring-boot version: 2.2.6.RELEASE

Issue reproduction and actual result

I have some simple constructor-bound ConfigurationProperties:

package com.example.demo;

import java.nio.file.Path;
import org.springframework.boot.context.properties.ConfigurationProperties;
import org.springframework.boot.context.properties.ConstructorBinding;
import org.springframework.boot.context.properties.bind.DefaultValue;

@ConfigurationProperties
@ConstructorBinding
public class ConfigurationPropertiesWithPathProperty {
	public static final String DEFAULT_VALUE = "default_value";

	private final Path somePathProperty;

	public ConfigurationPropertiesWithPathProperty(@DefaultValue(DEFAULT_VALUE) Path somePathProperty) {
		this.somePathProperty = somePathProperty;
	}

	public Path getSomePathProperty() {
		return somePathProperty;
	}
}

I test the class using a Binder:

package com.example.demo;

import static org.assertj.core.api.Assertions.assertThat;

import java.nio.file.Paths;
import java.util.HashMap;
import java.util.Map;
import org.junit.jupiter.api.Test;
import org.springframework.boot.context.properties.bind.BindResult;
import org.springframework.boot.context.properties.bind.Bindable;
import org.springframework.boot.context.properties.bind.Binder;
import org.springframework.boot.context.properties.source.MapConfigurationPropertySource;

public class PropertiesTest {

	@Test
	void bindsPathProperty() {
		String expectedPathValue = "some_value";
		Map<String, String> properties = new HashMap<>();
		properties.put("some_path_property", expectedPathValue);
		Binder binder = new Binder(new MapConfigurationPropertySource(properties));

		BindResult<ConfigurationPropertiesWithPathProperty> bindResult =
				binder.bind("", Bindable.of(ConfigurationPropertiesWithPathProperty.class));

		assertThat(bindResult.get().getSomePathProperty())
				.isEqualTo(Paths.get(expectedPathValue));
	}
}

So far so good - the test is green. Now when I try to bind the default value:

package com.example.demo;

import static org.assertj.core.api.Assertions.assertThat;

import java.nio.file.Paths;
import java.util.Collections;
import java.util.HashMap;
import java.util.Map;
import org.junit.jupiter.api.Test;
import org.springframework.boot.context.properties.bind.BindResult;
import org.springframework.boot.context.properties.bind.Bindable;
import org.springframework.boot.context.properties.bind.Binder;
import org.springframework.boot.context.properties.source.MapConfigurationPropertySource;

public class PropertiesTest {

	@Test
	void bindsDefaultValueToPathProperty() {
		Binder binder = new Binder(new MapConfigurationPropertySource(Collections.emptyMap()));

		BindResult<ConfigurationPropertiesWithPathProperty> bindResult =
				binder.bind("", Bindable.of(ConfigurationPropertiesWithPathProperty.class));

		assertThat(bindResult.get().getSomePathProperty())
				.isEqualTo(Paths.get(ConfigurationPropertiesWithPathProperty.DEFAULT_VALUE));
	}
}

I get an exception:

Failed to bind properties under '' to com.example.demo.ConfigurationPropertiesWithPathProperty
org.springframework.boot.context.properties.bind.BindException: Failed to bind properties under '' to com.example.demo.ConfigurationPropertiesWithPathProperty
	at org.springframework.boot.context.properties.bind.Binder.handleBindError(Binder.java:364)
	at org.springframework.boot.context.properties.bind.Binder.bind(Binder.java:324)
	at org.springframework.boot.context.properties.bind.Binder.bind(Binder.java:308)
	at org.springframework.boot.context.properties.bind.Binder.bind(Binder.java:238)
	at org.springframework.boot.context.properties.bind.Binder.bind(Binder.java:199)
	at com.example.demo.PropertiesTest.bindsDefaultValueToPathProperty(PropertiesTest.java:36)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:498)
	at org.junit.platform.commons.util.ReflectionUtils.invokeMethod(ReflectionUtils.java:675)
	at org.junit.jupiter.engine.execution.MethodInvocation.proceed(MethodInvocation.java:60)
	at org.junit.jupiter.engine.execution.InvocationInterceptorChain$ValidatingInvocation.proceed(InvocationInterceptorChain.java:125)
	at org.junit.jupiter.engine.extension.TimeoutExtension.intercept(TimeoutExtension.java:132)
	at org.junit.jupiter.engine.extension.TimeoutExtension.interceptTestableMethod(TimeoutExtension.java:124)
	at org.junit.jupiter.engine.extension.TimeoutExtension.interceptTestMethod(TimeoutExtension.java:74)
	at org.junit.jupiter.engine.execution.ExecutableInvoker$ReflectiveInterceptorCall.lambda$ofVoidMethod$0(ExecutableInvoker.java:115)
	at org.junit.jupiter.engine.execution.ExecutableInvoker.lambda$invoke$0(ExecutableInvoker.java:105)
	at org.junit.jupiter.engine.execution.InvocationInterceptorChain$InterceptedInvocation.proceed(InvocationInterceptorChain.java:104)
	at org.junit.jupiter.engine.execution.InvocationInterceptorChain.proceed(InvocationInterceptorChain.java:62)
	at org.junit.jupiter.engine.execution.InvocationInterceptorChain.chainAndInvoke(InvocationInterceptorChain.java:43)
	at org.junit.jupiter.engine.execution.InvocationInterceptorChain.invoke(InvocationInterceptorChain.java:35)
	at org.junit.jupiter.engine.execution.ExecutableInvoker.invoke(ExecutableInvoker.java:104)
	at org.junit.jupiter.engine.execution.ExecutableInvoker.invoke(ExecutableInvoker.java:98)
	at org.junit.jupiter.engine.descriptor.TestMethodTestDescriptor.lambda$invokeTestMethod$6(TestMethodTestDescriptor.java:202)
	at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
	at org.junit.jupiter.engine.descriptor.TestMethodTestDescriptor.invokeTestMethod(TestMethodTestDescriptor.java:198)
	at org.junit.jupiter.engine.descriptor.TestMethodTestDescriptor.execute(TestMethodTestDescriptor.java:135)
	at org.junit.jupiter.engine.descriptor.TestMethodTestDescriptor.execute(TestMethodTestDescriptor.java:69)
	at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$5(NodeTestTask.java:135)
	at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
	at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$7(NodeTestTask.java:125)
	at org.junit.platform.engine.support.hierarchical.Node.around(Node.java:135)
	at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$8(NodeTestTask.java:123)
	at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
	at org.junit.platform.engine.support.hierarchical.NodeTestTask.executeRecursively(NodeTestTask.java:122)
	at org.junit.platform.engine.support.hierarchical.NodeTestTask.execute(NodeTestTask.java:80)
	at java.util.ArrayList.forEach(ArrayList.java:1257)
	at org.junit.platform.engine.support.hierarchical.SameThreadHierarchicalTestExecutorService.invokeAll(SameThreadHierarchicalTestExecutorService.java:38)
	at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$5(NodeTestTask.java:139)
	at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
	at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$7(NodeTestTask.java:125)
	at org.junit.platform.engine.support.hierarchical.Node.around(Node.java:135)
	at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$8(NodeTestTask.java:123)
	at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
	at org.junit.platform.engine.support.hierarchical.NodeTestTask.executeRecursively(NodeTestTask.java:122)
	at org.junit.platform.engine.support.hierarchical.NodeTestTask.execute(NodeTestTask.java:80)
	at java.util.ArrayList.forEach(ArrayList.java:1257)
	at org.junit.platform.engine.support.hierarchical.SameThreadHierarchicalTestExecutorService.invokeAll(SameThreadHierarchicalTestExecutorService.java:38)
	at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$5(NodeTestTask.java:139)
	at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
	at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$7(NodeTestTask.java:125)
	at org.junit.platform.engine.support.hierarchical.Node.around(Node.java:135)
	at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$8(NodeTestTask.java:123)
	at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
	at org.junit.platform.engine.support.hierarchical.NodeTestTask.executeRecursively(NodeTestTask.java:122)
	at org.junit.platform.engine.support.hierarchical.NodeTestTask.execute(NodeTestTask.java:80)
	at org.junit.platform.engine.support.hierarchical.SameThreadHierarchicalTestExecutorService.submit(SameThreadHierarchicalTestExecutorService.java:32)
	at org.junit.platform.engine.support.hierarchical.HierarchicalTestExecutor.execute(HierarchicalTestExecutor.java:57)
	at org.junit.platform.engine.support.hierarchical.HierarchicalTestEngine.execute(HierarchicalTestEngine.java:51)
	at org.junit.platform.launcher.core.DefaultLauncher.execute(DefaultLauncher.java:220)
	at org.junit.platform.launcher.core.DefaultLauncher.lambda$execute$6(DefaultLauncher.java:188)
	at org.junit.platform.launcher.core.DefaultLauncher.withInterceptedStreams(DefaultLauncher.java:202)
	at org.junit.platform.launcher.core.DefaultLauncher.execute(DefaultLauncher.java:181)
	at org.junit.platform.launcher.core.DefaultLauncher.execute(DefaultLauncher.java:128)
	at org.gradle.api.internal.tasks.testing.junitplatform.JUnitPlatformTestClassProcessor$CollectAllTestClassesExecutor.processAllTestClasses(JUnitPlatformTestClassProcessor.java:99)
	at org.gradle.api.internal.tasks.testing.junitplatform.JUnitPlatformTestClassProcessor$CollectAllTestClassesExecutor.access$000(JUnitPlatformTestClassProcessor.java:79)
	at org.gradle.api.internal.tasks.testing.junitplatform.JUnitPlatformTestClassProcessor.stop(JUnitPlatformTestClassProcessor.java:75)
	at org.gradle.api.internal.tasks.testing.SuiteTestClassProcessor.stop(SuiteTestClassProcessor.java:61)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:498)
	at org.gradle.internal.dispatch.ReflectionDispatch.dispatch(ReflectionDispatch.java:36)
	at org.gradle.internal.dispatch.ReflectionDispatch.dispatch(ReflectionDispatch.java:24)
	at org.gradle.internal.dispatch.ContextClassLoaderDispatch.dispatch(ContextClassLoaderDispatch.java:33)
	at org.gradle.internal.dispatch.ProxyDispatchAdapter$DispatchingInvocationHandler.invoke(ProxyDispatchAdapter.java:94)
	at com.sun.proxy.$Proxy2.stop(Unknown Source)
	at org.gradle.api.internal.tasks.testing.worker.TestWorker.stop(TestWorker.java:132)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:498)
	at org.gradle.internal.dispatch.ReflectionDispatch.dispatch(ReflectionDispatch.java:36)
	at org.gradle.internal.dispatch.ReflectionDispatch.dispatch(ReflectionDispatch.java:24)
	at org.gradle.internal.remote.internal.hub.MessageHubBackedObjectConnection$DispatchWrapper.dispatch(MessageHubBackedObjectConnection.java:182)
	at org.gradle.internal.remote.internal.hub.MessageHubBackedObjectConnection$DispatchWrapper.dispatch(MessageHubBackedObjectConnection.java:164)
	at org.gradle.internal.remote.internal.hub.MessageHub$Handler.run(MessageHub.java:412)
	at org.gradle.internal.concurrent.ExecutorPolicy$CatchAndRecordFailures.onExecute(ExecutorPolicy.java:64)
	at org.gradle.internal.concurrent.ManagedExecutorImpl$1.run(ManagedExecutorImpl.java:48)
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
	at org.gradle.internal.concurrent.ThreadFactoryImpl$ManagedThreadRunnable.run(ThreadFactoryImpl.java:56)
	at java.lang.Thread.run(Thread.java:748)
Caused by: org.springframework.core.convert.ConverterNotFoundException: No converter found capable of converting from type [java.lang.String[]] to type [@org.springframework.boot.context.properties.bind.DefaultValue java.nio.file.Path]
	at org.springframework.core.convert.support.GenericConversionService.handleConverterNotFound(GenericConversionService.java:321)
	at org.springframework.core.convert.support.GenericConversionService.convert(GenericConversionService.java:194)
	at org.springframework.boot.context.properties.bind.BindConverter$CompositeConversionService.convert(BindConverter.java:170)
	at org.springframework.boot.context.properties.bind.BindConverter.convert(BindConverter.java:96)
	at org.springframework.boot.context.properties.bind.ValueObjectBinder$ConstructorParameter.getDefaultValue(ValueObjectBinder.java:234)
	at org.springframework.boot.context.properties.bind.ValueObjectBinder.bind(ValueObjectBinder.java:68)
	at org.springframework.boot.context.properties.bind.Binder.lambda$bindDataObject$5(Binder.java:452)
	at org.springframework.boot.context.properties.bind.Binder$Context.withIncreasedDepth(Binder.java:572)
	at org.springframework.boot.context.properties.bind.Binder$Context.withDataObject(Binder.java:558)
	at org.springframework.boot.context.properties.bind.Binder$Context.access$400(Binder.java:513)
	at org.springframework.boot.context.properties.bind.Binder.bindDataObject(Binder.java:450)
	at org.springframework.boot.context.properties.bind.Binder.bindObject(Binder.java:391)
	at org.springframework.boot.context.properties.bind.Binder.bind(Binder.java:320)
	... 92 more

Expected result

The default value is bound to the property. Binding a default value should not require additional converters when binding a non-default value doesn't.

[mbhave]

For this, we rely on Spring Framework's PathEditor for converting from String to Path. The PathEditor returns a null value if the source value is "". This might be something that needs to be fixed in Spring Framework. If the rest of the team agrees, this issue will need to be transferred to Spring Framework's issue tracker.

[philwebb]

Please excuse my editing of this issue. I managed to mix it up with #21263 and committed a fix with the wrong reference so I switched the descriptions.