Support rebind on ConfigurationProperties

Update `ConfigurationPropertiesBindingPostProcessor` to once again allow
beans to be bound again following changes to the underlying property
sources.

Fixes gh-9160

spring-boot/src/main/java/org/springframework/boot/context/properties/ConfigurationPropertiesBindingPostProcessor.java

@@ -37,6 +37,7 @@ import org.springframework.boot.context.properties.bind.BindHandler;
 import org.springframework.boot.context.properties.bind.Bindable;
 import org.springframework.boot.context.properties.bind.Binder;
 import org.springframework.boot.context.properties.bind.PropertySourcesPlaceholdersResolver;
+import org.springframework.boot.context.properties.bind.convert.BinderConversionService;
 import org.springframework.boot.context.properties.bind.handler.IgnoreErrorsBindHandler;
 import org.springframework.boot.context.properties.bind.handler.NoUnboundElementsBindHandler;
 import org.springframework.boot.context.properties.bind.validation.ValidationBindHandler;
@@ -60,6 +61,7 @@ import org.springframework.core.convert.converter.GenericConverter;
 import org.springframework.core.convert.support.DefaultConversionService;
 import org.springframework.core.env.ConfigurableEnvironment;
 import org.springframework.core.env.Environment;
+import org.springframework.core.env.MutablePropertySources;
 import org.springframework.core.env.PropertySource;
 import org.springframework.core.env.PropertySources;
 import org.springframework.core.env.StandardEnvironment;
@@ -121,7 +123,7 @@ public class ConfigurationPropertiesBindingPostProcessor implements BeanPostProc
 
 	private Iterable<ConfigurationPropertySource> configurationSources;
 
-	private Binder binder;
+	private BinderConversionService binderConversionService;
 
 	/**
 	 * A list of custom converters (in addition to the defaults) to use when converting
@@ -222,8 +224,14 @@ public class ConfigurationPropertiesBindingPostProcessor implements BeanPostProc
 					ConfigurableApplicationContext.CONVERSION_SERVICE_BEAN_NAME,
 					ConversionService.class);
 		}
-		this.configurationSources = ConfigurationPropertySources
-				.from(this.propertySources);
+		if (this.propertySources instanceof MutablePropertySources) {
+			this.configurationSources = ConfigurationPropertySources
+					.from((MutablePropertySources) this.propertySources);
+		}
+		else {
+			this.configurationSources = ConfigurationPropertySources
+					.from(this.propertySources);
+		}
 	}
 
 	@Override
@@ -317,7 +325,9 @@ public class ConfigurationPropertiesBindingPostProcessor implements BeanPostProc
 
 	private void postProcessBeforeInitialization(Object bean, String beanName,
 			ConfigurationProperties annotation) {
-		Binder binder = getBinder();
+		Binder binder = new Binder(this.configurationSources,
+				new PropertySourcesPlaceholdersResolver(this.propertySources),
+				getBinderConversionService());
 		Validator validator = determineValidator(bean);
 		BindHandler handler = getBindHandler(annotation, validator);
 		Bindable<?> bindable = Bindable.ofInstance(bean);
@@ -331,19 +341,17 @@ public class ConfigurationPropertiesBindingPostProcessor implements BeanPostProc
 		}
 	}
 
-	private Binder getBinder() {
-		Binder binder = this.binder;
-		if (binder == null) {
+	private BinderConversionService getBinderConversionService() {
+		BinderConversionService binderConversionService = this.binderConversionService;
+		if (binderConversionService == null) {
 			ConversionService conversionService = this.conversionService;
 			if (conversionService == null) {
 				conversionService = getDefaultConversionService();
 			}
-			binder = new Binder(this.configurationSources,
-					new PropertySourcesPlaceholdersResolver(this.propertySources),
-					conversionService);
-			this.binder = binder;
+			binderConversionService = new BinderConversionService(conversionService);
+			this.binderConversionService = binderConversionService;
 		}
-		return binder;
+		return binderConversionService;
 	}
 
 	private ConversionService getDefaultConversionService() {

spring-boot/src/main/java/org/springframework/boot/context/properties/source/ConfigurationPropertySources.java

@@ -101,6 +101,22 @@ public final class ConfigurationPropertySources {
 		return Collections.singleton(SpringConfigurationPropertySource.from(source));
 	}
 
+	/**
+	 * Return {@link Iterable} containing new {@link ConfigurationPropertySource}
+	 * instances adapted from the given Spring {@link MutablePropertySources}.
+	 * <p>
+	 * This method will flatten any nested property sources and will filter all
+	 * {@link StubPropertySource stub property sources}. Updates to the underlying source
+	 * will be automatically tracked.
+	 * @param sources the Spring property sources to adapt
+	 * @return an {@link Iterable} containing a single newly adapted
+	 * {@link SpringConfigurationPropertySource} instances
+	 */
+	public static Iterable<ConfigurationPropertySource> from(
+			MutablePropertySources sources) {
+		return new SpringConfigurationPropertySources(sources);
+	}
+
 	/**
 	 * Return {@link Iterable} containing new {@link ConfigurationPropertySource}
 	 * instances adapted from the given Spring {@link PropertySource PropertySources}.

spring-boot/src/test/java/org/springframework/boot/context/properties/ConfigurationPropertiesBindingPostProcessorTests.java

@@ -18,6 +18,7 @@ package org.springframework.boot.context.properties;
 
 import java.util.Collections;
 import java.util.HashMap;
+import java.util.LinkedHashMap;
 import java.util.List;
 import java.util.Map;
 
@@ -42,6 +43,7 @@ import org.springframework.boot.testutil.InternalOutputCapture;
 import org.springframework.context.annotation.AnnotationConfigApplicationContext;
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
+import org.springframework.context.annotation.Scope;
 import org.springframework.context.support.PropertySourcesPlaceholderConfigurer;
 import org.springframework.core.env.ConfigurableEnvironment;
 import org.springframework.core.env.MapPropertySource;
@@ -417,6 +419,27 @@ public class ConfigurationPropertiesBindingPostProcessorTests {
 		assertThat(foo).isEqualTo(10);
 	}
 
+	@Test
+	public void rebindableConfigurationProperties() throws Exception {
+		// gh-9160
+		this.context = new AnnotationConfigApplicationContext();
+		MutablePropertySources sources = this.context.getEnvironment()
+				.getPropertySources();
+		Map<String, Object> source = new LinkedHashMap<String, Object>();
+		source.put("example.one", "foo");
+		sources.addFirst(new MapPropertySource("test-source", source));
+		this.context.register(PrototypePropertiesConfig.class);
+		this.context.refresh();
+		PrototypeBean first = this.context.getBean(PrototypeBean.class);
+		assertThat(first.getOne()).isEqualTo("foo");
+		source.put("example.one", "bar");
+		sources.addFirst(new MapPropertySource("extra",
+				Collections.<String, Object>singletonMap("example.two", "baz")));
+		PrototypeBean second = this.context.getBean(PrototypeBean.class);
+		assertThat(second.getOne()).isEqualTo("bar");
+		assertThat(second.getTwo()).isEqualTo("baz");
+	}
+
 	private void assertBindingFailure(int errorCount) {
 		try {
 			this.context.refresh();
@@ -798,6 +821,43 @@ public class ConfigurationPropertiesBindingPostProcessorTests {
 
 	}
 
+	@Configuration
+	@EnableConfigurationProperties
+	public static class PrototypePropertiesConfig {
+
+		@Bean
+		@Scope("prototype")
+		@ConfigurationProperties("example")
+		public PrototypeBean prototypeBean() {
+			return new PrototypeBean();
+		}
+
+	}
+
+	public static class PrototypeBean {
+
+		private String one;
+
+		private String two;
+
+		public String getOne() {
+			return this.one;
+		}
+
+		public void setOne(String one) {
+			this.one = one;
+		}
+
+		public String getTwo() {
+			return this.two;
+		}
+
+		public void setTwo(String two) {
+			this.two = two;
+		}
+
+	}
+
 	@Configuration
 	@EnableConfigurationProperties
 	public static class ConfigurationPropertiesWithFactoryBean {