Improve @ConfigurationProperty binding exception

Include more details in the message including the class being bound
and the prefix from the annotation.

Fixes gh-2246

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

@@ -296,10 +296,30 @@ public class ConfigurationPropertiesBindingPostProcessor implements BeanPostProc
 			factory.bindPropertiesToTarget();
 		}
 		catch (Exception ex) {
-			throw new BeanCreationException(beanName, "Could not bind properties", ex);
+			String targetClass = "[unknown]";
+			if (target != null) {
+				ClassUtils.getShortName(target.getClass());
+			}
+			throw new BeanCreationException(beanName, "Could not bind properties to "
+					+ targetClass + " (" + getAnnotationDetails(annotation) + ")", ex);
 		}
 	}
 
+	private String getAnnotationDetails(ConfigurationProperties annotation) {
+		if (annotation == null) {
+			return "";
+		}
+		StringBuilder details = new StringBuilder();
+		details.append("target=").append(
+				(StringUtils.hasLength(annotation.value()) ? annotation.value()
+						: annotation.prefix()));
+		details.append(", ignoreInvalidFields=").append(annotation.ignoreInvalidFields());
+		details.append(", ignoreUnknownFields=").append(annotation.ignoreUnknownFields());
+		details.append(", ignoreNestedProperties=").append(
+				annotation.ignoreNestedProperties());
+		return details.toString();
+	}
+
 	private Validator determineValidator(Object bean) {
 		if (ClassUtils.isAssignable(Validator.class, bean.getClass())) {
 			if (this.validator == null) {

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

@@ -20,7 +20,9 @@ import javax.annotation.PostConstruct;
 import javax.validation.constraints.NotNull;
 
 import org.junit.After;
+import org.junit.Rule;
 import org.junit.Test;
+import org.junit.rules.ExpectedException;
 import org.springframework.beans.BeansException;
 import org.springframework.beans.factory.BeanCreationException;
 import org.springframework.beans.factory.FactoryBean;
@@ -55,6 +57,9 @@ import static org.junit.Assert.fail;
  */
 public class ConfigurationPropertiesBindingPostProcessorTests {
 
+	@Rule
+	public ExpectedException thrown = ExpectedException.none();
+
 	private AnnotationConfigApplicationContext context;
 
 	@After
@@ -198,6 +203,16 @@ public class ConfigurationPropertiesBindingPostProcessorTests {
 				equalTo("word".toCharArray()));
 	}
 
+	@Test
+	public void notWritablePropertyException() throws Exception {
+		this.context = new AnnotationConfigApplicationContext();
+		EnvironmentTestUtils.addEnvironment(this.context, "test.madeup:word");
+		this.context.register(PropertyWithCharArray.class);
+		this.thrown.expect(BeanCreationException.class);
+		this.thrown.expectMessage("test");
+		this.context.refresh();
+	}
+
 	@Configuration
 	@EnableConfigurationProperties
 	public static class TestConfigurationWithValidatingSetter {
@@ -314,7 +329,7 @@ public class ConfigurationPropertiesBindingPostProcessorTests {
 
 	@Configuration
 	@EnableConfigurationProperties
-	@ConfigurationProperties(prefix = "test")
+	@ConfigurationProperties(prefix = "test", ignoreUnknownFields = false)
 	public static class PropertyWithCharArray {
 
 		private char[] chars;