Allow binding to package private methods

Closes gh-17394

spring-boot-project/spring-boot/src/main/java/org/springframework/boot/context/properties/bind/JavaBeanBinder.java

@@ -149,9 +149,9 @@ class JavaBeanBinder implements DataObjectBinder {
 
 		private boolean isCandidate(Method method) {
 			int modifiers = method.getModifiers();
-			return Modifier.isPublic(modifiers) && !Modifier.isAbstract(modifiers) && !Modifier.isStatic(modifiers)
-					&& !Object.class.equals(method.getDeclaringClass())
-					&& !Class.class.equals(method.getDeclaringClass());
+			return !Modifier.isPrivate(modifiers) && !Modifier.isProtected(modifiers) && !Modifier.isAbstract(modifiers)
+					&& !Modifier.isStatic(modifiers) && !Object.class.equals(method.getDeclaringClass())
+					&& !Class.class.equals(method.getDeclaringClass()) && method.getName().indexOf('$') == -1;
 		}
 
 		private void addMethodIfPossible(Method method, String prefix, int parameterCount,

spring-boot-project/spring-boot/src/main/java/org/springframework/boot/context/properties/bind/ValueObjectBinder.java

@@ -192,8 +192,17 @@ class ValueObjectBinder implements DataObjectBinder {
 
 		@SuppressWarnings("unchecked")
 		static <T> ValueObject<T> get(Class<T> type) {
-			Constructor<?>[] constructors = type.getDeclaredConstructors();
-			return (constructors.length != 1) ? null : get((Constructor<T>) constructors[0]);
+			Constructor<?> constructor = null;
+			for (Constructor<?> candidate : type.getDeclaredConstructors()) {
+				int modifiers = candidate.getModifiers();
+				if (!Modifier.isPrivate(modifiers) && !Modifier.isProtected(modifiers)) {
+					if (constructor != null) {
+						return null;
+					}
+					constructor = candidate;
+				}
+			}
+			return get((Constructor<T>) constructor);
 		}
 
 		static <T> DefaultValueObject<T> get(Constructor<T> constructor) {

spring-boot-project/spring-boot/src/test/java/org/springframework/boot/context/properties/bind/JavaBeanBinderTests.java

@@ -529,6 +529,15 @@ class JavaBeanBinderTests {
 		assertThat(result.getNested().getBar()).isEqualTo(456);
 	}
 
+	@Test
+	void bindWhenHasPackagePrivateSetterShouldBind() {
+		MockConfigurationPropertySource source = new MockConfigurationPropertySource();
+		source.put("foo.property", "test");
+		this.sources.add(source);
+		PackagePrivateSetterBean bean = this.binder.bind("foo", Bindable.of(PackagePrivateSetterBean.class)).get();
+		assertThat(bean.getProperty()).isEqualTo("test");
+	}
+
 	public static class ExampleValueBean {
 
 		private int intValue;
@@ -1011,4 +1020,18 @@ class JavaBeanBinderTests {
 
 	}
 
+	public static class PackagePrivateSetterBean {
+
+		private String property;
+
+		public String getProperty() {
+			return this.property;
+		}
+
+		void setProperty(String property) {
+			this.property = property;
+		}
+
+	}
+
 }

spring-boot-project/spring-boot/src/test/java/org/springframework/boot/context/properties/bind/ValueObjectBinderTests.java

@@ -166,6 +166,16 @@ class ValueObjectBinderTests {
 		assertThat(bean.getDate().toString()).isEqualTo("2019-05-10");
 	}
 
+	@Test
+	void bindToClassWhenHasPackagePrivateConstructorShouldBind() {
+		MockConfigurationPropertySource source = new MockConfigurationPropertySource();
+		source.put("foo.property", "test");
+		this.sources.add(source);
+		ExamplePackagePrivateConstructorBean bound = this.binder
+				.bind("foo", Bindable.of(ExamplePackagePrivateConstructorBean.class)).get();
+		assertThat(bound.getProperty()).isEqualTo("test");
+	}
+
 	@Test
 	void createShouldReturnCreatedValue() {
 		ExampleValueBean value = this.binder.bindOrCreate("foo", Bindable.of(ExampleValueBean.class));
@@ -370,4 +380,18 @@ class ValueObjectBinderTests {
 
 	}
 
+	public static class ExamplePackagePrivateConstructorBean {
+
+		private final String property;
+
+		ExamplePackagePrivateConstructorBean(String property) {
+			this.property = property;
+		}
+
+		public String getProperty() {
+			return this.property;
+		}
+
+	}
+
 }