Prevent ValueBinder from being incorrectly used

Fix a regression caused by e41c5a4 which incorrectly allowed the
`ValueObjectBinder` to be picked when the `JavaBeanBinder` should
have been used.

Closes gh-18485

Author: philwebb

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

@@ -203,13 +203,12 @@ static <T> ValueObject<T> get(Class<T> type, Predicate<Constructor<?>> construct
 					constructor = candidate;
 				}
 			}
-			return (constructor != null) ? new DefaultValueObject<>((Constructor<T>) constructor) : null;
+			return get((Constructor<T>) constructor);
 		}
 
 		private static boolean isCandidateConstructor(Constructor<?> candidate, Predicate<Constructor<?>> filter) {
 			int modifiers = candidate.getModifiers();
-			return !Modifier.isPrivate(modifiers) && !Modifier.isProtected(modifiers)
-					&& candidate.getParameterCount() > 0 && filter.test(candidate);
+			return !Modifier.isPrivate(modifiers) && !Modifier.isProtected(modifiers) && filter.test(candidate);
 		}
 
 		static <T> DefaultValueObject<T> get(Constructor<T> constructor) {

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

@@ -807,6 +807,35 @@ void loadWhenBindingToNestedConstructorPropertiesShouldBind() {
 		assertThat(bean.getNested().getAge()).isEqualTo(5);
 	}
 
+	@Test // gh-18485
+	void loadWhenBindingToMultiConstructorConfigurationProperties() {
+		MutablePropertySources sources = this.context.getEnvironment().getPropertySources();
+		Map<String, Object> source = new HashMap<>();
+		source.put("test.nested[0].name", "spring");
+		source.put("test.nested[0].age", "5");
+		sources.addLast(new MapPropertySource("test", source));
+		load(MultiConstructorConfigurationPropertiesConfiguration.class);
+		MultiConstructorConfigurationListProperties bean = this.context
+				.getBean(MultiConstructorConfigurationListProperties.class);
+		MultiConstructorConfigurationProperties nested = bean.getNested().get(0);
+		assertThat(nested.getName()).isEqualTo("spring");
+		assertThat(nested.getAge()).isEqualTo(5);
+	}
+
+	@Test // gh-18485
+	void loadWhenBindingToMultiConstructorConfigurationPropertiesUsingShortcutSyntax() {
+		MutablePropertySources sources = this.context.getEnvironment().getPropertySources();
+		Map<String, Object> source = new HashMap<>();
+		source.put("test.nested[0]", "spring");
+		sources.addLast(new MapPropertySource("test", source));
+		load(MultiConstructorConfigurationPropertiesConfiguration.class);
+		MultiConstructorConfigurationListProperties bean = this.context
+				.getBean(MultiConstructorConfigurationListProperties.class);
+		MultiConstructorConfigurationProperties nested = bean.getNested().get(0);
+		assertThat(nested.getName()).isEqualTo("spring");
+		assertThat(nested.getAge()).isEqualTo(0);
+	}
+
 	private AnnotationConfigApplicationContext load(Class<?> configuration, String... inlinedProperties) {
 		return load(new Class<?>[] { configuration }, inlinedProperties);
 	}
@@ -1968,4 +1997,21 @@ int getAge() {
 
 	}
 
+	@ConfigurationProperties("test")
+	static class MultiConstructorConfigurationListProperties {
+
+		private List<MultiConstructorConfigurationProperties> nested = new ArrayList<>();
+
+		List<MultiConstructorConfigurationProperties> getNested() {
+			return this.nested;
+		}
+
+	}
+
+	@Configuration(proxyBeanMethods = false)
+	@EnableConfigurationProperties(MultiConstructorConfigurationListProperties.class)
+	static class MultiConstructorConfigurationPropertiesConfiguration {
+
+	}
+
 }

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

@@ -0,0 +1,54 @@
+/*
+ * Copyright 2012-2019 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.boot.context.properties;
+
+/**
+ * Class used to test multi-constructor binding. Must be public and have public
+ * constructors.
+ *
+ * @author Phillip Webb
+ */
+public class MultiConstructorConfigurationProperties {
+
+	private String name;
+
+	private int age;
+
+	public MultiConstructorConfigurationProperties() {
+	}
+
+	public MultiConstructorConfigurationProperties(String name) {
+		this.name = name;
+	}
+
+	public String getName() {
+		return this.name;
+	}
+
+	public void setName(String name) {
+		this.name = name;
+	}
+
+	public int getAge() {
+		return this.age;
+	}
+
+	public void setAge(int age) {
+		this.age = age;
+	}
+
+}