Allow binding when 'is' method also exists

Improve the `JavaBeanBinder` so that an bean that has both a `get` and
`is` method can still be bound.

Closes gh-23007

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2019 the original author or authors.
+ * Copyright 2012-2020 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.
@@ -140,9 +140,11 @@ class JavaBeanBinder implements DataObjectBinder {
 				}
 			}
 			for (Method method : declaredMethods) {
-				addMethodIfPossible(method, "get", 0, BeanProperty::addGetter);
 				addMethodIfPossible(method, "is", 0, BeanProperty::addGetter);
 			}
+			for (Method method : declaredMethods) {
+				addMethodIfPossible(method, "get", 0, BeanProperty::addGetter);
+			}
 			for (Method method : declaredMethods) {
 				addMethodIfPossible(method, "set", 1, BeanProperty::addSetter);
 			}
@@ -280,11 +282,15 @@ class JavaBeanBinder implements DataObjectBinder {
 		}
 
 		void addGetter(Method getter) {
-			if (this.getter == null) {
+			if (this.getter == null || isBetterGetter(getter)) {
 				this.getter = getter;
 			}
 		}
 
+		private boolean isBetterGetter(Method getter) {
+			return this.getter != null && this.getter.getName().startsWith("is");
+		}
+
 		void addSetter(Method setter) {
 			if (this.setter == null || isBetterSetter(setter)) {
 				this.setter = setter;

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2019 the original author or authors.
+ * Copyright 2012-2020 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.
@@ -540,6 +540,24 @@ class JavaBeanBinderTests {
 		assertThat(bean.getProperty()).isEqualTo("test");
 	}
 
+	@Test // gh-23007
+	void bindWhenBeanWithGetSetIsMethodsFoundUsesGetterThatMatchesSetter() {
+		MockConfigurationPropertySource source = new MockConfigurationPropertySource();
+		source.put("test.names", "spring,boot");
+		this.sources.add(source);
+		JavaBeanWithGetSetIs bean = this.binder.bind("test", Bindable.of(JavaBeanWithGetSetIs.class)).get();
+		assertThat(bean.getNames()).containsExactly("spring", "boot");
+	}
+
+	@Test // gh-23007
+	void bindWhenBeanWithGetIsMethodsFoundDoesNotUseIsGetter() {
+		MockConfigurationPropertySource source = new MockConfigurationPropertySource();
+		source.put("test.names", "spring,boot");
+		this.sources.add(source);
+		JavaBeanWithGetIs bean = this.binder.bind("test", Bindable.of(JavaBeanWithGetIs.class)).get();
+		assertThat(bean.getNames()).containsExactly("spring", "boot");
+	}
+
 	static class ExampleValueBean {
 
 		private int intValue;
@@ -1036,4 +1054,36 @@ class JavaBeanBinderTests {
 
 	}
 
+	static class JavaBeanWithGetSetIs {
+
+		private List<String> names = new ArrayList<>();
+
+		List<String> getNames() {
+			return this.names;
+		}
+
+		void setNames(List<String> names) {
+			this.names = names;
+		}
+
+		boolean isNames() {
+			return !this.names.isEmpty();
+		}
+
+	}
+
+	static class JavaBeanWithGetIs {
+
+		private List<String> names = new ArrayList<>();
+
+		boolean isNames() {
+			return !this.names.isEmpty();
+		}
+
+		List<String> getNames() {
+			return this.names;
+		}
+
+	}
+
 }