Use deterministic ordering of JavaBean methods

Update `JavaBeanBinder` so that methods and fields are sorted before
being processed. This ensures that setters are called in a deterministic
order, rather than the unspecified and variable order that reflection
provides.

Fixes gh-24068

Author: philwebb

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.
@@ -21,9 +21,12 @@
 import java.lang.reflect.Field;
 import java.lang.reflect.Method;
 import java.lang.reflect.Modifier;
+import java.util.Arrays;
+import java.util.Comparator;
 import java.util.LinkedHashMap;
 import java.util.Map;
 import java.util.function.BiConsumer;
+import java.util.function.Function;
 import java.util.function.Supplier;
 
 import org.springframework.beans.BeanUtils;
@@ -124,13 +127,19 @@ static class Bean<T> {
 
 		private void addProperties(Class<?> type) {
 			while (type != null && !Object.class.equals(type)) {
-				Method[] declaredMethods = type.getDeclaredMethods();
-				Field[] declaredFields = type.getDeclaredFields();
+				Method[] declaredMethods = getSorted(type, Class::getDeclaredMethods, Method::getName);
+				Field[] declaredFields = getSorted(type, Class::getDeclaredFields, Field::getName);
 				addProperties(declaredMethods, declaredFields);
 				type = type.getSuperclass();
 			}
 		}
 
+		private <S, E> E[] getSorted(S source, Function<S, E[]> elements, Function<E, String> name) {
+			E[] result = elements.apply(source);
+			Arrays.sort(result, Comparator.comparing(name));
+			return result;
+		}
+
 		protected void addProperties(Method[] declaredMethods, Field[] declaredFields) {
 			for (int i = 0; i < declaredMethods.length; i++) {
 				if (!isCandidate(declaredMethods[i])) {

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.
@@ -26,6 +26,7 @@
 import java.util.List;
 import java.util.Map;
 import java.util.Set;
+import java.util.concurrent.atomic.AtomicInteger;
 
 import org.junit.jupiter.api.Test;
 
@@ -540,6 +541,19 @@ void bindWhenHasPackagePrivateSetterShouldBind() {
 		assertThat(bean.getProperty()).isEqualTo("test");
 	}
 
+	@Test
+	void bindUsesConsistentPropertyOrder() {
+		MockConfigurationPropertySource source = new MockConfigurationPropertySource();
+		source.put("foo.gamma", "0");
+		source.put("foo.alpha", "0");
+		source.put("foo.beta", "0");
+		this.sources.add(source);
+		PropertyOrderBean bean = this.binder.bind("foo", Bindable.of(PropertyOrderBean.class)).get();
+		assertThat(bean.getAlpha()).isEqualTo(0);
+		assertThat(bean.getBeta()).isEqualTo(1);
+		assertThat(bean.getGamma()).isEqualTo(2);
+	}
+
 	static class ExampleValueBean {
 
 		private int intValue;
@@ -1036,4 +1050,40 @@ void setProperty(String property) {
 
 	}
 
+	static class PropertyOrderBean {
+
+		static AtomicInteger atomic = new AtomicInteger();
+
+		private int alpha;
+
+		private int beta;
+
+		private int gamma;
+
+		int getAlpha() {
+			return this.alpha;
+		}
+
+		void setAlpha(int alpha) {
+			this.alpha = alpha + atomic.getAndIncrement();
+		}
+
+		int getBeta() {
+			return this.beta;
+		}
+
+		void setBeta(int beta) {
+			this.beta = beta + atomic.getAndIncrement();
+		}
+
+		int getGamma() {
+			return this.gamma;
+		}
+
+		void setGamma(int gamma) {
+			this.gamma = gamma + atomic.getAndIncrement();
+		}
+
+	}
+
 }