Support primitive types in BeanUtils.instantiateClass args

This commit adds support for primitive default values for
BeanUtils.instantiateClass arguments in Java in order to provide
a consistent behavior in both Java and Kotlin languages.

Closes gh-22531

spring-beans/src/test/java/org/springframework/beans/BeanUtilsTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2018 the original author or authors.
+ * Copyright 2002-2019 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.
@@ -18,6 +18,7 @@ package org.springframework.beans;
 
 import java.beans.Introspector;
 import java.beans.PropertyDescriptor;
+import java.lang.reflect.Constructor;
 import java.lang.reflect.Method;
 import java.util.ArrayList;
 import java.util.List;
@@ -28,6 +29,7 @@ import org.springframework.beans.factory.BeanFactory;
 import org.springframework.beans.propertyeditors.CustomDateEditor;
 import org.springframework.core.io.Resource;
 import org.springframework.core.io.ResourceEditor;
+import org.springframework.lang.Nullable;
 import org.springframework.tests.sample.beans.DerivedTestBean;
 import org.springframework.tests.sample.beans.ITestBean;
 import org.springframework.tests.sample.beans.TestBean;
@@ -40,6 +42,7 @@ import static org.junit.Assert.*;
  * @author Juergen Hoeller
  * @author Rob Harrop
  * @author Chris Beams
+ * @author Sebastien Deleuze
  * @since 19.05.2003
  */
 public class BeanUtilsTests {
@@ -68,6 +71,31 @@ public class BeanUtilsTests {
 		}
 	}
 
+	@Test  // gh-22531
+	public void testInstantiateClassWithOptionalNullableType() throws NoSuchMethodException {
+		Constructor<BeanWithNullableTypes> ctor = BeanWithNullableTypes.class.getDeclaredConstructor(
+				Integer.class, Boolean.class, String.class);
+		BeanWithNullableTypes bean = BeanUtils.instantiateClass(ctor, null, null, "foo");
+		assertNull(bean.getCounter());
+		assertNull(bean.isFlag());
+		assertEquals("foo", bean.getValue());
+	}
+
+	@Test  // gh-22531
+	public void testInstantiateClassWithOptionalPrimitiveType() throws NoSuchMethodException {
+		Constructor<BeanWithPrimitiveTypes> ctor = BeanWithPrimitiveTypes.class.getDeclaredConstructor(int.class, boolean.class, String.class);
+		BeanWithPrimitiveTypes bean = BeanUtils.instantiateClass(ctor, null, null, "foo");
+		assertEquals(0, bean.getCounter());
+		assertEquals(false, bean.isFlag());
+		assertEquals("foo", bean.getValue());
+	}
+
+	@Test(expected = BeanInstantiationException.class)  // gh-22531
+	public void testInstantiateClassWithMoreArgsThanParameters() throws NoSuchMethodException {
+		Constructor<BeanWithPrimitiveTypes> ctor = BeanWithPrimitiveTypes.class.getDeclaredConstructor(int.class, boolean.class, String.class);
+		BeanUtils.instantiateClass(ctor, null, null, "foo", null);
+	}
+
 	@Test
 	public void testGetPropertyDescriptors() throws Exception {
 		PropertyDescriptor[] actual = Introspector.getBeanInfo(TestBean.class).getPropertyDescriptors();
@@ -458,4 +486,60 @@ public class BeanUtilsTests {
 		}
 	}
 
+	private static class BeanWithNullableTypes {
+
+		private Integer counter;
+
+		private Boolean flag;
+
+		private String value;
+
+		public BeanWithNullableTypes(@Nullable Integer counter, @Nullable Boolean flag, String value) {
+			this.counter = counter;
+			this.flag = flag;
+			this.value = value;
+		}
+
+		@Nullable
+		public Integer getCounter() {
+			return counter;
+		}
+
+		@Nullable
+		public Boolean isFlag() {
+			return flag;
+		}
+
+		public String getValue() {
+			return value;
+		}
+	}
+
+	private static class BeanWithPrimitiveTypes {
+
+		private int counter;
+
+		private boolean flag;
+
+		private String value;
+
+		public BeanWithPrimitiveTypes(int counter, boolean flag, String value) {
+			this.counter = counter;
+			this.flag = flag;
+			this.value = value;
+		}
+
+		public int getCounter() {
+			return counter;
+		}
+
+		public boolean isFlag() {
+			return flag;
+		}
+
+		public String getValue() {
+			return value;
+		}
+	}
+
 }