Consistent handling of null array for arguments

Issue: SPR-16075

spring-core/src/main/java/org/springframework/util/MethodInvoker.java

@@ -51,7 +51,7 @@ public class MethodInvoker {
 	private String staticMethod;
 
 	@Nullable
-	private Object[] arguments = new Object[0];
+	private Object[] arguments;
 
 	/** The method we will call */
 	@Nullable

spring-core/src/test/java/org/springframework/util/MethodInvokerTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2016 the original author or authors.
+ * Copyright 2002-2017 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.
@@ -49,18 +49,28 @@ public class MethodInvokerTests {
 		Integer i = (Integer) mi.invoke();
 		assertEquals(1, i.intValue());
 
+		// defensive check: singleton, non-static should work with null array
+		tc1 = new TestClass1();
+		mi = new MethodInvoker();
+		mi.setTargetObject(tc1);
+		mi.setTargetMethod("method1");
+		mi.setArguments((Object[]) null);
+		mi.prepare();
+		i = (Integer) mi.invoke();
+		assertEquals(1, i.intValue());
+
 		// sanity check: check that argument count matching works
 		mi = new MethodInvoker();
 		mi.setTargetClass(TestClass1.class);
 		mi.setTargetMethod("supertypes");
-		mi.setArguments(new Object[] {new ArrayList<>(), new ArrayList<>(), "hello"});
+		mi.setArguments(new ArrayList<>(), new ArrayList<>(), "hello");
 		mi.prepare();
 		assertEquals("hello", mi.invoke());
 
 		mi = new MethodInvoker();
 		mi.setTargetClass(TestClass1.class);
 		mi.setTargetMethod("supertypes2");
-		mi.setArguments(new Object[] {new ArrayList<>(), new ArrayList<>(), "hello", "bogus"});
+		mi.setArguments(new ArrayList<>(), new ArrayList<>(), "hello", "bogus");
 		mi.prepare();
 		assertEquals("hello", mi.invoke());
 
@@ -68,7 +78,7 @@ public class MethodInvokerTests {
 		mi = new MethodInvoker();
 		mi.setTargetClass(TestClass1.class);
 		mi.setTargetMethod("supertypes2");
-		mi.setArguments(new Object[] {new ArrayList<>(), new ArrayList<>(), "hello", Boolean.TRUE});
+		mi.setArguments(new ArrayList<>(), new ArrayList<>(), "hello", Boolean.TRUE);
 
 		exception.expect(NoSuchMethodException.class);
 		mi.prepare();
@@ -79,7 +89,7 @@ public class MethodInvokerTests {
 		MethodInvoker methodInvoker = new MethodInvoker();
 		methodInvoker.setTargetObject(new Greeter());
 		methodInvoker.setTargetMethod("greet");
-		methodInvoker.setArguments(new Object[] {"no match"});
+		methodInvoker.setArguments("no match");
 
 		exception.expect(NoSuchMethodException.class);
 		methodInvoker.prepare();
@@ -90,7 +100,7 @@ public class MethodInvokerTests {
 		MethodInvoker methodInvoker = new MethodInvoker();
 		methodInvoker.setTargetObject(new Greeter());
 		methodInvoker.setTargetMethod("greet");
-		methodInvoker.setArguments(new Object[] {new Purchaser()});
+		methodInvoker.setArguments(new Purchaser());
 		methodInvoker.prepare();
 		String greeting = (String) methodInvoker.invoke();
 		assertEquals("purchaser: hello", greeting);
@@ -101,7 +111,7 @@ public class MethodInvokerTests {
 		MethodInvoker methodInvoker = new MethodInvoker();
 		methodInvoker.setTargetObject(new Greeter());
 		methodInvoker.setTargetMethod("greet");
-		methodInvoker.setArguments(new Object[] {new Shopper()});
+		methodInvoker.setArguments(new Shopper());
 		methodInvoker.prepare();
 		String greeting = (String) methodInvoker.invoke();
 		assertEquals("purchaser: may I help you?", greeting);
@@ -112,7 +122,7 @@ public class MethodInvokerTests {
 		MethodInvoker methodInvoker = new MethodInvoker();
 		methodInvoker.setTargetObject(new Greeter());
 		methodInvoker.setTargetMethod("greet");
-		methodInvoker.setArguments(new Object[] {new Salesman()});
+		methodInvoker.setArguments(new Salesman());
 		methodInvoker.prepare();
 		String greeting = (String) methodInvoker.invoke();
 		assertEquals("greetable: how are sales?", greeting);
@@ -123,7 +133,7 @@ public class MethodInvokerTests {
 		MethodInvoker methodInvoker = new MethodInvoker();
 		methodInvoker.setTargetObject(new Greeter());
 		methodInvoker.setTargetMethod("greet");
-		methodInvoker.setArguments(new Object[] {new Customer()});
+		methodInvoker.setArguments(new Customer());
 		methodInvoker.prepare();
 		String greeting = (String) methodInvoker.invoke();
 		assertEquals("customer: good day", greeting);
@@ -134,7 +144,7 @@ public class MethodInvokerTests {
 		MethodInvoker methodInvoker = new MethodInvoker();
 		methodInvoker.setTargetObject(new Greeter());
 		methodInvoker.setTargetMethod("greet");
-		methodInvoker.setArguments(new Object[] {new Regular("Kotter")});
+		methodInvoker.setArguments(new Regular("Kotter"));
 		methodInvoker.prepare();
 		String greeting = (String) methodInvoker.invoke();
 		assertEquals("regular: welcome back Kotter", greeting);
@@ -145,7 +155,7 @@ public class MethodInvokerTests {
 		MethodInvoker methodInvoker = new MethodInvoker();
 		methodInvoker.setTargetObject(new Greeter());
 		methodInvoker.setTargetMethod("greet");
-		methodInvoker.setArguments(new Object[] {new VIP("Fonzie")});
+		methodInvoker.setArguments(new VIP("Fonzie"));
 		methodInvoker.prepare();
 		String greeting = (String) methodInvoker.invoke();
 		assertEquals("regular: whassup dude?", greeting);