Assert preconditions in ResourceDatabasePopulator

Prior to this commit ResourceDatabasePopulator did not assert any
preconditions for constructor and method arguments. Consequently,
errors would not be encountered until the populator was executed.

This commit addresses this issue by ensuring that preconditions for
constructor and method arguments are asserted immediately, throwing
IllegalArgumentExceptions where appropriate.

Issue: SPR-11690

spring-jdbc/src/test/java/org/springframework/jdbc/datasource/init/ResourceDatabasePopulatorTests.java

@@ -0,0 +1,88 @@
+/*
+ * Copyright 2002-2014 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
+ *
+ * http://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.jdbc.datasource.init;
+
+import org.junit.Test;
+import org.springframework.core.io.ClassPathResource;
+import org.springframework.core.io.Resource;
+
+import static org.junit.Assert.*;
+
+/**
+ * Unit tests for {@link ResourceDatabasePopulator}.
+ *
+ * @author Sam Brannen
+ * @since 4.1
+ * @see AbstractDatabasePopulatorTests
+ */
+public class ResourceDatabasePopulatorTests {
+
+	private static final Resource script1 = resource("script1");
+	private static final Resource script2 = resource("script2");
+
+
+	@Test(expected = IllegalArgumentException.class)
+	public void constructWithNullResource() {
+		new ResourceDatabasePopulator((Resource) null);
+	}
+
+	@Test(expected = IllegalArgumentException.class)
+	public void constructWithNullResourceArray() {
+		new ResourceDatabasePopulator((Resource[]) null);
+	}
+
+	@Test
+	public void constructWithResource() {
+		ResourceDatabasePopulator databasePopulator = new ResourceDatabasePopulator(script1);
+		assertEquals(1, databasePopulator.getScripts().size());
+	}
+
+	@Test
+	public void constructWithMulipleResources() {
+		ResourceDatabasePopulator databasePopulator = new ResourceDatabasePopulator(script1, script2);
+		assertEquals(2, databasePopulator.getScripts().size());
+	}
+
+	@Test(expected = IllegalArgumentException.class)
+	public void addScriptsWithNullResource() {
+		ResourceDatabasePopulator databasePopulator = new ResourceDatabasePopulator();
+		databasePopulator.addScripts((Resource) null);
+	}
+
+	@Test(expected = IllegalArgumentException.class)
+	public void addScriptsWithNullResourceArray() {
+		ResourceDatabasePopulator databasePopulator = new ResourceDatabasePopulator();
+		databasePopulator.addScripts((Resource[]) null);
+	}
+
+	@Test(expected = IllegalArgumentException.class)
+	public void setScriptsWithNullResource() {
+		ResourceDatabasePopulator databasePopulator = new ResourceDatabasePopulator();
+		databasePopulator.setScripts((Resource) null);
+	}
+
+	@Test(expected = IllegalArgumentException.class)
+	public void setScriptsWithNullResourceArray() {
+		ResourceDatabasePopulator databasePopulator = new ResourceDatabasePopulator();
+		databasePopulator.setScripts((Resource[]) null);
+	}
+
+	private static Resource resource(String path) {
+		return new ClassPathResource(path);
+	}
+
+}