Only unwrap when DataSource is a wrapper for required type

Closes gh-16863

spring-boot-project/spring-boot/src/main/java/org/springframework/boot/jdbc/DataSourceUnwrapper.java

 /*
- * Copyright 2012-2018 the original author or authors.
+ * Copyright 2012-2019 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.
@@ -76,11 +76,14 @@ public final class DataSourceUnwrapper {
 
 	private static <S> S safeUnwrap(Wrapper wrapper, Class<S> target) {
 		try {
-			return wrapper.unwrap(target);
+			if (wrapper.isWrapperFor(target)) {
+				return wrapper.unwrap(target);
+			}
 		}
 		catch (Exception ex) {
-			return null;
+			// Continue
 		}
+		return null;
 	}
 
 	private static class DelegatingDataSourceUnwrapper {

spring-boot-project/spring-boot/src/test/java/org/springframework/boot/jdbc/DataSourceUnwrapperTests.java

 /*
- * Copyright 2012-2018 the original author or authors.
+ * Copyright 2012-2019 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.
@@ -16,6 +16,8 @@
 
 package org.springframework.boot.jdbc;
 
+import java.sql.SQLException;
+
 import javax.sql.DataSource;
 
 import com.zaxxer.hikari.HikariDataSource;
@@ -27,6 +29,9 @@ import org.springframework.jdbc.datasource.DelegatingDataSource;
 import org.springframework.jdbc.datasource.SingleConnectionDataSource;
 
 import static org.assertj.core.api.Assertions.assertThat;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.verify;
+import static org.mockito.Mockito.verifyNoMoreInteractions;
 
 /**
  * Tests for {@link DataSourceUnwrapper}.
@@ -91,6 +96,17 @@ public class DataSourceUnwrapperTests {
 				.isSameAs(dataSource);
 	}
 
+	@Test
+	public void unwrappingIsNotAttemptedWhenDataSourceIsNotWrapperForTarget()
+			throws SQLException {
+		DataSource dataSource = mock(DataSource.class);
+		DataSource actual = DataSourceUnwrapper.unwrap(dataSource,
+				HikariDataSource.class);
+		assertThat(actual).isNull();
+		verify(dataSource).isWrapperFor(HikariDataSource.class);
+		verifyNoMoreInteractions(dataSource);
+	}
+
 	private DataSource wrapInProxy(DataSource dataSource) {
 		return (DataSource) new ProxyFactory(dataSource).getProxy();
 	}