Not allowing NPEs for DataSource name resolution; fixes gh-2076

spring-cloud-sleuth-instrumentation/src/main/java/org/springframework/cloud/sleuth/instrument/jdbc/DataSourceNameResolver.java

@@ -35,6 +35,9 @@ public class DataSourceNameResolver {
 	}
 
 	public String resolveDataSourceName(CommonDataSource dataSource) {
+		if (dataSource == null) {
+			return "dataSource";
+		}
 		return this.cachedNames.getOrDefault(dataSource, "dataSource");
 	}
 

spring-cloud-sleuth-instrumentation/src/test/java/org/springframework/cloud/sleuth/instrument/jdbc/DataSourceNameResolverTests.java

@@ -0,0 +1,30 @@
+/*
+ * Copyright 2013-2021 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
+ *
+ *      https://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.cloud.sleuth.instrument.jdbc;
+
+import org.junit.jupiter.api.Test;
+
+import static org.assertj.core.api.BDDAssertions.then;
+
+class DataSourceNameResolverTests {
+	@Test
+	void should_return_default_string_exception_when_datasource_is_null() {
+		DataSourceNameResolver resolver = new DataSourceNameResolver();
+
+		then(resolver.resolveDataSourceName(null)).isNotBlank();
+	}
+}