feat: omit explicit DB Statement for health check

server/src/main/java/org/cloudfoundry/identity/uaa/health/HealthzEndpoint.java

@@ -11,12 +11,15 @@
 
 import javax.sql.DataSource;
 import java.sql.Connection;
-import java.sql.Statement;
 
 /**
  * Simple controller that just returns "ok" in a request body for the purposes
  * of monitoring health of the application. It also registers a shutdown hook
  * and returns "stopping" and a 503 when the process is shutting down.
+ * The background database check only establishes a connection from the pool
+ * without executing an additional query. The configured DataSource already
+ * runs a validation query on every connection borrow ({@code testOnBorrow=true}),
+ * so obtaining a connection is sufficient to verify database connectivity.
  */
 @Controller
 public class HealthzEndpoint {
@@ -25,6 +28,7 @@ public class HealthzEndpoint {
     private volatile Boolean wasLastConnectionSuccessful = null;
     private DataSource dataSource;
 
+
     public HealthzEndpoint(
             @Value("${uaa.shutdown.sleep:10000}") final long sleepTime,
             final Runtime runtime,
@@ -71,8 +75,7 @@ public String getHealthz(HttpServletResponse response) {
 
     @Scheduled(fixedRateString = "${uaa.health.db.rate:10000}")
     void isDataSourceConnectionAvailable() {
-        try (Connection c = dataSource.getConnection(); Statement statement = c.createStatement()) {
-            statement.execute("SELECT 1 from identity_zone;"); //"SELECT 1;" Not supported by HSQLDB
+        try (Connection c = dataSource.getConnection()) {
             wasLastConnectionSuccessful = true;
             return;
         } catch (Exception ex) {

server/src/test/java/org/cloudfoundry/identity/uaa/health/HealthzEndpointTests.java

@@ -9,10 +9,8 @@
 import javax.sql.DataSource;
 import java.sql.Connection;
 import java.sql.SQLException;
-import java.sql.Statement;
 
 import static org.assertj.core.api.Assertions.assertThat;
-import static org.mockito.ArgumentMatchers.anyString;
 import static org.mockito.Mockito.mock;
 import static org.mockito.Mockito.verify;
 import static org.mockito.Mockito.when;
@@ -26,16 +24,13 @@ class HealthzEndpointTests {
     private Thread shutdownHook;
     private DataSource dataSource;
     private Connection connection;
-    private Statement statement;
 
     @BeforeEach
     void setUp() throws SQLException {
         Runtime mockRuntime = mock(Runtime.class);
         dataSource = mock(DataSource.class);
         connection = mock(Connection.class);
-        statement = mock(Statement.class);
         when(dataSource.getConnection()).thenReturn(connection);
-        when(connection.createStatement()).thenReturn(statement);
         endpoint = new HealthzEndpoint(SLEEP_UPON_SHUTDOWN, mockRuntime, dataSource);
         response = new MockHttpServletResponse();
 
@@ -51,14 +46,15 @@ void getHealthz() throws SQLException {
     }
 
     @Test
-    void getHealthz_connectionSuccess() {
+    void getHealthz_connectionSuccess() throws SQLException {
         endpoint.isDataSourceConnectionAvailable();
         assertThat(endpoint.getHealthz(response)).isEqualTo("ok\n");
+        verify(dataSource).getConnection();
     }
 
     @Test
     void getHealthz_connectionFailed() throws SQLException {
-        when(statement.execute(anyString())).thenThrow(new SQLException());
+        when(dataSource.getConnection()).thenThrow(new SQLException());
         endpoint.isDataSourceConnectionAvailable();
         assertThat(endpoint.getHealthz(response)).isEqualTo("Database Connection failed.\n");
         assertThat(response.getStatus()).isEqualTo(503);