fix: getting resultset metadata twice could skip row (#323)

* fix: getting resultset metadata twice could skip row If the client application would call ResultSet#getMetaData() more than once **before** calling ResultSet#next(), the ResultSet would skip a row when the rows would be consumed. Fixes #322 * test: add test for getMetaData twice

Author: olavloite

src/main/java/com/google/cloud/spanner/jdbc/JdbcResultSet.java

@@ -547,7 +547,7 @@ public InputStream getBinaryStream(String columnLabel) throws SQLException {
  @Override
  public JdbcResultSetMetaData getMetaData() throws SQLException {
  checkClosed();
- if (isBeforeFirst()) {
+ if (isBeforeFirst() && !nextCalledForMetaData) {
  // do a call to next() on the underlying resultset to initialize metadata
  nextCalledForMetaData = true;
  nextCalledForMetaDataResult = spanner.next();

src/test/java/com/google/cloud/spanner/jdbc/JdbcResultSetTest.java

@@ -25,6 +25,7 @@
 import static org.junit.Assert.assertTrue;
 import static org.junit.Assert.fail;
 import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.when;
 
 import com.google.cloud.ByteArray;
 import com.google.cloud.Date;
@@ -802,6 +803,32 @@ public void testGetMetaData() throws SQLException {
  assertNotNull(metadata);
  }
 
+ @Test
+ public void testGetMetaDataBeforeNext() throws SQLException {
+ ResultSet spannerResultSet = mock(ResultSet.class);
+ when(spannerResultSet.next()).thenReturn(true, false);
+
+ JdbcResultSet resultSet = JdbcResultSet.of(spannerResultSet);
+ assertNotNull(resultSet.getMetaData());
+ assertTrue(resultSet.next());
+ assertFalse(resultSet.next());
+ }
+
+ @Test
+ public void testGetMetaDataTwiceBeforeNext() throws SQLException {
+ ResultSet spannerResultSet = mock(ResultSet.class);
+ when(spannerResultSet.next()).thenReturn(true, false);
+
+ JdbcResultSet resultSet = JdbcResultSet.of(spannerResultSet);
+ assertNotNull(resultSet.getMetaData());
+ assertNotNull(resultSet.getMetaData());
+
+ // This would have returned false before the fix in
+ // https://github.com/googleapis/java-spanner-jdbc/pull/323
+ assertTrue(resultSet.next());
+ assertFalse(resultSet.next());
+ }
+
  @Test
  public void testFindColumn() throws SQLException {
  assertEquals(2, subject.findColumn(STRING_COL_NOT_NULL));