SOLR-14153: Return correct isolation level when retrieving it from the SQL Connection

As transactions are not supported a request to getTransactionIsolation() should return TRANSACTION_NONE (https://docs.oracle.com/javase/8/docs/api/java/sql/Connection.html#TRANSACTION_NONE)

Signed-off-by: Kevin Risden <krisden@apache.org>

solr/CHANGES.txt

@@ -109,6 +109,8 @@ Improvements
   hl.fragsizeIsMinimum, with defaults that aim to better center matches in fragments than previously. See the ref guide.
   Regardless of the settings, the passages may be sized differently than before. (Nándor Mátravölgyi, David Smiley)
 
+* SOLR-14154: Return correct isolation level when retrieving it from the SQL Connection (Nick Vercammen, Kevin Risden)
+
 Optimizations
 ---------------------
 (No changes)

solr/solrj/src/java/org/apache/solr/client/solrj/io/sql/ConnectionImpl.java

@@ -181,12 +181,30 @@ class ConnectionImpl implements Connection {
 
   @Override
   public void setTransactionIsolation(int level) throws SQLException {
-    throw new UnsupportedOperationException();
+    if(isClosed()) {
+      throw new SQLException("Connection is closed.");
+    }
+    if(Connection.TRANSACTION_NONE == level) {
+      throw new SQLException("Connection.TRANSACTION_NONE cannot be used.");
+    }
+    if(
+        Connection.TRANSACTION_READ_COMMITTED == level ||
+        Connection.TRANSACTION_READ_UNCOMMITTED == level ||
+        Connection.TRANSACTION_REPEATABLE_READ == level ||
+        Connection.TRANSACTION_SERIALIZABLE == level
+    ) {
+      throw new SQLException(new UnsupportedOperationException());
+    } else {
+      throw new SQLException("Unsupported transaction type specified.");
+    }
   }
 
   @Override
   public int getTransactionIsolation() throws SQLException {
-    throw new UnsupportedOperationException();
+    if(isClosed()) {
+      throw new SQLException("Connection is closed.");
+    }
+    return Connection.TRANSACTION_NONE;
   }
 
   @Override

solr/solrj/src/test/org/apache/solr/client/solrj/io/sql/JdbcTest.java

@@ -526,7 +526,6 @@ public class JdbcTest extends SolrCloudTestCase {
 //      assertEquals(0, databaseMetaData.getDriverMajorVersion());
 //      assertEquals(0, databaseMetaData.getDriverMinorVersion());
 
-
       List<String> tableSchemas = new ArrayList<>(Arrays.asList(zkHost, "metadata"));
       try(ResultSet rs = databaseMetaData.getSchemas()) {
         assertTrue(rs.next());
@@ -551,10 +550,8 @@ public class JdbcTest extends SolrCloudTestCase {
       solrClient.connect();
       ZkStateReader zkStateReader = solrClient.getZkStateReader();
 
-      SortedSet<String> tables = new TreeSet<>();
-
       Set<String> collectionsSet = zkStateReader.getClusterState().getCollectionsMap().keySet();
-      tables.addAll(collectionsSet);
+      SortedSet<String> tables = new TreeSet<>(collectionsSet);
 
       Aliases aliases = zkStateReader.getAliases();
       tables.addAll(aliases.getCollectionAliasListMap().keySet());
@@ -571,6 +568,15 @@ public class JdbcTest extends SolrCloudTestCase {
         assertFalse(rs.next());
       }
 
+      assertEquals(Connection.TRANSACTION_NONE, con.getTransactionIsolation());
+      try {
+        con.setTransactionIsolation(Connection.TRANSACTION_READ_COMMITTED);
+        fail("should not have been able to set transaction isolation");
+      } catch (SQLException e) {
+        assertEquals(UnsupportedOperationException.class, e.getCause().getClass());
+      }
+      assertEquals(Connection.TRANSACTION_NONE, con.getTransactionIsolation());
+
       assertTrue(con.isReadOnly());
       con.setReadOnly(true);
       assertTrue(con.isReadOnly());
@@ -579,7 +585,6 @@ public class JdbcTest extends SolrCloudTestCase {
       con.clearWarnings();
       assertNull(con.getWarnings());
 
-
       try (Statement statement = con.createStatement()) {
         checkStatement(con, statement);