fix(jdbc): cache database metadata per connection

libsql-jdbc/src/main/java/com/github/magnusp/libsql/jdbc/LibsqlConnection.java

@@ -47,6 +47,7 @@ public class LibsqlConnection implements Connection {
     private int transactionIsolation = TRANSACTION_SERIALIZABLE;
     private boolean closed = false;
     private TransactionMode transactionMode = TransactionMode.DEFERRED;
+    private LibsqlDatabaseMetaData meta;
 
     /**
      * Transaction begin mode, matching xerial sqlite-jdbc's
@@ -389,10 +390,19 @@ public boolean isClosed() throws SQLException {
         return closed;
     }
 
+    /**
+     * Returns the metadata for this connection, creating it on first use and reusing it afterwards,
+     * matching xerial sqlite-jdbc 3.53.4.0. The instance is cached for the lifetime of the
+     * connection, so repeated calls return the same object and separate connections get separate
+     * instances. Calling this on a closed connection throws.
+     */
     @Override
     public DatabaseMetaData getMetaData() throws SQLException {
         checkClosed();
-        return new LibsqlDatabaseMetaData(this);
+        if (meta == null) {
+            meta = new LibsqlDatabaseMetaData(this);
+        }
+        return meta;
     }
 
     @Override

libsql-jdbc/src/test/java/com/github/magnusp/libsql/jdbc/LibsqlConnectionTest.java

@@ -32,6 +32,17 @@ class LibsqlConnectionTest {
     private static final String SERVER_ERROR = "transaction end failed on server";
     private static final String TRANSPORT_ERROR = "Connection reset by peer";
 
+    @Test
+    void getMetaDataIsCachedPerConnection() throws SQLException {
+        LibsqlConnection connection = new LibsqlConnection(
+                CONFIG, new ScriptedClient((request, index) -> successResponse(request)));
+        LibsqlConnection other = new LibsqlConnection(
+                CONFIG, new ScriptedClient((request, index) -> successResponse(request)));
+
+        assertThat(connection.getMetaData()).isSameAs(connection.getMetaData());
+        assertThat(other.getMetaData()).isNotSameAs(connection.getMetaData());
+    }
+
     @Test
     void disablingAutoCommitBeginsTransactionImmediately() throws SQLException {
         ScriptedClient client = new ScriptedClient((request, index) -> successResponse(request));