Add columnNames to LimboResultSet

bindings/java/rs_src/limbo_statement.rs

@@ -2,7 +2,7 @@ use crate::errors::Result;
 use crate::errors::{LimboError, LIMBO_ETC};
 use crate::limbo_connection::LimboConnection;
 use crate::utils::set_err_msg_and_throw_exception;
-use jni::objects::{JObject, JValue};
+use jni::objects::{JObject, JObjectArray, JValue};
 use jni::sys::jlong;
 use jni::JNIEnv;
 use limbo_core::{Statement, StepResult};
@@ -125,6 +125,27 @@ fn row_to_obj_array<'local>(
     Ok(obj_array.into())
 }
 
+#[no_mangle]
+pub extern "system" fn Java_org_github_tursodatabase_core_LimboStatement_columnNames<'local>(
+    mut env: JNIEnv<'local>,
+    _obj: JObject<'local>,
+    stmt_ptr: jlong,
+) -> JObject<'local> {
+    let stmt = to_limbo_statement(stmt_ptr).unwrap();
+    let columns = stmt.stmt.columns();
+    let obj_arr: JObjectArray = env
+        .new_object_array(columns.len() as i32, "java/lang/String", JObject::null())
+        .unwrap();
+
+    for (i, value) in columns.iter().enumerate() {
+        let str = env.new_string(value).unwrap();
+        env.set_object_array_element(&obj_arr, i as i32, str)
+            .unwrap();
+    }
+
+    obj_arr.into()
+}
+
 /// Converts an optional `JObject` into Java's `LimboStepResult`.
 ///
 /// This function takes an optional `JObject` and converts it into a Java object

bindings/java/src/main/java/org/github/tursodatabase/core/LimboResultSet.java

@@ -19,6 +19,8 @@ public class LimboResultSet {
 
   private final LimboStatement statement;
 
+  // Name of the columns
+  private String[] columnNames = new String[0];
   // Whether the result set does not have any rows.
   private boolean isEmptyResultSet = false;
   // If the result set is open. Doesn't mean it has results.
@@ -136,6 +138,14 @@ public class LimboResultSet {
     return resultSet[columnIndex - 1];
   }
 
+  public String[] getColumnNames() {
+    return this.columnNames;
+  }
+
+  public void setColumnNames(String[] columnNames) {
+    this.columnNames = columnNames;
+  }
+
   @Override
   public String toString() {
     return "LimboResultSet{"

bindings/java/src/main/java/org/github/tursodatabase/core/LimboStatement.java

@@ -89,6 +89,23 @@ public class LimboStatement {
 
   private native void _close(long statementPointer);
 
+  /**
+   * Initializes the column metadata, such as the names of the columns. Since {@link LimboStatement}
+   * can only have a single {@link LimboResultSet}, it is appropriate to place the initialization of
+   * column metadata here.
+   *
+   * @throws SQLException if a database access error occurs while retrieving column names
+   */
+  public void initializeColumnMetadata() throws SQLException {
+    final String[] columnNames = this.columnNames(statementPointer);
+    if (columnNames != null) {
+      this.resultSet.setColumnNames(columnNames);
+    }
+  }
+
+  @Nullable
+  private native String[] columnNames(long statementPointer) throws SQLException;
+
   /**
    * Checks if the statement is closed.
    *

bindings/java/src/test/java/org/github/tursodatabase/core/LimboStatementTest.java

@@ -1,6 +1,8 @@
 package org.github.tursodatabase.core;
 
-import static org.junit.jupiter.api.Assertions.*;
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertTrue;
 
 import java.util.Properties;
 import org.github.tursodatabase.TestUtils;
@@ -28,4 +30,26 @@ class LimboStatementTest {
     assertTrue(stmt.isClosed());
     assertFalse(stmt.getResultSet().isOpen());
   }
+
+  @Test
+  void test_initializeColumnMetadata() throws Exception {
+    runSql("CREATE TABLE users (name TEXT, age INT, country TEXT);");
+    runSql("INSERT INTO users VALUES ('seonwoo', 30, 'KR');");
+
+    final LimboStatement stmt = connection.prepare("SELECT * FROM users");
+    stmt.initializeColumnMetadata();
+    final LimboResultSet rs = stmt.getResultSet();
+    final String[] columnNames = rs.getColumnNames();
+
+    assertEquals(columnNames[0], "name");
+    assertEquals(columnNames[1], "age");
+    assertEquals(columnNames[2], "country");
+  }
+
+  private void runSql(String sql) throws Exception {
+    LimboStatement stmt = connection.prepare(sql);
+    while (stmt.execute()) {
+      stmt.execute();
+    }
+  }
 }