fix(bigquery-jdbc): format nested ARRAY fields as valid JSON in Struct.toString()

java-bigquery-jdbc/src/main/java/com/google/cloud/bigquery/jdbc/BigQueryBaseStruct.java

@@ -29,6 +29,7 @@
 import java.sql.Timestamp;
 import java.util.Base64;
 import java.util.Map;
+import org.apache.arrow.vector.util.Text;
 
 /**
  * An abstract implementation of {@link java.sql.Struct} used as a base class for {@link
@@ -86,30 +87,24 @@ public String toString() {
         Object value = attributes[i];
 
         sb.append("\"").append(fieldName.replace("\"", "\\\"")).append("\":");
-
-        if (value == null) {
-          sb.append("null");
-        } else if (value instanceof String || value instanceof org.apache.arrow.vector.util.Text) {
-          String stringValue = value.toString().replace("\"", "\\\"");
-          sb.append("\"").append(stringValue).append("\"");
-        } else if (value instanceof Timestamp
-            && field.getType().getStandardType() == StandardSQLTypeName.TIMESTAMP) {
-          sb.append("\"")
-              .append(BigQueryTemporalUtility.formatTimestampToUtcString((Timestamp) value))
-              .append("\"");
-        } else if (value instanceof Time
-            && field.getType().getStandardType() == StandardSQLTypeName.TIME) {
-          sb.append("\"")
-              .append(
-                  BigQueryTypeRegistry.convert(
-                      getRawAttribute(i), StandardSQLTypeName.TIME, String.class, null))
-              .append("\"");
-        } else if (value instanceof Timestamp || value instanceof Date || value instanceof Time) {
-          sb.append("\"").append(value.toString()).append("\"");
-        } else if (value instanceof byte[]) {
-          sb.append("\"").append(Base64.getEncoder().encodeToString((byte[]) value)).append("\"");
+        if (value instanceof BigQueryBaseArray) {
+          BigQueryBaseArray arrayVal = (BigQueryBaseArray) value;
+          Object[] elements = (Object[]) arrayVal.getArray();
+          if (elements == null) {
+            sb.append("null");
+          } else {
+            sb.append("[");
+            for (int j = 0; j < elements.length; j++) {
+              if (j > 0) {
+                sb.append(",");
+              }
+              appendJsonValue(
+                  sb, field, elements[j], elements[j] == null ? null : arrayVal.getRawElement(j));
+            }
+            sb.append("]");
+          }
         } else {
-          sb.append(value.toString());
+          appendJsonValue(sb, field, value, value == null ? null : getRawAttribute(i));
         }
       }
       sb.append("}");
@@ -119,4 +114,33 @@ public String toString() {
       return "{ \"error\": \"Error converting struct to string: " + e.getMessage() + "\" }";
     }
   }
+
+  private static void appendJsonValue(StringBuilder sb, Field field, Object value, Object rawValue)
+      throws SQLException {
+    if (value == null) {
+      sb.append("null");
+    } else if (field.getType().getStandardType() == StandardSQLTypeName.JSON) {
+      sb.append(value);
+    } else if (value instanceof String || value instanceof Text) {
+      String stringValue = value.toString().replace("\"", "\\\"");
+      sb.append("\"").append(stringValue).append("\"");
+    } else if (value instanceof Timestamp
+        && field.getType().getStandardType() == StandardSQLTypeName.TIMESTAMP) {
+      sb.append("\"")
+          .append(BigQueryTemporalUtility.formatTimestampToUtcString((Timestamp) value))
+          .append("\"");
+    } else if (value instanceof Time
+        && field.getType().getStandardType() == StandardSQLTypeName.TIME) {
+      sb.append("\"")
+          .append(
+              BigQueryTypeRegistry.convert(rawValue, StandardSQLTypeName.TIME, String.class, null))
+          .append("\"");
+    } else if (value instanceof Timestamp || value instanceof Date || value instanceof Time) {
+      sb.append("\"").append(value).append("\"");
+    } else if (value instanceof byte[]) {
+      sb.append("\"").append(Base64.getEncoder().encodeToString((byte[]) value)).append("\"");
+    } else {
+      sb.append(value);
+    }
+  }
 }

java-bigquery-jdbc/src/test/java/com/google/cloud/bigquery/jdbc/BigQueryArrowStructTest.java

@@ -181,6 +181,20 @@ GEOGRAPHY, new Text("POINT(-122 47)"), new Text("POINT(-122 48)")),
         .isEqualTo(new String[] {"POINT(-122 47)", "POINT(-122 48)"});
     assertThat(((Array) attributes[11]).getArray())
         .isEqualTo(new byte[][] {"one".getBytes(), "two".getBytes()});
+    assertThat(struct.toString())
+        .isEqualTo(
+            "{\"INT64_arr_column\":[10,20],"
+                + "\"BOOL_arr_column\":[true,false],"
+                + "\"FLOAT64_arr_column\":[11.2,33.4],"
+                + "\"NUMERIC_arr_column\":[11.2657,33.4657],"
+                + "\"BIGNUMERIC_arr_column\":[11.2657,33.4657],"
+                + "\"STRING_arr_column\":[\"one\",\"two\"],"
+                + "\"TIMESTAMP_arr_column\":[\"2023-03-30 11:14:19.820227\",\"2023-03-31 11:14:19.820227\"],"
+                + "\"DATE_arr_column\":[\"2023-03-30\",\"2023-03-31\"],"
+                + "\"TIME_arr_column\":[\"11:14:19.820227\",\"11:14:20.820227\"],"
+                + "\"DATETIME_arr_column\":[\"2023-03-30 11:14:19.820227\",\"2023-03-30 11:15:19.820227\"],"
+                + "\"GEOGRAPHY_arr_column\":[\"POINT(-122 47)\",\"POINT(-122 48)\"],"
+                + "\"BYTES_arr_column\":[\"b25l\",\"dHdv\"]}");
   }
 
   @Test

java-bigquery-jdbc/src/test/java/com/google/cloud/bigquery/jdbc/BigQueryJsonStructTest.java

@@ -193,6 +193,20 @@ public void structOfArrays() throws SQLException {
         .isEqualTo(new String[] {"POINT(-122 47)", "POINT(-122 48)"});
     assertThat(((Array) attributes[11]).getArray())
         .isEqualTo(new byte[][] {"one".getBytes(), "two".getBytes()});
+    assertThat(struct.toString())
+        .isEqualTo(
+            "{\"INT64_arr_column\":[10,20],"
+                + "\"BOOL_arr_column\":[true,false],"
+                + "\"FLOAT64_arr_column\":[11.2,33.4],"
+                + "\"NUMERIC_arr_column\":[11.2657,33.4657],"
+                + "\"BIGNUMERIC_arr_column\":[11.2657,33.4657],"
+                + "\"STRING_arr_column\":[\"one\",\"two\"],"
+                + "\"TIMESTAMP_arr_column\":[\"2023-03-30 11:14:19.82\",\"2023-03-31 11:14:19.82\"],"
+                + "\"DATE_arr_column\":[\"2023-03-30\",\"2023-03-31\"],"
+                + "\"TIME_arr_column\":[\"11:14:19.82\",\"11:14:20.82\"],"
+                + "\"DATETIME_arr_column\":[\"2023-03-30 11:14:19.82\",\"2023-03-30 11:15:19.82\"],"
+                + "\"GEOGRAPHY_arr_column\":[\"POINT(-122 47)\",\"POINT(-122 48)\"],"
+                + "\"BYTES_arr_column\":[\"b25l\",\"dHdv\"]}");
   }
 
   @Test

java-bigquery-jdbc/src/test/java/com/google/cloud/bigquery/jdbc/it/ITBigQueryJDBCTest.java

@@ -71,6 +71,8 @@
 import org.junit.jupiter.api.BeforeAll;
 import org.junit.jupiter.api.Tag;
 import org.junit.jupiter.api.Test;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.ValueSource;
 
 public class ITBigQueryJDBCTest extends ITBase {
   static final String PROJECT_ID = ServiceOptions.getDefaultProjectId();
@@ -3095,4 +3097,33 @@ public void testSessionAbortedOnConnectionClose() throws SQLException {
       }
     }
   }
+
+  @ParameterizedTest
+  @ValueSource(strings = {"", FORCE_READ_API_PROPERTIES})
+  public void testStructWithNestedArraysValidJson(String extraProps) throws SQLException {
+    String sql =
+        "SELECT STRUCT("
+            + "1 AS id, "
+            + "['hello', 'world'] AS str_arr, "
+            + "[DATE '2026-01-01', DATE '2026-01-02'] AS date_arr, "
+            + "[TIME '12:34:56.789012'] AS time_arr, "
+            + "[TIMESTAMP '2026-01-01 00:00:00 UTC'] AS ts_arr, "
+            + "[b'abc', b'def'] AS bytes_arr"
+            + ") AS s_nested_arrays";
+
+    String expectedJson =
+        "{\"id\":1,"
+            + "\"str_arr\":[\"hello\",\"world\"],"
+            + "\"date_arr\":[\"2026-01-01\",\"2026-01-02\"],"
+            + "\"time_arr\":[\"12:34:56.789012\"],"
+            + "\"ts_arr\":[\"2026-01-01 00:00:00.0\"],"
+            + "\"bytes_arr\":[\"YWJj\",\"ZGVm\"]}";
+
+    try (Connection conn = DriverManager.getConnection(connection_uri + extraProps);
+        Statement stmt = conn.createStatement();
+        ResultSet rs = stmt.executeQuery(sql)) {
+      assertTrue(rs.next());
+      assertEquals(expectedJson, rs.getString("s_nested_arrays"));
+    }
+  }
 }