Fix list query history

databricks-sdk-java/src/main/java/com/databricks/sdk/core/ApiClient.java

@@ -93,21 +93,11 @@ private <I> Request withQuery(Request in, I entity) {
     }
     try {
       // deterministic query string: in the order of class fields
-      for (Field field : entity.getClass().getDeclaredFields()) {
-        QueryParam param = field.getAnnotation(QueryParam.class);
-        if (param == null) {
-          continue;
-        }
-        field.setAccessible(true);
-        Object value = field.get(entity);
-        field.setAccessible(false);
-        if (value == null) {
-          continue;
-        }
-        in.withQueryParam(param.value(), value.toString());
+      for (Map.Entry<String, Object> e : HeaderSerializer.serialize(entity).entrySet()) {
+        in.withQueryParam(e.getKey(), mapper.writeValueAsString(e.getValue()));
       }
       return in;
-    } catch (IllegalAccessException e) {
+    } catch (JsonProcessingException e) {
       throw new DatabricksException("Cannot create query string: " + e.getMessage(), e);
     }
   }

databricks-sdk-java/src/main/java/com/databricks/sdk/core/HeaderSerializer.java

@@ -0,0 +1,83 @@
+package com.databricks.sdk.core;
+
+import com.databricks.sdk.support.QueryParam;
+import com.fasterxml.jackson.annotation.JsonProperty;
+
+import java.lang.reflect.Field;
+import java.util.Arrays;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+
+public class HeaderSerializer {
+  public static Map<String, Object> serialize(Object o) {
+    Map<String, Object> flattened = flattenObject(o);
+    for (Field f : o.getClass().getDeclaredFields()) {
+      QueryParam queryParam = f.getAnnotation(QueryParam.class);
+      if (queryParam == null) {
+        flattened.remove(getFieldName(f));
+      }
+    }
+
+    return flattened;
+  }
+
+  private static final List<Class<?>> primitiveTypes = Arrays.asList(
+      boolean.class,
+      Boolean.class,
+      byte.class,
+      Byte.class,
+      char.class,
+      Character.class,
+      short.class,
+      Short.class,
+      int.class,
+      Integer.class,
+      long.class,
+      Long.class,
+      float.class,
+      Float.class,
+      double.class,
+      Double.class,
+      String.class
+  );
+
+  private static String getFieldName(Field f) {
+    JsonProperty jsonProperty = f.getAnnotation(JsonProperty.class);
+    if (jsonProperty != null) {
+      return jsonProperty.value();
+    } else {
+      return f.getName();
+    }
+  }
+
+  private static Map<String, Object> flattenObject(Object o) {
+    Map<String, Object> result = new HashMap<>();
+    Field[] fields = o.getClass().getDeclaredFields();
+    for (Field f : fields) {
+      f.setAccessible(true);
+      try {
+        String name = getFieldName(f);
+        Object value = f.get(o);
+        if (value == null) {
+          continue;
+        }
+        // check if object is a primitive type
+        if (primitiveTypes.contains(f.getType()) || Iterable.class.isAssignableFrom(f.getType())) {
+          result.put(name, value);
+        } else {
+          // recursively flatten the object
+          Map<String, Object> flattened = flattenObject(value);
+          for (Map.Entry<String, Object> entry : flattened.entrySet()) {
+            result.put(name + "." + entry.getKey(), entry.getValue());
+          }
+        }
+      } catch (IllegalAccessException e) {
+        throw new RuntimeException(e);
+      } finally {
+        f.setAccessible(false);
+      }
+    }
+    return result;
+  }
+}

databricks-sdk-java/src/main/java/com/databricks/sdk/support/Paginator.java

@@ -71,6 +71,9 @@ private Iterator<T> outerIterator() {
     return new Iterator<T>() {
       @Override
       public boolean hasNext() {
+        if (currentPage == null) {
+          return false;
+        }
         if (currentPage.hasNext()) {
           return true;
         }

databricks-sdk-java/src/test/java/com/databricks/sdk/integration/SqlIT.java

@@ -0,0 +1,28 @@
+package com.databricks.sdk.integration;
+
+import com.databricks.sdk.WorkspaceClient;
+import com.databricks.sdk.integration.framework.EnvContext;
+import com.databricks.sdk.integration.framework.EnvTest;
+import com.databricks.sdk.service.sql.ListQueryHistoryRequest;
+import com.databricks.sdk.service.sql.QueryFilter;
+import com.databricks.sdk.service.sql.QueryInfo;
+import com.databricks.sdk.service.sql.TimeRange;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.extension.ExtendWith;
+
+@EnvContext("workspace")
+@ExtendWith(EnvTest.class)
+public class SqlIT {
+  @Test
+  void listQueryHistory(WorkspaceClient w) {
+    TimeRange timeRange = new TimeRange()
+        .setStartTimeMs(1690243200000L)
+        .setEndTimeMs(1690329600000L);
+    ListQueryHistoryRequest request = new ListQueryHistoryRequest()
+        .setFilterBy(new QueryFilter().setQueryStartTimeRange(timeRange));
+    Iterable<QueryInfo> queries = w.queryHistory().list(request);
+    for (QueryInfo query : queries) {
+      System.out.println(query);
+    }
+  }
+}