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General Object Retrieval API

Advanced search use-cases supported by Backendless include:

  • Search with a query (a "where clause" search) -retrieves data objects which satisfy a condition.
  • Paged data retrieval - retrieves a "page" of data of the given size from the specified offset.
  • Sorted data object retrieval - retrieves a collection of data objects sorted by specified properties.
  • Retrieval of related objects - fetching data objects through special "relation" properties. See retrieval of related data objects.
  • Calculating aggregate values for a collection of objects - retrieves sum, average, min, max or count for all or a subset of objects in a table. See Aggregate Functions for more details.

Backendless supports the options listed above with a special class - DataQueryBuilder. The class includes various properties to configure paging and sorting, specify a search query (the where clause), and/or to request retrieval of objects for specific related properties. The DataQueryBuilder class provides the following properties:

Argument                Description
whereClause sets a search query. A query must be in the SQL-92 syntax (the "where" clause part).
sortBy sets an array of column names to sort the data objects in the response by.
related sets an array of related columns names. Objects from the related columns are included into the response. For information about relation retrieval, see the Relations (Retrieve) chapter of the documentation.
relationsDepth sets the number of "levels" in the hierarchy of related objects to include into the response.
pageSize sets the page size - which is the number of objects to return in the response. Maximum value is 100. For more information on paging, see the Data retrieval with Paging section.
offset sets the offset - an index in the server-side storage from where the data objects should be retrieved.
groupBy Used with Aggregate Functions. Sets the name of the columns to group the results by.
havingClause Used with Aggregate Functions. Sets a condition on a aggregate function to filter groups.

Method Signature

Method:

Future<List<Map>> Backendless.data.of("TABLE-NAME").find([DataQueryBuilder queryBuilder]);
Future<List<E>> Backendless.data.withClass<E>().find([DataQueryBuilder queryBuilder]);

where:

Argument                Description
TABLE-NAME Name of the table to retrieve data from.
E Java class identifying the table to retrieve data from. The name of the class must match the name of the table.
queryBuilder an instance of DataQueryBuilder - contains the search query and other search options.

Return Value

The collection of strongly typed objects found as a result of the query execution.

Examples

For examples on using the advanced object retrieval API, see the following sub-sections: