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Comment: Published by Scroll Versions from space WDESIGNER and version 22.2a

You can use the MongoDB adapter to interact with a MongoDB and to insert, get and manipulate documents.

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Using one of the find operations from the MongoDB adapter, you can retrieve data. MongoDB stores data in form of documents that are depicted in a JSON-like format. Queries always return one or more complete documents.

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For all actions that refer to existing documents, you need to provide a query string (queryString) to identify them. A query string contains all properties of the document you want to use for selection.

Assume we have the following sample Customer document structure:

{
  "id": "ebd7c78b-44e0-4cbd-8164-d28431716942"
  "name": "John Snow",
  "company": "Winter & Partners",
  "address": {
    "street": "99, Malamute Street",
    "city": "Anchorage, AK 99506",
    "country:": "USA"
  },
  orderValue: "16323.00
}

The simplest way to create a query string is the following:

  1. Create an object having the structure of the document (Customer in the example).

    Code Block
    create queryData;

  2. Set all query values to this object (the customerID in the example).

    Code Block
    set queryData.id = customerID;

  3. Provide this object as queryString by converting it to JSON using classToExtendedJSON().

    Code Block
    set queryString = queryData.classToExtendedJSON();

The MongoDB adapter comes with three find operations: two returning the result set in different formats, one returning a handle to the result set.

Name

Type

Description

result

Array of String

An array of all resulting documents in JSON format.

The complete set of found documents in an array.

result

Array of <document class>

An array of objects of an xUML class representing the document structure.

Tip

This only makes sense if you know the structure of the documents you are accessing.

handle

MongoDBHandle

A handle to a result set.

This is helpful if

  • you expect a huge amount of documents being returned, and do not want to load the complete result set to the memory

  • you want to iterate over the result set one by one anyway, and e.g. only regard a subset of the result for further processing.

You need to process the result set one by one using fetch.

Refer to the reference of find operations and fetch operations for a detailed description of all parameters and options.

Selecting Output Data

MongoDB uses the concept of "projection" to define which properties should be selected from a document. The projection is supplied to the adapter call via the projection attribute of the MongoDBFindOptions.

The following rules apply to projections:

Rule

Example

You can select dedicated properties.

{ name: 1 }

You can select all properties and omit dedicated properties.

{ name: 0 }

You cannot mix both above mentioned rules. This will lead to an exception.

{ name: 1, company: 0 }

You can select properties from within a structure.

{ address.street: 1 }

You cannot select all properties and omit dedicated properties from within a structure. This will be ignored.

{ address.street: 0 }

Sorting

You can sort the document list you get back from an adapter call by providing the sort attribute of MongoDBFindOptions. Parameter sort contains the document properties to sort by. Value 1 is ascending sorting, value -1 is descending sorting. The order of JSON properties reflects the sort hierarchy.

Code Block
create options;
set options.`sort` = "{\"company\":1,\"orderVolume\":-1}";

You can also create a class defining the sort options, and use classToExtendedJSON() to create the sort string.

Info

You need to escape the attribute name of sort because there is an operation having the same name.

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