4.5.3.2.3. Query Filter

A data source query can be modified during the work of the application, depending on conditions entered by the user. This allows you to efficiently filter data at the level of selection from DB.

The easiest way to provide such ability is to connect a special visual component, Filter, to a data source.

If by any reason the use of a universal filter is unwanted, a special XML markup can be embedded into a query text. This will allow to create a resulting query based on values entered by the user into any visual components of the screen.

In this filter the following elements can be used:

  • filter – a root element of the filter. It can directly contain only one condition.

    • and, or – logical conditions, may contain any number of other conditions and statements.

    • c – JPQL statement, which is added into the where section. It contains only the text and an optional join attribute, which value will be added into a corresponding place of the query.

Conditions and statements are added into the resulting query only if parameters inside contain values, i.e., they are not null.

Example: 

<query>
    select distinct d from app$GeneralDoc d
    <filter>
        <or>
            <and>
                <c join=", app$DocRole dr">dr.doc.id = d.id and d.processState = :custom$state</c>
                <c>d.barCode like :component$barCodeFilterField</c>
            </and>
            <c join=", app$DocRole dr">dr.doc.id = d.id and dr.user.id = :custom$initiator</c>
        </or>
    </filter>
</query>

In this case, if state and initiator parameters are passed into the refresh() method of a data source, and a visual component, barCodeFilterField, has some value specified, then the resulting query will be as follows: 

select distinct d from app$GeneralDoc d, app$DocRole dr
where
(
  (dr.doc.id = d.id and d.processState = :custom$state)
  and
  (d.barCode like :component$barCodeFilterField)
)
or
(dr.doc.id = d.id and dr.user.id = :custom$initiator)

If, for example, the barCodeFilterField component is empty and only one parameter, initiator, was passed into the refresh() method, the query will be as follows: 

select distinct d from app$GeneralDoc d, app$DocRole dr
where
(dr.doc.id = d.id and dr.user.id = :custom$initiator)

Do not use ds-parameters in query filters. They are intended for linking datasources and treated in a special way.

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