Using everest applications

Querying with GET

One of the main features of the collection resources in everest are their advanced querying capabilities. Query strings have to conform to

An incoming query through a GET request is processed by everest in two steps: First, the query string submitted by the client is parsed into a query specification; and second, this query specification is translated to an object that can be applied to the collection resource acting as the query context.

Collection Query Language (CQL)

everest supports a custom Collection Query Language (CQL) for querying collection resources.

CQL query expressions are composed of one or more query criteria separated by the tilde (“~”) character. Each criterion consists of three parts separated by a colon (”:”) character :

1. resource attribute name The name of the resource attribute to query. You can specify dotted names to query nested resources.
2. operator The operator to apply.
3. value The value to query for. It is possible to supply multiple values in a comma separated list, which will be interpreted as a Boolean “OR” operation on all given values.

Supported query criterion value types are:

String

Arbitrary string enclosed in double quotes.

Number

Integer or floating point, scientific notation allowed.

Boolean

Case insensitive string true or false.

Date/Time

ISO 8601 encoded string enclosed in double quotes.

Resource

URL referencing a resource.

As an example, querying a collection resource “”

If a query contains multiple criteria with different resource attribute names, the criteria are interpreted as a Boolean “AND” operation.

The following table shows the available operators and data types in CQL:

Operator	Data Type
Name	String	Number	Boolean	Date/Time	Resource
starts-with	x
not-starts-with	x
ends-with	x
not-ends-with	x
contains	x
not-contains	x
contained	x
not-contained	x
equal-to
not-equal-to
less-than
less-than-or-equal-to
greater-than
greater-than-or-equal-to
in-range

All attributes that are used to compose a query expression need to be mapped column properties in the ORM. Aliases are supported, CompositeProperties are not. All queried entities must have an “id” attribute.

It is by design that the power of CQL to express complex queries is far behind that of SQL.