The following information is an overview of Service Oriented
Architecture built into Leap,
and describes how to expose a service to Leap.
The
Leap has
an extensible services architecture which allows
Leap applications
to send and receive data from any external system. The Services Architecture
consists of the following components:
- Service Transports – The Service
Transport is the Java™ code responsible
for communicating with an external service, such as a public REST
service. It can send data out to the external service or receive data
from the external service. The transport also uses JDBC to store
and retrieve data from any database. Alternatively, the transport
can simply implement a “service” itself, such as a unit conversion
library. You can add any custom transport installation to the Leap installation
by placing an appropriate JAR file in a specific directory on the Leap server;
however, Leap already
includes a generic HTTP transport which can send and receive data
over the internet or intranet, and will suffice for many use cases.
For more information, see Service Description.
- Service Descriptions – The Service
Description provides the interface for a Service Transport. A Service
Description is usually described by an XML file, although it is also
possible to programmatically create a Service Description. The Service
Description specifies a service's name, description, input parameters,
and output parameters. These attributes are what appear to the application
designer when they are hooking up services to a Leap application.
- Data Mapping – Each service description
can contain an optional “mapping” component which describes how
the data coming from the Service Transport can be mapped to the outputs
defined in the Service Description, or vice versa. The advantage
of the mapping component is that it allows multiple Service Descriptions,
each with its own name, description, input, and outputs to use to
use the same generic transport. By using XPath-like references, the
mapping component supports the mapping of complex data structures
such as an XML document. The mapping of constant values is also supported.
- Service Configuration – The Service
Configuration is another layer of mapping meant for application designers.
It maps items in the form to the inputs and outputs of the Service
Description. The application designer is responsible for creating
service configurations and connecting form items to the service inputs
and outputs. Service configurations are stored inside the application.
Supporting documents
Use the following documents
to gain a better understanding of the steps required to expose a service
to Leap.
Understanding
the HTTP transport – The HTTP Service Transport
provides a mechanism to communicate with HTTP servers. The transport
allows configuration of the URL to request, HTTP method to use, query
parameters, and request headers. When combined with the service mapping
engine of Leap,
the HTTP Service Transport can extract data from an HTTP response
and make it available to your application. The HTTP Service Transport
can be used to communicate with any standard HTTP server. While there
are some limits on the capabilities of the HTTP Service Transport,
it is all that is needed to communicate with a basic HTTP server,
or RESTful service, in most cases. For more information, see HTTP Service Transport
Creating
and deploying service descriptions – The Service
Description provides an interface to Leap mapping
interface, and an interface to a Service Transport. For more information
on creating Service Descriptions, see Service Description