public interface ClientDataIntegration
Smart GWT server.
This approach is called Client-Side Data Integration, which means:
create DataSourcesprogrammatically in Java (with
databinding-capable UI components, which can provide a variety of complete user interactions (form-based editing, grid-based editing, load on demand, ..) based on these 4 core operations
REST integration with RestDataSource (preferred)
RestDataSource provides a complete XML or JSON-based
protocol that supports all
of the features of Smart GWT's databinding layer (data paging, queuing/batching of
requests for transactions, nested AdvancedCriteria, server-side validation errors, automatic
cache synchronization, etc). To use the RestDataSource, simply write server code that can
parse RestDataSource requests and produce the required responses; example requests and
If you have pre-existing XML or JSON formats, Smart GWT DataSources can be configured to work with them. However, only use this approach if you are unable to modify a pre-existing protocol. If you have a choice, use RestDataSource.
In particular, if you are choosing between tools that can automatically generate a REST service from an API vs using the pre-built RestDataSource protocol, definitely use RestDataSource. Automatically generated REST interfaces will not handle the needs of a modern GUI, such as transactional/batched saves and user-ready validation error messages. For a deeper discussion, see this FAQ.
Specifically for pre-existing WSDL web services, see the discussion of WSDL Integration below instead.
To display XML or JSON from a pre-existing service in a visual component such as a ListGrid,
you bind the component to a
DataSource which provides the
URL of the service, as well as a
declaration of how to form inputs
to the service and how to interpret service responses as DataSource records.
An XPath expression, the
recordXPath, is applied to
the service response to select the XML elements or JSON objects that should be interpreted
as DataSource records. Then, for each field of the DataSource, an optional
be declared which selects the value for the field
from within each of the XML elements or JSON objects selected by the recordXPath. If no
valueXPath is specified, the field name itself is taken as an XPath, which will select the
same-named subelement or property from the record element or object.
For example, the following code defines a DataSource that a ListGrid could bind to in order to display an RSS 2.0 feed.
DataSource ds = new DataSource(); ds.setDataURL(feedURL); ds.setRecordXPath("//item"); DataSourceField titleField = new DataSourceField(); titleField.setName("title"); DataSourceField linkField = new DataSourceField(); linkField.setName("link"); DataSourceField descriptionField = new DataSourceField(); descriptionField.setName("description"); ds.setFields(titleField, linkField, descriptionField);A representative slice of an RSS 2.0 feed follows:
<?xml version="1.0" encoding="iso-8859-1" ?> <rss version="2.0"> <channel> <title>feed title</title> ... <item> <title>article title</title> <link>url of article</link> <description> article description </description> </item> <item> ...Here, the recordXPath selects a list of <item> elements. Since the intended values for each DataSource field appear as simple subelements of each <item> element (eg <description>), the field name is sufficient to select the correct values, and no explicit valueXPath needs to be specified.
A running version of this example is available here: RSS Feed Example. Further examples of simple XML or JSON data loading using files stored on disk as the "service" to contact: the Simple JSON example shows loading data from a JSON file into a databound grid, and the XPath Binding example shows loading XML and processing it with XPaths.
If you have a choice between WSDL and REST integration, we recommend REST integration - it's
simpler, requires less specialized knowledge, is easier to troubleshoot and is faster. If
you need to use WSDL, see the
For WSDL web services, see the
WSDL binding topic
When using RestDataSource, see the
RestDataSource docs for
message formats for
saving, as well as expected responses.
When a user triggers a DSRequest (eg, completes an inline edit in a grid), the request
data will be sent to the dataURL. The
describes request and response data expected for each operation type.
By using settings such as
OperationBinding.dataProtocol, you can control how
DSRequests are sent to your backend so that you can handle them most easily. By using the
same properties used to initially load data (eg
recordXPath), you can control
how Smart GWT forms the
DSResponses that are then interpreted by
Controlling how DSRequests are sent
According to the
being used, the
DataSource request data, if any, either
params (sent by GET or POST), or an XML message as put together by
DataSource.xmlSerialize(). For a
DataSource invoking a WSDL-described web
service, XML serialization automatically handles namespacing and SOAP encoding.
The URL to contact is set via the
property. If using a Web Service, the
dataURL defaults to the service location
URL embedded in the WSDL file.
primaryKeyfield of "id" with value "5" on the record to be updated
Forming a DSResponse from the response data
See the "Edit and Save" example for sample XML responses for all four operationTypes.
Similar to input processing, by default DataSource layer metadata, such as
DSResponse.startRow, is not extracted
from the response data. You can
DataSource.transformResponse() to fill out the metadata fields of
DSResponse, in order to allow more DataSource features,
such as paging and
validation errors, to be used with a web service that supports such features.