public interface SpringIntegration
The Spring framework has many different parts, from integration with Object Relational Mapping (ORM) and transaction management systems, to a Model View Controller (MVC) architecture.
If you are building a new application from scratch and/or you are trying to
modernize the presentation layer of an existing application, most of Spring MVC is
inapplicable in the Smart GWT architecture.
Specifically,
Smart GWT renders all HTML on the client, and the server is responsible only for
retrieving data and enforcing business rules. This means that Spring's ModelAndView and all
functionality related to retrieving and rendering Views is unnecessary in Smart GWT.
Smart GWT only needs the Model, and provides methods to deliver that Model to Smart GWT
components (the server side method DSResponse.setData()).
However, Spring's DispatchServlet, Handler chain, and Controller architecture is applicable to Smart GWT. See "Using Spring Controllers" below.
Existing Spring Application
As discussed under the general server
integration
topic, integrating Smart GWT into your application involves finding a way to provide data
that fulfills the DataSource requests sent by Smart
GWT components.
There are 2 approaches for integrating Smart GWT into an existing Spring application:
DataSource requests to beans managed by
Spring, via
ServerObject.lookupStyle:"spring". Return data to the browser by either simply
returning it from your method, or via creating a DSResponse and calling DSResponse.setData()
(server-side method). Or, use a similar approach based on custom DataSource implementations
where the serverConstructor is of the pattern
"spring:{bean_name}"
This is the easiest method and produces the best result. A Collection of Java Beans, such
as EJB or Hibernate-managed beans, can be directly returned to Smart GWT as the result of
a DMI method, without the need to create an intervening
Data Transfer
Object to express
which fields should be delivered to the browser - instead, only the fields declared on the
DataSource are returned to the browser (see
dropExtraFields. In this
integration scenario, the
majority of the features of the Smart GWT Server framework still apply - see this
overview.
Note, there are special scoping considerations to bear in mind when using Spring-injected
DataSources or DMIs - see this
discussion of
caching and thread-safety issues.
RestDataSource provides a
standard "REST" XML or JSON-based protocol you can implement, or you can adapt generic
DataSources to existing formats.
In some Spring applications, all existing Spring workflows can be made callable by Smart GWT with a generic View class capable of serializing the Model to XML or JSON, combined with a Controller that always uses this View. Consider the following Java anonymous class, which uses the Smart GWT JSTranslater class to dump the entire Spring Model as a JSON response.
new View() {
public void render(Map model, HttpServletRequest request,
HttpServletResponse response) throws IOException {
final ServletOutputStream outputStream = response.getOutputStream();
response.setContentType("application/x-javascript");
outputStream.println(JSTranslater.get().toJS(model));
outputStream.close();
}
public String getContentType() {
return "application/x-javascript";
}
}
If you use this approach, you do not need to install the Smart GWT server, and can
deploy Smart GWT as simple web content (JS/media/HTML files). If you
are already familiar with how to generate XML from objects that typically appear in your
Spring Models, this may be the easiest path.
You can create a Controller that invokes standard Smart GWT server request processing, including DMI, like so:
public class SmartGWTRPCController extends AbstractController
{
public ModelAndView handleRequest(HttpServletRequest request,
HttpServletResponse response)
throws Exception
{
// invoke Smart GWT server standard request processing
com.isomorphic.rpc.RPCManager.processRequest(request, response);
return null; // avoid default rendering
}
}
This lets you use Spring's DispatchServlet, Handler chain and Controller architecture as a
pre- and post-processing model wrapped around Smart GWT DMI.
You can make DMI's participate in Spring's transaction management scheme by setting the
useSpringTransaction
flag on your DataSources or
operationBindings. This makes your DMI
method(s)
transactional, and ensures that any DSRequests and Spring DAO operations executed within
that DMI use the same Spring-managed transaction. See the documentation for
useSpringTransaction for more details.
In Power Edition and above, Smart GWT Server has its own transaction management system.
This allows you to send queues of
DSRequests to the server, and the entire queue will
be treated as a
single database transaction. This is not the same thing as Spring transaction
integration: Smart GWT's built-in transaction management works across an entire queue of
DSRequests, whereas Spring transactions are specific to a Java method that has been marked
@Transactional - the transaction starts and ends when the method starts and
ends.
It is possible to have an entire Smart GWT queue - including any
@Transactional
DMIs that contain both Spring DAO operations and DSRequests - use the same Spring-managed
transaction. To do this:
@Transactional method like this
(note, the isolation level can vary as you please, but the propagation type must be REQUIRED
to enable proper sharing of the transaction):
@Transactional(isolation=Isolation.READ_COMMITTED, propagation=Propagation.REQUIRED)
public class MyServiceBean {
public void processQueue(HttpServletRequest req, HttpServletResponse resp)
throws Exception
{
// invoke Smart GWT server standard request processing
public void processQueue(RPCManager rpc) throws Exception {
rpc.processRPCTransaction();
}
}
}com.isomorphic.servlet.IDACall servlet and
override its processRPCTransaction method to inject the service bean you just
created and invoke its transactional method. You will also have to change your
web.xml file to point at this new servlet rather than IDACallhandleRequest() implementation
inject your service bean and invoke its transactional method, as described for the
IDACall subclass