Getting Started with RequestFactory - Google Web Toolkit - Google Code - 0 views
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Entity Proxies
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anonymous on 10 Jan 11Proxy type (on the Client) vs Entity type (on the server)
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proxy types
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entity types
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methods that return service stubs
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one RequestFactory interface for your application
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employeeRequest();
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@Service(Employee.class)
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extends RequestContext
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extends RequestFactory
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service stub
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RequestFactory service stubs
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must extend RequestContext
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The methods in a service stub do not return entities directly
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return subclasses of com.google.gwt.requestfactory.shared.Request.
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This allows the methods on the interface to be invoked asynchronously with
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Request.fire()
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fire( new Receiver()
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onSuccess
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callers pass an AsyncCallback that implements onSuccess()
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takes a Receiver which must implement onSuccess()
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Receiver is an abstract class having a default implementation of onFailure()
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you can extend Receiver and override onFailure()
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onViolation()
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any constraint violations on the server
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The Request type returned from each method
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parameterized with the return type of the service method.
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Methods that have no return value should return type Request<Void>
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BigDecimal, BigInteger, Boolean, Byte, Enum, Character, Date, Double, Float, Integer, Long, Short, String, Void
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subclass of EntityProxy
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List<T> or Set<T>
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primitive types are not supported
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methods that operate on an entity itself
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like persist() and remove()
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return objects of type InstanceRequest rather than Reques
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Server Implementations
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methods defined in an
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entity's service interface
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implemented in the class named
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@Service annotation
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in these examples, is the entity class
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service implementations do not directly implement the RequestContext interface
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server-side implementations use the domain entity types
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@Entity
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EntityManager
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createQuery
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getResultList();
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entityManager()
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createEntityManager()
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em.persist(this);
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em.remove(attached
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em.close();
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defined in the service's
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RequestContext interface
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even though the implementation does not formally implement the interface in Java
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name and argument list for each method
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same on client and server
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Client side methods
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return Request<T>
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only T on the server
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EntityProxy types become the domain entity type on the server
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Methods that return a Request object in the client interface are implemented as static methods on the entity
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Methods that operate on a single instance of an entity, like persist() and remove(),
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eturn an
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InstanceRequest
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in the client interface
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Instance methods do not pass the instance directly, but rather via the
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using()
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instance methods must be implemented as non-static methods in the entity type
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Four special methods are required on all entities
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as they are used by the RequestFactory servlet:
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constructor
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findEntity
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An entity's getId()
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is typically auto-generated by the persistence engine (JDO, JPA, Objectify, etc.)
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"find by ID" method has a special naming convention
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find()
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"find" plus the type's simple name
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On the server
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getVersion() method is used by RequestFactory to infer if an entity has changed
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backing store (JDO, JPA, etc.) is responsible for updating the version each time the object is persisted,
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RequestFactoryServlet sends an UPDATE
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if an entity changes as
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Second, the client maintains a version cache of recently seen entities
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Whenever it sees an entity whose version has changed, it fires
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UPDATE events on the event bus
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so that listeners can update the view
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GWT.create
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and initialize it with your application's EventBus
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GWT.create
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requestFactory.initialize
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create a new entity on the client
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EmployeeRequest request
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EmployeeProxy newEmployee
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All client-side code should use the EmployeeProxy
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not the Employee entity itself
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unlike GWT-RPC, where the same concrete type is used on both client and server
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RequestFactory
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designed to be used with an ORM layer like JDO or JPA
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on the server
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to build data-oriented (CRUD) apps with an ORM-like interface
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on the client
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easy to implement a data access layer
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structure your server-side code in a data-centric way
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GWT-RPC, which is service-oriented
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On the client side, RequestFactory keeps track of objects that have been modified and sends only changes
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lightweight network payloads
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solid foundation for automatic batching and caching of requests in the future
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RequestFactoryServlet
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RequestFactory uses its own servlet
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own protocol
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not designed for general purpose services like GWT-RPC
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implements its
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It is designed specifically for implementing a persistence layer on both client and server.
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In persistence frameworks like JDO and JPA, entities are annotated with
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client-side representation of an entity
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known as a
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DTO (Data Transfer Object)
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hook used to indicate that an object can be managed by RequestFactory
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RequestFactory
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EntityProxy interface
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automatically populates bean-style properties between entities on the server and the corresponding EntityProxy on the client,
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send only changes ("deltas") to the server
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extends EntityProxy
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interface
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@ProxyFor
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reference the server-side entity being represented
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It is not necessary to represent every property and method from the server-side entity in the EntityProxy
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EntityProxyId returned by this method is used throughout RequestFactory-related classes
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while getId() is shown in this example, most client code will want to refer to
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EntityProxy.stableId() i
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to represent any type
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is not required to expose an ID and version
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often used to represent embedded object types within entities
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@Embedded
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Address
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Address type
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POJO with no persistence annotations
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Address is represented as a ValueProxy
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extends ValueProxy
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interface
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extends EntityProxy
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interface
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AddressProxy
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AddressProxy
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ValueProxy can be used to pass any type to and from the server
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RequestFactory
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interface between your client and server code
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RequestContext interface
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The server-side service
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must implement each method
