The language of the contract is a
Java interface. The syntax
of the interface is defined by the Java interface and the semantics
are defined by the comments. Service contracts should have meaningful
names, be well document, and be short / simple.
There are two types of service contracts developers can define:
1. Asynchronous Service Contracts
Used for non-blocking one-way communication.
- Each method must throw RemoteException.
- Have none, primitive, or object parameters that are serializable
or remote object references.
- Have no return values.
A example is the HelloWorldServiceAsyn interface we viewed
in the Getting Started trail:
2. Synchronous Service Contracts
Synchronous interfaces are used for blocking two-way communication.
- Each method must throw RemoteException
- Have none, primitive, or object parameters that are serializable
or remote object references.
- Return none, primitive, or object parameters that are serializable
or remote object references.
A example is the HelloWorldServiceSyn interface we viewed
in the Getting Started trail:
The user may want to define attributes associated with their
services. Attributes are objects that have all public objects.
This allows matching to be done by filling in the parameters.
We discuss attributes in more detail in the
ComponentComplex Interface discussion of this trail. For
now, understand there can exist an association between services
and their attributes. This is how we can specify a desired behavior.
To establish multiple connections between components, distributed
objectes are typically passed in the context of another connection. This
is the technique used to establish bi-directional synchronous and
asynchronous communications in Openwings.
Next: Defining
Components
