Examples
09 March 2013
More examples are available in the documentation and the JLCF distribution.
More examples are available in the documentation and the JLCF distribution.
Creating a simple modular application with 2 components
The definition and composition of the
components that form an application is done in the Application
Description file. This is an xml file which defines all components
and their interconnections.
Typically a user of the framework will define an Application Description file, implement the components and will then instantiate and interact with the component composition through the API that the framework provides.
A simple example of an Application Description below:
The application description defines 2 components, compA, which is
implemented by the ComponentA class and compB which is implemented
by the ComponentB class. compA has a receptacle pointing at an
interface provided by compB and also provides another interface
that is not used by any other component, but can be used by a user
of the framework.
The following code instantiates the application
Component
Implementation
So far we have seen hoe to define a simple application description and how to instantiate the framework, but not how to implement components.
The component implementation class must implement (at least) all formal interfaces that the component offers.
Below is the implementation of compB and its interface.
aThe component implementation follows a POJO approach with annotations. The @InitMethod (one of the annotations of the framework) instructs the JLCF framework to call this method after instantiating the object.
The implementation of compA, is more interesting as the component defines a Receptacle and a Property.
The constructor
must define which fields are of type Property and a Receptacle and their respective names. The constructor must not contain other arguments besides Receptacles and Properties as the framework will not be able to instantiate an instance of the component.
The output of the example:
[main] INFO org.jlcf.core.JLCFContainer - JLCF container instance initialized
[AbstractQueueProcessorThread :JLCFContainerProcessor] INFO org.jlcf.core.util.AbstractQueueProcessorThread - org.jlcf.core.util.AbstractQueueProcessorThread thread started.
[AbstractQueueProcessorThread :JLCFContainerProcessor] INFO org.jlcf.core.JLCFFrameworkUtilities - component:compA instantiated
[AbstractQueueProcessorThread :JLCFContainerProcessor] INFO org.jlcf.core.JLCFFrameworkUtilities - component:compB instantiated
[AbstractQueueProcessorThread :JLCFContainerProcessor] INFO org.jlcf.core.JLCFContainerProcessor - connecting compA / compoB -> compB/compbintf
[AbstractQueueProcessorThread :JLCFContainerProcessor] INFO ComponentA - component ComponentA version:1.01 initialized
[AbstractQueueProcessorThread :JLCFContainerProcessor] INFO ComponentB - Init method called
[main] INFO ComponentA - doTask called. Calling component B with input=HellO
[main] INFO ComponentB - method called, with input :HellO
[main] INFO ComponentA - received reply from component B :HELLO
[main] INFO ComponentA - doTask called. Calling component B with input=HellO
[main] INFO ComponentB - method called, with input :HellO
[main] INFO ComponentA - received reply from component B :HELLO
[main] INFO ComponentA - doTask called. Calling component B with input=HellO
[main] INFO ComponentB - method called, with input :HellO
[main] INFO ComponentA - received reply from component B :HELLO
[main] INFO ComponentA - doTask called. Calling component B with input=HellO
[main] INFO ComponentB - method called, with input :HellO
[main] INFO ComponentA - received reply from component B :HELLO
The framework also supports powerful concepts such as interceptors, callbacks and the ability to dynamically replace a component implementation at runtime. See the examples of the JLCF distribution and the documentation for more details.
Typically a user of the framework will define an Application Description file, implement the components and will then instantiate and interact with the component composition through the API that the framework provides.
A simple example of an Application Description below:
The following code instantiates the application
and the following code shows how to obtain a reference and use an interface provided by the components within the application.
Component
ImplementationSo far we have seen hoe to define a simple application description and how to instantiate the framework, but not how to implement components.
The component implementation class must implement (at least) all formal interfaces that the component offers.
Below is the implementation of compB and its interface.
aThe component implementation follows a POJO approach with annotations. The @InitMethod (one of the annotations of the framework) instructs the JLCF framework to call this method after instantiating the object.
The implementation of compA, is more interesting as the component defines a Receptacle and a Property.
The constructor
must define which fields are of type Property and a Receptacle and their respective names. The constructor must not contain other arguments besides Receptacles and Properties as the framework will not be able to instantiate an instance of the component.
The output of the example:
[main] INFO org.jlcf.core.JLCFContainer - JLCF container instance initialized
[AbstractQueueProcessorThread :JLCFContainerProcessor] INFO org.jlcf.core.util.AbstractQueueProcessorThread - org.jlcf.core.util.AbstractQueueProcessorThread thread started.
[AbstractQueueProcessorThread :JLCFContainerProcessor] INFO org.jlcf.core.JLCFFrameworkUtilities - component:compA instantiated
[AbstractQueueProcessorThread :JLCFContainerProcessor] INFO org.jlcf.core.JLCFFrameworkUtilities - component:compB instantiated
[AbstractQueueProcessorThread :JLCFContainerProcessor] INFO org.jlcf.core.JLCFContainerProcessor - connecting compA / compoB -> compB/compbintf
[AbstractQueueProcessorThread :JLCFContainerProcessor] INFO ComponentA - component ComponentA version:1.01 initialized
[AbstractQueueProcessorThread :JLCFContainerProcessor] INFO ComponentB - Init method called
[main] INFO ComponentA - doTask called. Calling component B with input=HellO
[main] INFO ComponentB - method called, with input :HellO
[main] INFO ComponentA - received reply from component B :HELLO
[main] INFO ComponentA - doTask called. Calling component B with input=HellO
[main] INFO ComponentB - method called, with input :HellO
[main] INFO ComponentA - received reply from component B :HELLO
[main] INFO ComponentA - doTask called. Calling component B with input=HellO
[main] INFO ComponentB - method called, with input :HellO
[main] INFO ComponentA - received reply from component B :HELLO
[main] INFO ComponentA - doTask called. Calling component B with input=HellO
[main] INFO ComponentB - method called, with input :HellO
[main] INFO ComponentA - received reply from component B :HELLO
The framework also supports powerful concepts such as interceptors, callbacks and the ability to dynamically replace a component implementation at runtime. See the examples of the JLCF distribution and the documentation for more details.