Examples

09 March 2013


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:

application description

component composition
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

and the following code shows how to obtain a reference and use an interface provided by the components within the application.

component referenceComponent 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.


component implementation
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.

component implementation 2
The constructor

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:

example-start

is the following:

[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.