Package org.apache.avalon.framework.component

Deprecated: use the interfaces in the org.apache.avalon.framework.service package instead.

See:
Description

Interface Summary

Component	This interface identifies classes that can be used as Components by a Composable.
ComponentManager	A ComponentManager selects Components based on a role.
ComponentSelector	A ComponentSelector selects Components based on a hint.
Composable	A Composable class is one that needs to connect to software components using a "role" abstraction, thus not depending on particular implementations but on behavioral interfaces.
Recomposable	Deprecated. Deprecated with no replacement.

Class Summary

DefaultComponentManager	This class is a static implementation of a ComponentManager.
DefaultComponentSelector	This is the default implementation of the ComponentSelector.
WrapperComponentManager	This is a ComponentManager implementation that can wrap around a ServiceManager object effectively adapting a ServiceManager interface to a ComponentManager interface.
WrapperComponentSelector	This is a ServiceSelector implementation that can wrap around a legacy ComponentSelector object effectively adapting a ComponentSelector interface to a ServiceSelector interface.

Exception Summary

ComponentException

The exception thrown to indicate a problem with Components.

Package org.apache.avalon.framework.component Description

Deprecated: use the interfaces in the org.apache.avalon.framework.service package instead. Interfaces and implementation of the component management services supporting container based management of componet lookup and decommissioning.

Migration from This Package

The Avalon team has determined that the best way to remove the need for this package in projects that existed before the team deprecated the package is to use a dynamic proxy. There are two ways of defining a dynamic proxy: using JDK 1.3's dynamic proxy generation code, and using BCEL to write a special purpose proxy.

All the Avalon containers now employ this technique so that you can confidently remove all deprecation warnings from your code by removing the Component interface.

The code snippet below describes how to use JDK 1.3 to create a dynamic proxy at runtime. The method getProxy is where the proxy is actually created. The class ComponentInvocationHandler takes care of handling the method calls.

    /**
     * Get the Component wrapped in the proxy.  The role must be the service
     * interface's fully qualified classname to work.
     */
    public Component getProxy( String role, Object service ) throws Exception
    {
        Class serviceInterface = m_classLoader.loadClass( role );

        return (Component)Proxy.newProxyInstance( m_classLoader,
                                                  new Class[]{Component.class, serviceInterface},
                                                  new ComponentInvocationHandler( service ) );
    }

    /**
     * Internal class to handle the wrapping with Component
     */
    private final static class ComponentInvocationHandler
        implements InvocationHandler
    {
        private final Object m_delagate;

        public ComponentInvocationHandler( final Object delegate )
        {
            if( null == delegate )
            {
                throw new NullPointerException( "delegate" );
            }

            m_delagate = delegate;
        }

        public Object invoke( final Object proxy,
                              final Method meth,
                              final Object[] args )
            throws Throwable
        {
            try
            {
                return meth.invoke( m_delagate, args );
            }
            catch( final InvocationTargetException ite )
            {
                throw ite.getTargetException();
            }
        }
    }