MentaContainer

package org.mentacontainer;

/**
 * A very simple container that provides:
 * <ul>
 *   <li> Bean instantiation (duh!)</li>
 *   <li> Constructor injection for bean setup</li>
 *   <li> Setter injection for bean setup</li>
 *   <li> Wiring based on name and type</li>
 *   <li> Scopes: Singleton and ThreadLocal</li>
 *   <li> Wiring of external beans with the beans configured in this container</li>
 *   <li> Annotation and XML free (programmatic configuration is the way to go!)
 * </ul>
 *
 * It does not get much simpler than that.
 *
 * @author sergio.oliveira.jr@gmail.com
 *
 */
public interface Container {
       
        /**
         * Get an instance from the container.
         *
         * The instance will be fully initialized (constructor and/or setters) and fully wired.
         *
         * @param key The key representing the bean to return. The name of the bean in the container.
         * @return The fully initialized and wired bean.
         */
        public <T> T get(String key);
       
        public Class<? extends Object> getType(String key);
       
        /**
         * Configure a bean to be returned with the given implementation when {@link #get(String)} is called.
         *
         * @param key The key representing the bean to return. The name of the bean in the container.
         * @param klass The class used to instantiate the bean, in other words, its implementation.
         * @param scope The scope of the component.
         * @return The component created as a ConfigurableComponent. (Fluent API)
         * @see Scope
         */
        public ConfigurableFactory ioc(String key, Class<? extends Object> klass, Scope scope);
       
        /**
         * Same as {@link #ioc(String, Class, Scope)} except that it assumes
         * there is no scope (Scope.NONE).
         *
         * @param key
         * @param klass
         * @return The component created as a ConfigurableComponent. (Fluent API)
         * @see Scope
         */
        public ConfigurableFactory ioc(String key, Class<?extends Object> klass);
       
        /**
         * Set up IoC based on the component passed. The scope assumed is NONE.
         *
         * @param key The key representing the bean to return. The name of the bean in the container.
         * @param component The component for the IoC.
         * @return The component passed as a parameter.
         * @see Factory
         */
        public Factory ioc(String key, Factory component);
       
        /**
         * Set up IoC based on the component passed. Specify the scope of the component.
         *
         * @param key The key representing the bean to return. The name of the bean in the container.
         * @param component The component for the IoC.
         * @param scope The scope used by the component.
         * @return The component passed as a parameter.
         * @see Factory
         * @see Scope
         */
        public Factory ioc(String key, Factory component, Scope scope);
       
        /**
         * Configure a bean dependency to be auto-wired by the container. In general you want the
         * type of the dependency to be an interface, for loosely couple dependencies. It works like that:<br/><br/>
         *
         * Whenever the container returns a bean, it checks to see if it has a property named <i>property</i>
         * and if the type of the property is <i>klass</i>. If it does, then it looks for a bean named
         * <i>source</i> and injects it inside the first bean it is returning. This approach is recursive
         * so all properties are checked up the class hierarchy, until it reaches Object.
         *
         * @param property a bean property that will require another bean, in other words, the required
         *                                 bean will be injected in the property of the bean been requested from the container. (auto-wiring by name)
         * @param klass the type of the dependency, in other words, the type of the auto-wiring. (auto-wiring by type)
         * @param source The dependency itself, coming from the container as well, in other words, the bean that will be injected in the original bean
         * @return The container itself. (Fluent API)
         */
        public Dependency wire(String property, Class<? extends Object> klass, String source);
       
        /**
         * Same as {@link #wire(String, Class, String)} except that it assumes that the property name will be the source name, in other words,
         * the property name is the same as the bean name that will be injected as the dependency.
         *
         * @param property
         * @param klass
         * @return The container itself. (Fluent API)
         */
        public Dependency wire(String property, Class<? extends Object> klass);
       
        /**
         * Setup a dependency.
         *
         * @param dependency The dependency to setup
         * @return The dependency itself. (Fluent API)
         * @see Dependency
         */
        public Dependency wire(Dependency dependency);
       
        /**
         * Take a given bean and populate its properties with other beans coming from this container. Perhaps you can call this auto-wiring.
         * You basically checking properties of the given bean and looking for values (by name and type!) inside the container. And injecting
         * in the given bean, in other words, populating it.
         *
         * @param bean The bean to be populated with other beans from the container.
         * @return The container itself. (Fluent API)
         */
        public Container populate(Object bean);
       
        /**
         * Check whether the container currently has a value for this key. For example,
         * if it is a singleton AND someone has requested it, the container will have it cached.
         * The method is useful to check for an instance without forcing her creation.
         *
         * @param key The key representing the bean inside the container.
         * @return true if the container has an instance cached in the scope for this key
         */
        public boolean check(String key);
       
        /**
         * Clear all cached instances for that scope. If you have a thread-pool for example you will
         * want to clear the THREAD scope when your thread is returned to the pool. Because you have a thread
         * pool you will have the SAME thread handling different requests and each request will need its own instances
         * from the container. Therefore, each time you are done with a thread and it is returned to your thread-pool
         * you can call clear to release the instances allocated and cached by the container. A web container and/or framework
         * can use this feature to implement a REQUEST scope which is nothing more than the THREAD scope with clear. If the web
         * container was not using a thread-pool, the THREAD scope would be equal to the REQUEST scope as each request would
         * always be handled by a different thread.
         *  
         * It does not make sense to clear a NONE scope (the method returns doing nothing). You can clear a SINGLETON scope if necessary.
         *
         * @param scope The scope to be cleared.
         */
        public void clear(Scope scope);
       
        /**
         * Clear a single key from cache and return the instance that was cached.
         *
         * @param key The key representing the bean inside the container.
         * @return The value that was cached and it is not anymore (was cleared) or null if nothing was cleared
         */
        public <T> T clear(String key);
}