componentprovider.java

来自「resetful样式的ws样例,一种面向资源的webservices服务」· Java 代码 · 共 173 行

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 *
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package com.sun.jersey.spi.service;

import java.lang.reflect.Constructor;
import java.lang.reflect.InvocationTargetException;

/**
 * A provider for the instantiation and management of components.
 * <p>
 * The runtime will defer to a registered component provider (if present)
 * for every component (application-defined or infrastructure-defined) that
 * needs to be instantiated. If the component provider does
 * not support the requested component it should return a null value and the
 * runtime will attempt to directly instantiate and manage the component.
 * <p>
 * A {@link ComponentProvider} instance may be registed by passing the 
 * instance to the 
 * {@link com.sun.jersey.spi.container.WebApplication#initiate(com.sun.jersey.api.core.ResourceConfig, ComponentProvider)}
 * method.
 * <p>
 * Applications may extend the {@link com.sun.jersey.spi.container.servlet.ServletContainer}
 * and override the method {@link com.sun.jersey.spi.container.servlet.ServletContainer#initiate(ResourceConfig, WebApplication)}
 * to initiate the {@link com.sun.jersey.spi.container.WebApplication} with the {@link ComponentProvider} instance.
 * 
 * @see com.sun.jersey.spi.container.WebApplication
 * @see com.sun.jersey.spi.container.servlet.ServletContainer
 * @author [e-mail]
 */
public interface ComponentProvider {
    /**
     * The scope contract for the instantiation of a component.
     */
    public enum Scope {
        /**
         * Declares that only one instance of a component shall exist 
         * per-web application instance. The runtime will manage the component
         * in the scope of the web application.
         */
        Singleton,
        
        /**
         * Declares that the scope is application defined and instances will 
         * be managed by the runtime according to this scope. This requires 
         * that a new instance be created for each invocation of 
         * <code>getInstance</code>.
         */
        PerRequest,
        
        /**
         * The JAX-RS application (jersey) does not care what the scope is,
         * the component provider can decide which to choose - the component
         * provider is responsible for managing instances of a type.
         */
        Undefined    
    }
    
    /**
     * Get the instance of a class. Injection will be performed on the
     * instance.
     * 
     * @param scope the scope of the instance
     * @param c the class
     * @return the instance, or null if the component cannot be instantaited
     *         and managed.
     * 
     * @throws java.lang.InstantiationException
     * @throws java.lang.IllegalAccessException
     */
    <T> T getInstance(Scope scope, Class<T> c) 
            throws InstantiationException, IllegalAccessException;
    
    /**
     * Get the instance of a class using a constructor and a corresponding
     * array of parameter values. Injection will be performed on the instance.
     * <p>
     * The array of parameter values must be the same length as that required
     * by the constructor. Some parameter values may be null, indicating that
     * the values are not set and must be set by the component provider before
     * construction occurs.
     * 
     * @param scope the scope of the instance
     * @param contructor the constructor to instantiate the class
     * @param parameters the array parameter values passed to the constructor
     * @return the instance, or null if the component cannot be instantaited
     *         and managed.
     * 
     * @throws java.lang.InstantiationException
     * @throws java.lang.IllegalArgumentException 
     * @throws java.lang.IllegalAccessException
     * @throws java.lang.reflect.InvocationTargetException
     */
    <T> T getInstance(Scope scope, Constructor<T> contructor, Object[] parameters) 
            throws InstantiationException, IllegalArgumentException, 
            IllegalAccessException, InvocationTargetException;

    /**
     * Get the instance of a class. Injection will be performed on the
     * instance. Additional context is provided that may be used to determine
     * the instance to return.
     * <p>
     * Implementations wishing to ignore the component context may defer 
     * to the implemented method {@link #getInstance(Scope, Class<T>).
     * 
     * @param cc the component context
     * @param scope the scope of the instance
     * @param c the class
     * @return the instance, or null if the component cannot be instantaited
     *         and managed.
     * 
     * @throws java.lang.InstantiationException
     * @throws java.lang.IllegalAccessException
     */
    <T> T getInstance(ComponentContext cc, Scope scope, Class<T> c) 
            throws InstantiationException, IllegalAccessException;
    
    /**
     * Get the injectable instance to inject JAX-RS and Jersey specific
     * instances on to fields.
     * <p>
     * If the injectable instance is the same as the instance that was passed in
     * then the provider MUST return that instance.
     * 
     * @param instance the instance returned by one of the getInstance methods.
     * @return the injectable instance.
     */
    <T> T getInjectableInstance(T instance);
    
    /**
     * Perform injection on an instance. This may be used when a
     * component is instantiated by means other than the component
     * provider.
     * 
     * @param instance the instance to perform injection on.
     */
    void inject(Object instance);
}