servicefinder.java

来自「resetful样式的ws样例,一种面向资源的webservices服务」· Java 代码 · 共 689 行 · 第 1/3 页

     * @param loader The class loader to be used to load provider-configuration files
     *                and instantiate provider classes, or <tt>null</tt> if the system
     *                class loader (or, failing that the bootstrap class loader) is to
     *                be used
     * @param ignoreOnClassNotFound If a provider cannot be loaded by the class loader
     *                              then move on to the next available provider.
     * @param componentProvider the component provider responsible for instantiating
     *                          the provider implementation
     * @throws ServiceConfigurationError If a provider-configuration file violates the specified format
     *                                   or names a provider class that cannot be found and instantiated
     * @see #find(Class)
     * @return the service finder
     */
    public static <T> ServiceFinder<T> find(Class<T> service, 
            ClassLoader loader, 
            boolean ignoreOnClassNotFound,
            ComponentProvider componentProvider) throws ServiceConfigurationError {
        return new ServiceFinder<T>(service,
                loader,
                ignoreOnClassNotFound,
                componentProvider);
    }
    
    /**
     * Locates and incrementally instantiates the available providers of a
     * given service using the context class loader.  This convenience method
     * is equivalent to
     * <p/>
     * <pre>
     *   ClassLoader cl = Thread.currentThread().getContextClassLoader();
     *   return Service.providers(service, cl, false);
     * </pre>
     * @param service The service's abstract service class
     * @throws ServiceConfigurationError If a provider-configuration file violates the specified format
     *                                   or names a provider class that cannot be found and instantiated
     * @see #find(Class, ClassLoader)
     * @return the service finder
     */
    public static <T> ServiceFinder<T> find(Class<T> service) 
            throws ServiceConfigurationError {
        return find(service,
                Thread.currentThread().getContextClassLoader(), 
                false,
                DEFAULT_COMPONENT_PROVIDER);
    }
    
    /**
     * Locates and incrementally instantiates the available providers of a
     * given service using the context class loader.  This convenience method
     * is equivalent to
     * <p/>
     * <pre>
     *   ClassLoader cl = Thread.currentThread().getContextClassLoader();
     *   boolean ingore = ...
     *   return Service.providers(service, cl, ignore);
     * </pre>
     * @param service The service's abstract service class
     * @param ignoreOnClassNotFound If a provider cannot be loaded by the class loader
     *                              then move on to the next available provider.
     * @throws ServiceConfigurationError If a provider-configuration file violates the specified format
     *                                   or names a provider class that cannot be found and instantiated
     * @see #find(Class, ClassLoader)
     * @return the service finder
     */
    public static <T> ServiceFinder<T> find(Class<T> service, 
            boolean ignoreOnClassNotFound) throws ServiceConfigurationError {
        return find(service,
                Thread.currentThread().getContextClassLoader(), 
                ignoreOnClassNotFound,
                DEFAULT_COMPONENT_PROVIDER);
    }
    
    /**
     * Locates and incrementally instantiates the available providers of a
     * given service using the context class loader.  This convenience method
     * is equivalent to
     * <p/>
     * <pre>
     *   ClassLoader cl = Thread.currentThread().getContextClassLoader();
     *   boolean ingore = ...
     *   return Service.providers(service, cl, ignore);
     * </pre>
     * @param service The service's abstract service class
     * @param ignoreOnClassNotFound If a provider cannot be loaded by the class loader
     *                              then move on to the next available provider.
     * @param componentProvider the component provider responsible for instantiating
     *                          the provider implementation
     * @throws ServiceConfigurationError If a provider-configuration file violates the specified format
     *                                   or names a provider class that cannot be found and instantiated
     * @see #find(Class, ClassLoader)
     * @return the service finder
     */
    public static <T> ServiceFinder<T> find(Class<T> service, 
            boolean ignoreOnClassNotFound, ComponentProvider componentProvider) 
            throws ServiceConfigurationError {
        return find(service,
                Thread.currentThread().getContextClassLoader(), 
                ignoreOnClassNotFound,
                componentProvider);
    }
    
    private ServiceFinder(Class<T> service, ClassLoader loader, 
            boolean ignoreOnClassNotFound, ComponentProvider componentProvider) {
        this.serviceClass = service;
        this.classLoader = loader;
        this.ignoreOnClassNotFound = ignoreOnClassNotFound;
        this.componentProvider = componentProvider;
    }
    
    /**
     * Returns discovered objects incrementally.
     *
     * @return An <tt>Iterator</tt> that yields provider objects for the given
     *         service, in some arbitrary order.  The iterator will throw a
     *         <tt>ServiceConfigurationError</tt> if a provider-configuration
     *         file violates the specified format or if a provider class cannot
     *         be found and instantiated.
     */
    public Iterator<T> iterator() {
        return new LazyObjectIterator<T>(serviceClass,classLoader,
                ignoreOnClassNotFound, componentProvider);
    }
    
    /**
     * Returns discovered classes incrementally.
     *
     * @return An <tt>Iterator</tt> that yields provider classes for the given
     *         service, in some arbitrary order.  The iterator will throw a
     *         <tt>ServiceConfigurationError</tt> if a provider-configuration
     *         file violates the specified format or if a provider class cannot
     *         be found.
     */
    public Iterator<Class<T>> classIterator() {
        return new LazyClassIterator<T>(serviceClass,classLoader,
                ignoreOnClassNotFound, componentProvider);
    }
    
    /**
     * Returns discovered objects all at once.
     *
     * @return
     *      can be empty but never null.
     *
     * @throws ServiceConfigurationError If a provider-configuration file violates the specified format
     *                                   or names a provider class that cannot be found and instantiated
     */
    @SuppressWarnings("unchecked")
    public T[] toArray() throws ServiceConfigurationError {
        List<T> result = new ArrayList<T>();
        for (T t : this) {
            result.add(t);
        }
        return result.toArray((T[])Array.newInstance(serviceClass,result.size()));
    }
    
    /**
     * Returns discovered classes all at once.
     *
     * @return
     *      can be empty but never null.
     *
     * @throws ServiceConfigurationError If a provider-configuration file violates the specified format
     *                                   or names a provider class that cannot be found
     */
    @SuppressWarnings("unchecked")
    public Class<T>[] toClassArray() throws ServiceConfigurationError {
        List<Class<T>> result = new ArrayList<Class<T>>();
        
        Iterator<Class<T>> i = classIterator();
        while (i.hasNext())
            result.add(i.next());
        return result.toArray((Class<T>[])Array.newInstance(Class.class,result.size()));
    }
    
    private static void fail(Class service, String msg, Throwable cause)
    throws ServiceConfigurationError {
        ServiceConfigurationError sce
                = new ServiceConfigurationError(service.getName() + ": " + msg);
        sce.initCause(cause);
        throw sce;
    }
    
    private static void fail(Class service, String msg)
    throws ServiceConfigurationError {
        throw new ServiceConfigurationError(service.getName() + ": " + msg);
    }
    
    private static void fail(Class service, URL u, int line, String msg)
    throws ServiceConfigurationError {
        fail(service, u + ":" + line + ": " + msg);
    }
    
    /**
     * Parse a single line from the given configuration file, adding the name
     * on the line to both the names list and the returned set iff the name is
     * not already a member of the returned set.
     */
    private static int parseLine(Class service, URL u, BufferedReader r, int lc,
            List<String> names, Set<String> returned)
            throws IOException, ServiceConfigurationError {
        String ln = r.readLine();
        if (ln == null) {
            return -1;
        }
        int ci = ln.indexOf('#');
        if (ci >= 0) ln = ln.substring(0, ci);
        ln = ln.trim();
        int n = ln.length();
        if (n != 0) {
            if ((ln.indexOf(' ') >= 0) || (ln.indexOf('\t') >= 0))
                fail(service, u, lc, SpiMessages.ILLEGAL_CONFIG_SYNTAX());
            int cp = ln.codePointAt(0);
            if (!Character.isJavaIdentifierStart(cp))
                fail(service, u, lc, SpiMessages.ILLEGAL_PROVIDER_CLASS_NAME(ln));
            for (int i = Character.charCount(cp); i < n; i += Character.charCount(cp)) {
                cp = ln.codePointAt(i);
                if (!Character.isJavaIdentifierPart(cp) && (cp != '.'))
                    fail(service, u, lc, SpiMessages.ILLEGAL_PROVIDER_CLASS_NAME(ln));
            }
            if (!returned.contains(ln)) {
                names.add(ln);
                returned.add(ln);
            }
        }
        return lc + 1;
    }
    
    /**
     * Parse the content of the given URL as a provider-configuration file.
     *