| /* |
| * Licensed to the Apache Software Foundation (ASF) under one or more |
| * contributor license agreements. See the NOTICE file distributed with |
| * this work for additional information regarding copyright ownership. |
| * The ASF licenses this file to You under the Apache License, Version 2.0 |
| * (the "License"); you may not use this file except in compliance with |
| * the License. You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| */ |
| package org.apache.commons.configuration2.builder; |
| |
| import java.util.Collection; |
| import java.util.concurrent.CopyOnWriteArrayList; |
| |
| /** |
| * <p> |
| * A class for managing a set of {@link DefaultParametersHandler} objects. |
| * </p> |
| * <p> |
| * This class provides functionality for registering and removing {@code DefaultParametersHandler} objects for arbitrary |
| * parameters classes. The handlers registered at an instance can then be applied on a passed in parameters object, so |
| * that it gets initialized with the provided default values. |
| * </p> |
| * <p> |
| * Usage of this class is as follows: First the {@code DefaultParametersHandler} objects to be supported must be |
| * registered using one of the {@code registerDefaultHandler()} methods. After that arbitrary parameters objects can be |
| * passed to the {@code initializeParameters()} method. This causes all {@code DefaultParametersHandler} objects |
| * supporting this parameters class to be invoked on this object. |
| * </p> |
| * <p> |
| * Implementation note: This class is thread-safe. |
| * </p> |
| * |
| * @since 2.0 |
| */ |
| public class DefaultParametersManager { |
| /** |
| * A data class storing information about {@code DefaultParametersHandler} objects added to a {@code Parameters} object. |
| * Using this class it is possible to find out which default handlers apply for a given parameters object and to invoke |
| * them. |
| */ |
| private static final class DefaultHandlerData { |
| /** The handler object. */ |
| private final DefaultParametersHandler<?> handler; |
| |
| /** The class supported by this handler. */ |
| private final Class<?> parameterClass; |
| |
| /** The start class for applying this handler. */ |
| private final Class<?> startClass; |
| |
| /** |
| * Creates a new instance of {@code DefaultHandlerData}. |
| * |
| * @param h the {@code DefaultParametersHandler} |
| * @param cls the handler's data class |
| * @param startCls the start class |
| */ |
| public DefaultHandlerData(final DefaultParametersHandler<?> h, final Class<?> cls, final Class<?> startCls) { |
| handler = h; |
| parameterClass = cls; |
| startClass = startCls; |
| } |
| |
| /** |
| * Checks whether the managed {@code DefaultParametersHandler} can be applied to the given parameters object. If this is |
| * the case, it is executed on this object and can initialize it with default values. |
| * |
| * @param obj the parameters object to be initialized |
| */ |
| @SuppressWarnings("unchecked") |
| // There are explicit isInstance() checks, so there won't be |
| // ClassCastExceptions |
| public void applyHandlerIfMatching(final BuilderParameters obj) { |
| if (parameterClass.isInstance(obj) && (startClass == null || startClass.isInstance(obj))) { |
| @SuppressWarnings("rawtypes") |
| final DefaultParametersHandler handlerUntyped = handler; |
| handlerUntyped.initializeDefaults(obj); |
| } |
| } |
| |
| /** |
| * Tests whether this instance refers to the specified occurrence of a {@code DefaultParametersHandler}. |
| * |
| * @param h the handler to be checked |
| * @param startCls the start class |
| * @return <b>true</b> if this instance refers to this occurrence, <b>false</b> otherwise |
| */ |
| public boolean isOccurrence(final DefaultParametersHandler<?> h, final Class<?> startCls) { |
| return h == handler && (startCls == null || startCls.equals(startClass)); |
| } |
| } |
| |
| /** A collection with the registered default handlers. */ |
| private final Collection<DefaultHandlerData> defaultHandlers; |
| |
| /** |
| * Creates a new instance of {@code DefaultParametersManager}. |
| */ |
| public DefaultParametersManager() { |
| defaultHandlers = new CopyOnWriteArrayList<>(); |
| } |
| |
| /** |
| * Initializes the passed in {@code BuilderParameters} object by applying all matching {@link DefaultParametersHandler} |
| * objects registered at this instance. Using this method the passed in parameters object can be populated with default |
| * values. |
| * |
| * @param params the parameters object to be initialized (may be <b>null</b>, then this method has no effect) |
| */ |
| public void initializeParameters(final BuilderParameters params) { |
| if (params != null) { |
| defaultHandlers.forEach(dhd -> dhd.applyHandlerIfMatching(params)); |
| } |
| } |
| |
| /** |
| * Registers the specified {@code DefaultParametersHandler} object for the given parameters class. This means that this |
| * handler object is invoked every time a parameters object of the specified class or one of its subclasses is |
| * initialized. The handler can set arbitrary default values for the properties supported by this parameters object. If |
| * there are multiple handlers registered supporting a specific parameters class, they are invoked in the order in which |
| * they were registered. So handlers registered later may override the values set by handlers registered earlier. |
| * |
| * @param <T> the type of the parameters supported by this handler |
| * @param paramsClass the parameters class supported by this handler (must not be <b>null</b>) |
| * @param handler the {@code DefaultParametersHandler} to be registered (must not be <b>null</b>) |
| * @throws IllegalArgumentException if a required parameter is missing |
| */ |
| public <T> void registerDefaultsHandler(final Class<T> paramsClass, final DefaultParametersHandler<? super T> handler) { |
| registerDefaultsHandler(paramsClass, handler, null); |
| } |
| |
| /** |
| * Registers the specified {@code DefaultParametersHandler} object for the given parameters class and start class in the |
| * inheritance hierarchy. This method works like {@link #registerDefaultsHandler(Class, DefaultParametersHandler)}, but |
| * the defaults handler is only executed on parameter objects that are instances of the specified start class. Parameter |
| * classes do not stand in a real inheritance hierarchy; however, there is a logic hierarchy defined by the methods |
| * supported by the different parameter objects. A properties parameter object for instance supports all methods defined |
| * for a file-based parameter object. So one can argue that |
| * {@link org.apache.commons.configuration2.builder.fluent.FileBasedBuilderParameters FileBasedBuilderParameters} is a |
| * base interface of {@link org.apache.commons.configuration2.builder.fluent.PropertiesBuilderParameters |
| * PropertiesBuilderParameters} (although, for technical reasons, this relation is not reflected in the Java classes). A |
| * {@link DefaultParametersHandler} object defined for a base interface can also deal with parameter objects "derived" |
| * from this base interface (i.e. supporting a super set of the methods defined by the base interface). Now there may be |
| * the use case that there is an implementation of {@code DefaultParametersHandler} for a base interface (e.g. |
| * {@code FileBasedBuilderParameters}), but it should only process specific derived interfaces (say |
| * {@code PropertiesBuilderParameters}, but not |
| * {@link org.apache.commons.configuration2.builder.fluent.XMLBuilderParameters XMLBuilderParameters}). This can be |
| * achieved by passing in {@code PropertiesBuilderParameters} as start class. In this case, |
| * {@code DefaultParametersManager} ensures that the handler is only called on parameter objects having both the start |
| * class and the actual type supported by the handler as base interfaces. The passed in start class can be <b>null</b>; |
| * then the parameter class supported by the handler is used (which is the default behavior of the |
| * {@link #registerDefaultsHandler(Class, DefaultParametersHandler)} method). |
| * |
| * @param <T> the type of the parameters supported by this handler |
| * @param paramsClass the parameters class supported by this handler (must not be <b>null</b>) |
| * @param handler the {@code DefaultParametersHandler} to be registered (must not be <b>null</b>) |
| * @param startClass an optional start class in the hierarchy of parameter objects for which this handler should be |
| * applied |
| * @throws IllegalArgumentException if a required parameter is missing |
| */ |
| public <T> void registerDefaultsHandler(final Class<T> paramsClass, final DefaultParametersHandler<? super T> handler, final Class<?> startClass) { |
| if (paramsClass == null) { |
| throw new IllegalArgumentException("Parameters class must not be null!"); |
| } |
| if (handler == null) { |
| throw new IllegalArgumentException("DefaultParametersHandler must not be null!"); |
| } |
| defaultHandlers.add(new DefaultHandlerData(handler, paramsClass, startClass)); |
| } |
| |
| /** |
| * Removes the specified {@code DefaultParametersHandler} from this instance. If this handler has been registered |
| * multiple times for different start classes, all occurrences are removed. |
| * |
| * @param handler the {@code DefaultParametersHandler} to be removed |
| */ |
| public void unregisterDefaultsHandler(final DefaultParametersHandler<?> handler) { |
| unregisterDefaultsHandler(handler, null); |
| } |
| |
| /** |
| * Removes the specified {@code DefaultParametersHandler} from this instance if it is in combination with the given |
| * start class. If this handler has been registered multiple times for different start classes, only occurrences for the |
| * given start class are removed. The {@code startClass} parameter can be <b>null</b>, then all occurrences of the |
| * handler are removed. |
| * |
| * @param handler the {@code DefaultParametersHandler} to be removed |
| * @param startClass the start class for which this handler is to be removed |
| */ |
| public void unregisterDefaultsHandler(final DefaultParametersHandler<?> handler, final Class<?> startClass) { |
| defaultHandlers.removeIf(dhd -> dhd.isOccurrence(handler, startClass)); |
| } |
| } |