001// Licensed under the Apache License, Version 2.0 (the "License");
002// you may not use this file except in compliance with the License.
003// You may obtain a copy of the License at
005//     http://www.apache.org/licenses/LICENSE-2.0
007// Unless required by applicable law or agreed to in writing, software
008// distributed under the License is distributed on an "AS IS" BASIS,
009// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
010// See the License for the specific language governing permissions and
011// limitations under the License.
013package org.apache.tapestry5.ioc.def;
015import org.apache.tapestry5.ioc.ModuleBuilderSource;
016import org.apache.tapestry5.ioc.ServiceDecorator;
017import org.apache.tapestry5.ioc.ServiceResources;
020 * Definition of a service decorator, which (by default) is derived from a service decorator method.
021 *
022 * A note on decorator scheduling. The scheduling is based on the desired order of <em>behavior</em>. Thus, if logging
023 * should occur before security checks, and security checks should occur before transaction management, then the desired
024 * decorator order is Logging, Security, Transactions. This might be specified as having Security occur after Logging,
025 * and Transactions occur after Security. It might also be specified by having Logging ordered "before:*", and
026 * Transactions ordered "after:*" with no specified scheduling for Security.
027 *
028 * Once this order is established, decorators are <em>applied</em> in reverse order. Each decorator's job is to create
029 * an <em>interceptor</em> for the service, that delegates to the next implementation. This implies that the decorators
030 * are executed last to first. In the above example, the core service implementation would be passed to the Transaction
031 * decorator, resulting in the Transaction interceptor. The Transaction interceptor would be passed to the Security
032 * decorator, resulting in the Security interceptor. The Security interceptor would be passed to the Logging decorator,
033 * resulting in the Logging interceptor. Thus at runtime, the Logging interceptor will execute first, then delegate to
034 * the Security interceptor, which would delegate to the Transaction interceptor, which would finally delegate to the
035 * core service implementation.
036 *
037 * Service decorators are part of the initial version of Tapestry IoC.  Starting in release 5.1, their use has been
038 * deprecated, in favor of {@link org.apache.tapestry5.ioc.AdvisorDef}, which is based on {@link
039 * org.apache.tapestry5.ioc.services.AspectInterceptorBuilder}.
040 *
041 * Note: service decorators are applied <em>around</em> the interceptor generated via any {@link
042 * org.apache.tapestry5.ioc.AdvisorDef}s (for compatibility with Tapestry 5.0). In general, you should use service
043 * decoration or service advice, not both.
044 */
045public interface DecoratorDef
047    /**
048     * Returns the id of the decorator, which is derived from the decorator method name.
049     */
050    String getDecoratorId();
052    /**
053     * Returns zero or more ordering constraint strings, used to order the decorated relative to the other decorators.
054     */
056    String[] getConstraints();
058    /**
059     * Creates an object that can perform the decoration (in the default case, by invoking the decorator method on the
060     * module class or instance.
061     *
062     * @param moduleSource access to the the module  instance associated with the module containing the decorator (not
063     *                     necessarily the module containing the service being decorated)
064     * @param resources    the resources visible <em>to the decorator</em> (which may be in a different module than the
065     *                     service being decorated). Other resource properties (serviceId, serviceInterface, log, etc.)
066     *                     are for the service being decorated.
067     */
068    ServiceDecorator createDecorator(ModuleBuilderSource moduleSource,
069                                     ServiceResources resources);
071    /**
072     * Used to determine which services may be decorated by this decorator. When decorating a service, first the
073     * decorators that target the service are identified, then ordering occurs, then the {@link ServiceDecorator}s are
074     * invoked.
075     *
076     * @param serviceDef
077     * @return true if the decorator applies to the service
078     */
079    boolean matches(ServiceDef serviceDef);