    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
    004//
    005//     http://www.apache.org/licenses/LICENSE-2.0
    006//
    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.
    012
    013package org.apache.tapestry5.ioc.def;
    014
    015import org.apache.tapestry5.ioc.ModuleBuilderSource;
    016import org.apache.tapestry5.ioc.ServiceDecorator;
    017import org.apache.tapestry5.ioc.ServiceResources;
    018
    019/**
    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
    046{
    047    /**
    048     * Returns the id of the decorator, which is derived from the decorator method name.
    049     */
    050    String getDecoratorId();
    051
    052    /**
    053     * Returns zero or more ordering constraint strings, used to order the decorated relative to the other decorators.
    054     */
    055
    056    String[] getConstraints();
    057
    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);
    070
    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);
    080}