001// ***************************************************************************************************************************
002// * Licensed to the Apache Software Foundation (ASF) under one or more contributor license agreements.  See the NOTICE file *
003// * distributed with this work for additional information regarding copyright ownership.  The ASF licenses this file        *
004// * to you under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance            *
005// * with the License.  You may obtain a copy of the License at                                                              *
006// *                                                                                                                         *
007// *  http://www.apache.org/licenses/LICENSE-2.0                                                                             *
008// *                                                                                                                         *
009// * Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an  *
010// * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.  See the License for the        *
011// * specific language governing permissions and limitations under the License.                                              *
012// ***************************************************************************************************************************
013package org.apache.juneau.rest.annotation;
014
015import static java.lang.annotation.ElementType.*;
016import static java.lang.annotation.RetentionPolicy.*;
017
018import java.lang.annotation.*;
019
020import jakarta.servlet.*;
021
022import org.apache.juneau.rest.*;
023
024/**
025 * Identifies a method that gets called during servlet initialization.
026 *
027 * <p>
028 * This method is called from within the {@link Servlet#init(ServletConfig)} method after the {@link org.apache.juneau.rest.RestContext.Builder}
029 * object has been created and initialized with the annotations defined on the class, but before the
030 * {@link RestContext} object has been created.
031 *
032 * <p>
033 * The only valid parameter type for this method is {@link org.apache.juneau.rest.RestContext.Builder} which can be used to configure the servlet.
034 *
035 * <p>
036 * An example of this is the <c>PetStoreResource</c> class that uses an init method to perform initialization
037 * of an internal data structure.
038 *
039 * <h5 class='figure'>Example:</h5>
040 * <p class='bjava'>
041 *    <ja>@Rest</ja>(...)
042 *    <jk>public class</jk> PetStoreResource <jk>extends</jk> BasicRestServlet <jk>implements</jk> BasicUniversalJenaConfig {
043 *
044 *       <jc>// Our database.</jc>
045 *       <jk>private</jk> Map&lt;Integer,Pet&gt; <jf>petDB</jf>;
046 *
047 *       <ja>@RestInit</ja>
048 *       <jk>public void</jk> onInit(RestContext.Builder <jv>builder</jv>) <jk>throws</jk> Exception {
049 *          <jc>// Load our database from a local JSON file.</jc>
050 *          <jf>petDB</jf> = JsonParser.<jsf>DEFAULT</jsf>.parse(getClass().getResourceAsStream(<js>"PetStore.json"</js>), LinkedHashMap.<jk>class</jk>, Integer.<jk>class</jk>, Pet.<jk>class</jk>);
051 *       }
052 *    }
053 * </p>
054 *
055 * <h5 class='section'>Notes:</h5><ul>
056 *    <li class='note'>
057 *       The method should return <jk>void</jk> although if it does return any value, the value will be ignored.
058 *    <li class='note'>
059 *       The method should be <jk>public</jk> although other visibilities are valid if the security manager allows it.
060 *    <li class='note'>
061 *       Static methods can be used.
062 *    <li class='note'>
063 *       Multiple init methods can be defined on a class.
064 *       <br>Init methods on parent classes are invoked before init methods on child classes.
065 *       <br>The order of init method invocations within a class is alphabetical, then by parameter count, then by parameter types.
066 *    <li class='note'>
067 *       The method can throw any exception causing initialization of the servlet to fail.
068 *    <li class='note'>
069 *       Note that if you override a parent method, you probably need to call <code><jk>super</jk>.parentMethod(...)</code>.
070 *       <br>The method is still considered part of the parent class for ordering purposes even though it's
071 *       overridden by the child class.
072 * </ul>
073 *
074 * <h5 class='section'>See Also:</h5><ul>
075 *    <li class='link'><a class="doclink" href="../../../../../index.html#jrs.LifecycleHooks">Lifecycle Hooks</a>
076 * </ul>
077 */
078@Target({METHOD,TYPE})
079@Retention(RUNTIME)
080@Inherited
081@Repeatable(RestInitAnnotation.Array.class)
082public @interface RestInit {
083
084   /**
085    * Dynamically apply this annotation to the specified methods.
086    *
087    * <h5 class='section'>See Also:</h5><ul>
088    *    <li class='link'><a class="doclink" href="../../../../../index.html#jm.DynamicallyAppliedAnnotations">Dynamically Applied Annotations</a>
089    * </ul>
090    *
091    * @return The annotation value.
092    */
093   String[] on() default {};
094}