001/*
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements.  See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License.  You may obtain a copy of the License at
008 *
009 *      http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 */
017package org.apache.juneau.rest.annotation;
018
019import static java.lang.annotation.ElementType.*;
020import static java.lang.annotation.RetentionPolicy.*;
021
022import java.lang.annotation.*;
023
024import org.apache.juneau.rest.*;
025
026import jakarta.servlet.*;
027
028/**
029 * Identifies a method that gets called during servlet initialization.
030 *
031 * <p>
032 * This method is called from within the {@link Servlet#init(ServletConfig)} method after the {@link org.apache.juneau.rest.RestContext.Builder}
033 * object has been created and initialized with the annotations defined on the class, but before the
034 * {@link RestContext} object has been created.
035 *
036 * <p>
037 * The only valid parameter type for this method is {@link org.apache.juneau.rest.RestContext.Builder} which can be used to configure the servlet.
038 *
039 * <p>
040 * An example of this is the <c>PetStoreResource</c> class that uses an init method to perform initialization
041 * of an internal data structure.
042 *
043 * <h5 class='figure'>Example:</h5>
044 * <p class='bjava'>
045 *    <ja>@Rest</ja>(...)
046 *    <jk>public class</jk> PetStoreResource <jk>extends</jk> BasicRestServlet <jk>implements</jk> BasicUniversalJenaConfig {
047 *
048 *       <jc>// Our database.</jc>
049 *       <jk>private</jk> Map&lt;Integer,Pet&gt; <jf>petDB</jf>;
050 *
051 *       <ja>@RestInit</ja>
052 *       <jk>public void</jk> onInit(RestContext.Builder <jv>builder</jv>) <jk>throws</jk> Exception {
053 *          <jc>// Load our database from a local JSON file.</jc>
054 *          <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>);
055 *       }
056 *    }
057 * </p>
058 *
059 * <h5 class='section'>Notes:</h5><ul>
060 *    <li class='note'>
061 *       The method should return <jk>void</jk> although if it does return any value, the value will be ignored.
062 *    <li class='note'>
063 *       The method should be <jk>public</jk> although other visibilities are valid if the security manager allows it.
064 *    <li class='note'>
065 *       Static methods can be used.
066 *    <li class='note'>
067 *       Multiple init methods can be defined on a class.
068 *       <br>Init methods on parent classes are invoked before init methods on child classes.
069 *       <br>The order of init method invocations within a class is alphabetical, then by parameter count, then by parameter types.
070 *    <li class='note'>
071 *       The method can throw any exception causing initialization of the servlet to fail.
072 *    <li class='note'>
073 *       Note that if you override a parent method, you probably need to call <code><jk>super</jk>.parentMethod(...)</code>.
074 *       <br>The method is still considered part of the parent class for ordering purposes even though it's
075 *       overridden by the child class.
076 * </ul>
077 *
078 * <h5 class='section'>See Also:</h5><ul>
079 *    <li class='link'><a class="doclink" href="https://juneau.apache.org/docs/topics/LifecycleHooks">Lifecycle Hooks</a>
080 * </ul>
081 */
082@Target({METHOD,TYPE})
083@Retention(RUNTIME)
084@Inherited
085@Repeatable(RestInitAnnotation.Array.class)
086public @interface RestInit {
087
088    /**
089     * Optional description for the exposed API.
090     *
091     * @return The annotation value.
092     * @since 9.2.0
093     */
094    String[] description() default {};
095
096    /**
097    * Dynamically apply this annotation to the specified methods.
098    *
099    * <h5 class='section'>See Also:</h5><ul>
100    *    <li class='link'><a class="doclink" href="https://juneau.apache.org/docs/topics/DynamicallyAppliedAnnotations">Dynamically Applied Annotations</a>
101    * </ul>
102    *
103    * @return The annotation value.
104    */
105   String[] on() default {};
106}